Plant Pedia: Plant Environment | Plant Biotechnology | Plant Science | Plant Tissue Culture
Showing posts with label Plant Environment. Show all posts
Showing posts with label Plant Environment. Show all posts

Sunday, July 22, 2012

Green Revolution to Gene Revolution

After World War II, as the world’s population spiraled out of control, many governments became concerned that they would not be able to feed everyone within their borders. The specter of mass starvation loomed. Mexico was one of the first countries to sound the alarm. In 1944, it imported half the wheat it needed but wanted to become self-sufficient. The government hired the agronomist Norman Borlaug, who had worked with the Civilian Conservation Corps during the Great Depression, the U.S. Forestry Service, and at the DuPont Chemical Company, to find a solution. Funded with grants from the Ford Foundation and the Rockefeller Foundation, Borlaug turned his attention to the problem, and by 1956 Mexico was producing enough wheat to feed its population. Furthermore, within a few short years it was exporting wheat to other countries. Mexico’s quick turnaround combined with that seen in other populous countries was dubbed the Green Revolution.
Borlaug was a plant geneticist and microbiologist for DuPont when he accepted the position in Mexico. In the first few years, he experimented with 6,000 crossbreeds of wheat, producing varieties that were high yield and disease resistant. More important, he instituted two growing seasons per year, thereby doubling the amount of wheat the country produced. With Mexico as a template for success, Borlaug assisted other countries such as India and Pakistan in attaining food security. In 1970, Borlaug received the Nobel Peace Prize for his role in alleviating world hunger. He is often credited with saving more than 1 billion people from starvation through his work. Although Borlaug’s initial success predated the introduction of GM foods, as a plant geneticist he has always been a supporter of biotechnology as a solution to world hunger.
Among the critics of GM foods are those who do not object to them on principle but on the circumstances of their development. For instance, most GM crops have been developed to benefit the bottom line of large agricultural corporations. While GM seed may yield a greater harvest and prevent pest damage, it is also more expensive than non–GM seed, promotes environmentally damaging monoculture, cannot legally be reused by farmers, and sometimes requires the application of a corresponding herbicide (such as Monsanto’s Roundup). These conditions bode well for those who hold the patent on the seed but are not necessarily conducive to helping those who need help the most—subsistence farmers in the developing world who cannot afford the high-priced seed and herbicides. In fact, Vandana Shiva, a respected agriculture activist from India, believes that conditions surrounding the distribution of GM seed are destroying subsistence farmers’ ability to feed themselves.46 What smallholder farmers need, Shiva believes, is access to a variety of crops suitable for the land they cultivate and the promotion of time-honored traditions that protect the environment, such as crop rotation and natural pest control. What they do not need, she says, is GM seed that is grown specifically to become feed for livestock or as an ingredient in another product in which the farmer has no stake.
The Food and Agriculture Organization (FAO) of the United Nation’s 2004 annual report, The State of Food and Agriculture 2003–2004, called for a “gene revolution” on par with the Green Revolution of the 1960s that would bestow GM seed on those who would most benefit. In the next 30 years, the population of the poorest countries is forecasted to swell by 2 billion.
The gains of the Green Revolution have made continued population growth possible, and a new solution is needed. However, most GM seed planted worldwide is corn, along with lesser amounts of soybeans, canola, and cotton. The gene revolution needs to apply biotechnology to a wider range of crops. According to the FAO Director-General Dr. Jacques Diouf, “Neither the private nor the public sector has invested significantly in new genetic technologies for the so-called ‘orphan crops’ such as cowpea, millet, sorghum and tef that are critical for the food supply and livelihoods of the world’s poorest people.” Furthermore, according to the FAO: [GMOs] can provide farmers with disease-free planting materials and develop crops that resist pests and disease, reducing use of chemicals that harm the environment and human health. It can provide diagnostic tools and vaccines that help control devastating animal diseases. It can improve the nutritional quality of staple foods such as rice and cassava and create new products for health and industrial uses. India could also greatly benefit from a gene revolution. Predicted to overtake China as the world’s most populous country by 2050, India must attain food security by addressing the problems of soil erosion, water shortages, and rural poverty. According to C. S. Prakash, the director of the Center for Plant Biotechnology Research at Alabama’s Tuskegee University, “India also has serious problems of blast in rice, rust in wheat, leaf rust in coffee, viruses in tomato and chilies and leaf spot in groundnut across the country. These problems can be significantly minimised in an ecologically-friendly manner with the development of genetically reprogrammed seeds designed to resist these disease attacks, while minimising or even eliminating costly and hazardous pesticide sprays.” Even in the United States, some farmers are transitioning from traditional crops, such as wheat and corn (whose markets have fluctuated unfavorably) to transgenic crops that can benefit third world countries. Rice genetically modified
with proteins from human milk, saliva, and tears is being test-grown in Missouri in the hopes that it may be consumed by at-risk populations in countries that suffer from high death rates due to diarrhea.50 These GM crops could produce food that is medically beneficial in areas that have inadequate health care or sanitation systems. It could also help domestic farmers gain a better foothold in an industry that suffered an almost total collapse in the 1980s.
But would a gene revolution be overkill? Some believe the food problem requires a more simple solution. A low-tech agricultural practice called the system of rice intensification (SRI) could produce greater yields and require little in the way of scientific intervention. More than half of the world’s population depends on rice, and between 2007 and 2008 its price tripled, laying the groundwork for a possible humanitarian crisis in some of the world’s most fragile economies. Norman T. Uphoff, the former director of the Cornell International Institute for Food, Agriculture and Development (CIIFAD), developed the SRI as a way to help solve the global food crisis. No genetic engineering is necessary, according to Uphoff. Farmers simply plant rice early, give seedlings more room to grow, water them less, and rotate crops annually. Fewer seeds and deeper roots make for harvests roughly two to three times larger than traditional cultivation practices allow.51 If such processes are so easy, then why have farmers not adopted them sooner, ask critics of SRI. They believe the claims made for SRI are exaggerated and that the system cannot be replicated on a wide scale. While basic, it also requires much old-fashioned weeding by farmers. Some believe that this will negatively affect women in developing countries, who often undertake much of the heavy labor. Experts believe that GM food has yet to make an impact on securing the global food supply because it is not practiced on the crops that matter most to people in developing countries: potatoes, cassava, rice, wheat, millet, and sorghum.52 Ignoring these in favor of frost-resistant strawberries and stay-ripe bananas leaves GM food in the realm of a boutique industry rather than a marketplace necessity. There is no economic incentive for private companies to invest in research and development into the crops grown by subsistence farmers in the developing world, a phenomenon known as the “molecular divide.” Technology typically originates in the developed world but without economic incentives does not transfer to areas where it could help others most, particularly sub-Saharan Africa. That may be changing. In 2008, Monsanto announced plans to develop seeds that would double corn, soybean, and cotton yields by 2030 using less land and water. The effort is directed at “improv[ing] the lives of small and poor farmers by sharing [Monsanto’s] technology” without
charging royalties. As the journalist Andrew Pollack explained, the plan is “aimed at least in part at winning acceptance of genetically modified crops by showing that they can play a major role in feeding the world.”

Sunday, April 10, 2011

Agricultural Biotechnology for Developing Countries

Since the early 1970s, when the exploitation of biotechnology started to soar in the industrialised countries, developing countries—representing about 80% of the world's population—have progressively adopted and adapted biotechnology as a contribution to solving their social and economic development problems. At the beginning of the 21st century, most developing countries use biotechnology in one form or another, at scales and complexities that depend on their economic, scientific and technological status. In particular, they often rely on agricultural biotechnology, such as in vitro micropropagation of plant tissues or organs, followed by clonal multiplication of herbaceous or tree crops to produce virus and pathogen-free plants. They also use a wide range of food fermentations.

