Seed Biology Of Dendrobium Sinense, An Endangered Epiphytic Orchid

Dendrobium is the second genus of Orchidaceae, which has important ornamental and medicinal value. However, due to climate change, habitat fragmentation and artificial excessive digging by human activities, wild Dendrobium plant resources reduced drastically. Dendrobium sinense is an endangered epiphytic, Hainan endemic species, due to its harsh requirements of the living environment and the plant itself complex breeding system, resulting in the wild species is extremely scarce. And the seeds as the most basic breeding material of D. sinense, which has the large number of , made it is of great significance by related biological research on D. sinense conservation.In this paper, the seed biological characteristics of D. sinense were studied in four parts: the seed morphology, the determination of vitality, the seed preservation and Asymbiotic germination germination. The results were as follows:(1) Seeds morphologySeed morphology was observed by the technique of microscopic. The length of the seeds was 0.273±0.016mm,the width was 0.096±0.006mm,the volume was 0.65±0.005mm3, the embryo was 0.167±0.013mm,the embryo width was 0.077± 0.005mm,the embryo volume was 0.53 ±0.005mm3, the ratio of embryo and seed volume was 0.81±0.03, and one capsule contained 12～24 million seeds. D.sinens is a medium～sized seed in Dendrobium.(2) Determination of seeds vitalityThe seed vitality of D. sinense was determined by TTC method and ultraviolet spectrophotometer. TTC reasonable staining method for seeds is using 5% Ca(CIO)2 soaking 120min or 2.5% NaClO soaking 60-90min, and then staining 24h using 1% TTC in dark,but the better effect of using 5% Ca(C10)2. UV spectrophotometry method to determine the soaking 4h absorbance value can best reflect the seed vitality.(3) Seeds preservationThe colored silica gel, anhydrous lithium chloride and rice flour were used to storage the seeds of D. Sinense. Silica gel and anhydrous lithium chloride can be used to storage the seeds of D. Sinense. Low water content suitable for storage the seeds of D. Sinense, the range of storage temperature with 4% water content is wider, and the vitality is best kept for storage at -20 ℃. Low temperature suitable storage the seeds of D. Sinense,and the optimum temperature for storage is affected by the moisture content of the seeds. The 35.4% of water content seeds should not be stored in the environment of -20℃, 8.9% and 18.9% were suitable for storage in 4℃,while the 4% water content of the seed were suitable for storage in -20℃. The seeds of D.sinense are normal seeds.(4) Asymbiotic germination of the seedsThe asymbiotic germination of D. sinense was studied from the MS medium concentration, the type and concentration of hormones and the species of plant additives.The seed germination and protocorm growth of D.sinense were the best by use 1/2MS.The effects were significant on the germination and protocorm growth of D. sinense used different hormones and different concentrations, 0.5 mg/L NAA was the best. The effects of different plant additions on the seed germination and protocorm growth of D. sinense were different. 10% potatoes homogenate, coconut water and banana homogenate significantly promoted seed germination, while only 10% banana homogenate promotes the growth of protocorms, leaves and roots.