| Ectropis obliqua Prout(Lepidoptera, Geometridae) is one of the major pests of tea garden. Ectropis obliqua distributed throughout all the main tea producing garden, the most serious occurred in Zhejiang, Jiangsu, Anhui, Xinyang (Henan), etc. area. They overwinter as pupae in rhizospheric soils of tea bushes. In order to understand the mechanisms of cold hardiness in the overwintering pupae and predict the mortality rate and the variation of population, the supercooling point and freezing point, the survival rate after exposed to low temperature, the supercooling point and freezing point after cold hardening, biochemical substances and stress-tolerance enzymatic activities in different geographical populations were investigated in this thesis, the main results are as follows:1. The research about the supercooling points and freezing points of different geographical populations showed that the supercooling points of Huangshan, Hangzhou, Xinyang population were-12.59℃,-13.40℃,-14.16℃, respectively. The freezing points were -6.68℃,-7.07℃,-7.21℃, respectively. And they were reduced with increasing latitude, and the magnitude of variations in supercooling points was lager. The low-lethal temperature of Huangshan, Hangzhou, Xinyang population after exposed to low temperature of 6℃,3℃,0℃,-3℃,-6℃ for 12h were -2.62℃,-3.34℃,-4.84℃, after 24h cold exposure were -1.56℃,-3.05℃,-3.53℃, after 36h cold exposure were-0.61℃-1.64℃,-2.01℃, and after 48h cold exposure were-0.22℃,-1.33℃,-1.65℃, respectively. The lethal temperature were significantly reduced with increasing latitude in different geographical populations and the reduction increased with the extension of exposure time,which showed that the higher the latitude, the stronger the cold tolerance of the E. obliqua population became.2. The supercooling points and freezing points in different geographical populations after cold hardening treatment were tested, the supercooling points of Huangshan population after rapid cold hardening treatments (0℃,5℃ for 2h) and cold acclimation treatments (5℃ for 24h,48h) were-14.05℃,-14.08℃,-15.07℃,-14.76℃, respectively. Which were-15.01℃,-15.21℃,-16.22℃,-15.42℃ in Hangzhou population and-15.33℃,-15.41℃,-16.50℃,-15.55℃ in Xinyang population, respectively. The supercooling points were reduced by 8.72% to 21.04% than control and was significantly different(P<0.05), and the supercooling points conformed to the relationship of Huangshan population> Hangzhou population> Xinyang population in general; the freezing points of pupae were less affected by cold hardening than the supercooling points,5℃ for 24h cold exposure groups of each population and 5℃ for 48h cold exposure group of Huangshan population were significantly decreased than the control, the rest of the groups also had decreased but there was no significant difference (P<0.05). It showed that cold hardening might enhance the cold hardiness of the pupae,there was certain plasticity of cold hardiness.3. The analysis of biochemical substances in different geographical populations showed that the weight and water contents had no relation with latitude, however the lipid, protein, glycogen contents were increased with increasing latitude. The lipid contents of Huangshan, Hangzhou, Xinyang population were 50.02%,51.07%,52.52%, respectively, differed significantly among the populations(P<0.05), and the ptotein contents were 78.85 ug/mg,82.03 ug/mg,82.44 ug/mg, respectively, Huangshan population was significantly lower than that of Hangzhou, Xinyang population, the glycogen contents were 8.78ug/mg, 8.79 ug/mg,8.80 ug/mg, respectively, and there was no significant difference among the populations(P<0.05). The research about the stress-tolerance enzymatic activities showed that the SOD,POD and CAT three protective enzymes activites were significantly increased with increasing latitude, the activity of ATP which involved in energy metabolism was significantly depressed with increasing latitude. There was no significant difference in POD, CAT activites of different populations, the SOD activites of Huangshan population were significantly lower than Hangzhou, Xinyang population, but the ATP activites were significantly higher than Hangzhou, Xinyang population (P<0.05). It showed that the lipid, protein, glycogen contents and the stress-tolerance enzymatic activities were directly related to cold hardiness of the E. oblique pupae.4. The analysis of several biochemical substances and stress-tolerance enzymatic activities in different geographical populations after cold hardening showed that the water contents and supercooling points were positively correlated, the water contents of cold acclimation treatments were significantly depressed compared with the control,5℃ for 24h cold exposure groups of Huangshan, Hangzhou, Xinyang population were 2.83%, 2.61%,3.16%, respectively, and 5℃ for 48h cold exposure groups were 2.96%,3.16%, 3.26%, respectively, the rapid cold hardening groups also had decreased but there was no significant difference(P<0.05); the lipid contents of the cold hardening treatments were increased by 1.20% to 8.44% than control, which had better effects in cold acclimation treatments, there was significant difference with the exception of 5℃ for 2h cold exposure group of Xinyang population; the protein, glycogen contents of rapid cold hardening groups were increased by 7.34% to 24.85% and 13.99% to 24.85% than control respectively, and there was significant difference(P<0.05), however the protein, glycogen contents of cold acclimation groups were a little increased and reduced than control respectively; but SOD, POD and CAT three protective enzymes activites were obviously increased by the cold hardening, and ranged from 8.28 U/mgprot to 13.14 U/mgprot, 13.10U/mgprot to 17.11 U/mgprot,6.34 U/mgprot to 11.60 U/mgprot respectively, then the activity of ATP ranged from 8.28 U/mgprot to 13.14 U/mgprot, significantly depressed than control (P<0.05).The above results show that there are certain differences in cold hardiness of E. obliqua (pupae) in different geographical populations, the cold hardiness will be enhanced by the increasing latitude, and the differences are colsely related to the content variations in body water, lipid, protein, glycogen,etc. and stress-tolerance enzymatic activities. |
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