Kimmo NURMI-a, Vladimir OSSIPOV-a,b, Eriki HAUKIOJA-b and
Kalevi PIHLAJA-1
a-Department of Chemistry and b-Department of Biology, University of Turku, FIN
20014 Turku, Finland
Many studies have shown that the nutrient and allelochemical contents of leaves vary temporally and spatially. Since food quality atrophy influences herbivore performance (e.g. growth, survival, and reproduction) the high intra~ific variation may concentrate feeding to only certain individual plants, or their parts. The aim of this study was to determine the role of different nutritive components water-soluble carbohydrates, starch and nitrogen constituent (protein and free amino acids) in regulation of birch-insect interactions. Therefore, the composition and content of these nutritive components in leaves of mountain birch trees (Betula pubescens ssp. tortuosa) were studied, with regard to the seasonal and among-tree variation. Water-soluble carbohydrates were analyzed as TMS-derivatives by GC. The average content of total water-soluble carbohydrates, fructose, galactose, glucose, inositol and sucrose, in the leaves in early, mid and late summer was ca 139, 116, 112 mglg of dry wt. respectively. The average decline was 19%. The major carbohydrate in early summer was galactose (49 mg/g of dry wt), but its quantity declined evenly during the season. However, the content of sucrose increased at the same time from 29 to 60 mg/g of dry wt. and it was the major compound in mid and late season. The coefficient of among-tree variation (CV) of total and individual water-soluble carbohydrates varied during the season only between 6% and 9-27%, respectively Starch content was analyzed by W spectrophotometry with enzymatic method. The average content of starch in early, mid and late summer was ca 21, 38 and 32 mg/g of dry wt. respectively. The CV among trees varied at the same time between 3152%. E ree amino acids were analyzed by amino acid analyzer. The average content of total free amino acids in early, mid and late summer was ca 2380, 1220 and 910 Gig of dry wt. respectively. The average seasonal decline was 62%. At the same time protein content varied between 3.6 - 4.8%, respectively. On the basis of the collected data the role of nutritive components in plant-insect interactions will be discussed.