The Physiological And Biochemial Effects Of Tolerant And Susceptible Rice Varieties Under Nilaparvata Lugens(St(?)l) Infestation

This paper investigated distribution of sucrose, soluble sugar, dry biomass, hormones contents in roots and shoots using typical tolerant and susceptible rice varieties as materials,. Main results were as follows:1. Changes of distribution of assimilates (sucrose and soluble sugar) in roots and shoots of rice following Nilaparvata lugens infestationSucrose contents in shoots decreased significantly under N.lugens infestaion, but that in roots did not compared to the control. So R/S ratio of sucrose increased significantly at the tilling stage. At 3d after N.lugens infestation (3 DAI) for all densities, sucrose contents in shoots for Xieyou963 dereased significantly, at 6DAI, the other treatments did not show significant differences except 80 nymphs /plant infestaiton significantly decreased sucrose content compared to the control. At 3 DAI, the sucrose contents in roots under 40 nymphs /plant infestaiton did not show significant changes except for 60 and 80 nympgs infestation. Sucrose rcontent in Roots to that in shoots (R/S ratio) at 3 DAI significantly increased. Sucrose contents in shoots and roots under high N.lugens dentsity infestation for Xieyou963 decreased significantly, but the low N.lugens dentsity infestation did not. The variation of soluble sugar of the two rice varieties under N.lugens infestation was consistent with that of sccrose. From the variation of R/S ratio of sucrose contents, we could understand the distribution of the assimilates in roots and shoots. Variation of R/S raito of assimilates was different between tolerant and susceptible varieties.2. Allocation of dry biomass in shoots and roots.Effects of N. lugens infestation on changes of dry biomass of roots and shoots and on allocation of R/S ratio of dry biomass for four varieties, Xieyou 963, chaojidao, Xieyou 63 and TN1 were examined. The results showed reduction of dry biomass of roots for Xieyou 963 was maxinum among four varieties and that for TN1 was minimum compared to the control. Reduction of dry biomass of shoots for TN1 was maxinum and that for Chaojidao was minimum. The order of the regression coefficients between ratio values of dry biomass of roots and shoots (R/S) and N. lugens density at 3 DAI was TN1 > Xieyou 63. In contrast, the regression coefficients between ratio values of dry biomass of roots and shoots (R/S) and N. lugens density increased. At 6 DAI, the order of the regression coefficients between ratio values of dry biomass of roots and shoots (R/S) and N. lugens density was TN1 > Xieyou 63 > Chaojidao. At 9 DAI, the regression coefficient for various treatments became large and the order of the coefficient was TN1 > Xieyou 63 > Xieyou 963, indicating that tha allocation of dry substance in plant parts varied with rice variety. Allocation for TN1 was significantly affected by N. lugens infestation. Resistant varieity showed compensation for N. lugens infestation. Thus, the allocation of dry substance for resistant variety was few affected.3. Hormorns contents in roots and shoots of riceEffects of N. lugens infestation on hormones (ABA) content in roots and shoots and R/S ratio of ABA were also studied for rice varieties Xieyou 963 Chaojidao Peiai and TN1. The results showed that at 3 DAI at the tillering stage, ABA contents in roots and shoots for Chaojidao and TN1 significantly increased and R/S value of ABA significantly decreased compared to the control. At 6 DAI, ABA content in roots and shoots for Chaojidao peiai significantly significantly decreased but R/S ratio of ABA increased. ABA content in roots for TN1 decreased, in contrast, that in shoots increased, thus, R/S ratio of ABA decreased significantly. At the grain-filling stage, change trend of ABA content of Xieyou 963 was similar to that of Chaojipeiai at the tillering stage. For TN1, ABA concent in roots and shoots and R/S ratio of ABA at 3 DAI increased except 40 and 80 nymphs infestation. At 6 DAI ABA content in roots and shoots and the R/S ratio under 40 nymphs infestation increased significantly, and that under other infestation densities did not show a significant change. These findings demonstrated that ABA content in roots and shoots varied with rice varieties and developmental stages.