Sexual differences in biomass and nutrient allocation of first-year Silenedioica plants

Reproductive and somatic biomass, nitrogen (N), and phosphorus (P) pools we re compared between females and males in Ist-year plants of Silene dioica. We estimated irretrievable resources allocated to seeds, pollen, flowers, a nd unrecovered summer leaf investment by collecting plant parts at abscissi on throughout the season. At the end of the season, we determined resources lost through senescent stems and autumn leaf turnover and resources stored in perennial roots and overwintering buds. Sexual differences in allocatio n patterns depended on the resource used for comparison, and whether absolu te or proportional resource pools were assessed. Total resource pools in te rms of biomass and N were similar for females and males. However, male plan ts acquired relatively more P. The proportional reproductive investment, i. e., reproductive effort, was similar for males and females in terms of biom ass and N. In terms of P, male reproductive effort was higher. There was no difference between sexes in the proportional and relative biomass allocate d to perennial roots and overwintering buds. However, in terms of absolute and relative N allocation to belowground parts, females had larger reserves than males. Females, moreover, had a larger proportion of their P in below -ground parts. However, as male total P pools were larger, absolute P reser ves did not differ between sexes. The high reproductive effort and N deplet ion of below-ground parts in males resulted largely from higher flower prod uction compared to females. In females, seeds were the major component of r eproductive effort. These results show that if biomass and nutrient allocat ion are assessed in parallel for dioecious plants, we obtain a more complet e view of their sexual differences.