Sequential softening of hard seeds in burrs of annual medics

Abstract

Two experiments were done with nine lines from seven species of Medicago to discover if hard seeds softened more easily out of the burr, and whether there was any sequence of softening according to seed position in the burr. It was found that seeds extracted from burrs showed more softening than seeds left in the burrs, when both were given nine months fluctuating temperature treatment (15°- 16°C daily), in M. littoralis, M. scutellata, M, tornata and M. truncatula, but there was no difference in M. polymorpha and M. rugosa. In all lines the seeds softened first at the calyx end of the burr, and then softened in sequence up the burr spiral.