The effects of seed size and pericarp on seedling recruitment and biomass in Cryptocarya alba (Lauraceae) under two contrasting moisture regimes

Establishment success of plants derived from large seeds has been proposed to be greater than that of those derived from smaller ones, particularly un der unfavourable conditions of moisture. Therefore, the advantages conferre d by large seeds in terms of seedling performance may be modulated by abiot ic conditions. The effect of seed size on Cryptocarya alba seedling perform ance (as determined by seedling recruitment and seedling size) was evaluate d under two contrasting rainfall regimes (wet and dry year regime), simulat ed in the laboratory. It was also determined whether the presence of a peri carp, which had been shown to reduce germination, decreases desiccation and if this counterbalances the greater recruitment of seeds without a pericar p, especially under unfavourable conditions of moisture. Large seeds had a greater probability of recruitment and their seedlings attained a greater b iomass, independently of the amount of water applied. In the simulated wet year regime, seeds with a pericarp showed a greater probability of recruitm ent than those lacking a pericarp. However, seedlings derived from both see d types attained a similar biomass. Under the dry year regime, seeds with a nd without a pericarp showed similar recruitment probabilities and their se edlings had similar biomasses. These results do not support the assumption that under favourable conditions of moisture, individual differences in see d size would not matter in term of seedling performance. A possible explana tion in this case, is the presence of recalcitrant seeds in C. alba, which determines a very short time period for germination following dispersal. Th erefore, any attribute that increases germination (e.g., large seeds) would be advantageous, independently of the prevailing abiotic conditions.