The Response Of Aphids Density To Potassium Levels And Its Physiological And Biochemical Mechanism Of Wheat

Two wheat cultivars, Aikang58and Zhengmai9023, and fivepotassium (K) levels (K+:0.005,0.05,0.5,2and10mmol/L) were used in thehydroponic culture.To study the response of aphids density to potassium levels and itsrelationships with some biochemical substance of Wheat leaves, wheat leaves weresampled for nutrients and secondary metabolites analysis after0,4,8d aphidsinfestation or not, respectively.And then its results would provided useful referencefor the rational fertilization to improve plant resistance to insects. The main resultswere listed as follows:1.The amount of Macrosiphum aveane was significantly decreased with theincrement of potassium application levels, no matter4days or8days after aphidsinfestation. The minimum number of aphids in Aikang58was observed at0.5mM Klevel, while Zhengmai9023needed a higher K level to get the minimum aphisnumber.2. Soluble sugar was no obvious changes of two wheat cultivars with theincrement of K application level. After aphids infestation, there was no significantdifference except for K level was2or10mM，Aikang58decreased significantly.Freeamino acid contents of both wheat cultivars would decreased significantly when Klevel was from0.005mM to0.5mM. However, there was no significant differencewhen K level continued to rise. After aphids infestation, free amino acid contentsignificantly increased.Protein contents were improved significantly with theincrement of K application level. However, when K level was over2mM, thesecontents of Aikang58would decreased significantly, while Zhengmai9023was stable.Soluble protein contents of two wheat cultivars were increased significantly. When Kapplication level was from0.005to0.05mM, total phenols and tannin contents weredecreased remarkably with the increment of K level. When K level was over0.5mM,there were no obvious changes of the both substances in Aikang58. Total phenolscontent of Zhengmai9023was continued to decrease, whereas tannin contentincreased significantly when K level was over0.5mM. After aphids infestation, thecontent of total phenols was increased but tannin was decreased at K0.005and K0.05levels. However, when K application level was increased from0.5to10mM, the content of total phenols was decreased. Along with the increasing of K applicationlevel, the contents of flavonoids of Aikang58were increased, whereas that ofZhengmai9023were first decreased and then increased. Its content decreased in4days and increased in8days after infestation. When K level was from0.005to0.05mM, there was decreased remarkably of lignin content of Aikang58with theincrement of K level. it was no obvious changes when K level was over0.5mM.However, Lignin content of Zhengmai9023was no obvious changes at all of K levels.With the exception of tannin and lignin, the changing rule of free amino acid, solublesugar, soluble protein, total phenols and flavonoids contents of aphids infestationtreatment was similar with no infestation treatment.3. Significant or highly significant negative correlation relationships wereobserved between soluble protein content, lignin content and aphid amounts. Onlywhen K level was from0.005to0.5mM, highly significant positive correlation couldbe observed between free amino acid and aphids amount. The relationship amongsoluble sugar content, secondary metabolites and aphis amount depended on thecultivars, the aphids amount correlated significantly positive with total phenol,significantly negative with flavonoids content, showed none relationship with tannincontent in Aikang58; While the relationship between aphids amount of Zhengmai9023with total phenol content, soluble sugar content, flavonoids content wassignificant positive, negative and negative correlation, respectively. It showed nonerelationship with soluble sugar content. While it was only after8days aphidsinfestation that highly significant positive relationship could be observed betweentannin content and aphis quantity of Zhengmai9023.4. Correlation analysis of nutrients and secondary substances in the metabolismrelating to aphids shows that, significant positive or negative relationship wasobserved between these biochemical substance with the exception of tannin content inAikang58and tannin or soluble sugar content in Zhengmai9023according tocorrelation analysis. Thus, stronger interactions between these metabolites could bededuced and correlated to affect the quantity of aphis. The leading biochemicalsubstance that played a leading role on the aphids amount were clarified by furtherpath analysis. These substance were lignin after4days infestation, soluble sugarcontent and flavonoid after8days infestation in Aikang58, while soluble sugar, totalphenols and lignin content after4days infestation, soluble sugar, protein content,lignin content and tannin content after8days infestation in Zhengmai9023.