Many developing countries, for example India, China, Thailand, Brazil, Mexico, Egypt and South Africa, utilise the so-called modern biotechnology, based on genetic engineering and genomics. Agricultural biotechnology is the most widespread biotechnology in developing countries, but only a few of them are able to carry out all of the research and development activities leading to the commercialisation of genetically modified seeds. These include basic research in molecular and cell biology and genetics; greenhouse and field trials according to internationally agreed biosafety standards; risk assessment and management; respect for intellectual property rights relating to the transferred genes and to the creation of new crop varieties; production of genetically modified (GM) seeds by private corporations or working in cooperation with the public agricultural research sector; extension activities aiming at delivering the new seeds to the farmers and biovigilance in the fields of GM crops so as to detect any abnormalities or any hazards caused to the environment and to conventional crops. It is therefore important to follow the strategy of the countries capable of going through all these steps in order to understand how agricultural biotechnology supply meets economic and social demand (Sasson, 2000). A number of these countries are considered in more detail in later chapters in this section. Unfortunately, due to time constraints, it was not possible to include all of the key countries, so that the geographical coverage of this section is not complete. In particular China, where agricultural biotechnology has a rapidly growing role, is not covered in a separate chapter. The editors believe that the current coverage presents the reader with a detailed discussion of the major issues and opportunities of agricultural biotechnology in developing countries but they plan to extend the coverage in future editions of the Handbook.

It should be emphasised that the developing countries whose economies still largely depend on their food supply, exports and employment on agriculture that is not (or very little) subsidised by the government, must face the following challenges:

*
increase in production and productivity, and in competitiveness at national, regional and international levels (within the framework of the rules being established or revised by the World Trade Organization);
* protection of the environment and biological diversity, while reducing agricultural inputs (water, fertilizers and biocides), improving soil fertility and conservation (e.g. biological nitrogen fixation), increasing nitrogen and phosphorus absorption by crops, without significantly decreasing yields;
* diversification of agro-food production so as to meet the evolving needs of consumers and the food industry.

These challenges are similar to those faced by industrialised countries whose intensive agriculture employs, nevertheless, a very small proportion of the active population and is generally heavily subsidised (which leads to unfair competition with food-exporting developing countries).

Although food self-sufficiency is not an intangible rule anymore, and countries can devote land to high value-added export products and buy cereals or legumes on international markets at rather low prices, it is important to keep in mind the strategic role of efficient agriculture.

Population Growth and the Food-Production Challenge

Norman Borlaug (2002, 2004) has analysed the ways in which the birth of agriculture some 10 000–12 000 years ago, led to a stable food supply and enabled humankind to increase its population from some 15 million at that time to about 250 million by the start of the Christian era. Borlaug (2004) noted that that population doubled by 1650, then doubled again (to one billion) by 1850, redoubled by 1930 and doubled again by 1975, when the global population reached four billion. The next doubling is projected by 2020 and this will represent a 530-fold increase since the origin of crop improvement by selection of seeds from the best plants for sowing to deliver the next generation. Although the rate of increase of the world's population is now decreasing, the current rate in much of the developing world is still so high that the world's population is likely to increase to at least 10 billion people over the next 50 years, with 90–95% of them living in low-income developing countries and under conditions of poverty. Although it is hoped that the world's population will stabilise at 11–12 billion by the end of the 21st century, we have to confront a situation today where more than two billion people have no food security and 840 million of them are chronically malnourished. Six million children under the age of five die each year as a result of hunger and malnutrition. Of these millions, relatively few are the victims of famines. Most die unnoticed, killed by the effects of chronic hunger and malnutrition that leaves them weak, underweight and vulnerable. Health and mortality indicators are closely correlated with the prevalence of hunger. Common childhood diseases are far more likely to be fatal in children who are even mildly undernourished, and the risk increases sharply with the severity of malnutrition. Eliminating hunger and malnutrition could save millions of lives each year (FAO, 2002).

There are two major challenges that mankind must confront. The first is to produce enough food to satisfy the needs of the huge population. The second, even more complex problem is to ensure that the food is equitably distributed. The chief impediment to equitable food distribution is poverty (lack of purchasing power). Some 42% (2.6 billion people) of the world's population live on the land and rely on their own efforts to feed themselves. Only increases in agricultural productivity in food-deficient areas can enable the millions of rural poor to become food-secure.

The possibility of expansion of arable land area is limited for most regions of the world and the International Food Policy Research Institute (IFPRI) has estimated that more than 85% of the essential increase in cereal production (which represents two-thirds of human calorific intake) must come from increasing yields on land that is already in production. These productivity increases must come from varieties with higher genetic yield potential and greater tolerance of drought, insects and diseases. Crop management must emphasise soil and water conservation, reduced tillage, fertilization, weed and pest control and post-harvest handling.

Irrigated crops, which account for 70% of global water withdrawals, cover some 17% of cultivated land and yet provide nearly 40% of the world's food production. The rapid increase in land irrigation and in urban and industrial water usage has resulted in growing water shortages. It seems likely that two-thirds of the world's population will be suffering from water stress by 2025 (Borlaug, 2004).

The efficiency of water use in agriculture can be improved by several technologies. Wastewater treatment enables use for irrigation, especially for peri-urban agriculture. New improved varieties which require less water can achieve significant savings, especially if they are used in systems with more efficient crop rotation and more timely planting. Technologies are now available for saving water by increasing water productivity (yield per unit of water used). Reduction of soil salinity is now a matter of the highest priority. Borlaug (2004) has emphasised the need to bring about a ‘blue revolution’ by marrying water-use productivity to land-use productivity.

The conclusion that cereal yields must be increased on lands currently farmed, using less water and biocides means that in addition to conventional agricultural techniques, other techniques relating to protection of the environment and preservation of natural resources, drastic reduction of postharvest losses and control of biotic and abiotic stresses should be utilised (Borlaug, 2002). This is where agricultural biotechnology will help; it is not a panacea, nor a substitute for established agronomic techniques, but it represents another tool for increasing productivity and improving food quality.

During the World Food Summit, organised in 2002 in Rome by the Food and Agriculture Organization of the United Nations (FAO), it was again emphasised that developing countries should rely on agricultural biotechnology along with other agricultural technologies, while respecting internationally agreed biosafety standards. One year earlier, in its Report on Human Development, the United Nations Development Programme (UNDP) recommended the widest application of biotechnology (and other advanced technologies) in developing countries.

There is indeed an overall consensus on the utility of in vitro production of plantlets, derived from plant tissue or organ micropropagation, that are free of viruses and other pathogens and can contribute to increasing agricultural production, provided that small and poor farmers can purchase them at a low cost. In vitro production, which also concerns ornamental and forest species, is widespread in developing countries. It has become an important element of agro-food production, as it is applied to potato and several other tuber and root crops, high value-added horticultural varieties, oil palms and date palms, banana and plantain, which are the staple food of several hundred million people worldwide (Sasson, 2000).

Friday, February 25, 2011

How to Managing Compost?


A variety of techniques may be used to increase the rate of compost decomposition. One technique is to cut the starting materials into 10- to 15-cm (4- to 6-in) pieces to increase the surface area on which the microorganisms act. Increased surface area accelerates decomposition, much like a large ice chunk melts faster if broken up into small pieces. The microorganisms in the compost pile also thrive when oxygen and moisture are present. Fluffing the compost pile every week or so with a pitchfork or other tool introduces oxygen into the pile, and sprinkling water on the pile when it dries out provides the necessary moisture.

