关键词: 核桃属, 展叶期, 抗寒性, 电导法, 半致死温度, 叶片解剖结构

Abstract: 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.

Key words: Juglans, leaf-expansion period, cold resistance, electric conductivity method, semi-lethal temperature, leaf anatomical structure