Factors Influencing Seed Germination and Seedling Survival of Rhododendron Subgenus Hymenanthes

Because most of the species of Rhododendron Subgenus Hymenanthes locate at high altitude in southwest of China,it is very difficult for us to collect and plant them.However,semination and seedling growth are used to solve this problem.Experiments indicate that:(1)Temperatures of environment and the systematic position of species have certain influence to the speed of seed germination.The germination speed is faster with the temperature rising when the average temperature is below 20℃.Among the four subsection of which we have ample materials for testing,subsect.Fortunea has the fastest germination speed,subsect.Pontica has the slowest germination speed,while subsect.Argyrophylla,subsect.Irrorata have the germination speed in between.(2)The rate of emergence and survival,the growth of young plant are closely correlated with the media of semination,the producing area,source and the systematic position.The medium for higher rate of emergence is humic soil,but the best medium for rate of survival and the growth of young plant are humic soil plus moss.In effect of seedling growth,the plants from east China,south China and central China are better than those from southwest China,and the plants from Japan and North American are prior to those from Europe.Domesticated plants are better than native ones.The species distributed in the east have better effects of seedling growth than those in southwest.(3)Because of the humid and cool environment at Lushan,it is suitable to propagation of Rhododendron Subgenus Hymenanthes and growth its seedlings there.The management during seedling growth,the prevention and cure of Rhizoctonia solani are critical to success of propagation.