Heterocarpy and Seed Polymorphism in Ceratocapnos heterocarpa (Fumariaceae)

Abstract

Ceratocapnos heterocarpa produces two types of fruits: the "short" fruit, which is monospermous, indehiscent, and only likely to achieve short-distance dispersal, and the "long" fruit, which is dispermous, dehiscent, and adapted to long-distance dispersal (epizoochore). The two types of propagules are produced in seasonally varying proportions. In January, 95% of the fruits are short and 5% long, whereas in May, only 51% are short and 49% long. The overall proportion for the growing period is roughly 75: 25, short/long, respectively. Three types of seeds are produced-the lower seed of the long fruit, the upper seed of the long fruit, and the seed of the short fruit. These differ in morphology and in germination patterns, the lower seed of the long fruit showing the greatest potential for germination. Light causes a reduction in the final percentage of germination of all three seed types and also reduces the temperature ranges in which germination can take place. The lower seeds from the long type are least affected by light. The pericarp of the short (indehiscent) fruits and the testa of the upper seeds of the long (dehiscent) fruits enforce dormancy, resulting in delayed, spread out germination. The testa of the lower seeds of the long fruits, which is usually split dorsally, does not hinder germination.