Showing papers in "Basic life sciences in 1977"

The Ti-plasmid of Agrobacterium tumefaciens, a natural vector for the introduction of nif genes in plants?

Abstract: There are several natural barriers to the introduction, maintenance and proper expression of “foreign” DNA into plant cells. First of all the foreign DNA must be taken up by the recipient plant cells without drastic alterations (e.g. extensive breakdown), secondly the introduced DNA must be replicated and the new copies must be distributed among the daughter cells at mitosis. Finally the introduced DNA must be expressed via transcription, translation and possibly correct processing and the proteins produced by these processes must be able to function in the new cellular environment. It would therefore appear that the possibilities for genetic engineering of plant cells with genes from bacterial origin, must be rather remote.

Nitrogen Fixation by Azolla in Rice Fields

Abstract: Azolla is a floating aquatic fern widely distributed throughout temperate and tropical fresh waters. There are two indigenous species in the Sacramento Valley of central California: A. filiculoides and A. mexicana (Mason, 1957). Their natural habitats include agricultural drainage waters, ponds, and calm waters of rivers. Azolla like many species of legumes, harbors a symbiotic microorganism capable of reducing atmospheric nitrogen and supplying this fixed nitrogen to the higher plant. The prokaryote associated with Azolla is a blue-green alga (Anabaena azollae) which is able to photosynthesize independently. Unlike legumes, however, the Azolla-Anabaena pair apparently continues to fix atmospheric nitrogen in the presence of significant quantities of combined nitrogen (Becking, 1976; Peters et al., 1976). This property and high rates of acetylene reduction demonstrated for Azolla (Becking, 1976) suggest a potential agronomic role for temperate Azolla species in photosynthetic production of fertilizer nitrogen.

The Azolla-Anabaena azzolae symbiosis.

Abstract: Free-living, nitrogen fixing blue-green algae occur in soils and in both fresh water and marine habitats from the tropics to the antarctic.l–3 Moreover, symbiotic relationships with nitrogen-fixing blue-green algae encompass members of a relatively large and diverse segment of the plant kingdom. In particular, blue-green algae in the Nostoc-Anabaena group exist in symbiotic associations as lichens and with liverworts, water-ferns, cycads and the angiosperm, Gunnera.3,4

Natural variation and its conservation.

Abstract: 1. The diversity of species used by preagricultural peoples contracted as a result of domestication, but intraspecific diversity greatly expanded with worldwide migrations of crops, to be drastically contracted as a consequence of modern plant breeding. 2. Wild progenitors and other relatives of crops have much to contribute to plant breeding, but this is inhibited by inadequate collections and quite insufficient information. Although many of these crops are still relatively safe in their natural habitats, they should be extensively collected and studied. 3. The natural gene pools of many of the wild species directly used by humans, and particularly many tropical forest species (including tree fruits as well as forestry species) will be lost through replacement of indigenous forests by farmland and by planting with selected forest species. Extensive nature reserves are essential for gene-pool conservation, which would also help to preserve species that may become useful in the future. 4. In general, wild species are best preserved within the community of which they form a part. Ex situ preservation presents many difficulties, but it may be inevitable in some cases. Seed conservation is a practical alternative and should be more widely explored. 5. Because of the enormous genetic diversity between and within the local land races of crops evolved over long periods in diverse areas with traditional farming systems, they constitute a most valuable source of genetic materials for plant improvement. Such crops are threatened by the rapid advances of much higher-yielding advanced cultivars, and efforts for their preservation are of the highest priority. The situation in Pakistan and neighboring countries is discussed. 6. Advanced cultivars (produced by modern plant-breeding methods) have been the principal genetic resources used in developed countries, but there are good reasons for enlarging gene pools used by plant breeders, one being the danger of “genetic vulnerability” that results from homogeneity. “Primitive” gene pools are of special importance for plant improvement in the countries in which they are situated. 7. Methods for the exploration and collection of genetic materials have been clarified. The urgent need now is to safeguard representative samples of what is left in the field, as well as the material now in collections, much of which is inadequately maintained. 8. Methods and procedures for the long-term conservation of seeds have been worked out, and the organization for international collaboration of seed-storage laboratories is in an advanced stage of preparation. 9. The conservation of genetic resources is solely directed toward utilization by present and future generations; hence, the evaluation and documentation of collected material is of the greatest importance. Evaluation must be directed toward the practical objectives of breeding projects, and information made available to all users. 10. Current developments are briefly recorded.

