Nitrogen Productivity Depends on Photosynthetic Nitrogen Use Efficiency and on Nitrogen Allocation Within the Plant

Abstract

The concept of plant nitrogen productivity was introduced at the end of the 1970s to interpret the dependency of plant growth on internal nitrogen. It is defined as the increase in plant dry matter per unit time and per unit plant nitrogen content. Recently, plant nitrogen productivity has been expressed as the product of two terms: the leaf nitrogen ratio, which is the proportion of the plant's nitrogen present in the leaves, and the leaf nitrogen productivity, which is defined as the increase in plant dry matter per unit time and leaf nitrogen content. In the present paper we use two data sets obtained from C3 herbaceous species to evaluate the relative importance of variation in leaf nitrogen ratio and leaf nitrogen productivity in determining interspecific variation in plant nitrogen productivity. Further, we analyse to what extent leaf and plant nitrogen productivities depend on photosynthetic nitrogen use efficiency. Results show that in all cases, photosynthetic nitrogen use efficiency is a major determinant of both plant and leaf nitrogen productivities. A positive relationship between leaf nitrogen ratio and plant nitrogen productivity was found only when comparisons were made over broad taxonomic groups.