Plants and Soils

It is generally agreed that in addition to major elements necessary to support plant growth, the elements boron, manganese, copper, zinc, molybdenum, and iron are required in trace quantities. In addition to these essential elements, some 40 other elements have been detected in plant tissue. Spectroscopic methods have been used to detect most of the above list of elements and quantitative data have been obtained in most cases. 

If plants do not obtain sufficient quantities of the essential trace elements, growth is inhibited and crop yields are decreased. Spectroscopic methods are used to study trace element composition of plants and to diagnose deficiency problems in them. Recommendations can then be proposed for remedial treatment by application of deficient elements through soil applications or through sprays applied to the leaves. There are many examples of deficiencies that have been corrected through application of specific trace elements. Molybdenum frequently is added to fertilizers, as are boron and copper. In some areas iron and zinc are deficient and are added to fertilizers. 

Soil analyses frequently will reveal the lack of the abundance of trace elements in the soil. The important question is not the total amount of the element in the soil, but the amount present that is available to the plant. For this reason soil extracts are a better index of trace element availability than is a total trace element determination. Extraction solutions of various compositions have been proposed for this purpose. If research of this type is planned, reference should be made to the AOAC methods book.  

---

Microtubulin Polymerization Inhibitors. The ben2imida2oles were first reported to have systemic fungicidal activity in 1964 (29). Prominent examples include thiabendazole [148-79-8] (42) fuberida2ole [3878-19-1] (43) carbendazim [10605-21-7] (44) benomyl [17804-35-2] (45) and thiophanate methyl [23564-05-8] (46). Benomyl (45), the most widely used member of this group is almost certainly inactive as a fungicide until it is converted in plants and soil to carbendazim (44). Likewise, thiophanate and thiophanate methyl (46) are nonfungitoxic until converted to carbendazin (44). 

Numerous theories exist as to how the Chilean deposits formed and survived. It has been postulated that the unique nitrate-rich caUche deposits of northern Chile owe their existence to an environment favorable to accumulation and preservation of the deposits, rather than to any unusual source of the saline materials (2). The essential conditions are an extremely arid climate similar to that of the Atacama desert in the 1990s, slow accumulation during the late Tertiary and Quaternary periods, and a paucity of nitrate-utilizing plants and soil microorganisms. 

Figure 2 Terrestrial plant and soil mieroorganism seeondary metabolites eurrently used as drugs...

The interest in gaseous losses of nitrogen from soil is now extensive and includes the well established community of soil scientists concerned with losses of fertilizer-applied nitrogen by nitrification and denitrification. More recently, interest in ammonia losses from plants and soil has been stimulated by the very large emissions from intensive cattle production in the Netherlands and their... 

Important intermedia transfer mechanisms affecting soil contaminants include volatilization or resuspension to the atmosphere and biouptake by plants and soil organisms. These, in turn, introduce contaminants into the food chain. 

Domenach, A.M., Kurdali, F. and Bardin, R. 1989 Estimation of symbiotic dinitrogen fixation in alder forest by the method based on natural N-abundance. Plant and Soil 118 51-59. 

Mariotti, A., Germon, J.C., Hubert, P., Kaiser, R, Letolle, R., Tardieux, A. and Tardieux, P. 1981 Experimental determination of nitrogen kinetic isotope fractionation some principles illustration for the denitrification and nitrification processes. Plant and Soil 62 413-430. 

Yoneyama, T., Murakami, T., Boonkerd, N., Wadisirisuk, P., Siripin, S. and Kouno, K. 1990 Natural N-abundance in shrub and tree legumes, Casuarina, and non- N2 -fixing plants in Thailand. Plant and Soil 128 287-292. 

Malik, R.S., Dhankar, J.S. Turner, N.C. (1979). Influence of soil water deficits on root growth of cotton seedlings. Plant and Soil, 53, 109-15. 

Spiegel-Roy, M.P. Ben Hayyim, G. (1985). Selection and breeding for salinity tolerance in vitro. Plant and Soil, 89, 243-52. 

Khammas, K M. and Kaiser, P., 1991. Characterization of a pectinolytic activity in Azospirillum irakense. Plant and soil 137, 75-79. 

