Thermoperiodic control of germination of Fraxinus mandshurica var. japonica seeds

Abstract

Fraxinus mandshurica var. japonica seeds have a special temperature requirement for germination after compound stratification. The stratified seeds show marked thermoperiodic responses in relation to germination, which depend upon the durations of both 8°C.- and 25°C.- temperature periods. So far as is known at present, 8°C. -4 hr. day results in the best percentage of germination. Active inhibitory processes are assumed for the inhibition under higher constant temperatures, which can be slowly reversed by keeping at 2°C. Thermoperiodic responses become faint by lengthening the cold period after the same warm period in stratification. In stratified seed the embryo is independent of an inhibitory effect upon germination, the possible role of which seems to be played by the suberized membrane.