Nutritional Aspects of Cereal Proteins

Abstract: Recent years have brought a greater awareness of the need for more plentiful as well as more nutritious foods. Discoveries of strains of maize, barley, and other crops having higher levels of essential amino acids have shown the differences in nutritional quality that can occur among strains of crop varieties. Comparisons are made between the total lysine content of common cereals and selected high-lysine mutants. It appears from these comparisons that the total lysine content expressed in percent of protein is very high in some varieties. However, if the digestibility of the individual amino acid components is taken into consideration the picture is somewhat different. Experimental data show that lysine especially has a low availability in several of the cereal grains. It is assumed that this is because lysine is mainly deposited in the protein fractions of lowest digestibility. Based on these observations, the validity of the concept of additivity of gross values can be questioned. It is documented that when barley, rye, wheat, maize, and sorghum are fertilized with increasing amounts of nitrogen more protein will be deposited in the prolamins. As the prolamin fraction is a poor but highly digestible source of lysine, more digestible protein but of lower biological value is obtained. For oats and rice the situation is different as glutelin (relatively rich in lysine) is the main storage protein in these grains. Tannins are present in a number of plant materials. Present work shows that barley also contains significant amounts of tannins. Experiments with rats showed that a highly significant negative correlation exists between the tannin contents of barley and protein digestibility. By adding increasing amounts of tannin to rat diets it was found that tannin has a specific affinity for proline, glycine, and glutamic acid. Protein quality of cereal grains with modified amino acid pattern is discussed and compared with common varieties. The comparison is based mainly on nitrogen-balance experiments with rats. The nutritional superiority of several of these high-lysine varieties is obvious. However, the necessity of taking the availability of the nutrients into consideration in this type of biological study is emphasized. To stress this further, experimental data are given for gross energy and digestible energy in cereal grains. The differences between gross energy and digestible energy vary considerably between different grains. In oats, for instance, only 70% of the energy is digestible, whereas for polished rice almost all the energy is available. It is therefore concluded that in cereal grains neither gross energy values nor crude protein values are additive from a nutritional point of view.

Prospects and perspectives in mutation breeding.

Abstract: Induction of mutations, primarily a method of generating genetic variation, can contribute to plant improvement when combined with selection, or recombination and selection, or with other methods of manipulating genetic variation. As a source of variability, induced mutations supplement naturally occurring variation. When specific mutants are selected following mutagenic treatments it is highly likely that a number of mutational changes will have occurred in the selected genotype. Hence, although most of the mutant varieties released so far have resulted from mutation and direct selection, the future trend will be for increasing use of mutants in association with recombination. Whereas induced mutations are generally regarded as random events, there are suggestions of some mutational specificity in response to different mutagenic agents and treatments. The best immediate prospects for increasing specificity lie in the manipulation of the selection environment. Biochemical selection applied to large numbers of plant cells in culture to locate mutations in specific biosynthetic pathways and the subsequent regeneration of whole plants offers great prospect for reducing the cost of breeding programs and altering the amount or composition of a desired end or intermediate product. Mutations in combination with other techniques of genetic engineering will constitute the tools of the plant breeders of the future. Their present role in plant breeding has been established. They have advantages in certain situations, disadvantages in others. Greater understanding will lead to their more widespread use.

Energy coupling efficiency of symbiotic nitrogen fixation.

