The influence of nitrogen nutrition on plant response to greenbug infestation 1

The influence of nitrogen nutrition and greenbug (Schizaphis graminum Rondani) infestation on growth, chlorophyll content, soluble amino acids, and soluble protein of barley plants (Hordeum vulgare L.) was studied in growth chamber experiments. Plants were grown for 21 days using complete or minus nitrogen nutrient solution. First leaves were then fitted with cages containing eight apterous adult greenbugs. After 7 days, the greenbugs were removed and the plants harvested. The plants given complete nutrient solution grew more rapidly than those given minus nitrogen. Plants grown with minus nitrogen had fewer greenbugs per plant but had much higher numbers of greenbugs per square centimeter of total plant leaf area than plants given complete nutrient solution. All leaves of infested plants grown with minus nitrogen had decreased dry weight, decreased chlorophyll, and increased soluble amino acids when compared with minus nitrogen uninfested plants. Infestation of first leaves of plants grown on complete nutrient solution increased soluble amino acids in all leaves. However, there was little change in the dry weight or chlorophyll level in leaves other than the first leaf. It is concluded that adequate nitrogen nutrition produces plants that can better withstand localized greenbug feeding damage than plants deficient in nitrogen.