Salt resistant crop plants

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Sugars in crop plants

We review current knowledge of the most abundant sugars, sucrose, maltose, glucose and fructose, in the world's major crop plants. The sucrose‐accumulating crops, sugar beet and sugar cane, are included, but the main focus of the review is potato and the major cereal crops. The production of sucrose in photosynthesis and the inter‐relationships of sucrose, glucose, fructose and other metabolites in primary carbon metabolism are described, as well as the synthesis of starch, fructan and cell wall polysaccharides and the breakdown of starch to produce maltose. The importance of sugars as hormone‐like signalling molecules is discussed, including the role of another sugar, trehalose, and the trehalose biosynthetic pathway. The Maillard reaction, which occurs between reducing sugars and amino acids during thermal processing, is described because of its importance for colour and flavour in cooked foods. This reaction also leads to the formation of potentially harmful compounds, such as acrylamide, and is attracting increasing attention as food producers and regulators seek to reduce the levels of acrylamide in cooked food. Genetic and environmental factors affecting sugar concentrations are described.     

Microbial inoculation of crop plants

Book Review

Microbial inoculation of crop plantsR. Campbell and R.M. MacDonald (Eds.), Special publication of the Society for General Microbiology, Volume 25. IRL Press, 1989. xi+118 pages. £40. ISBN 0-19-963016-X     

Glycerol concentrations in crop plants

A procedure has been developed for preparation of plant extracts for quantitation of their glycerol content using high performance liquid chromatography or enzymatic analysis. Fifteen crop plants grown under field conditions had leaf concentrations of glycerol between 10 and 39 μg/g wt weight of tissue. Approximately 12 h after relatively heavy rains leaves of maize, sugar beet, soybean, bean, pumpkin and alfalfa had several fold increases in concentrations of leaf glycerol. When barley plants were made anaerobic for 24 h, large increases in leaf glycerol concentrations were observed. It is proposed that part of the glycerol observed in anaerobic plants comes from glycerol synthesis in the root and transport to the leaves and part is produced in the leaves.     

RNAi-mediated crop protection against insects

Downregulation of the expression of specific genes through RNA interference (RNAi), has been widely used for genetic research in insects. The method has relied on the injection of double-stranded RNA (dsRNA), which is not possible for practical applications in crop protection. By contrast, specific suppression of gene expression in nematodes is possible through feeding with dsRNA. This approach was thought to be unfeasible in insects, but recent results have shown that dsRNA fed as a diet component can be effective in downregulating targeted genes. More significantly, expression of dsRNA directed against suitable insect target genes in transgenic plants has been shown to give protection against pests, opening the way for a new generation of insect-resistant crops.     

Natural products in crop protection

The tremendous increase in crop yields associated with the ‘green’ revolution has been possible in part by the discovery and utilization of chemicals for pest control. However, concerns over the potential impact of pesticides on human health and the environment has led to the introduction of new pesticide registration procedures, such as the Food Quality Protection Act in the United States. These new regulations have reduced the number of synthetic pesticides available in agriculture. Therefore, the current paradigm of relying almost exclusively on chemicals for pest control may need to be reconsidered. New pesticides, including natural product-based pesticides are being discovered and developed to replace the compounds lost due to the new registration requirements. This review covers the historical use of natural products in agricultural practices, the impact of natural products on the development of new pesticides, and the future prospects for natural products-based pest management.     

Alkyne chemistry in crop protection

An overview is given of the significance of alkyne derivatives in crop protection chemistry. The main herbicidally, fungicidally, insecticidally and acaricidally active alkyne classes are presented, together with their synthetic routes, their mode of action and their biological efficacies. Also the importance of alkynes as intermediates in the preparation of agrochemicals is demonstrated.     

Analysis of the gas exchange components in chilled tomato plants

A positive linear relationship between the net CO₂ exchange rate (P _N) and the leaf stomatal conductance (g_s) under an optimal temperature, and even more distinct one after a short-term chilling (CH, 15-17 h, 2 °C in darkness), that was found in two tomato cultivars (sensitive to a low temperature cv. Robin and tolerant cv. New Yorker) suggested a partial stomatal limitation of photosynthesis. The CH treatment of cv. Robin resulted in an intercellular CO₂ concentration (C _i) increase because of which a negative correlation between C _i and P _N was observed. In cv. New Yorker a positive correlation was observed. Detrimental effect of the low temperature in cv. Robin was more evident in plants with a relatively small root system (SR), but drought-hardening positively affected the response to CH only in the plants with bigger roots (BR). On the contrary, in cv. New Yorker the favourable effect of such pre-treatment was more evident in SR than in BR plants. This revised version was published online in June 2006 with corrections to the Cover Date.