In a well-managed compost pile, the microorganisms eat and reproduce rapidly, and heat is released as a byproduct of their intense biochemical activity. The heat in the pile kills most plant diseases and weed seeds that may have been present on the starting materials. The increased heat may also kill the microorganisms doing the decomposing as well, especially those at the center of the pile where temperatures may climb to 90° C (200° F). Mixing the materials well about once a week prevents lethal temperature increases by distributing the heat evenly throughout the pile.

The time it takes microorganisms to decompose the starting materials in compost varies. Factors include the size of the pile, the techniques used to manage the pile, and the nature of the starting materials—green materials decompose readily, while brown materials take longer to break down. In an actively managed compost pile, microorganisms use up their food supply and become less active after about six weeks. Then the pile slowly cools, signaling the near-final stages of decomposition. If the materials in a compost pile are relatively large, if the pile is not kept moist, and if oxygen is not introduced, microorganism activity is slow and the pile does not heat up. Depending upon the climate, it may take months or years for decomposition to occur.
No matter how long decomposition takes, when in its final stage, the compost pile is about half its original size and resembles dark soil. The material in the pile is now called humus—although the terms humus and compost sometimes are used interchangeably. Humus is the highly beneficial material that is added to the garden soil. Once in or on the soil, it continues to decompose at a very slow rate, releasing ammonia, carbon dioxide, and salts of calcium, phosphorus, and other elements that are beneficial for plant growth.

Humus can be added to the soil at any time of year. It can be worked into the soil, where its benefits take effect most rapidly, or it can be left on the soil surface. Humus can be used year after year, and there is never danger of adding too much, since this remarkable substance only enhances soil and encourages plants to thrive.

Cities compost on a large scale to reduce yard waste so that it does not take up space in landfills. Industries compost hazardous materials because the activities of the microorganisms help break down toxic substances into less-harmful or harmless materials. Many municipalities provide information on composting as part of their programs to reduce the amount of solid waste entering their landfills. County or regional offices of the state Cooperative Extension Service also have information on composting.

How to Making Compost?


Compost is made by harnessing the natural decomposition process carried out by certain species of microorganisms. These microorganisms, primarily bacteria and fungi, live in intimate association with their food supply—on the surface of dead plants, in soil, or on or in animal waste. By breaking down these materials with their digestive enzymes, the tiny creatures release and absorb the nutrients within. For home gardeners, making compost is simply a matter of collecting food for microorganisms in one place and letting them go to work.

A broad range of organic matter, including manure from plant-eating animals, grass clippings, and dead leaves or garden plants, provides a veritable feast for microorganisms. For optimal decomposition, the combined starting materials should have an appropriate carbon to nitrogen ratio, preferably 30 parts carbon to 1 part nitrogen. Leaves, straw, and paper, called brown materials, have a high carbon to nitrogen ratio, about 300 to 1, while grass clippings, kitchen scraps, and manure, called green materials, have a low carbon to nitrogen ratio, about 15 to 1. For the best mix, green materials should be added in abundance; brown materials should be used more sparingly. Materials that should not be used to make compost include manure from meat-eating animals, because it may contain disease-causing organisms that can harm humans who eat plants grown in the compost. Meat should be avoided since it may attract rodents. Fatty foods such as cheese also should not be added to the compost pile, as they are hard for most microorganisms to digest.

The starting materials are heaped into a pile—in a home garden, the pile is typically about a meter high and a meter wide (about three feet high and three feet wide); on farms, composting is done on a larger scale. The pile may sit loose on the ground or it may be enclosed using a variety of materials, including wire fencing, wood boards, cinder blocks, or widely stacked bricks.

Decomposed Organic Material Used In Gardening


Compost, partially decomposed organic material used in gardening to improve soil and enhance plant growth. Compost improves the movement of water, dissolved nutrients, and oxygen through the soil, making it easier for plant roots to absorb these vital substances.

A versatile material, compost benefits virtually any soil type. Clay soil, for example, has tiny, tightly packed particles that hamper the flow of water, nutrients, and oxygen. Compost reconfigures the clay into larger, more loosely packed particles. The larger spaces between the particles improve the flow of water, oxygen, and nutrients to roots. In addition, the roots are able to penetrate deeper into the soil and contact more nutrients. Compost also improves sandy soil, where the large spaces between loosely packed particles enable water and its dissolved nutrients to drain too quickly for optimum root absorption. Compost soaks up and holds these substances so that the roots have more time to absorb them. Compost also adds small amounts of zinc, copper, boron, and other vital nutrients to soils.

Wednesday, February 2, 2011

Mycorrhiza as Biofertilizers


Mycorrhiza (fungus roots) is a distinct morphological structure which develops as a result of mutualistic symbiosis between some specific root - inhabiting fungi and plant roots. Plants which suffer from nutrient scarcity, especially P and N, develop mycorrhiza i.e. the plants belong to all groups e.g. herbs, shrubs, trees, aquatic, xerophytes, epiphytes, hydrophytes or terrestrial ones. In most of the cases plant seedling fails to grow if the soil does not contain inoculum of mycorrhizal fungi.

In recent years, use of artificially produced inoculum of mycorrhizal fungi has increased its significance due to its multifarous role in plant growth and yield, and resistance against climatic and edaphic stresses, pathogens and pests.

Mechanism of Symbiosis

The mechanism of symbiosis is not fully understood. Biorkman (1949) postulated the carbohydrate theory and explained the development of mycorrhizas in soils deficient in available P and N, and high light intensity. Slankis (1961) found that at high light intensity, surplus carbohydrates are formed which are exuded from roots. This in turn induces the mycorrhizal fungi of soil to infect the roots. At low light intensity, carbohydrates are not produced in surplus, therefore, plant roots fail to develop mycorrhizas.

Types of Mycorrhizas

By earlier mycologists the mycorrhizas were divided into the following three groups :

(i) Ectomycorrhiza. It is found among gymnosperms and angiosperms. In short roots of higher plants generally root hairs are absent. Therefore, the roots are infected by mycorrhizal fungi which, in turn, replace the root hairs (if present) and form a mantle. The hyphae grow intercellularly and develop Hartig net in cortex. Thus, a bridge is established between the soil and root through the mycelia.

(ii) Endomycorrhiza. The morphology of endomycorrhizal roots, after infection and establishment, remain unchanged. Root hairs develop in a normal way. The fungi are present on root surface individually. They also penetrate the cortical cells and get established intracellulary by secreting extracellular enzymes. Endomycorrhizas are found in all groups of plant kingdom.

(iii) Ectendomycorrhiza. In the roots of some of the gymnosperms and angiosperms, ectotrophic fungal infection occur. Hyphae are established intracellularly in cortical cells. Thus, symbiotic relation develops similar to ecto- and endo-mycorrhizas.

Marks (1991) classified the mycorrhizas into seven types on the basis of types of relationships with the hosts (i) vesicular-arbuscular (VA) mycorrhizas (coiled, intracellular hyphae, vesicle and arbuscules present), (ii) ectomycprrhizas (sheath and inter-cellular hyphae present), (iii) ectendomycorrhizas (sheath optional, inter and intra-cellular hyphae present), (iv) arbutoid mycorrhizas (seath, inter-and coiled intracellular hyphae present), (v) monotropoid mycorrhizas (sheath, inter- and intra- cellular hyphae and peg like haustoria present), (vi) ericoid mycorrhizas (only coiled intracellular hyphae, long coiled hyphae present), and (viii) orchidaceous mycorrhizas (only coiled intracellujlar hyphae present). Type (i) is present in all groups of plant kingdom; Types (ii) and (iii) are found in gymnosperms and angiosperms. Types (iv), (v) and (vi) are restricted to Ericales, Monotropaceae and Ericales respectively. Types (vii) is restricted to Orchidaceous only. Types (iv) and (v) were previously grouped under ericoid mycorrhizaes.

