Photoperiodic Control of Germination in Seed of Birch (Betula pubescens Ehrh.)

Abstract

IT is well known that the flowering response of both short-day and long-day herbaceous species is governed by the day-length conditions to which the mature leaves are exposed, and that the meristematic tissue of the shoot apex is insensitive. It has been shown for certain woody species, however, that direct photoperiodic perception may occur in the meristematic tissue of both dormant resting-buds and actively growing apices, in relation to dormancy phenomena. Thus, the unchilled resting-buds of dormant leafless seedlings of Fagus sylvatica and Betula pubescens ^1,2 may be induced to expand by exposure to long-day conditions. Similarly, actively growing, leafy seedlings of Betula pubescens may be induced to form resting-buds by direct exposure of the apical region of the shoot to short-day conditions, regardless of the conditions of day-length under which the mature leaves are maintained. It is of interest, therefore, to investigate whether the embryos of such woody species also show photoperiodic effects in relation to dormancy, and experiments have been carried out with seeds of birch for this purpose.