| In early 2008,the south of China suffered a exceptional continuous low-temperature snow storm and frozen rain in history,which caused serious damage to economic bamboos and ornamental bamboos.We urgently need intensive studies on cold resistance of bamboos. This study selected four species of City Ornamental Bamboo which are typical to Sichuan, and studied seven physiological indexes as Relative Conductivity, Chlorophyll, SOD, POD, MDA, Soluble Sugar and Soluble Protein under the natural temperature decreasing and the artificial low-temperature,to analysis their changes with temperature.Through Correlation Analysis and Principal Component Analysis,the correlation between indexes and the contribution rate were determined. By the subordination analysis, a comprehensive assessment of the cold resistance of four species of Bamboo was made.Analysis the relationship between cold resistance and Physiological index,to providing methods for the identification of cold resistance of bamboos,as well as the theoretical reference to reduce disasters and the induct new species of bamboo.The results show that,from 2005 to 2007,with the rise of winter temperature, the stalk diameter of B. multiplex cv.sliverstripe,B. chungii Muclur,P. aureosulcata appears a increasing trend. The low temperature in 2008 winter affected the bamboo shoots of these four kinds of bamboos. The low temperature has delayed the shoot time, while the number and diameter of shoots were also affected, and the number of shoots back was increased.B. multiplex cv.sliverstripe has the maximum ratio of shoots back, and has the strongest adaptability, while B. chungii Muclur has the minimum ratio of shoots back with the weakest adaptability.Under the natural temperature decreasing,the order of cold resistance of four species of Bamboo was made by the subordination analysis:B. multiplex cv.sliverstripe>P. aureosulcata>B.multiplex>B. chungii Muclur. Under the artificial low-temperature,it was:P. aureosulcata>B. multiplex cv. sliverstripe>B.multiplex>B. chungii Muclur.Under the natural temperature decreasing and the artificial low-temperature process, the relative conductivity of four bamboos increase with the decrease of temperature. The bamboos with strong cold-resistance have a lower.average relativre conductance than the bamboos with weak cold-resistance.The relative:conductance can be used as an index to evaluate bamboos' cold-resistance. After the calculation, the LT50 of these four bamboos were B. multiplex cv.sliverstripe -7.78℃>B.multiplex-5.77℃,B:chungii Muclur-1.74℃, P.aureosulcata -8.27℃.During the two temperature decreasing processes, the chlorophyll contents of four bamboos decrease with the decrease of temperature. The bamboos with strong cold-resistance have lower chlorophyll content change rates, while the bamboos with weak cold-resistance have a higher one.The chlorophyll content change rate can be used as an index to evaluate bamboos'cold-resistance.According to the two temperature decreasing experiments,SOD and POD can be proved that they are one kind of protection material to bamboos for their cold resistance. The bamboos who have strong cold-resistance have higher SOD activities and POD activities than the weaker ones. The activity of SOD and POD can be used as an index to evaluate bamboos'cold-resistance.During the two temperature decreasing processes, the MDA contents fluctuated with the decrease of temperature, and the total contents increased slowly.MDA contents reflect bamboos'cold-resistance. Under the low-temperature stress,the bamboos who have strong cold-resistance have lower MDA contents than the weaker ones.Under the natural temperature decreasing, the soluble sugar contents of four bamboos decreased after a increasing, and changes significantly with the temperature.Under the artificial low-temperature,the soluble sugar contents fluctuated with the decrease of temperature.The soluble sugar can act as a special regulating substance which take part in the physiology prosess of cold-resistance, and with the accumulation of the soluble sugar, the physiological reaction level of bamboos can be improved. The bamboos with strong cold-resistance have higher soluble sugar contents, and the bamboos with weak cold-resistance have lower ones. The soluble sugar contents can be used as an index to evaluate bamboos'cold-resistance.During the two temperature decreasing processes, the soluble protein contents of four bamboos increased after a decreasing, and have a significant relationship with temperature. The soluble protein contents also have affinity relationship between SOD,POD,MDA. It can be considered that soluble protein will take part in the physiological activities during the cold-resistance process, which provide substrate and base material for bamboos. And the soluble protein can be regarded as an important protection material during the process of cold-resistance, which has an important contribution to increase bamboos' cold-resistance. In the study, the bamboos with strong cold-resistance have higher soluble protein contents, while the bamboos with weak cold-resistance have lower ones.By comprehensive analysis, the result showed that monopodial bamboo P. aureosulcata shows a strong cold-resistance ability during low-temperature stress. In the other three clumping bamboos, B. multiplex cv.sliverstripe has the strongest cold-resistance ability, B.multiplex weaker than it, and B. chungii Muclur is the weakest. So P. aureosulcata and B. multiplex cv.sliverstripe can be promoted and introduced to the areas where have the lowest temperature above-7.78℃.B. chungii Muclur should have to be practiced in more low-temperature experiments to improve its' cold-resistance before it can be introduced smoothly to the cold areas.
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