Comparative Ecophysiology of Seed Germination Strategies in the Seven Pine Species Naturally Growing in Greece

Abstract

Seven out of the eleven European pine species grow naturally in Greece. Pinus halepensis, P. brutia and P. pinea are low-altitude, typical Mediterranean species. The Greek populations of P. nigra, P. heldreichii, P. sylvestris and P. peuce grow in high altitudes and are located at the southern limits of their natural world distributions. Seed germination data concerning temperature dependence as well as light and/or stratification requirements are presented and discussed in relation to the individual species characteristics. Fire resilient P. halepensis and P. brutia are characterized by quite low germination in the dark, throughout their optimal temperature range (10-20 degrees C); in addition, their germination is photosensitive (white-light promoted and far-red inhibited). Prolonged stratification is always beneficial to P. brutia but detrimental to P. halepensis seeds. Germination of P. pinea seeds is also slow but indifferent to light conditions and restricted to a very narrow temperature range, around 20 degrees C. P. nigra seeds are fast germinating over a wide temperature range and rather indifferent to light. Germination of the deeply dormant P. heldreichii seeds as well as of the less dormant ones of P. sylvestris requires Light and/or stratification. By combining germination data for each species with the particular seasons of seed dispersal and the climatic conditions of the respective habitats, timing schedules of seed germination and subsequent seedling emergence in nature are proposed.