Influence of Prokelisia Planthoppers on Amino Acid Composition and Growth of Spartina alterniflora

Abstract

The effects of feeding by the planthopper Prokelisia dolus on its hostSpartina alterniflorawere examined under conditions of both high and low plant-nitrogen subsidy. Phloem feeding by P. dolus reduced the concentrations of γ-aminobutyric acid, isoleucine, leucine, lysine, threonine, and valine in S. alterniflora leaves. In contrast, glutamic acid was the only amino acid that increased in plants fed upon by planthoppers, and this increase was only observed in plants in the high N-fertilizer treatment. Planthopper feeding reduced the total concentration of amino/imino acids tested, and the concentration of essential amino acids, although this difference was not quite statistically significant. Generally, concentrations of individual amino acids in Spartina were higher in the high N-fertilizer treatment. Planthopper feeding and nitrogen fertilization also significantly impacted Spartina growth and production. Culm elongation, new leaf production, and tiller elongation were reduced and leaf mortality was increased on plants fed upon by planthoppers. Furthermore, planthoppers showed enhanced survival on the high-N plants. Nitrogen fertilization also moderated the effects of sap feeding on plant growth because the reduction of culm elongation associated with planthopper feeding was more pronounced in the low N-fertilizer treatment. Thus, feeding by P. dolus adversely affected both the nutritional quality and growth of Spartinaeffects that were tempered, in part, in plants receiving high nitrogen subsidy. Our results are discussed in the context of feeding-induced changes in plant quality and quantity as possible mechanisms mediating competitive interactions in Prokelisia planthoppers.