Abstract: The early evidence of a relationship between H2 metabolism and N2 fixation was reviewed by Wilson and Burris in 1947 (31). Phelps and Wilson in 1941 (20) reported the presence of a hydrogenase in the nodules of garden peas (Pisum sativum) that were inoculated with Rhizobium leguminosarum strain ONA 311. In 1956, however, Shug et al. (27) stated that the experiments with hydrogenase in pea nodules were not reproducible. These early studies were conducted before cell-free nitrogenase preparations had been demonstrated and consequently it was not possible at that time to distinguish between nitrogenase dependent H2 evolution and hydrogenase activity that was not associated with the nitrogenase system. By use of mass spectrometric methods, Hoch et al. in 1957 (15) showed conclusively that soybean nodules evolved H2 and that the H2 evolution process required O2. The extent of H2 evolution decreased as nodules aged and the leghemoglobin began to deterioriate. Hoch, Schneider and Burris in 1960 (16) indicated that H2 evolution from soybean nodules was inhibited by N2 and N2O, but was insensitive to low concentrations of CO.

Artificial mutagenesis as an aid in overcoming genetic vulnerability of crop plants.

Abstract: Artificially induced genetic variation is being used effectively to supplement or complement sources of natural origin for practical plant breeding Thus, creating genetic variation will become increasingly important as crop genetic resources become more difficult to obtain via plant exploration The artificial induction of useful genetic variation offers important elements that can be used for overcoming genetic vulnerability: (1) new, previously unknown alleles can be induced in crop plant species to broaden the base of variation; (2) useful genetic variation can be induced in modern cultivars helping to shorten breeding time or to extend production “life”; (3) characteristics of existing genetic resource stocks can be improved to make them more useful in breeding; and (4) recombination in crosses may be enhanced The performance of induced mutant crop cultivars and the successful uses of induced genetic variation in cross breeding indicate that artificial mutagenesis will play an increasingly greater role in plant breeding

Rate-Limiting Steps in Biological Photoproductivity

Abstract: An average crop of soybeans has a seed yield of about 1800 kg·ha−1·yr−1 and that of corn about 6000 kg·ha−1 yr−1. Expressed on another basis an average crop of soybeans, wheat, or corn converts only 0.2 to 0.4% of the incident solar radiation to dry matter with maximum short-term efficiencies of 1.4 to 2.9%. What are the factors limiting biological photoproductivity or the efficiency of conversion of solar radiation by crops? Identification of these ratelimiting factors and developing practical solutions must be the primary goal of world crop production research. A doubling in biological photoproductivity is the minimal requirement during the next 25 years (Hardy, 1976a,b). Biological photoproductivity is considered as the spacetime yield of the economic component of crops as described in the introductory sentence of this paragraph and is synonymous with yield.

Plant responses to high temperatures.

Abstract: Research has shown that there are wide diversities in heat tolerance among crops, and that differences occur not only between crop species, but also among genotypes within the species. Sufficient variability occurs to select for genotypes with high heat tolerance. Under field conditions, drought stress often accompanies heat stress, and there are usually interactions of plant response to these two stresses. Consequently, heat and drought resistance are usually considered together in field response, but each mechanism must be considered separately in order fully to understand the response. An example is given in which sorghum is regarded as having greater stress resistance than corn from field performance. However, results showed that cellular tolerance to high temperatures was higher in corn than in sorghum and higher in pearl millet than in corn. This was true not only of cellular membrane stability, but also of isolated chloroplast activity and photosynthesis of intact leaves under controlled conditions. Results also showed that the drought-avoidance mechanisms were inadequate in corn as compared to sorghum; therefore, corn-leaf tissue may be more frequently exposed to high temperatures owing to decreased evaporative cooling, and the critical limits of high temperature and desiccation tolerance exceeded, resulting in leaf “firing,” even though cellular tolerance is greater than that of sorghum. In pearl millet, both heat tolerance and drought-avoidance mechanisms appear well developed. Tests have shown that heat tolerance frequently correlates positively with desiccation tolerance, but because they do not always correlate, different mechanisms must be involved in each kind of tolerance. Heat hardening occurs under natural conditions and may contribute significantly to total plant performance. Once plants are heat hardened there may be long-lasting effects. The age or stage of development of the plants at which high-temperature exposure occurs may also have a marked influence on the response. The relative resistance to high-temperature injury may change among genotypes as they age. Leaf temperatures in the range of 43°–45°C may have marked effects on photosynthesis of sorghum, with distinct differences shown in genotype response. The response of hybrids to high temperatures may be determined by one or both parents. Photosynthesis by plants selected for high heat tolerance by a leaf-disc technique was shown to be more stable at high temperatures than that of plants with low heat tolerance. The leaf-disc technique may be used for rapid field screening.