N. C. Uren, Mucilage. secretion and its interaction with soil, and contact reduction. Plant and Soil 155/156 19 (1993). 

A. A. Meharg, A critical review of labelling techniques used to quantify rhizosphere carbon flow. Plant and Soil 166 55 (1994). 

R. Merckx, J. H. Van Ginkel, J. Sinnaeve, and A. Cremers, Plant induced changes in the rhizosphere of maize and wheat. Plant and Soil 96 85 (1986). 

D. L. Jones and P. R. Darrah, Re-sorption of organic compounds by roots of Zea mays L. and its consequences in the rhizosphere I. Re-sorption of C labelled glucose, mannose and citric acid, Plant and Soil 143 259 (1992). 

L. S. Brophy and G. H. Heichel, Nitrogen release from root of alfalfa and soybean grown in sand culture. Plant and Soil 116 11 (1989). 

J. P. Wacquant, N. Ouknider, and P. Jacquard, Evidence for a periodic excretion of nitrogen by roots of grass-legume associations. Plant and Soil 116 51 (1989). 

A. D. Rovira, Plant root excretions in relation to the rhizosphere effect I. The nature of root exudates from oats and peas. Plant and Soil 7 178 (1956). 

A. D. Boulter, J. J. Jeremy, and M. Wilding, Amino acids liberated into the culture medium by pea seedling roots. Plant and Soil 24 121 (1966). 

J. J. Patel, Microorganisms in the rhizosphere of plants inoculated with Azotobucter chroococcum, Plant and Soil 57 209 (1969). 

V. Vancura and A. Hanzlikova, Root exudates of plants IV. Differences in chemi-eal composition of. seed and seedlings exudates. Plant and Soil 36 27 (1972). 

C. Chrislensen-Weniger, A. F. Groneman, and J. A. Van Veen, Associative fixation and root exudation of organic acids from wheat cultivars of different aluminium tolerance. Plant and Soil I39A67 (1992). 

Z. Prikryl and V. Vancura, Root exudates of plants VI. Wheat root exudation as dependent on growth, concentration gradient of exudates and the presence of bacteria, Plant and Soil 57 69 (1980). 

W. K. Gardner. G. D. Parbery, D. A. Barber, and L. Swinden, The acquisition of phosphorus by Litpimts albus L. V. The diffusion of exudates away from roots a computer simulation. Plant and Soil 72 13 (1983). 

A. A. Meharg and K. Killham, A novel method of determining root exudates in the presence of soil microflora. Plant and Soil I33 11 (1991). 

K. J. Lee and M. H. Gaskins, Increased root exudation of C-compounds by sorghum. seedlings inoculated with nitrogen-fixing bacteria. Plant and Soil 69 391 (1982). 

M. C. Hawes, Living plant cells released from the root cap a regulator of microbial populations in the rhizosphere. Plant and Soil 729 19 (1990). 

X. L. Li. E. George, and H. Marschner, Extension of the phosphorus depletion zone in VA-mycorrhizal white clover in calcareous. soil. Plant and Soil I3I 4 (1991). X. L. Li, E. George, and H. Marschner, Acquisition of phosphorus and copper by VA-mycorrhizal hyphac and root-to-shoot transport in white clover. Plant and Soil 135 49 (1991). 

N. S. Bolan, A. D. Robson, and N. J. Barrow, Effects of vesicular-arbuscular mycorrhiza on the availability of iron phosphates to plants. Plant and Soil 99 40l (1987). 

N. S. Bolan, M. J. Hedley, and R. E. White, Processes of soil acidification during nitrogen cycling with emphasis on legume based pastures, Plant and Soil 134 53 (1991). 

N. S. Bolan, A critical review on the role of mycorrhizal fungi in the uptake of phosphorus by plants. Plant and Soil /.W 189 (1991). 

P. H. Vaast and R. J. Zasoski, Effect of VA-mycorrhizac and nitrogen sources on rhizosphere soil characteristics, growth and nutrient acquisition of coffee seedlings (Coffea arahica L.), Plant and Soil I473. ... 

T. S. Gahoonia, N. Claassen, and A. Jungk, Mobilisation of phosphate in different soils by ryegrass supplied with ammonium or nitrate. Plant and Soil 740 241 (1992). 

---