Intraspecific Variation in Photosynthetic Light Response and Photosynthetic Nitrogen Utilization in the Mountain Birch, Betula pubescens ssp. tortuosa

Abstract

Variation among individuals and sites in photosynthetic light-response characteristics and nitrogen use efficiency in the mountain birch (Betula pubescens ssp. tortuosa) is described and related to leaf nitrogen status. Significant differences among both individuals and sites were found for light-saturated photosynthetic rate (P max ) and leaf nitrogen concentration. P max was correlated with leaf nitrogen concentration. No such relationship was found for quantum yield efficiency or the convexity of the light response curve. The maximum photosynthetic rate and the daily amount of CO 2 assimilated increase with increasing leaf nitrogen content. Both instantaneous and daily photosynthetic production per unit leaf nitrogen decrease with increasing leaf nitrogen content. The daily assimilation per unit leaf nitrogen lost through leaf abscission was inversely related to the proportion leaf nitrogen lost at leaf abscission