| Response of zeatin ribosides (ZRs) in roots and leaves at different developmental stages of two representative rice varieties to N. lugens nymph infestation and pesticides stresses was studied using Enzyme Linked Immuno-sorbent Assay (ELISA). The main results were as followings:1 Experiment of N. lugens nymph infestation at tillering stage of Zhendao2(japonica rice),which plants were subjected to N. lugens nymph infestation at three non-hopperbum causing densities (15, 30 and 60 nymphs per hill) for 2, 4, 6 and 8 days and at one hopperbum causing density (240 nymphs per hill) for 2,4 and 6 days, respectively. When the non-hopperburn-causing densities N. lugens nymph infested rice plants, ZR content in leaves varied significantly with the infestation density; the influence of N. lugens on ZR content in rice roots was more complex, depending significantly on both infestation duration and density. As compared to the control plants, ZR content in rice leaves decreased significantly after infestation by 60 nymphs per hill for 2 days, but it tended to increase due to prolonged infestation at all the non-hopperburn-causing densities, In contrast, ZR content in rice roots significantly reduced after the plants being infested at all densities for prolonged duration, except for the plants infested by 60 nymphs for 6 and 8 days, in which the ZR content rather increased or did not change significantly, in comparison to the control plants. On the other hand, infestation at the hopperburn-causing density caused significant reduction in ZR content in rice roots, regardless of infestation duration, and in rice leaves from the plants subjected to 2-day infestation.2 At rice different developmental stages(heading stage and grain-filling stage), two representative rice varieties, Zhendao 2 and Xieyou 63 (hybrid indica rice), were subjected to N. lugens nymph infestation. As compared to grain-filling stage, ZR at the heading stage of Zhendao 2 was more sensitive to N. lugens infestation, with significant reduction of ZR contents in roots and leaves at 3,6 and 9 days after 15,30, 60 and 120 nymphs infestations (3, 6 and 9 days) compared to control. While for the grain-filling stage of Zhendao 2, N. lugens infestation did not result in significant reduction of ZR content in roots except 3 days after 120 nymph infestations, but significantly reduced ZR content in leaves at 9 days. However, the response of ZR in Xieyou 63 to N. lugens stresses was different fromZhendao 2. ZR content in leaves at 3 days after 15, 30 and 60 infestations significantly increased, and there was no significant alterations of ZR content at 6 days and 9 days although ZR content in roots at the heading stage significantly reduced as compared to control. For the grain-filling stage of Xieyou 63, N. lugens infestation did not affect ZR content in roots and leaves except there were significant increases in ZR content in leaves at 6 days after 30,60, and 120 nymph infestations and at 9 days after 120 nymph infestation.3 During rice tiller stage, experimental rice(Zhendao 2) were subjected to rice foliar spraying and root treatment with different concentrations of these pesticides. Zeatzn ribiside content in rice leaves decreased significantly three days after foliar sprays (3 days) with 150 and 300 mg/L buprofezin, 30 and 60 mg/L imidacloprid, 200 mg/L jinganmycin, and 480 ml/L triazophos. At 7 days a significant reduction occurred irrespective of the pesticide concentration. The ZR content in rice roots did not change so dramatically as in rice leaves. At 3 days, it reduced significantly only in the plants subjected to a foliar spray with 100 mg/L jinganmycin or significantly increased in the plants sprayed with 480 ml/L triazophos, while at 7 days, there were no significant differences in ZR content under all circumstances. When subjected to root treatment with these pesticides, rice plants were extremely sensitive to triazophos and even wilted three days after the treatments (3 days). Root treatment with 150 mg/L buprofezin, 100 mg/L jinganmycin, 60 mg/L imidaclopr... |
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