Growth and leaf life-span of a floating-leaved plant, Trapa natans L., as influenced by nitrogen flux

Abstract

Trapa natans L., cultured in tanks under varying nitrogen flux, was examined with particular reference to the change in foliage structure. Leaf initiation rate, leaf loss rate and leaf life-span were independent of nitrogen flux and ranged from 140 to 250 mg N m −2 day −1. In contrast, leaf and rosette size were positively correlated with nitrogen flux. The maximum biomass was estimated to be 487 g dry weight m −2 in the most nitrogen-enriched tank. With increasing nitrogen flux, proportions of petiole and reproductive parts (fruit) in the total biomass increased, while those of stem and root decreased. Net production of T. natans was also positively correlated with nitrogen flux and ranged from 5 to 14 g dry weight m −2 day −1 for all experimental tanks, excluding a tank with algal competition.