核桃属4 树种展叶期抗寒性鉴定

 以普通核桃（Juglans regia L.）、核桃楸（J. mandshurica Maxim.）、河北核桃（J. hopeiensis Hu）和黑核桃（J. nigra L.）4种核桃属植物的20份种质展叶期叶片为试验材料，采用电导法并配合Logistic方程确定其低温半致死温度（LT₅₀）；分析了LT₅₀与叶片解剖结构之间的相关性。结果表明，随着处理温度的降低，核桃叶片的相对电导率（REC）均呈上升趋势；供试核桃种质间的抗寒性差异较大，低温半致死温度在–8 ~ 2 ℃之间，在黑核桃、核桃楸及普通核桃中均有抗寒性强的种质资源。利用略高于大部分核桃种质LT₅₀的温度（0 ℃或–3 ℃）处理叶片，其相对电导率与低温半致死温度之间达到极显著正相关，而且相关系数高，此温度下处理12 h后叶片的相对电导率以及叶片的LT₅₀均可作为鉴定展叶期核桃种质抗寒性强弱的物理指标。核桃属不同种间的叶片结构类似，但各有特点。栅栏组织厚度和叶片总厚度与其LT₅₀之间均达到极显著负相关，可作为核桃叶片抗寒性鉴定的形态结构指标。

Evaluation on Cold Resistance of Four Juglans Species in Leaf-expansion Period

The test materials were leaves in leaf-expansion period of 20 Juglans germplasms that belong to four species including J. regia L.，J. hopeiensis Hu，J. mandshurica Maxim.，or J. nigra L. The semi-lethal temperatures（LT₅₀）were estimated by electric conductivity method with Logistic equation. Leaf anatomical structures were observed with paraffin section. The correlations between leaf anatomical structures and its cold resistance were analyzed. The results as follows：The relative electrical conductivities（REC）of walnut leaves were rising with the decrease of the temperature. There were great differences in cold resistance of Juglans germplasms in leaf-expansion period. The semi-lethal temperatures of leaves were from–8℃to 2℃. There were cold resistant germplasms among J. nigra L.，J. mandshuria Maxim. and J. regia L. in leaf-expansion period. There were significant positive correlations（P < 0.01）between the LT₅₀ and REC of leaves treated at 0 ℃ or–3 ℃，and the correlation coefficients were high. LT₅₀ and the REC of leaves treated at 0 ℃ or–3 ℃ for 12 h could be used as physical indicators for cold resistance of Juglans leaves. The main structures of Juglans germplasms leaves were similar，meanwhile there were some specific characteristics for each species. There were significant negative correlations（P < 0.01) between LT₅₀ and the thickness of palisade tissue or leaf blade. The thickness of palisade tissue and leaf blade could be anatomical structure indicators for cold resistance of leaves.