Physiological basis of salt tolerance in plants.

Abstract: For most plants, and under most field conditions, osmotic effects of salinity greatly predominate in restricting growth and yields. In certain cases, however, specific ion effects may be decisive. These may involve either nutrition, as in calcium deficiency in some lettuce varieties, tomato, and bell peppers, or direct toxicity (chloride or sodium toxicity, or both) in tree and vine crops. Rootstocks, or varieties that restrict the uptake of toxic ions, increase the salt tolerance of some susceptible fruit crops. Salinity-induced nutritional imbalance can, in some cases, be corrected by selecting better adapted varieties and in others by the use of foliar nutrient sprays. Recent evidence indicates simple single-gene control over uptakes of chloride and sodium, but the more general osmotic effects appear to be complex and under multigenic control.

Cloning nitrogen fixing genes from Klebsiella pneumoniae in vitro and the isolation of NIF promoter mutants affecting glutamine synthetase regulation.

Abstract: The vast majority of terrestial nitrogen fixation occurs in the soil and in plants which possess prokaryotic nitrogen fixing symbionts (1). Industrial nitrogen fixation probably accounts for less than 10% of the total amount fixed, and the amount fixed by free-living soil bacteria is agronomically negligible (2). Unfortunately, nitrogen fixing symbiont plants do not include the world’s major cereal crops such as wheat, rice or corn; or grass, the world’s major forage crop. Thus, in technologically underdeveloped countries, agricultural productivity of the soil is frequently limited by the amount of nitrogen contributed to the soil by the growth of leguminous crops.

Engineered Plant Cell or Fungal Association with Bacteria that Fix Nitrogen

Abstract: It is a well recognized fact that one of the most important factors limiting significant increases in the yield of agronomic crops is the availability of fixed nitrogen, which is almost totally dependent on two sources. The principal biological source of fixed nitrogen is through the symbiotic association of bacteria of the genus Rhizobium with leguminous plants. The other major source of nitrogen for agriculture are the synthetic fertilizers, which require a high initial input of energy, and have become increasingly expensive and scarce. In addition, the exploding human population and the demands of an increasingly affluent society impose a more acute challenge to agriculture than ever before for supplying high protein foods without exhausting the natural sources of energy. Biologists have reacted with vigor to this challenge, and are exploring novel approaches for alleviating the shortage of food proteins that is responsible for much of the malnutrition in the world, and for conserving our natural energy resources (Hardy and Havelka, 1975; Vasil, 1976).

Biochemistry of Nitrogenase.

Abstract: The biochemistry of nitrogenase has been reviewed so frequently in the past few years that the production of a comprehensive review at this point seems unwarranted. My colleagues and I have published two lengthy reviews in which most of the recent developments have been analyzed (Orme-Johnson and Davis, 1977; Orme-Johnson et al., 1977). Along with the article by Winter and Burris (1976) and the Symposium Proceedings of the 1974 Conference at Pullman, Washington (Newton and Nyman, 1976) and the forthcoming symposium volumes from the 1976 International Conference on Nitrogen Fixation (Barrueco and Newton, 1977), these should be a sufficient introduction of the literature. In this paper I propose to concentrate on properties nitrogenase which seem to be relevant to problems that may be encountered in the establishment of a functioning nitrogen fixation system, particularly in novel cellular settings. The emphasis will be on attempting to second-guess the physiology of nitrogen fixation so that we can predict how much the physiology of a host organism may have to be altered or modified in order that nitrogenase not only function but function efficiently, to the extent that its presence is not detrimental to the host organism.

