Acta Phytopathologica physiology of detoxification Entomoligica Ramakrishnayya: Physiology of rice tungro virus disease: Water relations physiology of detoxification diseased plants Sridhar et al: Rice tungro virus Discussion Tungro development caused marked reductions in transpiration rates of the sensitive, intermediate and tolerant plants Table 2. Since tungro-affected leaf blades displayed greater number of stomata and an enhanced diffusive resistance when compared to healthy leaf blades Table 3it seems likely that stomatal regulation is mainly responsible for the inhibition of transpiration.
Actually virus infections reduce stomatal aperture in many plants Kruger, ; Muller, ; Harrison, ; Hall and Loomis, ; Lindsey and Gudauskas, Generally, it is held that decrease in physiology of detoxification balances the reduced ability of the plants to absorb water as reflected by reduced root development in barley plants infected with barley yellow dwarf virus Orlob and Amy, Although tungro infection negatively affected the root physiology of detoxification in the sensitive cultivar, it enhanced the root to shoot rations of the intermediate cultivar and of the tolerant line Table 4 and was accompanied by reductions in transpiration rates.
Increase in dry weight of the diseased leaf blades of the intermediate cultivar Table 5the root to shoot ratio of which was not affected by the infection, suggests that the increase in dry weight is not due to disturbances in water absorption. Tungro infection causes the accumulation of low molecular weight compounds Sridhar et al.
The reduced cell permeability would prevent the mobilization of these compounds out of the cells where they are synthesized and eventually out of the leaf blades to growing tissues, thus explaining the increased dry weight of the diseased leaf blades. Necrosis of phloem cells is also common in tungro diseased plants Saito et ah, This might upset the anatomy and functioning of the phloem, and the dysfunction may extend to the vascular bundle as a whole and into adjacent tissues Bennett, It is reasonable to believe that the distribution of water in the leaf tissues in hampered due to this phloem necrosis.
This might be the cause for lowering of the leaf water potential Table physiology of detoxification provides evidence for an internal water stress in the diseased plants, even though they were always maintained sintomas por oxiuros flooded conditions similar to flooded paddieswhich would not have limited the availability of water.
Water stress leads to a significant increase in abscisic acid concentration in leaves Wright, ; Wright and Hiron, An earlier report Mohanty et al. ABA has pronounced effects on stomatal opening, and thus influence transpiration Mittelheuser and Van Steveninck, ; Jones and Mansfield, Consequently, changes in stomatal behaviour of tungro-diseased plants resulting in decreased transpiration rate may well be mediated by alterations in endogenous ABA activity due to infection. Clearly, tungro infection causes an internal water stress in plants leading to an hormonal imbalance concerned with increase in ABA.
Obviously, an external stress caused by drought, salt and temperature and leading to water stress may accentuate the sequential metabolic and physiology of detoxification changes of the diseased plants mediated by ABA, thus enhancing the deleterious effect of the disease.
physiology of detoxification
Acta Phytopathologica et Entomologica Hungarica 29,