ECOPHYSIOLOGY OF SEED GERMINATION IN ENDEMIC LABIATES OF CRETE

Abstract

Ecophysiological aspects of seed germination were investigated in four aromatic labiate plants of Crete Origanum dictamnus (dittany), Sideritis syriaca L. ssp. syriaca (Cretan mountain tea), Salvia pomifera L. ssp. pomifera (gall-bearing sage), and Salvia fruticosa (three-lobed sage). Experiments were performed both at constant temperatures and darkness as well as under temperature and light conditions simulating those prevailing in nature during the main germination periods (i.e., start and middle of the rainy season, November and February-March, respectively). In three out of the four species, no particular dormancy was revealed and germination occurred rather promptly, although in a rather narrow range of cool temperatures and at a relatively slow rate; both characteristics determine and/or support an early, autumn seed germination and seedling establishment. In the fourth plant, Sideritis syriaca, germination was manifested at relatively warm temperatures and at a considerably faster rate, in accordance with its alpine distribution favoring spring seedling emergence and establishment. All four species tested showed an intermediate response towards light, as a result of their intermediate levels of active phytochrome maintained in darkness. Therefore seed germination was partially manifested in darkness but it was significantly enhanced (particularly at suboptimal temperatures) by white or red light; on the other hand, illumination with far-red light (simulating light conditions under a canopy) resulted in significant inhibition compared to dark controls.