Studies of seed development in Pisum sativum : I. Seed size in reciprocal crosses.

Variation in cell population size and cell weight in the cotyledons are important factors in determining seed weight in Pisum sativum. The regulation of these parameters as well as that of growth rate has been examined. The use of reciprocal crosses between varieties of contrasting seed size has allowed the recognition of two systems of control-an intrinsic one dependent on the seed's own genotype, and the extrinsic control of the maternal environment. It is shown that the use of particular kinds of crosses can aid in discriminating the separate roles of sinks and sources as determinants of seed size.