Photosynthesis and Symbiotic Nitrogen Fixation in Phaseolus Vulgaris L.

Abstract: More than 40 years ago, Wilson et al. emphasized the importance of photosynthesis for symbiotic nitrogen fixation in legumes by increasing N2 fixation with CO2-enrichment techniques.1 Since that time numerous experiments have suggested a connection liqetween those processes by demonstrating that defoliation,2 surgical treatment,3 supplemental light,4 and grafting a second shoot on a rootstock5 produced changes in symbiotic N2 reduction with paralleled changes in net photosynthesis. More recent experiments with CO2 enrichment of field-grown legumes have shown that both the total amount of N2 fixed and the proportion of nitrogen derived from N2 as opposed to soil nitrogen increased.6

Transformation of Nitrogen Fixation Genes in Azotobacter

Abstract: The genus, Azotobacter, is one of the few genera of N2-fixing bacteria that are obligate aerobes. These organisms are widely distributed in the soil and some species have been reported to be associated with the rhizosphere of certain tropical grasses (6). Azotobacter sp. are capable of utilizing a wide variety of carbon sources.

Plant Genotype Effects on Nitrogen Fixation in Grasses

Abstract: Potentials for nitrogen fixation of economic importance have been shown now for a number of tropical forage grasses, sorghum, maize, rice, and perhaps even wheat. The exploitation of this potential, however, will be dependent on the identification of the limiting factors and agronomically feasible practices to eliminate them. Environmental effects are pronounced but rather difficult to manipulate. Whenever possible, preference should be given to plant-breeding practices.

Plasmids as Vectors for Gene Cloning

Abstract: A variety of plasmid elements have been developed for the cloning of genes in the bacterium Escherichia coli (1–5). Many of these plasmids are derivatives of colicinogenic plasmid El (ColE1) or plasmids closely related to ColEl. ColE1 is a relatively low molecular weight plasmid, naturally occurring in E. coli, that specifies the production of antibiotically active protein, colicin El, and conveys to cells harboring the plasmid immunity to this colicin. The ColE1 plasmid, while effective as a cloning vehicle in E. coli, is not maintained stably in gram-negative bacteria distantly related to E. coli and, therefore, is likely to be of limited use in agriculturally important bacteria not closely related to E. coli. This review will consider certain basic aspects of gene cloning in E. coli and the development of plasmid cloning vehicles for bacteria distantly related to E. coli. Brief consideration also will be given to the possibility of establishing gene cloning systems in plant cells.

Lectins as determinants of specificity in legume-Rhizobium symbiosis.

Abstract: About four years ago several investigators (myself included) independently developed the hypothesis that plant lectins might be determinants of the host range specificity of microbial pathogens and symbionts, enabling the host plants to recognize such microorganisms through binding of the lectins to characteristic carbohydrate structures on the bacterial or fungal cell surfaces. Several kinds of evidence were available then which made the lectin recognition hypothesis an attractive one. Lectins (or phytohemagglutinins) had been found in a great many plant species of diverse taxonomic groups (1,2). Bacteria and fungi were known to have complex carbohydrates on their cell surfaces (e.g. lipopolysaccharides, teichoic acids, exopolysaccharides, cell wall polysaccharides, etc.). There were also indications at that time that lectins were involved in the species-specific cellular aggregation of slime mold (3), and sponge cells (4).