Methods of Inoculum Production and Inoculation

Methods of inoculum production of VAM fungi differ; however, some of these two are briefly described here.

(a) Ectomycorrhizal fungi: The basidiospores, chopped sporocarp, sclerotia, pure mycelia culture, fragmented mycorrhizal roots or soil from mycorrhizosphere region can be used as inoculum. The inoculum is mixed with nursery soils and seeds are sown.

Institute for Mycorrhizal Research and Development, U.S.A., Athens and Abbort Laboratories (U.S.A) have developed a mycelial inoculum of Pisolithus tinctorius in a vermiculite-peat moss substrate with a trade name ‘Myco-Rhiz’ which is now commercially available on large quantities. In 1982, about 1.5 million pine seedlings were produced with MycoRhiz in the U.S.A. (Marx and Schenck, 1983).

(b) VA mycorrhizal fungi : VA mycorrhizas can be produced on a large scale by pot culture technique. This requires the host plants, mycorrhizal fungi and natural soil. The host plants which support large scale production of inoculum are sudan grass, strawberry, sorghum, maize, onion, citrus, etc.

The starter inoculum (spores) of VA mycorrhizal fungi can be isolated from soil by wet sieving and decantation technique (Gerdeman and Nicolson, 1963). VA mycorrhizal spores are surface sterilized and brought to the pot culture. Commonly used pot substrates are sand: soil (1:1, w/w) with a little amount of moisture. An out line for inoculum production is given in Fig. 12.5.

There are two methods of using the inoculum : (i) using a dried spore-root- soil to plants by placing the inoculum several centimeters below the seeds or seedlings, (ii) using a mixture of soil-roots, and spores in soil pellets and spores adhered to seeds with adhesives.

Commercially available pot culture of VA mycorrhizal hosts grown under aseptic conditions can provide effective inoculum. Various types of VA mycorrhizal inocula are currently produced by Native Plants, Inc (NPI), Salt Lake City.

In India, Forest Research Institute, Dehra Dun has established mycorrhizal bank in different states of the country. Inocula of these can be procured as needed and used in horticulture and forestry programmes.

Benefits from Mycorrhizas to Plants

(i)

They increase the longevity of feeder roots, surface area of roots by forming mantle and spreading mycelia into soil and, in turn, the rate of absorption of major and minor nutrients from soil resulting in enhanced plant growth.

(ii)

They play a key role for selective absorption of immobile (P, Zn and Cu) and mobile (S, Ca, K, Fe, Mn, Cl, Br, and N) elements to plants. These are available to plants in less amount (Tinker, 1984).

(iii)

Some of the trees like pines cannot grow in new areas unless soil has mycorrhizal inocula because of limited or coarse root hairs.

(iv)

VA mycorrhizal fungi enhance water uptake in plants,

(v)

VA mycorrhizal fungi reduce plant response to soil stress such as high salt levels, toxicity associated with heavy metals, mine spoils, drought and minor element (e.g. Mn) imbalance.

(vi)

VA mycorrhizal fungi decrease transplant socks to seedlings. They produce organic 'glues' which bind soil particles into semistable in aggregates. Thus, they play a significant role in augmenting soil fertility and plant nutrition.

(vii)

Some of them produce metabolites which change the ability of plants to induce roots from woody plant cuttings and increase root development during vegetative propagation.

(viii)

They increase resistance in plants and with their presence reduce the effects of pathogens and pests on plant health.



Monday, January 31, 2011

Genetics and Phytoremediation Strategies

Genetic Engineering Possibilities

To determine possible mechanisms for genetically engineering a plant to increase its remediation ability, it is best to begin with the mechanism for arsenic uptake and storage. It is believed that arsenate is taken up from the soil by the phosphate transporter. This has been suggested by exclusion experiments in which inorganic arsenate competed with inorganic phosphate for transport by a phosphate transporter. (Csanaky and Gregus 2001) It is believed that the high affinity phosphate uptake system is involved, because it has a lower selectivity than the low affinity system, and suppression of the high affinity system results in smaller arsenic uptake and accumulation. (Fitz and Wenzel 2002) One mechanism that could be useful would be to overexpress the phosphate ion transporter gene in plant roots. This would allow for more arsenic uptake by the plant, and could therefore lead to greater arsenic sensitivity, due to increased concentration of arsenate in the plant, and accumulation.

Once inside the plant, the arsenate travels with the transpiration flow through the xylem and into the stems and leaves. (Tu et.al 2002) Here it is reduced, possibly by an arsenate reductase enzyme (ArsC) into its more toxic form, arsenite. (Dhankher et.al 2002) Another possible mechanism would be to overexpress the arsenate reductase gene in plant shoots. Studies have coupled the arsenate reductase gene to a soybean ribulose bisphosphate carboxylase small-subunit gene promoter, which will give it strong light-induced expression, insuring that the arsenate is reduced in the shoots, not roots. (Dhankher et.al 2002) Since arsenite is more toxic than arsenate, all the transgenic plants were more sensitive to arsenic in the growing medium. (Dhankher et.al 2002)

Arsenite has a great affinity for thiol groups and consequently binds to peptide-thiol molecules, also known as phytochelatins. (Dhankher et.al 2002) Phytochelatin production appears to be activated by the presence of heavy metals and arsenic. (Sauge-Merle et.al 2003) One enzyme critical in the pathway for the formation of these peptide-thiol molecules is y-glutamylcysteine synthetase (y-ECS). (Dhankher et.al 2002) This enzyme produces the first, and possibly limiting enzyme in the phytochelatin producing pathway. (Dhankher et.al 2002) Studies have coupled this gene to a constitutively expressed actin promoter, giving a constant high level of phytochelatins in the plant and providing a sink for reduced arsenite within the cells. (Dhankher et.al 2002) Plants transformed with both ArsC and y-ECS produced four times more biomass than the control when grown four weeks on a 200 micromolar arsenate medium, showing greater tolerance as well as accumulation. (Dhankher et.al 2002)

This complex is then transported via a specific transport mechanism into a vacuole or into the cell wall. (Pickering et.al 2000) Another possible genetic approach would be to overexpress the gene for the transport protein into the vacuole or cell wall. This would remove the arsenite more quickly from the cells, to reduce the toxicity to the cell, and allow for more arsenic to be taken up.

Arsenic has been shown to have deleterious effects on seed germination, as well as root length and mass, which can detract from the effectiveness of a phytoremediation treatment. (Nie et.al 2002) Some bacteria, such as Enterobacter cloacae promote plant growth and minimize arsenic stress on the roots. (Nie et.al 2002) The Enterobacter cloacae UW4 1-aminocyclopropane-1-carboxylate deaminase gene in plants has been shown to increase the interaction between plants and these growth promoting bacteria. (Nie et.al 2002) In addition, transformed plants accumulated four times as much arsenic as non-transformed plants. (Nie et.al 2002) Overexpression of this gene is another possible mechanism to increase plant growth and phytoremediation of arsenic-contaminated soils.

