Physiological and biochemical responses of rice plant to salinity at seedling stage
1989
Zongli, W. | Qiujie, D. | Xiaozhong, L. | Zhixia, W. | Jian, K.L. (Jiangsu Academy of Agricultural Sciences (China). Inst. of Agrobiological Genetics and Physiology)
The physiological and biochemical effects of salinity (0.5% NaCl) on rice seedlings were studied during 1985-1987 at Jiangsu Academy of Agricultural Sciences, China; by using three rice varieties, "80-85" (salt-tolerant), "83-35" and "83-51" (salt susceptible). Reduction in net photosynthetic rate caused by salinity in susceptible variety was due to higher stomatal resistance and low relative water content. The higher K: Na ratio in leaves of the tolerant variety indicates its greater capacity to adopt salinity. Excess Na+ is the major cause of injury to the rice plant under salt treatment. Malonyldialdehyde (MDA) content was highly correlated with plasmalemma permeability. MDA accumulation induced by higher peroxidase activity occurred before the appearance of salt stress symptoms in younger leaf and much more in the susceptible variety. Increase in peroxidase activity was not proportional to the increase in plasmalemma permeability and MDA accumulation. Nucleic acid content decreased sharply with prolonged salinity treatment; RNA was more sensitive to salt stress than DNA. The ribonuclease activity in susceptible variety was much higher than in the tolerant one. The amount of soluble protein and RNA were positively correlated but the ribonuclease activity and the quantity of RNA was negatively correlated. The protein to RNA ratio was similar in tolerant and susceptible varieties, indicating similar effectiveness of their RNA in protein production. The ratio of RNA to DNA was higher in the tolerant variety.
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