Overview of Nitrogen Fixation

Abstract: The assignment to give an overview of biological N2 fixation implies that we should spend a little time in discussing the history of the subject It is somewhat over 90 years now since Hellriegel and Wilfarth clearly indicated that biological N2 fixation occurs in leguminous plants There had been earlier indications of this as evidenced by the long-accepted practice of crop rotation between leguminous and nonleguminous plants In the 1830’s Boussingault furnished data from his greenhouse and field tests that certain leguminous plants fixed N2 and added nitrogen to the soil However, this concept was challenged by the careful work of Lawes and Gilbert, and the matter was left in question until it was resolved by Hellriegel and Wilfarth For many years following their observations, developments in the field of biological N2 fixation were concerned primarily with microbiological and agronomic concepts The practice of inoculating leguminous plants with bacterial cultures was accepted widely Only during the last 50 years has there been serious study of the biochemistry of N2 fixation

Storage proteins in cereals.

Abstract: The seed protein of cereals comprises many different proteins that are synthesized and accumulated in the endosperm during seed development The total amount of protein produced depends heavily on the availability of nitrogen High-yielding cereals are generally very effective in their utilization of the available nitrogen for protein production, and the prospect of genetic improvements in this respect seems limited Traditionally, the protein of the cereal endosperm is classified into albumin, globulin, prolamin, and glutelin The most typical and best-known storage protein is found in the prolamin fraction, which is present in high or medium amounts in maize, sorghum, wheat, and barley, whereas the prolamin content is low in rice and oats Prolamin is deposited in protein bodies in the starchy endosperm, and it has a low content of the amino acids that are essential for man and nonruminant animals It has been shown in maize, sorghum, and barley that prolamin synthesis is controlled by a limited number of genes and that an inactivation of these genes is not lethal for the plant Genotypes with reduced prolamin synthesis have a substantially increased concentration of lysine and other essential amino acids in the seed protein, because these amino acids are much more abundant in the other endosperm proteins The low-prolamin genotypes, normally termed high-lysine types, offer great possibilities for improving the nutritional value of cereal protein However, the somewhat reduced grain yield of most high-lysine types indicates that an inactivation of the prolamin synthesis impairs the accumulation of carbohydrates in the endosperm

Effect of high-temperature stress on the growth and seed characteristics of barley and cotton.

Abstract: The existence of a sensitivity gradient to a uniform high-temperature stress applied at stages during seed maturation can be demonstrated in barley. The germination of freshly harvested seed is depressed following heat stress at 7–10 days after awn emergence, but is enhanced by the same stress applied 3 weeks after awn emergence. The depression is attributed to reduced viability associated with thermal injury. The stimulation following stress at more mature stages of seed development is related to a thinner seed coat, increased permeability as evidenced by faster imbibition rate, and decreased content of water-soluble inhibitors in the seed. These effects of environmental stress during seed maturation aid in explaining differences noted in the germinability at harvest of seed produced in successive years or produced in the same year at different locations.

Norin-10-based semidwarfism.

Abstract: Many short-strawed wheats, including the Norin-l0-based semidwarfs now grown in many countries, are characterized by their relative “insensitivity” to gibberellic acid. The nature of this insensitivity, its genetic control, and the relationships between the Gai genes and the Rht genes, which control height reduction in Norin-10 and Tom Thumb wheats, are described. The role and potential of these genes in agriculture and their relationship to other genes affecting yield, height, and other agronomic features are considered.

Plant protoplast fusion and hybridization.

Abstract: For some time we have been exposed to popular articles describing the magic and more recently some of the potential terror which lies before us as scientists acquire sophisticated skills in the engineering of new genes. We hear also of the construction of new plants with unsurpassed qualities and with an inbuilt nitrogen fixing system. Very recently the following appeared in a well known newspaper: “The first aim of scientists is to introduce into cereals the ability to fix nitrogen which would massively increase yield and eliminate the need for nitrogen fertilizers.”

