XVI International Botanical Congess

A previous study found that the cost of producing a gram of capsules in terms of reduced vegetative growth was greater in P. major than P. rugellii. The present study explains this difference in cost in terms of the nitrogen allocation patterns of these two species. Nitrogen concentrations were similar in the roots and leaves of the two species, but concentration in the stem of P. rugellii was much greater than that of P. major. In P. major the nitrogen content of the stems, leaves and roots decreased with reproduction. In P. rugellii root and leaf nitrogen content changed little, but stem nitrogen decreased with reproduction. It would appear that in P. rugellii reproduction has little immediate effect on growth because reproduction draws on stored reserves rather than competing directly with vegetative growth.