Optimum seed germination requirements of Ulmus wallichiana - an endagered tropical highland tree species

Tree seeds of tropical highlands species are among the least explored in forestry research in India. Ulmus wallichiana Planchon, a tree of large proportions, is listed as endangered by the IUCN. Seeds of this species are scarcely available for afforestation due to very high incidence of empty seeds, therefore detailed investigation on the physiology of germination are required to optimize the use of seed. The optimum conditions of germination were determined at different temperatures (15, 20, 25, 30 and 20/30 deg C), media (top of the paper, between paper and sand) and light (continuous light and darkness and 8/16 hr cycle) on one batch of seed collected from Manali. A second batch of seed collected from Chakrata, Manali and Sangla Valley was germinated on a Thermogradient Plate (TGP) at constant temperatures ranging from 14 to 34 deg C at 2 deg C intervals and at five alternating temperatures, viz., 10/20 (16-8 hr), 15/25 (16-8 hr), 15/30 (16-8 hr), 20/30 (16-8 hr) and 20/30 deg C (12-12 hr). The optimum conditions were evaluated in terms of germination percentage, Germination Value (GV), Mean Germination Time (MGT) and Rate of 50% Germination (RG sub 50). The first batch of seed exhibited significantly higher maximum germination percentage, GV and minimum MGT at 25 deg C. The top of paper (TP) resulted in significantly (p=0.05) higher germination than Between Paper (BP) and sand media. Seed germinated both in light and in total darkness showed that 8 hours light had significant beneficial on germination, GV and MGT. The statistical comparison of TGP experiment data revealed constant temperatures at par or superior to the alternating temperatures in germination, GV, MGT and RG sub 50. Of the three sources, the seed lots from the outer or middle Himalayas, i.e., Chakrata and Manali, respectively, germinated best at 24 deg C. U. wallichiana is one of the tropical highland species which has a relatively high temperature requirement for germination. A slight difference in temperature requirements appears somewhat related to the severity of low temperature from the origin of the species