Crop plants

LPC Product Quality. Table 10 gives approximate analyses of several LPC products. Amino acid analyses of LPC products have been pubhshed including those from alfalfa, wheat leaf, barley, and lupin (101) soybean, sugar beet, and tobacco (102) Pro-Xan LPC products (100,103) and for a variety of other crop plants (104,105). The composition of LPCs varies widely depending on the raw materials and processes used. Amino acid profiles are generally satisfactory except for low sulfur amino acid contents, ie, cystine and methionine. 

It is possible to breed plants that have more efficient systems for utilization of water, and agricultural technology can help existing crop plants by spraying impervious coatings on them. Extremely small amounts of long-chain, fatty alcohols reduce evaporation losses from quiet lakes or reservoirs to less than 5% of the normal surface evaporation. 

In addition to the use of 2,4-dichlorophenol in the synthesis of 2,4-D herbicides (acid 2,4-D, acid 2,4-DP, acid 2,4-DB), it is also found in the selective post-emergence herbicide, diclofop-methyl [51338-27-3] (61) and as a selective pre-emergence herbicide, oxadia2on [19666-30-9] (62). A postemergence herbicide is appHed between the emergence of a seedling and the maturity of a crop plant. 

J. P. F. D Mello, C. M. DuffusandJ. FI. Duffus, Toxic Substances in Crop Plants,The Royal Society of Chemistry, Cambridge, 1991. 

The preparation of soils for crops, planting, and tilling raises dust as a fugitive emission. Such operations are shll exempt from air pollution regulations in most parts of the world. The application of fertilizers, pesticides, and herbicides is also exempt from air pollution regulations, but other regulations may cover the drift of these materials or runoff into surface waters. This is particularly true of the materials are hazardous or toxic. 

In addition, naturally growing plants resist plant pathogen and Insect attack because resistance develops over time via natural selection (35). Also, most natural and crop plants have, as a part of their basic physical and chemical makeup, a wide array of mechanisms that help them resist pest attack. These Include chemical toxicants, repellents, altered plant nutrients, hairiness, thorns, and diverse combinations of these (35). 

What will happen under field conditions is, however, highly uncertain. Laboratory experiments have been conducted under conditions of abundant nutrients and water, ideal temperatures, and no competition among experimental plants. Such conditions are rare in the field. The best prediction is that, whereas increases similar to those found in the laboratory are unlikely under field conditions, increased concentrations of CO2 are likely to ameliorate to some extent the detrimental effects of climate change. However, field-scale experiments under a variety of soils and climates and with several crop plants are needed to provide information on effects of climate change accompanied by higher concentrations of CO2 on agricultural productivity. 

Soils properties are very sensitive to the type of exchangeable ions. Calcium imparts favorable physical properties to the soil, while adsorbed sodium causes clay dispersion and swelling. It is generally recognized that an exchangeable sodium percentage of 10 is sufficient to cause soil dispersion, reduction of soil permeability and impaired growth of some crop plants. On the other hand, excess salt concentration prevents the dispersive effect of adsorbed sodium. 

Menzel, R.G. and Heald, W.R. 1959 Strontium and calcium contents of crop plants in relation to exchangeable strontium and calcium in the soil. Proceedings of the Soil Science Society of America 23 110-112. 

There are several aspects of different environmental stresses that either have common features or the plant responses or adaptations to those stresses may have common components or indicate general principles. It is an objective of this volume to identify such features where they exist so as to help in the development of stress-tolerant crop plants by making the best use of the newer techniques of molecular biology. Particular examples will be discussed in more detail in succeeding chapters. 

The techniques of molecular biology have particular potential for rapidly introducing small numbers of single genes. Unfortunately there is strong evidence that the complex compensation mechanisms that exist in plants, and the interactions between different whole-plant and biochemical responses to stress, will make the direct improvement of environmental stress tolerance in crop plants by genetic engineering rather more difficult... 

Quarrie, S.A. (1984). Abscisic acid and drought resistance in crop plants, British Plant Growth Regulator Group News, 1, 1-15. 

The use of plants from extreme environments Wild plants from extreme environments may possess genes and gene combinations which confer stress tolerance. We must realise, however, that many of their characteristics, e.g. leaf pubescence and succulence in drought-resistant plants, are incompatible with the high yield potential required for crop plants. In addition, most of these species contain compounds such as phenolics and mucilages which interfere with conventional molecular biology techniques. 

Wyn Jones, R.G. (1980). An assessment of quarternary ammonium and related compounds as osmotic effectors in crop plants. In Genetic Engineering of Osmoregulation, ed. D.W. Rains, R.C. Valentine and A. Hollaender, pp. 155-70. New York Plenum Press. 

Bidinger, F.R., Mahalakshmi, V., Talukdar, B.S. Alagarswamy, G. (1982). Improvement of drought resistance in millet. In Drought Resistance in Crop Plants with Emphasis on Rice, pp.357-76. Los Banos, Philippines International Rice Research Institute. 

International Rice Research Institute (1982). Drought Resistance in Crop Plants with Emphasis on Rice. Los Banos, Philippines International Rice Research Institute. 

Gutschick, V.P. (1987). A Functional Biology of Crop Plants. London Croom Helm. 

A considerable number of mycotoxins that show high toxicity to vertebrates and/ or invertebrates are produced by organisms associated with crop plants (Flannigan 1991). There are many known cases of human poisoning caused by such compounds. There are three broad categories of mycotoxins represented here, based on the structures of the intermediates from which these secondary metabolites are derived. They are (1) compounds derived from polyketides, (2) terpenes derived from mevalonic acid, and (3) cyclic peptides and derivatives thereof. 

D Mello, J.P.F., Duffus, C.M., and Duffus, J.H. (Eds.) (1992). Toxic Substances in Crop Plants. London Royal Society of Chemistry. 

The product (4) is a synthetic germination stimulant for parasitic plants. Normally these plants germinate only when the host is growing. Premature germination induced by (4) increases yields of sorghum (an African food crop) planted later. 

Ironically, coffee does need relatively acidic soil, with pH between 5 and 6. Conifers and shmbs such as azaleas and rhododendrons thrive on soils with this acidity, as do tea, potatoes, rice, and rye. The vast majority of crop plants, including most vegetables, need soils just on the acidic side of neutral, pH between 6 and 7. Only a few crops—barley, sugar beets, cotton, and sugarcane—like soils on the mildly basic side, between pH 7 and 8, and only desert plants can cope with soils whose pH is greater than 8. 

---