核桃属植物休眠期的抗寒性鉴定

Assessment of Freezing Tolerance of Juglans Germplasms by Using Annual Dormant Branches

以核桃属（Juglans）中的普通核桃、核桃楸、河北核桃和黑核桃4个种的18份种质休眠期的1年生枝条为试验材料，采用电解质渗出率法、组织褐变法及氯化三苯基四氮唑（TTC）染色法并配合Logistic方程确定枝条的低温半致死温度（LT50）；分析了LT50与枝条解剖结构之间的相关性。结果表明：随着处理温度的降低，休眠期各核桃种质1年生枝条的相对电导率（REC）均呈上升趋势；供试种质问抗寒性差异大，LT50在-38—-22℃之间；种间抗寒性差异明显，依次为黑核桃〉核桃楸、河北核桃〉普通核桃。电解质渗出率法、组织褐变法及TTC染色法均可用于休眠期核桃属植物的抗寒性鉴定，尤其以电解质渗出率法准确度高。用略高于大部分核桃种质LT50的温度（-24℃）处理枝条，其相对电导率与LT50之间达到极显著正相关，此温度处理下的相对电导率以及枝条的LT50均可作为休眠期核桃属抗寒性鉴定的理化指标。核桃属4树种1年生茎粗大致相同的枝条中各组织的厚度差异显著，其中木栓层厚度及其在茎结构中所占的比率与枝条的LT50之间达到极显著负相关，可作为休眠期核桃抗寒性鉴定的形态结构指标。

The test materials were annual dormant branches of 18 Juglans germplasms that belong to 4 species including J. regia L., J. hopeiensis Hu., J. mandshurica Maxim., and J. nigra L. The semi-lethal temperatures （LT50） were assessed separately by electrolyte leakage, tissue browning, and triphenyl tetrazolium chloride （TTC） dyeing method with Logistic equation. Branch anatomical structures were observed with paraffin sections. The correlations between branch anatomical structures and freezing tolerance were analyzed. The results showed that relative electrical conductivities （REC） of walnut annual branches were rising with the temperature drop. The significant differences of LT50 of Juglans germplasms were observed between - 38 ℃ and - 22 ℃. The interspecific differences were distinct, and the order of freezing tolerance was J. nigra 〉 J. mandshurica, J. hopeiensis 〉 J. regia. Electrolyte leakage, tissuebrowning, and TTC dyeing method all could be used for assessment of the freezing tolerance in dormant period, but LTs0 assessed by electrolyte leakage was more accurate than the other methods. There was significant positive correlation （P 〈 0.01 ） between LTs0 and REC at - 24℃, which was a little higher than LTso of the most Juglans germplasms. LTs0 and REC at - 24℃ could be used as physicochemical indexes for freezing tolerance identification of Juglans in dormant period. In addition, the tissues thickness of annual branches with roughly similar stem diameter had significant differences. The significant negative correlation （P 〈 0.01 ） was showed between LTs0 and phellem layer thickness or phellem layer ratio in the branch, which provided morphological indexes to assess the freezing tolerance of Juglans in dormant period.