Seed Germination and Dormancy of Psychotria gerdneri as a Dominant Forest Species of Tropical Montane Forest in Sri Lanka

Abstract

Tropical Montane forest in Sri Lanka is rich in endemism and biodiversity. However most ofmontane forests are degraded as result of natural and anthropogenic activities. SincePsychotria gardneri is a very dominant endemic species in Sri Lankan montane forest,knowledge of seed germination and seed Dormancy is very essential in restoration activities.

Fully ripen seeds of P. gardneri were collected from Hantana forest range (altitude: 1,000-1,250 m). Seed: embryo ratio was taken of ripen and germinated seeds, water imbibition ofseeds of non-scarified and manually scarified were measured and tests of standardgermination and gibberellic acid (GA) treatment were conducted to identify the dormancyclasses. Seed germination under light/ dark and dark condition were tested to identify thegermination requirement.

Embryo: seed ratio of ripened seeds and germinated seeds was 0.5 and 0.7 respectively.Water Imbibition pattern was similar in both non-scarified and manually scarified seeds. Seedstarted their germination within 15 days and 50% of seeds germinated within 65 days forstanders germination. 53% of seeds germinated within 28 and 38 days respectively for 100ppm and 500 ppm of GA. Under the fully dark condition 57% seeds germinated within 56days.

P. gardneri has a combination of morphological and physiological dormancy. 100 ppm GA isa suitable treatment for breaking the physiological dormancy. Although Light is not agermination requirement, dark condition has enhanced the germination of P. gardneri. If weuse bulk of seed to get seedling of P. gardneri for restoration purposes, treating of seeds with100 ppm GA is a best option. If not seeds should be sown in more than 65 days in wetmedium.