Shoot density of Carex rostrata Stokes in relation to internal carbon : nitrogen balance

Initiation of new shoots originating from basal meristems of older shoots o f Carer rostrata was studied in relation to the internal carbon/nitrogen ba lance. In a greenhouse experiment, individual shoots with a vigorous format ion of a new shoot contained the highest concentrations of free amino acids (FAA) and the lowest concentrations of total nonstructural carbohydrates ( TNC), resulting in a low TNC/FAA ratio. Thus shoots with high availability of nitrogenous compounds in relation to carbohydrates started growing a new shoot. The results suggest that TNC/FAA ratios could affect shoot densitie s. Field measurements supported this view: TNC/FAA ratios were lower in a m esotrophic site with a high density of shoots than in an oligotrophic site with a low density of shoots. Compared with roots, TNC/FAA ratios of shoots seemed to be more decisive both in the greenhouse experiment and in the fi eld. In the greenhouse experiment, initiation of new shoots was measured in fragmented shoots of Carer having no intraclonal connections. Even if phys iological integration was lacking due to fragmentation, shoot initiation wa s efficiently controlled in relation to the internal carbon/nitrogen balanc e.