| With typical tolerant and susceptible rice varieties as materials, this paper investigated allocation of sucrose, soluble sugar, dry weight, nitrogen, phosphorus, potassium contents in rice plants,hormones contents in roots and shoots, and roots vigor and water uptake by roots, nitrogen, phosphorus, potassium contents in water solution. Results were as follows:1.Allocation of assimilates (sucrose and soluble sugar) in roots and shootsAt the tilling stage,sucrose contents in shoots decreased significantly under N.lugens infestation. Sucrose contents in roots did not decrease significantly compared to control. Thus R/S ratio of sucrose increased significantly. Shoots sucrose contents at 3d after 20,40,60 and 80 nymphs /plant and at 6d under 80 nymphs/plant infestation for Xieyou963 decreased significantly, with percent reduction of 14.79%,36.60%,18.70%,15.71% and 26.41%, respectively. Sucrose contents in roots at 3d after 40 nymphs /plant and at 6d under 60,80 nymphs /plant infestation decreased significantly, with percent reduction of 30.96%, 47.19% and 65.51%, respectively.R/S ratio of sucrose contents at 3d after 20,60 and 80nymphs /plant infestation increased but R/S ratio at 6d after 40,60 and 80 nymphs/plant infestation decreased significantly.Change of soluble sugar for two rice varieties under N.lugens infestation was similar to sucrose. R/S ratio of sucrose contents could be used as an index of assimilates allocation in roots and shoots. The present findings showed that R/S ratio in tolerant variety was different from that in susceptible one. 2.Allocation of dry weight in shoots and roots.At the tillering stage, allocation of dry weight in roots and shoots under N.lugens infestation varied with rice variety.Roots dry weight of Xieyou963 decreased significantly. shoots dry weight of TN1 decreased significantly.Relationship between R/S ratio of dry weight and N. lugens density showed a lineal trend. R/S ratio at 3d,6d and 9d after N. lugens infestation for TN1 increased with increase of N.lugens density and infestation time. There was significant correlation between R/S ratio of dry weight at 3d and 9d after N. lugens infestation for TN1 and N.lugens denstity (R~2 = 0.9076* for 3d;R~2= 0.7815* for 9d).There also was significant correlation between R/S ratio of dry weight at 9d after N.lugens infestation for Xieyou63 and Super-highyield rice-peiai 64S/E32 and N. lugens density(R~2 = 0.9585* for Xieyou 63;R~2= 0.9631* for Super-highyield rice-peiai 64S/E32), indicating that R/S ratio increased with increase of N.lugens density. In contrast, for Xieyou 963, R/S ratio at 3d and 6d decreased significantly. There were significant negative correlation between R/S ratio at 3d and 6d and N.lugens denstiy (R~2 =- 0.7120* for 3d;R~2= 0.8856* for 6d).3.Root vigor and nutrient uptake.Response of roots at the tillering stage varied with rice variety. The vigor of root system of TN1 and Xieyou63 were more sensitive to N.lugens infestation, with significant reduction at 3d and 6d after 15 and 30nymphs/plant infestations compared to control, while Xieyou963 and Super-highyield rice-peiai 64S/E32 did not decrease significantly.Water absorbing capacity of TN1 decreased significantly at 3d, 6d and 9d, while at 3d Xieyou63 did not change significantly, but water absorbing capacity at 6d and 9d after 40,60 and 80 nymphs/plant infestation decreased significantly.Water absorbing capacity at 3d and 6d after N.lugens infestations for Xieyou963 did not result in significant reduction compared to control, while water absorbing capacity at 9d after 40 nymphs/plant infestation increased significantly. Water absorbing capacity at 3d after 10, 20 and 40nymphs/plant infestation for Super-highyield rice-peiai 64S/E32 increased, while that at 6d and 9d did not. N uptake by roots at 9d for TN1, Xieyou63 and Xieyou963 decreased, while N uptake at 3d after 20, 40, 60 and 80nymphs/plant infestation and at 6d after 60 nymphs/plant for Super-highyield rice-peiai 64S/E32 increased significantly.P and K uptake by roots for four varieties under high N.lugens denstity decreased significantly,but did not increase under low N.lugens denstity. Effect of N. lugens infestation on K uptake was the most distinct.4. Nitrogen(N), phosphorus(P) and potassium(K) content in roots and shoots of riceN, P and K content in roots and shoots at 3d after 60 and 120 nymphs/plant infestation at at and N contents in roots and shoots at 6d at the tillering stage for Xieyou963 did not show significant reduction.P content in roots and shoots at 6d, K content in roots at 6d, P content in shoots at 9d and K content in roots and shoots at 9d after 120nymphs/plant infestation decreased significantly but 60 nymphs/plant infestation did not result in significant reduction of P and K; K content in shoots