Quantitative genetically nonequivalent reciprocal crosses in cultivated plants.

Abstract: Quantitative expressions of character difference between reciprocal crosses have been studied by different researchers in a number of plant species, such as Epilobium, Zea mays, Oryza sativa, Hordeum sativum, Triticum aestivum, Trifolium hybridum, Linum usitatissimum, Nicotiana rustica, and others In all cases it was found that the nonequivalence of reciprocal crosses manifested itself beginning with the F1 generation, with the exception of some flax crosses in which reciprocals differed beginning with the F2 generation The nonequivalence of reciprocal crosses usually manifested itself in the inequality of their F1 and/or F2 or backcross means; however, there were instances in which their means were the same but the variances were different Both matroclinous and patroclinous inheritances were reported in plants Because of the causal complexity of reciprocal differences the experimental results often lack a simple explanation

Nitrogen Fixation (NIF) Regulatory Mutants of Klebsiella: Determination of the Energy Cost of N2 Fixation In Vivo

Abstract: Experiments carried out in a number of laboratories have established that biological nitrogen fixation requires a large input of metabolic energy (see Burns & Hardy, 1975; Winter and Burris, 1976; Zumft & Mortenson, 1975). Evidence has been presented by Hardy & Havelka (1973) that the supply of energy may often be a rate-limiting step in symbiotic N2 fixation. It has, however, proved difficult to determine exactly how much energy is required. In vitro experiments with nitrogenase from various organisms have established that reduction of N2 or alternate substrates requires ATP in addition to a suitable reductant. Most recent in vitro studies have reported a minimal requirement of 12–15 moles ATP per mole N2 reduced to 2NH 4 + , but the values vary considerably with the experimental conditions (see Burns & Hardy, 1975; Winter and Burris, 1976; Zumft & Mortenson, 1975).

Uptake of the nitrogen fixing blue-green alga Gloeocapsa by plant protoplasts.

Abstract: In the face of rising world population and diminishing reserves of fossil fuels needed to produce chemical fertilizers, scientists have been motivated to study the process of biological nitrogen fixation. At present nitrogen fixation is limited to certain prokaryotic organisms, which are either free living or are symbionts with plants (chiefly legumes). High demand for chemical fertilizers, and the energy needed to produce them, could be alleviated by introducing the nitrogen fixation process into economically important non-leguminous crop plants. Recent developments in plant protoplast technology have made this goal seem more attainable. Of particular interest was the discovery by Kao and Michayluk (13 in 1974 that polyethylene glycol (PEG) stimulates high frequencies of protoplast fusion.

The Variability of Free Amino Acids and Related Compounds in Legume Seeds

Abstract: Legume seeds are an important source of protein for humans and domestic animals. The Leguminosae contain more than 700 genera and 25,000 species, yet fewer than 20 of these are grown as major world crops. The nutritional value of legume seeds is frequently less than ideal, however, because their proteins contain lower concentrations of certain “essential” amino acids than do animal proteins. The fact that “free” amino acids frequently constitute more than 10% of the weight of legume seeds is often overlooked when considering their nutritional value, as free amino acids tend to be lost in traditional methods of cooking. Toxins, such as the alkaloids, cyanogenic glycosides, and certain of the “nonprotein” amino acids are also found in the seeds of numerous legumes. An understanding of their nature, concentration, and distribution is necessary if we are to exploit the great potential food reserve represented by the thousands of legume species that have never been brought into cultivation or used for the improvement of established crop species. During the past few years we have studied the free amino acids in the seeds of more than 1500 legume species representing 300 of the 700 known genera, and in time propose to make a complete survey of the family. For ease of retrieval, we are assembling analytical data on magnetic tape in a computer bank. Complementary information on the presence of alkaloids, cyanogenic glycosides, toxic amino acids, and physiologically active amines in these seeds is also being accumulated, and we are presently seeking funds to extend this work and determine the protein content and composition of the seeds of this unique collection.