| The drought resistance mechanism of Castanopsis fissa seedling was researched in this paper in nine indicators:the seedling height growth, diameter growth, hydrogen peroxide enzyme (POD),malondialdehyde (MDA),chlorophyll content, net photosynthetic rate, stomatal conductance, transpiration rate and intercellular CO2concentration. The drought resistance mutation of Castanopsis fissa was screened through the ISSR molecular markers technology. The results were as follows:1. Drought stress had obvious effects on morphological characteristics of Castanopsis fissa seedling. With increase of drought stress, Castanopsis fissa leaf wilting phenom, enon began to appear.And the leaf blight all started from old leaves. With increase of drought stress, Castanopsis fissa seedlings leaves became smaller, fewer, and the growth slowed down. Drought stress had more sensitivity to the height growth than to the diameter growth of Castanopsis fissa. The less soil water, inhibiting of height growth was more obvious.2. Variation of protein content in leaves was not sensitive to drought severity. It could not be used to define an indicator of drought resistance of Castanopsis fissa.As the drought time passing, the POD ratio activity rised first, then went downward. As the drought degree increasing, range of POD ratio activity rised. POD activity ratio was sensitive to drought stress. The moment when POD activity ratio fell can be used to define the length of time when Castanopsis fissa are under drought stress. For regarding POD activity ratio as the indicator in the study of leaf oak drought-tolerant, it needed a long time for observation and comparison.As the time of drought stress on the leaf of oak went on, MDA content in leaves gradually increase. With the increase of drought degree, increasing speed of MDA content became faster. Big oak leaf MDA content change was sensitive to drought stress degree. Using the change of MDA content as the indicator to determine the level of Castanopsis fissa persecuted by the drought stress levels and determines its hurt time was more accurate.3. As the drought time passing, chlorophyll relative content of the Castanopsis fissa leaves decreased first, then increased. Drought stress leaded net photosynthetic rate of Castanopsis fissa leaf to decrease.With increase of drought stress, the effect of drought on net photosynthetic rate was more obvious. With longer duration of drought stress, Castanopsis fissa leaves stomatal conductance decreased first, then increased. But the Castanopsis fissa seedling leaf stomatal conductance was not sensitive to the degree of drought stress. Affected by drought stress, transpiration rate of oak leaf is restrained. With increase of drought stress, the inhibition of transpiration rate enhanced. Intercellular CO2concentration in drought stress group and matched group had no significant difference. Along with drought stress effecting, change of intercellular CO2concentration in Castanopsis fissa was small, so the intercellular CO2concentration could not be the indicator of the degree of drought stress.4. According to the criterion that the change trend of all the indicators under drought stress could be deduced by measuring one of the indicators, minimum of4set of indicators were selected:(1) seedling height, protein content and chlorophyll content;(2) the diameter, protein content and chlorophyll content (3) protein content, stomatal conductance and chlorophyll content,(4) protein content, net photosynthetic rate and chlorophyll content.5. Selected drought-resistant plant Numbers were13,57,70,85,70,85; hypo-drought-tolerant plants Numbers were:1,5,21,43,58,60,66,76,66,78,82,89,92,93.6.10ISSR primers generated154legible bands, of which140were polymorphic, the percentage of polymorphic bands was90.91%. Amplified bands of molecular weight were100bp-3700bp. In10primers,857primers amplified polymorphic point, point, percentage of polymorphic loci were the largest, the percentage of polymorphic loci reached95%. The indicated that Castanopsis fissa selection with genetic basis of wide, high levels of variation, survival potential of adaptation to the environment.7. According to the genetic similarity, cluster analysis of94Castanopsis fissa were showed as follow:with the threshold value of0.77,94Castanopsis fissa could be divided into six classes. Drought-resistant plants distributed in the first and the third class, hypo-drought-resistant plants distributed in first class, second class, third, fourth and sixth class.8. according to the stripe arrangement characteristic expanded from94Castanopsis fissa plants, primers of single drought-resistant plant could be selected directly from94Castanopsis fissa plants. The maximum number of drought-resistant plants (all except No.13) could be selected according to840primer. Under the principle of using least primers to distinguish all drought-resistant Castanopsis fissa plant, selected primer combinations to build fingerprint of drought-resistant big oak leaf plant were (1)835+840;(2)840+844. |
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