at 6d and N content in roots at 9d after 60 and 120 nymphs/plant infestation showed significant reduction.For Xieyou 63, N content in shoots at 3d, P content in roots and shoots at 3d, N and P contents at 6d and 9 d after 60 and120 nymphs/plant infestation did not show significant reduction.N and P contents in roots at 6d, K contents in roots and shoots at 6d and N contents in roots at 9d after 120nymphs /plant infestation decreased significantly but 60 nymphs /plant infestation did not result in significant reduction.K contents in roots and shoots at 3d and 9d and P contents in roots at 9d after 60 and120 nymphs/plant infestation showed significant reduction.The results showed that the nutrient elements in rice plants under N.lugens infestation varied with rice variety. Percent reduction of K contents was the largest, the next was P and the last was N. Root was more sensitive to N.lugens infestation compared to shoot.5.Hormorns contents in roots and shoots of rice(1)ABAAt the tillering stage, ABA contents in roots and shoots at 3d after N.lugens infestation for Super-highyield rice-peiai 64S/E32 and TN1 increased significantly. R/S ratio of ABA contents decreased significantly. ABA contents in roots and shoots at 6d for Super-highyield rice-peiai 64S/E32 decreased significantly but R/S ratio increased significantly.Change of ABA in roots for TN1 was similar to Super-highyield rice-peiai 64S/E32 but that in shoots of two varieties was obviously different.Change of R/S ratio was similar to that in root .At the grain-filling stage, change of ABA for Xieyou963 was similar to Super-highyield rice-peiai 64S/E32 at tillering stage. For TN1, ABA content in roots and shoots and R/S ratio at 3d after N.lugens infestation increased.R/S of ABA at 6d after 30 nymphs /plant infestation increased. However, ABA in roots and R/S ratio after 30 and 90 nymphs /plant infestation did not show significant change.(2)GAAt the tillering stage, GA contents in roots at 3d after 60 and 90 nymphs/plant infestation for Super-highyield rice-peiai 64S/E32 increased significantly, while GA contents in roots after 30 nymphs/plant infestation did not, and also GA contents in shoots and R/S ratio after 30, 60 and 90 nymphs/plant infestation did not. GA content in roots at 3d after 30, 60 and 90 nymphs/plant infestation and that in shoots after 30 and 60 nymphs/plant infestation for TN1 increased significantly. R/S ratio of GA contents after 90 nymphs/plant infestation increased significantly. GA contents in shoots at 6d after 60 and 90 nymphs/plant infestation for Super-highyield rice-peiai 64S/E32 decreased significantly, while that in roots and R/S ratio 30, 60 and90 nymphs/plant infestation.did not. GA contents in roots and R/S ratio at 6d after 90 nymphs/plant infestation for TN1 increased significantly, while that in shoots after 30, 60 and 90 nymphs/plant infestation did not.At the grain-filling stage,GA content in roots at 3d after 40, 80 and 120 nymphs/plant infestation for Xieyou963 decreased significantly and that in shoots after 30, 60 nymphs/plant infestation also increased significantly.GA contents after 90 nymphs/plant infestation decreased significantly and R/S ratio after 30 and 60 nymphs/plant infestation decreased significantly.GA content in roots and R/S ratio At 6d after 90 nymphs/plant infestation for Xieyou963 and that in shoots after 30 nymphs/plant infestation increased significantly.For TN1,GA content in roots at 3d and 6d after 40,80 and 120 nymphs/plant infestation and R/S ratio after 90 nymphs/plant infestation decreased significantly, but that in shoots did not.(3)ZRZR content at the heading stage of Zhendao2 was more sensitive to N.lugens infestation compared with that at the grain filling stage, with significant reduction of ZR content in roots and shoots at 3, 6 and 9d after 15,30,60 and 120nymphs/plant infestations compared to control. At the grain-filling stage of Zhendao2,N.lugens infestation did not result in significant reduction of ZR content in roots and shoots except ZR contents in shoots at 9d after15,30,60 and 120nymphs/plant infestation and ZR content in roots at 9d after 120nymph/plant infestations. However, the response of ZR in Xieyou 63 to N.lugens stress was different from Zhendao2. ZR contents in shoots at 3d after15, 30 and 60nymph/plant infestation at the heading stage increased significantly, and there were no significant alterations of ZR content at the grain filling except with significant increase of ZR contents in shoots at 6d after 30, 60 and 120nymphs/plant infestation and at 9d after 120 nymphs/plant infestation.The present findings demonstrated that the effect of N.lugens infestation on ZR,GA and ABA contents varied with rice variety and developmental stage. |
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