Lucerne Saponins As Inhibitors Of Cotton Seed-Germination - Their Effect On Diffusion Of Oxygen Through Seed Coats

The site of inhibition of cotton-seed germination by lucerne saponins seems to be associated with tissues other than the embryo. The rate of water uptake during imbibition was similar for intact seeds immersed in water and for those in 0.5 per cent saponin solution. Seeds previously immersed in saponin solution showed a lower rate of respiration, absorbing about 60 per cent less oxygen than those pre-immersed in water. Yet the respiration rate of excised embryos from both treatments was the same. The extent of the inhibition of germination was not affected when oxygen was either bubbled through the saponin-containing immersion-solution or passed through the flasks in which the seeds were germinated after 24 h of pre-immersion. The rates of oxygen diffusion through the seed coats and membranes of seeds pre-immersed in water or in saponin solution were measured. They were distinctly lower for seed coats and membranes which had been exposed to the saponin treatment. It has been concluded that the seed coat and/or the membrane of intact cotton seeds pre-immersed in saponin solution serve as a barrier for oxygen diffusion to the embryo, resulting in inhibition of germination.