Leaf, leaves wilting

Stomata tend to close as a leaf wilts, a common response of plants to water stress. Assuming that gfw decreases 20-fold, and using values presented in Figure 8-7, g ° al then decreases about 15-fold from 154 mmol mT2 s-1 for a g,, of 200 mmol m-2 s-1 to 9.9 mmol mT2 s-1 for a g, of 10 mmol mT2 s-1. The decrease in g ° al causes transpiration to decrease to only 6% of its former... 

Many plant diseases cause similar symptoms in the host plants. Such things as leaf spots, wilts, galls on roots, or stunted growth may be caused by many... 

The disease resistance of wheat was also enhanced by treatment with epibrassinolide, e.g.y in Henan Province. Leaf wilt of wheat is one of the most harmful effects induced by environmental stress during the period from the filling stage to the ripening stage. Epibrassinolide simultaneously reduced the incidence of this phenomenon and the accumulation of free ammonia and putrescine which are regarded as an indicator of this phenomenon as shown in Table IV. 

Table IV, Effect of Epibrassinolide on Content of Free Ammonia and Putrescine and Incidence of Leaf Wilt...

Arsenic toxicity occurs commonly in plants growing on mine waste, on soils treated with arsenical pesticides, and on soils fertilized with As-containing sewage sludge. Symptoms of As toxicity are leaf wilting, violet coloration, root discoloration and cell plasmalysis. The most common symptom, however, is growth reduction (Kabata-Pendias and Pendias 2001, Anke 2003a). 

Dutch elm disease, caused by the fungus Ceratocystis ulmi, is disseminated by a bark beetle of the genus Scolytus. The fungus produces toxins that cause necrotic lesions and leaf wilting. These toxins consist of a mixture of glycoproteins and three low-molecular-weight phenolic compounds (Fig. 5.25) (Claydon et al., 1974 Harbome, 1982, 1986 Wood et al., 1972). 

Alvim (1) in Costa Rica confirmed in part the studies of Pound (Al), Voelcker (50), and Humphries (22) and found that higher incidence of Cherelle wilt usually occurred after periods of intense growth of the leaf flushes and/or when the rate of growth in trunk diameter decreased or was checked. Spraying the fruits with p-chlorophenoxyacetic acid did not reduce the condition, as reported by Naundorf and Gardner (30). Alvim concluded that Cherelle wilt in Costa Rica is apparently caused by food strain (carbohydrates) or by depression in the mechanism of food translocation, and not by hormonal or mineral deficiencies. 

Tomato leaf-curl Tomato spotted wilt... 

Swaaij, van A.C., Jacobsen, E. Feenstra, W.J. (1985). Effect of cold hardening, wilting and exogenously applied proline on leaf proline content and frost tolerance of several genotypes of Solanum. Physio-logia Plantarum 64, 230-6. 

White phosphorus exposure to plants results in a variety of deleterious effects which are based upon the species of plant, the smoke concentration, the duration of exposure, the relative humidity, and the wind speed. These effects can include leaf tip bum, leaf curl, leaf abscission and drop, floral abortion, chlorosis, neucrotic spotting, wilting, dessication, and dieback. Other factors influencing the effects of white phosphorus upon plants are whether or not there is a post-exposure rainfall and whether the exposure is a large acute dose or several lower chronic doses (Van Voris et al. 1987). 

One further problem is the large overshoot in ABA production in wilted leaves. With applied ABA a doubling of the ABA content of the leaf is usually adequate for stomatal closure, while increases up to 40-fold have been reported in wilted leaves. However, extractions of whole leaves do not take into account the location of ABA within the leaf. Perhaps much of the hormone is sequestered in a compartment that has no access to the guard cells. Thus, it would be of much importance to determine the distribution of ABA at the tissue level as well as its intracellular location. Since ABA is a small water-soluble molecule, conventional fractionation techniques may not be suitable to determine its distribution in various organelles. A highly specific immunological method for detection of ABA has recently been developed (38, 39). It is conceivable that this technique could be further developed for determining the cellular localization of ABA as has already been done for the photoreceptor phytochrome (77, 78). 

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