SIZE DEPENDENCY OF SEXUAL REPRODUCTION AND OF CLONAL GROWTH IN 2 PERENNIAL PLANTS

We compared the size dependency of sexual reproduction and clonal grow th in two clonal perennials that inhabit old fields, Aster lanceolatus and Solidago canadensis. In both species there was a threshold size r equired for sexual reproduction to occur, and above that threshold rep roductive output increased linearly with vegetative mass. Biomass allo cated to clonal growth was also highly correlated with vegetative mass in both species, but there was no evidence of a threshold size for cl onal growth. The absence of a clear size threshold for clonaI growth e mphasizes the similarity between clonal growth (vegetative reproductio n) by rhizomes and growth of other vegetative parts, as opposed to sex ual reproductive allocation. In both species there were differences in the allocation patterns of plants derived from seeds and those derive d from rhizomes. Although seed- and rhizome-derived plants did not dif fer in phenology and size, the latter allocated more biomass to sexual reproduction and clonal growth in both species.