A combination of these transformations and others could create a plant that was capable of high levels of arsenic accumulation and tolerance, when used to transform a species with high biomass that is adapted to living in the environment in which the arsenic-contaminated site exists. A tree such as cottonwood would be ideal for this purpose, and researchers are concentrating their efforts on performing this transformation. (www.edie.net) Further studies must be performed on the unique hyperaccumulating species, such as Pteris vittata and Pityrogramma calomelanos, to determine if they possess a novel mechanism or just an abnormally high expression of a given enzyme in the accumulation pathway. These hyperaccumulators or the transgenic accumulators can then be used with various phytoremediation strategies.

Phytoremediation Strategies

Phytostabilization is a possible strategy for control of arsenic, where arsenic tolerant plants, such as Spergularia grandis and Agrostis catellana are used to keep Arsenic contaminated soil in place to prevent erosion and leaching of the contaminant. (Fitz and Wenzel 2002)

Phytovolatilization is the use of plants to turn a pollutant into a gas to remove it from a site. Although this does occur to some extent in nature, volatile arsenic is still toxic, so phytovolatilization is not really a feasible option. (Fitz and Wenzel 2002)

One positive phytoremediation option is rhizofiltration, the removal of pollutants from water using a hydroponic system. Arsenic contaminated runoff could be run through a set-up with Lepidium sativum, which has been shown to remove arsenic from anaerobic flooded environments. (Robinson et.al 2003) This can also be used in conjunction with bioleaching, which would produce a heavily arsenic-contaminated runoff from soil with initially low arsenic bioavailability. (Seidel et.al 2002)

One positive phytoremediation option is rhizofiltration, the removal of pollutants from water using a hydroponic system. Arsenic contaminated runoff could be run through a set-up with Lepidium sativum, which has been shown to remove arsenic from anaerobic flooded environments. (Robinson et.al 2003) This can also be used in conjunction with bioleaching, which would produce a heavily arsenic-contaminated runoff from soil with initially low arsenic bioavailability. (Seidel et.al 2002)

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Phytoremediation: Cleaning Up With Plants

Have you ever heard of locoweed? As a child, I watched a lot of Bgrade movie Westerns and one thing I learned was that, if you are a rancher, you don’t want your cattle grazing on locoweed! Locoweed is the common name given to several species of Astragalus, a genus in the Fabaceae or pea family. Also known as milk vetch or poison vetch, many species of Astragalus take up unusually large quantities of selenium from the alkaline soils of the western plains.

The high selenium content contributes to a disease known as alkali poisoning or “blind staggers” in cattle unfortunate enough to graze on this plant—the cattle literally behave as though they are crazy. There are many regions where natural geochemical processes have produced soils that are rich in metals such as nickel, chromium, gold, cadmium, selenium, and arsenic. Normally high levels of heavy metals would be toxic to plants, just as they are to humans, yet many plants actually thrive on soils rich in such metals. For some plants, the metals are not a problem simply because the cell membranes surrounding the root cells prevent the metals from entering the root. Other plants actually take up the metals and accumulate them to levels that would be toxic to most other plants.

In Astragalus, for example, selenium may account for as much as 10% of the dry weight of the seeds. In soils that are rich in nickel, some plants may contain 200,000 times more nickel than plants growing in normal soils. Many years ago, such plants were known as “indicator species,” and prospectors would take the presence of such plants as an early indication that the soils may have contained a mineral of interest, such as gold. This was called phytoprospecting. We now call these plants accumulator species, which are not injured by high concentrations of heavy metals because they sequester (isolate) the metals with small proteins called phytochelatins.

The sequestered metals are then stored in the large central vacuole of the plant cell, where they cannot interfere with the cell’s metabolism. There has recently been a renewed interest in accumulator species because these plants may have the potential to assist in cleaning up soils contaminated with heavy metals as a result of twentieth-century industrial activities. Using plants to clean up soils is called phytoremediation (phyto meaning “plant” and remediation meaning “to correct a fault”).

The idea is to grow accumulator species on mine tailings and wastes from paper mills, for example, where they would extract the heavy metals. Plants will naturally take longer to do the job, but plants are much more cost-effective and would not create even more ecological problems as engineering-based technologies often do.

Phytoremediation would also help to stabilize contaminated sites because the plants help to control erosion. An additional benefit of accumulator species is that they begin the revegetation of barren industrial sites and assist in the recovery of useful metals. Phytomining, as it is called, has proven effective in the recovery of both nickel and thallium in demonstrations. Inother trials, various species of willows (Salix) have shown promise for extraction of heavy metals from soils treated with sewage sludge. The advantage of using plants is that they can be harvested and burned. The heavy metals remain concentrated in the ash, which makes their disposal much easier.

Sunday, January 23, 2011

The retractable liquid foam technology improved greenhouse climate

study in HortTechnology featured a new technology that improved greenhouse climates by reducing solar heat radiation and temperatures during the hot summer season. The study, published by a team of Canadian researchers, was the first investigation into the effects of application of the liquid foam technology as a shading method. Results showed that the technology improved greenhouse and plant microclimates and decreased air temperature more than conventional shading curtains traditionally used by greenhouse growers.

Excess temperature, solar radiation, and high vapor pressure deficit are major greenhouse concerns during the summer season. These extreme conditions increase plant stress and decrease crop productivity and fruit quality. Methods such as cooling pads and fogging systems have been used to prevent plant heat stress during the day, and various shading techniques are often used by growers to decrease solar radiation and reduce air and leaf temperatures. Shade cloths reduce the amount of solar energy entering the greenhouse and consequently decreased air temperature by partially cutting the heat portion of the solar radiation, but this incoming energy commonly contains more than 50% heat (infrared radiation), which is not useful for plant growth in the summer.

Sunarc of Canada, Inc. developed an innovative new shading technology that generates retractable liquid foam and distributes it between two layers of polyethylene film used as a greenhouse covering material. The Canadian research team set out to determine the effects of different shading strategies using the liquid foam technology on greenhouse and plant microclimates. The research was conducted over 2 years in two different areas of Canada, where experimental greenhouses were retrofitted with the new technology. Tomato and sweet pepper plants were used with two shading strategies: a conventional nonmovable shading curtain in comparison to the liquid foam shading system based only on outside global solar radiation, and foam shading applications based on both outside global solar radiation and greenhouse air temperature. The team recorded data on the greenhouse microclimate (global solar radiation, air temperature, and relative humidity), the canopy microclimate (leaf and bottom fruit temperatures), and ventilation (opening/closing).

"This study showed that the retractable liquid foam technology improved greenhouse climate", noted Kamal Aberkani, main author of the report. "Under very sunny, very hot conditions, a difference of up to 6 �C in air temperature was noted between the unshaded and shaded greenhouses as a result of liquid foam application at 40-65% shading".

As per the report, additional benefits of the technology included an increase of up to 12% in greenhouse relative humidity, a decrease in the frequency of roof ventilation operation, and an increase in the length of time bottom fruit temperature remained cool after shading ended.

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Wednesday, January 12, 2011

Winter Temperatures Play Complex Role in Triggering Spring Budburst


The opening of buds on Douglas-fir trees each spring is the result of a complex interplay between cold and warm temperatures during the winter, scientists with the U.S. Forest Service's Pacific Northwest Research Station have found.

Their research -- which is featured in the December issue of Science Findings, a monthly publication of the station -- led to the development of a novel model to help managers predict budburst under different scenarios of future climate.

"We take it for granted that buds will open each spring, but, in spite of a lot of research on winter dormancy in plants, we don't really understand how the plants are sensing and remembering temperatures," said Connie Harrington, research forester and the study's lead. "The timing of budburst is crucial because, if it occurs prematurely, the new growth may be killed by subsequent frosts, and if it occurs too late, growth will be reduced by summer drought."

