| Browning is a serious problem in in vitro culture of flower stalks in Cymbidium longibracteatum.Browning rate was not only affected by the internal factors,such as the flower stalk number,maturity of the explants,but also by external factors,such as the growth environment,explant isolation month,the way of laying,anti-oxidants,absorbents, dark culture and heat shock,Fe salt,and so on.The studies presented in this dissertation were designed to analyze the internal and external factors affecting browning of the explants to establish an in vitro culture system using the flower stalks for explants.The main results are as follows.1.Single node with bracteal leaf on semi-embedded medium,or single node in the middle and top section without bracteal placed flat on the plane medium,multiple nodes with bracteals placed on semi-polar embedded slant medium could effectively reduce browning and allow explants to live longer.2.Single node in the middle and top section isolated in February could effectively reduce browning.3.The browning rate rosed with the increase of concentration of activated charcoal and PVP in the media.4.Citric acid and ascorbic acid had a good effect on browning inhibition;2g / L(ascorbic Acid) and 5g / L(citric acid) were the best concentrations,respectively.However,the use of sodium thiosulfate was not as effective as that of control.5.Cut-end sealing had the best result of browning prevention;sealing using medical Vaseline was more effective than paraffin.6.The browning rate was smaller on 1/2 MS medium than on MS and 1/4MS.7.56℃15S thermal shock could effectively reduce browning rate,but when the temperature was over 56℃the browning rate increased with the increases of temperature and exposure time.8.Browning rate was slightly lower,the explants remained greener and the survival time extended in Fe salt doubled medium.However,adding 4 times Fe salt to the medium gave rise to browning rate increase.9.Dark culture for 20d could effectively reduce browning rate.
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