Regulation der Reproduktion bei Epilobium Dodonaei Vill

Abstract

Plasticity of reproductive components in Epilobium dodonaei. — Shoots of the clonal perennial Epilobium dodotyaei Vill. develop flowers and fruits acropetally in an open inflorescence. In this study we examine the effects of competition, fertilization and defoliation of shoots on three consecutive regulatory levels of reproduction: (1) inflorescence size and abortion rate of flowers and fruits, (2) number of ovules and abortion of seeds and (3) variation in seed weight. In a three-way factorial experiment we recorded the fate of all meristems within an inflorescence, the fate of all ovules within a median fruit and the weight of seeds. All treatment factors significantly influenced fertility, however the level at which the regulatory response occurred differed among factors. Competition as a permanent stress resulted in an early regulation and reduced potential fecundity by 31 %. Compared to the treatments without competition, shoots of plants under competition initiated fewer flower buds (37.9 < 49.3) and aborted more flowers, but matured more seeds per remaining fruit (55.3 > 16.7). Defoliation resulted in late regulation, mainly via increased abortion of fruits and reduced potential fecundity by only 16 %. Both competition and defoliation significantly reduced seed size. Fertilizer application affected plants growing under competition and resulted in an increase in number of ripe fruits and seed size. Our results suggest that under shortage of resources Eplobium dodonaei maximizes fertility by early regulation of reproduction, thus avoiding waste of resources. However, in the absence of stress vegetative growth has priority and waste of resources for reproductive structures is tolerated.