Study On Rapid Propagation Of Dendrobium Officinale

Dendrobium officinale Kimura et Migo, belonging to Dendrobium SW.(Orchidaceae), isa perennial herbaceous plant, and it is one of the traditional rare medicinal herbs in China. Asits pharmacological functions are getting more and more consumers’ recognition, its marketdemand is growing larger and larger. In the past years, the supply of D. officinale mainlyrelied on the wild resources，which led people to excavate it excessively. In addition, itsnatural reproduction speed was extremely slow. As a result, the wild resource was under thethreat of extinction. Therefore, the realization of its rapid propagation is imperative. Thus, thisthesis mainly focused on the fruit growth of D. officinale germplasms after4different ways ofartificial pollinations, and tissue culture of D. officinale under different light and temperature.The main results were as follows:1. Artificial pollinations of D. officinale germplasms. Artificial pollinations of differentD. officinale germplasms were conducted using four different ways including autogamy,geitonogamy, crossing within germplasm and crossing between germplasms. The resultsshowed that:(1) Only a few of germplasms (29.73%) could be self-pollinated successfully,and there was significant difference in autogamy fruit-set rate among different germplasms.Most of the germplasms had relatively low fruit-set rate (<38.46%) by autogamy andgeitonogamy, and the fruit-set rate by crossing within germplasm was higher(35.71%-68.42%), however, it was still lower than that by crossing between germplasms.Almost all of the germplasms could be pollinated successfully between germplasms, and thefruit-set rate of most germplasms (64.29%) could reach to100%, which indicated thatself-incompatibility widely existed in D. officinale.(2) The fruit size of D. officinale becameslightely smaller at about120days after pollination, and then it would dehydrate a little andcrack afterwards. Thus, it was advisable to harvest the fruits at about120days afterpollination. There was no significant relationship between fruit size and the way of pollination.(3) For the germination rate and protocorm developmental speed, the seeds from crossingbetween germplasms were both better than that of the other3ways of pollinations, and theseeds from crossing within germplasm came to the second. In all, the offsprings of crossingbetween germplasms had better vitality.2. The effects of culture conditions on seed germination of D. officinale. The seedgermination and protocorm development under conditions of different light and temperature were investigated, and several results were obtained:(1) Seeds of D. officinale were easy togerminate (6-9DAS) as soon as their embryos develop completely and the medium wasnutrient-sufficient.(2) It was found that light had little effect on seed germination rate of D.officinale, however it could affect the protocorm development after seed germination.Protocorms could not develop normally in dark, and the speed of protocorm developmentdepends upon light sources and their intensity. The protocorms develop fast with increase oflight intensity under all light sources.(3) Using sunlight as the light source, the seedgermination rate differs under different temperature. Lower temperature (25℃) was suitablefor seed germination, and with the rise of temperature, the seed germination rate bame lower.3. The effects of culture conditions on the seedling growth of D. officinale. The seedlinggrowth was observed under conditions of different light and temperature. The results showedthat:(1) With the increase of light intensity, the seedlings grew better under all light sources.Seedlings grew robustly under higher light intensity of sunlight, then came the seedlings growunder LED, and seedlings grew poor under fluorescent light. Hybrid germplasms grow morestable than selfing germplasms under different light conditions, and the growth of tissueculture seedlings had affect on the survival rates after transplant.(2) The leaf chlorophyllcontent of seedlings grew under fluorescent light was significantly higher than those undersunlight and LED.(3) The leaf stomata of seedlings under sunlight were significantly greaterthan that in the evening during the day, and the difference was not obvious under the othertwo light sources. It implied that the stomata function was not completely lost when seedlingsgrew under sunlight.(4) The power consumption of sunlight culture room was lower than thatof fluorescent light culture room, and appropriate size of the culture room could help reducethe energy cost.(5) Using sunlight as the light source, the coordinated optimum temperaturefor growth of D. officinale seedlings was about27℃.