Although scientists have long recognized that some plants require a certain amount of exposure to cold temperatures in the winter and warm temperatures in the spring to initiate the opening of buds, the precise interaction between these chilling and forcing requirements has, until now, been largely unexplored. Harrington and her station colleagues Peter Gould and Brad St Clair addressed this knowledge gap, which has implications for forecasting the effects of climate change on plants, by conducting greenhouse experiments in Washington and Oregon using Douglas-fir, an ecologically and economically important species.

For their experiments, the researchers exposed Douglas-fir seedlings from 59 areas in western Oregon, western Washington, and northern California to a range of winter conditions. After the seedlings finished their first year of growth, they were divided into groups and placed in different locations where their exposure to temperatures varied according to predetermined scenarios. In the spring, the scientists monitored the seedlings and documented the length of time it took for their buds to open.

"We found that, beyond a minimum required level of chilling, many different combinations of temperatures resulted in spring budburst," Harrington said. "Plants exposed to fewer hours of optimal chilling temperatures needed more hours of warmth to burst bud, whereas those exposed to many hours of chilling required fewer hours of warm temperatures for bud burst."

The plants were responding, the researchers found, to both warm and cold temperatures they experienced during the winter and spring. And, they noted that the same temperatures can have different effects depending on how often they occur -- a fact that may seem counterintuitive at first. While some winter warming may hasten spring budburst, substantial periods of mid-winter warming, such as is projected under several future climate scenarios, may actually delay, not promote, normal budburst.

Harrington and her colleagues used their findings and research results from other species to develop a novel model that depicts this gradual tradeoff between chilling and forcing temperatures and have verified its accuracy using historical records. They found that the model was fairly accurate in predicting past budburst in Douglas-fir plantations, which indicates it works well with real-world conditions.

Because the model is based on biological relationships between plants and temperature, the researchers expect it will be fairly straightforward to modify for use with other species and for other areas. Managers, for example, could use the model to predict changes in budburst for a wide range of climatic projections and then evaluate the information to determine if selecting a different species to plant or stock from a different seed zone would be a useful management strategy.

Full report in Science Findings: http://www.treesearch.fs.fed.us/pubs/36960

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Thursday, December 2, 2010

The social life of plants


Did you see this article in the NYT yesterday? (Warning-registration may be required.) Canadian researchers are examining the ability of plants to distinguish members of its own species from “outsiders.” Last summer scientists at McMaster University in Hamilton, Ontario published a study on the sea rocket (Cakile edentula), a native member of the mustard (Brassicacaea) family that grows above the high tide line on sandy beaches.

Yet scientists have found evidence that the sea rocket is able to do something that no other plant has ever been shown to do.

The sea rocket, researchers report, can distinguish between plants that are related to it and those that are not. And not only does this plant recognize its kin, but it also gives them preferential treatment.

If the sea rocket detects unrelated plants growing in the ground with it, the plant aggressively sprouts nutrient-grabbing roots. But if it detects family, it politely restrains itself.

The finding is a surprise, even a bit of a shock, in part because most animals have not even been shown to have the ability to recognize relatives, despite the huge advantages in doing so.

If an individual can identify kin, it can help them, an evolutionarily sensible act because relatives share some genes. The same discriminating organism could likewise ramp up nasty behavior against unrelated individuals with which it is most sensible to be in claws- or perhaps thorns-bared competition.

Pretty cool that sea rocket can distinguish between its family members! (That’s a photo of it at right.) Dr. Dudley and his colleagues have since then discovered evidence that three other species can do the same thing, but in different ways.

Plants" social life may have remained mysterious for so long because, as researchers have seen in studies of species like sagebrush, strawberries and thornapples, the ways plants sense can be quite different from the ways in which animals do.

Some plants, for example, have been shown to sense potentially competing neighboring plants by subtle changes in light. That is because plants absorb and reflect particular wavelengths of sunlight, creating signature shifts that other plants can detect.

Reserachers also studied a certain parasitic weed called dodder (genus Cuscuta, absolutely terrible vampire-like plant, maybe I’ll do a post on it one day). Dodder can “sense” chemicals released in the air by nearby plants and use it to “sniff out” its victim:

Scientists also find plants exhibiting ways to gather information on other plants from chemicals released into the soil and air. A parasitic weed, dodder, has been found to be particularly keen at sensing such chemicals.

Dodder is unable to grow its own roots or make its own sugars using photosynthesis, the process used by nearly all other plants. As a result, scientists knew that after sprouting from seed, the plant would fairly quickly need to begin growing on and into another plant to extract the nutrients needed to survive.

But even the scientists studying the plant were surprised at the speed and precision with which a dodder seedling could sense and hunt its victim. In time-lapse movies, scientists saw dodder sprouts moving in a circular fashion, in what they discovered was a sampling of the airborne chemicals released by nearby plants, a bit like a dog sniffing the air around a dinner buffet.

Then, using just the hint of the smells and without having touched another plant, the dodder grew toward its preferred victim. That is, the dodder reliably sensed and attacked the species of plant, from among the choices nearby, on which it would grow best.

"When you see the movies, you very much have this impression of it being like behavior, animal behavior," said Dr. Consuelo M. De Moraes, a chemical ecologist at Pennsylvania State University who was on the team studying the plant. "It"s like a little worm moving toward this other plant."

The movie that she’s referring to? YOU HAVE TO SEE IT! Go to the NYT article link and scroll down until you see the link for the movie. It’s worth getting an account to see it if you don’t have one (it’s free). The movie a time-lapse of a dodder seedling putting the moves on a tomato plant that it’s in the pot with it. (A still from the movie is at the top of the page). It truly looks like it’s sniffing the tomato plant out as it looks for its next victim.

Plants sure is crazy peoples!

ALL PHOTOS COURTESY OF THE NEW YORK TIMES

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Tuesday, July 27, 2010

Maize: food from the Gods?


In a 1982 exhibition, the Mexican National Museum of Culture claimed that maize was “not domesticated, but created”. Indeed, maize is accepted as Man’s first, and perhaps his greatest, feat of genetic engineering. So much so, that it is even said to be a gift from the gods.

Great civilisations need a great asset. Ancient Egypt had the Nile. The Mayans had maize, or corn as others call it. Maize is accepted as Man’s first, and perhaps his greatest, feat of genetic engineering. It nevertheless remains a largely enigmatic crop. Despite decades of research, there is no known wild ancestor; there is no known way to evolve a non-shattering variant; it is known that maize does not have a method to propagate itself – and thus relies on humans to survive as a species. Indeed, the human race – and definitely in the pre-Columbian New World – has entered into a powerful symbiosis with this cereal that has fed – and continues to feed – us.

At DNA level, all major cereals – rice, wheat, barley and maize – are very much alike. But maize is and acts differently from the rest. Left unattended, the other cereals will propagate themselves; maize will not. The reason for this is that maize kernels are located inside a tough husk, and hence it requires humans to sow maize – it cannot reproduce on its own. This is, of course, a major evolutionary disadvantage, but as maize has been created by Mankind, we have always guaranteed that the species does not die out – far from it.

No wild ancestor of maize has ever been found, despite decades of research. Maize’s closest relative is a mountain grass called teosinte, which looks nothing like maize. It is neither a practical food source. Most grasses develop grain near the top of the stem, which, when mature, will let the seed “shatter”, and the grains will fall to the ground, from which new grasses will grow. It guarantees the survival of the species, but is ill-suited for human agriculture. In wild wheat and barley, a single-gene mutation has blocked such shattering, which meant that these cereals became more easily harvestable for humans.

