Increased sensitivity to green light during transition from conditional dormancy to nondormancy in seeds of three species of Solidago (Asteraceae)

Germination responses of nonstratified (conditionally dormant) and of cold-stratified (nondormant) seeds of three Solidago species were tested in darkness at 30/15°C following various lengths of exposure [0 (control), 5 and 30 min, 1, 6 and 14 h] to green (mostly 500-600 nm) or white (400-700 nm) light. Prior to exposures, nonstratified seeds were imbibed in darkness at laboratory conditions for 24 h, and cold-stratified seeds were kept in darkness at 5°C on a moist substrate for 8 wk. Nonstratified seeds of S. altissima, S. nemoralis and S. shortii germinated to 0-46%, 0-25% and 36-99%, respectively, in darkness following 5 min to 14 h of green or white light, whereas cold-stratified seeds germinated to 53-98%, 31-85% and 82-100%, respectively. Thus, sensitivity of seeds to both green and white light increased as they passed from conditional dormancy to nondormancy. Moreover, sensitivity to green and white light was similar to the hierarchy of seed size. Green safe lights must be used with caution in interpreting the results of studies on light/dark responses of seeds.