Research Of Resistance To Temperature Stresses In Different Provenances Of Betula Alnoides Buch Ham

Chen Zhigang (Silviculture)Directed by Prof. Zheng haishui & associate Prof. Chen Qingdu In accordance with the global climate changes, temperature abnormality has occurred in recent years in some regions in China. The influences of such abnormality on tree growth are increasingly drawn attentions of foresters and the related communities. In this paper provenance variation of resistance to temperature stresses in Betula alnoides Buch Ham was studied. A total of twelve provenances collected from Guangxi and Yunnan provinces in China were employed, and such physiological factors as the conductivity, the net photosynthetic rate, the transpiration rate and the root system activity under the temperature stresses as well as anatomical structure of leaf were analyzed. The measures for improving the seedling resistance to temperature stresses were also preliminarily screened. The results are showed as follows.1) the conductivity, net photosynthesis rate, transpiration rate and the activity of root system all have apparent changing rules under the prescribed temperature gradients. -3℃ and 50℃ are two typical temperatures on behalf of low-temperature stress and high-temperature stress respectively, under which the inter-provenances differences reach a distinct level. Therefore, the above four factors can be used to measure the resistance of temperature stresses.2) Leaves structure of different provenances vary greatly in the thickness of keratoid layer, epidermal layer, palisade mesophyll, spongy mesophyll and the stomatal density. The CTR value is negatively related to the temperature of growing site and the SR value is positively related to it, which is an evidence for the plant to adapt to the environment. 3) Integrative analysis for the physiological factors and anatomical structure shows that, among the 12 provenances of Betula alnoides Buch Ham tested, K,D,G,B are those that are more cold-resistant, while F,A,C,K are the ones that are more hot-resistant. Among them, K shows strong resistance in both low and hot temperatures, and can be recommended as an excellent provenance. 4) In the aspect to improve the cold resistance of Betula alnoides Buch Ham seedling, apparent results are obtained with three pre-treatment methods( ABA,PP333,citric acid). In the case of ABA, 10-6mol/L, 24hr is the best; as to PP333, 1/1000 is the best concentration with a treating time of 36 hr; while to citric acid, treatment with concentrations from 1/1000 to 4/1000 also show good resistance to low temperature stress. As to the methods in improving its hot resistance, good results of salicylic acid treatment are obtained, 10-5mol/l,24hr is the best model. Seedlings with mycorrhiza have more apparent resistance to temperature stresses than those without, that is, good results shows in its cold resistance and heat resistance.