Teosinte shatters too and there is no known non-shattering variant. Furthermore, at least sixteen genes control teosinte and maize shattering, resulting in a complex problem for those trying to figure out how a non-shattering variation of maize might have occurred naturally – by accident – or how our distant ancestors figured out how to create such a feat; scientists continue to have no idea.

Pennsylvania geneticist Nina V. Federoff states that “to get corn out of teosinte is so – you couldn’t get a grant to do that now, because it would sound so crazy. Somebody who did that today would get a Nobel Prize! If their lab didn’t get shut down by Greenpeace.” Indeed, maize is, in origin, genetically modified food, which is at the centre of much controversy today. Still, our ancestors seem to not only have had no such social opposition, but more importantly, were able to pull this stunt off.

In July 2008, the date when maize might have been genetically engineered – i.e. created – was put even further back, to 10,000 years ago. The debate on the origins of maize had been transformed as scientists are now using new genetic and microbotanical techniques to distinguish domesticated maize from its wild relatives as well as to identify ancient sites of maize agriculture. These new analyses suggested that maize may have been domesticated in Mexico as early as 10,000 years ago.

Dr. John Jones and his colleagues, Mary Pohl, and Kevin Pope, evaluated multiple lines of evidence, including paleobotanical remains such as pollen, phytoliths, and starch grains, as well as genetic analyses, to reconstruct the early history of maize agriculture. Jones and his co-workers analyzed the sediments from San Andrés, in the state of Tabasco on the Mexican Gulf Coast. Analysis of area sediments revealed phytoliths of domesticated varieties of maize as well as those of agricultural weeds. These data, along with evidence of burning, suggested that agriculturalists were active in that part of the Yucatan Peninsula around 7,000 years ago.

Archaeological remains of early maize ears, found at Guila Naquitz Cave in the Oaxaca Valley, date back ca. 3450 BC, with the oldest ears from caves near Tehuacán, Puebla, dating to ca. 2750 BC. In the 1960s, Richard S. MacNeish found more than 20,000 whole or partial maize cobs in five caves in the Tehuacán Valley. The natural refuse he was investigating was an archaeological treasure, which became used in the debate between Harvard botanist Paul C. Mangelsdorf and Stanford geneticist George Beadle. In the late 1930s, both had proposed theories on the origins of maize, with Beadle arguing that maize was a direct descendent from teosinte. Beadle’s camp is largely seen as the most widely followed, but as usual, popularity should not be equated with scientific validity.
Mangelsdorf’s rejection of Beadle’s theory was harsh, stating that teosinte played no role in the origins of maize at all, and argued it originated from a mixture of now extinct wild maize and wild grasses of the genus Tripsacum. Mangelsdorf worked with MacNeish and used his archaeological discovery to cement his theory in the minds of his peers, largely killing the teosinte theory.
However, in 1970, the teosinte theory was taken up again by Wisconsin botanist Hugh Iltis. But… in 1997, Duke biologist Mary W. Eubanks resurrected Mangelsdorf’s theory, but with a twist, arguing that maize had been created by repeatedly crossing zeo diploperennis, a rare maize relative, and another cousin species, Eastern gamagrass. As proof for this latest of theories, she announced the creation of a Zea diploperennis-gamagrass hybrid in the laboratory, which displayed the characteristics of ancient maize. But because the combination of these two plants is not “normal”, Eubanks argued that the mixture of both plants occurred by coincidence. The alternative would be that someone, millennia before Christ, was a far better genetic engineer than any currently working in the hundreds of scientific laboratories on the planet.

Yale archaeologist Michael D. Coe has labelled maize the key to the understanding of Mesoamerican civilisation: “Where it flourished, so did high culture.” Coe’s research has led him to the conclusion that the harvest of maize became an economical asset between 2000 and 1500 BC. Little change occurred in ear form until ca. 1100 BC, when great changes appeared in ears, as found in those Mexican caves. Maize diversity rapidly increased; as it was introduced to new cultures, new uses were developed and new varieties selected to better serve in those preparations.
In Mexico alone, more than fifty races have been identified. As a rule, domesticated plants are less genetically diverse than wild species, but maize is one of the few farm species that is more diverse than most wild plants. Of these fifty variations, at least thirty are native to Oaxaca, according to Flavio Aragón Cuevas, a maize researcher at the Oaxaca office of the National Institute for Forestry, Agriculture and Fisheries Research.

It is at around 1500 BC that the first evidence of large-scale land clearing for milpas appears, and with it appeared the Olmecs. Indian farmers grow maize in a milpa, a “maize field”, which, unlike modern farming methods, is not always recently cleared. Farmers plant a dozen crops together, including maize, avocados, melon, tomatoes, sweet potato, and varieties of squash and beans. Some of these plants lack nutrients which others have in abundance, resulting in a powerful, self-sustaining symbiosis between all plants grown in the milpa. The milpa is therefore seen by some as one of the most successful human inventions – alongside maize.

A traditional milpa

There are places in Mesoamerica that have been continuously cultivated for 4000 years and are still productive. The milpa is the only system that permits that kind of long-term use. Hugo Perales notes that amongst the Tzotzil of San Juan Chamula, 85 percent of the farmers planted the same maize landraces as their fathers, varieties that have been passed on and maintained for generations.
Alas, the milpa cannot be applied on an industrial scale, but it is clear that it comes with none of the deficits industrial farming has.

Riding on the maize revolution, it shouldn’t come as a surprise that Olmec art has a central place for this crop, with ears of maize springing from the skulls of supernatural beings. The king’s clothes often included a headdress with an ear of maize emblazoned on the front. Later, the Mayans too would hold maize centrally important. In Mayan hieroglyphics, the ear of maize became equivalent with the highest royal title, ahaw. In the Popul Vuh, the Maya creation story, humans were created from maize. And, indeed, for those who have seen in the Popol Vuh evidence of extra-terrestrial intervention, and who are equally aware that the invention of maize was a tremendous display of genetic engineering, these people have argued that maize has been created by extra-terrestrial beings.
Maize was definitely seen as a gift from the gods. One version of the creation myth states that when the Medicine Rite was first created by the good spirits, each of them contributed something that would help the humans overcome the evil spirits. After all the spirits had made their contributions, Grandmother (Earth) came forward and spoke to Hare: “Look at my breast, grandson.” Then, unexpectedly, there grew from one of Grandmother’s breasts a plant that no-one had ever seen before. It grew immediately from her nipple into a full stalk with ripe ears of corn ready to eat. “This, grandson,” said Earth, “is maize. The two-legged walkers may eat its corn forevermore.” As sexual as the story may be, it also has a practical usage: when the corn is white and milky in the centre, it is time to harvest the crop.
Other myths are trying to incorporate the diversity of maize, and thus read how the Mother of Maize changed her dove appearance to a human one. At one point, she identified her five daughters to a young man; the daughters symbolise the five maize sacred colours: white, red, yellow, spotted and blue.

So, in the beginning was the word, and the word was maize. Among the Maya of Guatemala, the maize deity is still worshipped today, and today, it is variously a male and female deity, whereas in origin, it seems to have been specifically linked with female deities.
The question is whether science and myth agree or disagree over the place of birth of this new species. Science believes that Oaxaco was the centre of the cereal’s emanation. According to the Popol Vuh, Paxil was the name of the place where maize originated. Paxil is part of Tamoanchan, the mythical homeland of the Mayans, which is also where the “Mother of Maize” is said to reside. Evidence to its whereabouts are scant, but descriptions of Tamoanchan appearing in the Florentine Codex indicate that at least the Postclassic Nahuas thought that it was located in the humid lowlands region of the Gulf Coast of Mexico, inhabited by the Huastec Maya people. That, of course, is also the area that we today associate most intimately with the Olmecs.

