Abstract:

Abstract：【Objective】This study was to elucidate the effect of potassium levels on plant aphid resistance in wheat at late growing stage and the relative physiological mechanism.【Method】A pot experiment with three K levels treatments of K0(0mgK2O/kg soil) , K1(0.1mgK2O/kg soil)and K2(0.15mgK2O/kg soil),combined with laboratory plant analysis was conducted to study the effects of K levels on the content of plant phenol, lignin and enzyme activity which play roles in the phenolics and lignin metabolism in wheat at late growing stage and investigate the difference of aphid population among the treatments.【Result】The aphid population per plant showed significant variance among the three treatments during 14d to 28d after inoculation with K0 having the largest aphid population , K2 the medium, K1 the minimum. The aphid population peak time was postponed about 2-3d for K0 and K2 compared with K1. The content of total phenol, phenolic acids, lignin and the enzyme activity of phenylalanine ammonia lyase (PAL),tyrosine ammonia lyase (TAL) , peroxidase (POD) polyphenol oxidase (PPO) were in the order of K1> K2>K0. There were significant correlation between the content of total phenol, phenolic acids, lignin, enzyme activity of phenylalanine ammonia lyase (PAL),tyrosine ammonia lyase (TAL) , peroxidase (POD) , polyphenol oxidase (PPO) and the dry weight or grain weight, but not between the content of total phenol, phenolic acids, lignin, enzyme activity of phenylalanine ammonia lyase (PAL),tyrosine ammonia lyase (TAL) , peroxidase (POD) , polyphenol oxidase (PPO) and plant potassium content.【Conclusion】Supplying potassium with sufficient quantum can increase wheat aphid resistance at late growing stage by improving phenolics or lignin metabolism combined with enhanced plant dry weight, supplying potassium with over or deficient quantum may both decrease aphid resistance by depressing phenolics or lignin metabolism combined with reduced plant dry weight. Keyword：Potassium; Wheat; Phenolics Metabolism ;Dynamic of aphid population