Effect of various treatments on hardening and softening of seeds in pods of barrel medic (Medicago truncatula)

Abstract

Experiments to determine ways of softening seeds in the field were designed to maintain stands of barrel medic (Meclicago truncatula). Under moist temperate conditions, at Canberra, seeds in pods above ground readily hardened during December but none softened during the following two months. At Coonamble, under hotter conditions and with less rainfall, approximately 13 per cent of the hard seeds in pods above ground softened during the summer but 96 per cent of pods contained at least one soft seed. Covering the pods with about one inch of soil early in December greatly increased softening of their seeds both at Canberra and Coonamble, but the response to seed burial was seen at Coonamble only after 134 days. Holding pods in a hot humid atmosphere also hastened seed softening. In all experiments, seed softening in pods began at the peduncle end and proceeded along the spiral as time went on. A method of determining intensity of hardseededness is described. Although the method is arbitrary it indicated a reduction in intensity of hardseededness preceding softening of the seed.