Comprehensive Evaluation Of Heat Tolerance Of Half-sib Families Of Ginkgo Biloba L.

In past years, extremely high temperatures occured frequently, this is a serious threat to the growth of plants. Ginkgo (Ginkgo biloba L.) is a multi-value deciduous tree species for the production of nuts,timber and leaves. To study heat resistance of Ginkgo is important to the introduction and cultivation of the tree species.To determine the reactions of physiological and biochemical characteristics, 38 Half-sib families of Ginkgo were used to grow in a pot. Using artificial climate chamber, we make the intermittent use of high-temperature-stage to simulate natural high temperature on the impact of Ginkgo. Heat indexes and heat resistance of Half-sib families of Ginkgo were evaluated. The results were shown as follows:1. High temperature has a significant impact on the membrane permeability and SOD activity. After high temperature stress, permeability of the membrane increased, the lipid per oxidation occurred, MDA content increased, scavenging system of SOD in the protective effect was strengthened. The water content of 38 Half-sib families of Ginkgo in leaves is declining. The free water content was decline; bound water content was increased, the ratio of bound water /free water was increased and the difference between 38 Half-sib families of Ginkgo was significantly.2. The content of soluble sugar, soluble protein and proline responsed to 45℃temperature treatment. The soluble sugar content of 33 families of Ginkgo increased significantly; the proline content of all the families increased and the differences between families increased with the increase of temperature. Relatively, the soluble protein content increased a little.3. Photosynthesis of 38 families of Ginkgo had a marked response to the heat stress. The high leaf temperature led to the closure of some stomatal, the CO₂ concentration of leaf cells reduced, the net photosynthetic rate decline and affected the normal growth of Ginkgo. The transpiration rate decline and its drop were related to the decline of stomatal conductance. The chlorophyll content and Chla/Chlb ratio hadn't changed regularly in the heat stress.4. The heat resistance of Ginkgo is a multigenic trait. Through relevant analysis, the six indicators of relative conductivity, MDA, SOD activity, the leaves water content, soluble protein and net photosynthetic rate can be used to screen and evaluate index of heat resistance Ginkgo, the corresponding regression equation was established: y=-0.06871-0.00610X₁-0.0392 0X₂+0.02678X₃+0.42523X₅+0.07607X₆+0.13379X₉, and the correlation coefficient achieve a significant level.5. Using the principal component analysis and cluster analysis, 38 half-sib families of Ginkgo were divided into heat-sensitive, medium-and heat-resistant-3 rating. Heat-sensitive half-sib are:53#,33#, 15#,40#, 14#,43#,45#,39#,26#, 19#, 18#,44#,50#,9#, 17#; medium-resistant half-sib are:20#,55#,13#,21#,38#,11#,37#; and heat-resistant half-sib are:30#,57#,12#,29#,54#, 42#,56#,16#,28#,10#,27#,41#,32#,35#,34#,31#,respectively.