Vegetative Responses of Deschampsia flexuosa (L.) Trin. (Poaceae) Seedlings to Nitrogen Supply and Photosynthetically Active Radiation

Abstract

1 When Deschampsia flexuosa (L.) Trin. was grown from seedlings in a glasshouse in summer, growth of the shoots declined (P < 0.001) as photosynthetically active radiation (PAR) and nitrogen concentration (N) decreased. These responses were largely a function of a reduction in numbers of tillers. PAR and N interacted positively at P < 0-001. 2 Individual tillers of D. flexuosa responded to reduced nitrogen and PAR (except at the lowest PAR level) by an increase in shoot dry weight, shoot length, leaf dry weight, leaf length, leaf number, leaf length ratio (=SLA) and leaf weight fraction. At the lowest PAR used, this trend was reversed. Leaf length ratio was the variable which showed the largest relative change and was the most consistent in its response to variation in PAR. 3 These results suggest that D. flexuosa has a greater capacity to respond morphologically to variation in nutrient levels than has previously been reported. The increase in the magnitude of tiller variables with decreasing nitrogen and PAR levels may be an adaptation which allows the species to be successful in shaded, low fertility