Growth Regulation Of Plantlets And Formation And Development Characters Of Pseudobulbs Of Cymbidium Hybridium

Cymbidium hybridium is an evergreen perennial herbs belonging to genus ofCymbidium (Orchidaceae).It has become one of the most popular orchids in the worldbecause of its great shape, colorful and long-life flowers. Now the market of C.hybridium became bigger and more companies enter this production in China. But thereare still some problems hindered the development of production of C.hybridium such aslong-growth period and high cost. Plant tissue culture is the main multiplication way ofC.hybridium. To solve the problems in the plant tissue culture was important forpromoting growth and development and improving quality of plantlets. Pseudobulb is animportant organ for storage water and nutrition and multiplication of C.hybridium. It issignificant of the research on growth and development of pseudobulbs for improvegrowth and development of plantlet and flowering control. In this thesis, cultivar 4073was tested to investigate the effects of high PPFD and high CO₂ concentration on growthand development of plantlets by auto-control system of gaseous micro-environment forplant tissue culture. And systematic study with cultivar 4021 on induction, growth anddevelopment of pseudobulbs, and histological, physiological and biochemicalcharacteristics during pseudobulbs formation was carried out. The results are as follows.1. It indicated that the growth and development of plantlets was promoted andphotosynthetic capacity and plantlets quality of plantlets in vitro of C. hybridium couldbe improved. It was found that compare to the common culture condition, dry weight,growth of roots, root vigour, content of chlorophyll a/b and soluble saccharide ofplantlets in vitro of C. hybridium were increased 32%,29%,63%,73% and 6% under1000μmol·mol^-1CO₂ and 105μmol·m^-2s^-1 PPFD after 30day's culture. And thephotosynthesis rate was promoted 7 times than plantlets' in common culture conditionafter 50 day's culture.2. The research of plant growth regulators, nutrition, sucrose and temperature onformation of pseudobulbs of C.hybridium in vitro was carried out. The result indicated that 50mg·L^-1SA and 1.0mg·L^-1PP₃₃₃, Hyponex NO.3 culture medium, 40g·L^-1sucrose,15/25℃fluctuating temperature can improve the development of pseudobulbs.3. Using Response Surface Methodology to optimize the medium with sucrose,salicylic acid and Hyponex NO.3, the three factors had the effect on the induction rate. Itcame into conclusion that optimal combination of sucrose, salicylic acid and HyponexNO.3 were 48.74g·L^-1, 44.76mg·L^-1, 3.32g·L^-1, and in this condition the predictableinduction rate was 65.28%.4. Histological study on the pseudobulbs formation and development showed that,the histoligical structure included epidermis, cortex and vascular cylinder. Epidermalcells consisted of one layer cells of closely arranged with thickened outer walls. Groundcells consisted of water-storage and assimilatory cells. There is none vascular bundles inground tissue about 20 layers cells near epidermis. But inside there were numbers ofvascular bundles which were collateral vascular bundles scattered in ground cells. Starchgrains scattered in ground cells near vascular bundles. There were lots of starch grains inprotocorms and pseudobulbs, while a little of starch grains in rhizomes. The formation ofpseudobulbs was a process of increase of vascular bundles from inside to outside.5. Changes of content soluble saccharide, soluble protein and starch correlated withthe process of pseudobulb formation and development. The development of fromprotocorm to rhizomei, content of soluble saccharide and starch decreased 80% and 76%respectively, so it was a course of nutrition consumption to improve growth anddevelopment. The development of from rhizomei to pseudobulb, content of solublesaccharide and starch increased 14% and 212%, so it was a process of nutrition storage.During the whole period, content of soluble protein of protocorm and rhizomei werehighest, and other stages were lower.This indicated that protocorm accumulated a lot ofnutration for growth of plantlet, and during rhizomei stage plantlets had high metabolicactivity. By analysis Electrophoretic patterns of the proteins during the development ofpseudobulbs of SDS-PAGE, it was found that, there was 105KD specific protein in laterpseudobulb stage.