适宜钾浓度降低小麦蚜虫密度的生理代谢机理

【目的】从对植物基础代谢影响的角度，研究施钾降低麦株蚜虫密度的作用机理，为田间小麦蚜虫的生态调控提供科学依据。【方法】采用水培试验，设置5个钾水平（KCl 0.005、0.05、0.5、2、10 mmol/L），每个钾水平均进行蚜虫侵染和不侵染处理，每个处理重复3次，并于麦株五叶一心时进行蚜虫侵染，将虫龄大小一致的成年无翅蚜虫接种在小麦的最新完全展开叶上，每株小麦用5头蚜虫侵染。然后，分别于蚜虫侵染4天和8天两个时间节点调查麦株蚜虫密度并取样，分析钾水平和蚜虫取食对小麦叶片游离氨基酸、可溶性蛋白和可溶性糖含量的影响。【结果】钾水平在0.005~0.5 mmol/L范围内，蚜虫侵染后第4天，单位干物质重的蚜虫密度随着钾水平的提高显著降低，进一步提高钾水平，蚜虫的群体密度差异并不显著；而在蚜虫侵染后第8天，蚜虫的群体密度随着钾水平的升高而显著降低。随着钾水平提高，未被蚜虫侵染的小麦植株其游离氨基酸含量呈降低趋势，而可溶性蛋白和可溶性糖含量则呈先升高后降低趋势；被蚜虫侵染的小麦植株其游离氨基酸和可溶性蛋白含量的变化趋势不变，而可溶性糖含量则呈持续增加趋势。同一测定时间与不接虫处理相比，接虫处理随着钾水平的提高，蚜虫侵染诱导的游离氨基酸和可溶性蛋白含量降低，而可溶性糖含量增加。两个时间节点相比，随时间推移，不接虫处理游离氨基酸、可溶性蛋白、可溶性糖含量的平均增幅分别为2.6%、18.1%、2.0%，而接虫处理上述指标平均增幅分别为67.3%、20.9%、22.9%，与不接虫处理相比，接虫处理麦株游离氨基酸和可溶性糖含量增幅较大。此外，蚜虫侵染诱导的游离氨基酸、可溶性蛋白和可溶性糖含量的增加量，都与相应时间节点的蚜虫群体密度显著或极显著相关，其中，接虫4天和接虫8天的相关系数分别为0.948、0.920、-0.908和0.944、0.985、-0.991。而组成型的可溶性蛋白和可溶性糖含量与相应时间节点蚜虫群体密度间相关性不显著，游离氨基酸含量却与之呈极显著正相关，接虫4和8天的相关系数分别为0.995和0.944。【结论】提高钾水平可能通过降低小麦组成型游离氨基酸的含量，降低蚜虫取食诱导型游离氨基酸和可溶性蛋白积累，提高诱导型可溶性糖的积累，共同降低麦长管蚜密度。

Physiological mechanism of potassium application in decreasing density of aphid (Sitobion avenae F.) in wheat

Objectives] Based on the view of plant basic metabolism,the experiment revealed the mechanism of reducing aphid (Sitobion avenae F.) population density of wheat by applying potassium,and provided scientific basis for ecological regulation of wheat aphids in the field.Methods] A solution culture method and fully balancing design with five potassium levels (0.005,0.05,0.5,2 and 10 mmol/L KCl,respectively) and two aphid infection levels (aphid infection and not infection) were used in this experiment,and three repetitions were arranged for each treatment.When the wheat seedlings had 5 expanded leaves,5 adult wingless aphids in the same size and age were set on the latest fully expanded leaves per wheat plant.Then the density of aphids were surveyed and the wheat samples were collected respectively at the fourth and eighth days after the aphid infection to study effects of potassium level and aphid feeding on free amino acids,soluble protein and the content of soluble sugar of wheat leaves.Results] The results showed that at the fourth day after the infection of aphids and in the range of K 0.005-0.5 mmol/L,the aphid density of unit dry weight of wheat decreased significantly as potassium level increased,and if improving the potassium level further,the aphids population density did not increase significantly.At the eighth day after the aphid infection,the aphid population density decreased significantly with the increase of potassium levels in the arranged range.As potassium level increased,the free amino acid contents in the wheat plants uninfected by aphids showed a decreasing trend,while both soluble protein and soluble sugar contents showed increasing trends at first and then showed decreasing trends.In the wheat plants infected by aphids,the free amino acids and soluble protein contents showed the same changing trend as in the former,however,the soluble sugar content showed a continuously increasing trend.Comparing the treatment infected by aphids with the treatment uninfected by aphids at the same time nodes,as potassium level increased,the free amino acids and soluble protein contents of wheat plant were decreased by aphid infection,while the soluble sugar contents were increased.By comparison of the involved indexes in the two time nodes,as the time prolongation,there were average increments of 2.6％,18.1％,2.0％ for free amino acid,soluble protein and soluble sugar contents respectively in the uninfected wheat,and of 67.3％,20.9％ and 22.9％ for infected wheat respectively,which showed greater increase for free amino acids and soluble sugar content in infected wheat plants than in uninfected wheat plant.In addition,the contents of induced free amino acid,soluble protein and soluble sugar,had significant or extremely significant correlation with the aphid population density in relevant each time node,and the correlation coefficients were 0.948,0.920 and-0.908 in the fourth day,and 0.944,0.985 and-0.991 in the eighth day respectively.The contents of constitutive soluble protein and soluble sugar had no significant correlation with aphid density,but the content of constitutive free amino acid had extremely significant correlation with aphid density,and the correlation coefficients were 0.995 and 0.944 respectively at the fourth and eighth days after the aphid infection.Conclusions] Our results showed that increasing potassium supply could significantly reduce aphid population density by significantly reducing constitutive free amino acid content,inhibiting the accumulation of free amino acids and soluble protein and promoting the induced soluble sugar content.