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 dark ness at 30/15 degreesC 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 darknes s at laboratory conditions for 24 h, and cotd-stratified seeds were kept in darkness at 5 degreesC 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 whit e light, whereas cold-stratified seeds germinated to 53-98%, 31-85% and 82- 100%, respectively. Thus, sensitivity of seeds to both green and white ligh t increased as they passed from conditional dormancy to nondormancy. Moreov er, sensitivity to green and white light was similar to the hierarchy of se ed size. Green safe lights must be used with caution in interpreting the re sults of studies on light/dark responses of seeds.