So, at present, myth and scientific theories seem to be at odds. What about its origins? The myths state that in ancient times there was no maize, and that humans ate the roots of a plant called txetxina (mother Maize), a plant with a very large root and a single stalk. “It was then that the ancients realised that the excrement of the mountain cat (wech) contained maize.” This would argue for Mary W. Eubanks’ conclusion, that the actual discovery of maize was a coincidence, which humans chanced upon, rather than the end result of a series of genetic manipulations.
A more elaborate rendition of this account goes that “In those distant times, it is said that animals could speak. This was why the people of the region asked the mountain cat where he went to feed, and they asked him to show them this place. The mountain cat told them that someone should go with him to see the place where he fed. So the ancients sent the louse to travel on the back of the mountain cat to see where his mount went; but the louse fell off on the way and never reached the place where the maize grew. They immediately sent the flea, again on the back of the mountain cat; but the flea also fell off though it managed to jump back on and cling to the cat’s back to reach the place that was sought. Thus, when the flea returned, he was able to tell the ancients the place where the maize grew. From then on, people stopped eating the root of txetxina.”

But the Mayan creation myths go further than merely pointing out where and how they chanced upon maize, and explain it in a far richer context. In practice, maize and Man lived in a form of symbiosis, and though it might appear that the gods showed Man where this plant was living, in mythology, and in the symbolism of the Ixquic’s children and their origin, maize is seen as the material from which the first humans were actually created. After all, Tamoanchan was the residence of the gods, and the place of birth not only of maize, but also of Mankind. And what came first, Man or Maize, is a matter of some mythological debate.

The Mayan creation myths have other episodes involving maize. Ixquic was made pregnant by the skull of Hun Hunahpu, which hung from the calabash tree. Hun Hunahpu is often seen as a manifestation of the god of maize. Since she was repudiated by her father Cuchumaquic, the Lord of Xibalbá, she went to find the mother of Hun Hunahpu, Ixmucané. When she arrived and announced herself, her grandmother told her to go and bring food for those who needed to be fed: “go and harvest a large net of maize and come back at once”, she said. Ixquic went to the maize field, but there was only one stalk of maize, one stalk with its single ear of grain. The girl’s heart was filled with anguish and hence she invoked the guardians of the crops, imploring them to help: “Ixtoc, Ixanil, Ixcacau, you who cook the maize.” Then she took the tuft of red hairs of the maize, without cutting the cob, and she placed them in the net as if they were corncobs. The net filled itself completely. The animals of the field took the maize to the house.
“Where did you get all this maize from?” asked Ixmucané. “You must have finished our maize field off.” She herself then went to the maize field and saw that there was still the single stalk of maize with its cob. “This is the proof that you are my daughter-in-law,” she said. And Ixquic had proven her state as a deity to Ixmucané.

Maize also placed a central role in the story of Hun Hunahpu itself. He descended into the underworld realm of Xibalba, to confront the twin lords of death. After a number of trials, the maize god was defeated and sacrificed and the underworld lords took his head and placed it in the branches of a dead tree. The instant the head touched the tree, it miraculously came to life with abundant foliage and fruits that resembled the god’s skull.
It is clear that there are several parallels here: like the maize god, the dead seed of maize is planted beneath the earth in the underworld. With time, the grain of maize germinates and sprouts new life from its dry, bony husk. Ancient art often depicts the maize god rising out of a cleft in the earth with his arms outstretched, a symbol of his rebirth from death as a maize plant. In the central panel from the Temple of the Foliated Cross at Palenque, the World Tree appears as a fruitful stalk of maize, each ear bearing the head of the maize god.

These and other myths involving maize show that it was primarily the role of women who conserved maize. Indeed, the introduction of maize into society also came with a new social responsibility: to make sure that the crops would never fail. For once a society had made this unique – and vital – bond with the crop, any disaster befalling the crop, would mean disaster would befall society.
One of the most repeated stories, told in many villages of Guatemala and Mexico, talks about the participation of ants in the appropriation of maize by man, which is what happens during a famine. We also find other stories, which suggest that our ancestors realised the danger of relying on one crop, and made alternative arrangements, in case of disaster. This back-up crop was a plant known as “donkey’s or mule’s helmet”, a plant the people of Guatemala and Mexico knew could be found in the mountains, where their ancestors went to gather it. They used it to make tortillas or drinks to compensate f
In Central America, the cultivation of maize also lies at the foundation of the calendar, divided into a rain and a dry season. The year is divided into ritual periods of sowing and harvesting of 260 days respectively, with 100 surplus days. The first phase starts on February 14. It is the period of the preparation of the land, in which there are 73 distinct days for the burning of the fields and the tilling of the earth and 67 for the sowing, the sprouting and the growing of the stalks (140 days). The second phase (starting in July) of 120 days, corresponds to the flowering and maturation of the maize. In November, the end of the ritual year is marked and signals the start of both the harvest and the sowing season, as well as the hundred day break, in which other crops are grown.
This calendar varies according to the altitude and the climate of the region among other circumstances, but, of course, it is also clear that the 260 days calendar of the Mayans that is currently so in vogue, finds it origins in the cultivation of maize. Is it any wonder that of all regions, specifically some regions of Oaxaca, where maize is thought to have originated from, this calendar is still in use there?

The sanctified, yet precarious relationship Man had with maize was also apparent in a number of rituals and observances. Gonzalez Pacheco, for example, gave a detailed description of the beliefs and religious behaviour of the Maya-Kekchi culture in the Alta Verapaz, Guatemala. He pointed out that maize had been the staple food of this people for thousands of years, with clear periods of abundance and scarcity. As a result, a series of rites developed which reflected the various stages of the maize production cycle and their relation to human survival.
For example, during the sowing, sexual abstinence was observed by the owners of the maize fields. The time of sowing was related to the moon, but was also accompanied by a ritual meal of maize cooked without lime. Then, and at other times, prayers were said for the soul of the maize. When tender maize shoots sprouted, the new maize was blessed. When the first food from the harvest was prepared, the ritual atoll – a maize-flour drink – was consumed and a rite was there to augment the strength required to feed on the grain.

For a modern mind, the Mayan methodology of working with maize, and how it became to dominate life far beyond a means of food, becoming the backbone of their religion, folklore and calendar, is excessive. The modern mind will want to strip it all down to basics, to the bare bones of an accidental discovery of maize, and how this coincidence created the Olmec and Maya civilisations.

But it is clear that reality is not that simple. The Mayans, for one, were not simple folk. Their attitude towards maize was clearly scientific: they genetically modified – diversified – it themselves, and worked out the milpa as the optimal means of food production. These are practical, hard scientific facts of history. But for that same Mayan mind, coincidences did not exist, and hence the “coincidence” that somehow maize was created by accident, was unacceptable to it; for the Mayans, maize was a gift from the gods, placed on earth for Mankind to find. And once they found it, they cultivated it, and through it, thanked and worshipped the gods for feeding them, and allowing them to grow and excel. The Mayan mind believed – or realised – that not only had the gods given them maize, the gods would continually need to be thanked for guaranteeing the success of the yearly crops. In the end, the symbiosis between Man and maize was a contract between us and the gods.

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