Factors Affecting Germination in Greehouse-Produced Seeds of Oxalis corniculata, a Perennial Weed

A study was conducted to investigate the physiological responses of greenhouse-produced Oxalis corniculata seeds to light, temperature, moist heat treatment, aging, and season of production. Fresh seeds exhibited over 90% germination and required low levels of light (5 μmol m-2 s-1, 400–700 nm) to germinate. Seeds germinated over a broad, yet seasonally-dependent range of incubation temperatures. Seeds produced in winter had the narrowest temperature range of germination (15 to 25 C) and the lowest germination percent (44% at 2 wk) at optimum temperature (17 C); seeds produced in summer had the widest temperature range of germination (10 to 30 C) and the highest germination percent (93% at 2 wk) at optimum temperature (17 C). Incubation at non-optimum temperatures between 5 and 40 C suppressed or slowed the rate of germination until seeds were placed at optimum temperature, where full germination subsequently occurred. Moist heat treatment at temperatures over 40 C resulted in varying degrees of inhibition of subsequent germination. When seeds were stored dry in laboratory conditions, three of four seed lots examined retained over 80% germination capacity until ca. 8 months; 50% capacity remained after ca. 15 months. These results indicate that the seasonal temperature and daylength effects on maternal plants in the greenhouse environment are major determinants of seed germination characteristics of O. corniculata.