Studies On Light Adaptation And Genesis Improvement Of Pharmaceutical Dendrobium

Dendrobiums, perennial herbages in orchidaceae family, normally grow in shadow environment as facultative CAM plants. Wild resources of many species in dendrobium genus, as medicinal plants and rare traditional Chinese medicines, are approached in exhausted or endanger because of manmade effect and non-limited utilization. Although artificial cultivation of dendrobium is useful for protecting wild resources and satisfying medical demand, artificial cultivation techniques are still no success because there are no systemic research on cultural physiology, adaptive mechanism for light intensity and genesis improvement of dendrobium. In this research, phenological phase, companion plants, relation between stem growth and ecosystem factors are conducted to study light adaptive mechanism of facultative CAM plants and physiological bases of artificial cultivation in 3 dendrobium species in Huoshan County, Anhui Province. Genesis improvement of dendrobium is also researched through comparison study of growth, physiological characteristics, available components, structure and function of polysaccharide complex between F₁ generation and parents in dendrobium. The results are as follows:1. Phenological phase of 3 dendrobiums in Huoshan is illustrated. Ecosystem factors affecting growth, correlations between growth and endogenous hormones and available companion plants for dendrobium had been indicated.There are different in phenological phase of growth and development among three dendrobiums in Huoshan. Sustainable growth time of new stem for D. huoshanense, D. candidum and D. moniliforme is 150 days, 154 days and 160 days respectively, and growth curve of stem height and diameter is 'S' type. Growth procedure of D.candidum and D. moniliforme has two growth peaks from May to August and late August while D. huoshanense has only one from May to July.Ardisia japonica, Selaginella tamariscina, Lepisorus thunbergianus, Pyrrosia lingua, Pyrrosia petiolosa, Ptychomitrium linearifolium, Thuidium cymbifolium, Claopodium assurgens and Lichen are available companion plants for dendrobium cultivation, which were found through wild dendrobium community investigation.Environment of RH 80% is available for dendrobiums growing, and high light intensity, high temperature and low RH will influence growth of dendrobium. The annual accumulated temperature is 2070'C, 2256 °C and 2248 *C respectively for effective growth of D.Huoshanense, D.candidum and D.moniliforme. The most optimal temperature for growth of D. Huoshanense and D. candidum is 16°C²0"C as well as 19 °C ²2"C for D. moniliforme. Feasible precipitation is necessary for dendrobium growth.There is a significant positive correlation between content of endogenous GAi+3 and stem growth of dentrobiums in Huoshan, as well as a significant negative correlation between content of endogenous ABA and stem growth of dentrobiums in Huoshan. Suitable GA1+3/ABA is important factor affecting stem growth of dentrobiums in Huoshan. Low GAi+yABA in D. huoshanense may be one of reasons to grow slowly.2. Mechanism easily damaged by intensive light for dendrobium is illustrated through studying relation between parameters of chlorophyll fluorescence and light intensity; and effects of light intensity on dendrobium photosynthesis are systemically studied, which provide the foundation for selecting optimal light intensity during dendrobium cultivation.Their light saturation point, net photosynthesis rate, apparent quantum yield, carboxylation efficiency and RuBP recovering rate point are low during photosynthesis, light compensative point and CO2 compensative point are high during photosynthesis, which is meaning that dendrobium is a plant for shadow responsibility on light intensity. Under cultivation environment of forest shadow, photosynthesis rate of dendrobium is reduced gradually. Daily change of photosynthesis for dendrobium shows V type and there is the lowest photosynthesis at noon under natural light. Photosynthesis rate is negative value and there is no photosynthesis accumulation from 9:00 A.M. to 17:00 P.M. because light intensity is higher than 800 u mol photons-m^s"1, as well as there is photosynthesis accumulation only during low light intensity on morning or night. Suitable tight intensity for photosynthesis of dendrobiums in Huoshan is 400 u mol photons-m"2s"1⁶00n mol photonsm^s*1 normally.3. Dendrobim genesis improvement is achieved through dendrobium cross. The researching results primarily illuminate that Fi generation of cross dendrobium has not only hybrid advantage and cultivation significance, but also significant economic benefit.D. Huoshanense (male) has better quality and lower yield while D. moniliforme (female) reverse, so they are selected as parents for interspecific hybridization. Fresh weight of annual stem of Fi generation is as 4.23,1.08 times as ones of A Huoshanense and D. moniliforme respectively; yield of it is as 3.91,1.11 times as ones of D. Huoshanense and D. moniliforme respectively. Available medical and nutritive components of Fi generation are higher than D. moniliforme and almost similar with D. Huoshanense. Physiological characters of Fi generation are greatly improved with wide adaptivecapacity and high photosynthesis for Fi generation has more photosynthetic area, higher content of chlorophyll, lower chla/b rate, higher light saturation point, lower light compensative point, higher carboxylation efficiency and net photosynthesis rate than its' parents. Content of endogenous hormones in Fj generation is intervened parents. Rate of GAi+3/ABA and ZR+GA1+.3 /ABA in Fi generation is almost similar with D. moniliforme, which is one of reasons why growth quantity of Fi generation approaches D. moniliforme. Not only does Fi generation integrate characteristic enzyme spectrum of parents and express hybrid characters from their POD and EST isoenzyme spectrum, but it form itself specific isoenzyme spectrum. All results indicate that Fi generation expresses advantages on physiology.4. Composition and effects cleaning up oxygen free radical of polysaccharide from Fi and parents are similar, which further proofs dendrobium improved through hybrid.Polysaccharide extracted and purified from Fi and parents is a neutral polysaccharide or a complex of polysaccharide and protein containing glucuronic acid and protein without reductive sugar. The monosacchride composition of polysaccharide in D, Huoshanens and in Fi generation is similar mainly including L-Rha, L-Ara, D-Man and D-Glc, but their molar ratio is 0.087 : 1.000 : 102.000 : 79.500 in D. Huoshanens as well as 0.170 : 1.000 : 81.900 : 52.100 in Fi generation. Polysaccharide in D.moniliforme is mainly composed of L-Rha, L-Ara, D-Xyl, D-Man and D-Glc, and their molar ration is 0.400: 1.000: 1.510: 63.000: 35.400. The results mean that composition characters of polysaccharide complex in Fi generation have no big variation and are similar with parents.Dendrobium polysaccharides have certain inhibitory action on OH and O2' within experimental concentration range, and their inhibitory actions increase with the raising of concentration. The inhibitory concentration of 50% (IC50) on OH of polysaccharides in D. Huoshanens, D. moniliforme and Fi generation is 6.79 mgml"1, 6.75 mg-ml"1, 7.09 mgml"1 respectively and their IC50 on O2 * is 3.04 mg-ml"1, 3.44 mg-ml"1, 3.02mg-ml"1 respectively. Moreover, dendrobium polysaccharides have inhibitory action on lipid peroxidation of mice liver homogents in vitro and can alleviate oxidation damage of mice liver mitochondria induced by Vc-Fe2+ system. The results means that polysaccharide function for oxygen free radical clearance in Fi generation is similar with parents and hybrid has no damage on capacity for polysaccharide cleaning oxygen free radical.