Seed-setting in subterranean clover (Trifolium subterraneum L.) 1. The importance of the microevironment

Abstract

An investigation was made of the relative efficiency of above- and belowground seeding, under unfavourable environmental conditions, in the subterranean clover variety Red Leaf, which normally sets some seed above and some below the ground. The experiment included artificial shielding of burrs in sponge rubber to simulate the protective effects of natural burial. Seed-setting, expressed in terms of mature seeds as percentage of reflexed florets, was considerably better when development occurred at or below the soil surface, or when burrs were enclosed in rubber, than when untreated burrs did not come in contact with the soil.The presence of moisture in the surface soil improved seed-setting above the ground. Breakdown of seed-forming processes occurred both before and after the stage at which seed development could be detected. Seeds formed above the surface were of light weight and gave very poor germination; seeds which had been buried or enclosed in rubber were much heavier and percentage germination was high; and those formed on the surface were intermediate.The results emphasize the importance of the microenvironment of individual inflorescences and burrs, and the value of protective or modifying influences, during the whole period of seed development in this species.