低温胁迫下佛手半致死温度测定和抗寒性分析

 以‘青皮’和‘矮化’佛手(Citrus medica var. sarcodactylis Swingle)为试材，测定不同低温下处理24 h后，叶片的电解质外渗率(REC)，计算半致死温度(LT₅₀)；在半致死温度下设置不同处理时间，测定REC、超氧化歧化酶(SOD)活性、游离脯氨酸(Pro)和丙二醛(MDA)含量，进行抗寒性分析。结果表明：佛手REC随温度降低及处理时间延长呈“S”形上升， LT₅₀在-4~ -5℃之间；在LT₅₀下，随着处理时间的延长SOD活性呈先上升后下降的趋势， Pro和MDA含量逐渐上升；12~ 24 h为佛手在LT₅₀下冷害发生的临界时间。

Semilethal Temperature of Fingered Citron (Citrus medica var.sarcodactylis Swingle) under Low Temperature Stress and Evaluation on Their Cold Resistance

The semilethal temperatures (LT₅₀) of two cultivars of fingered citrons (Citrus medica var. sarcodactylis Swingle), C. medica 'Qingpi' and C. medica 'Aihua', were calculated and their resistance to low temperature stress were evaluated. The relative electric conductivity (REC) in leaves of the two cultivars were determined and their semilethal temperatures (LT₅₀) were determined after the plants had been treated under a series of low temperatures for 24 h. Then the REC, superoxide dismutase (SOD) activity, the malondialdehyde (MDA) and free proline (Pro) contents were analyzed under LT50 after a serial treatment period. The results showed that the REC of the both cultivars increased following an S-curve with temperature drop and treatment length and the LT₅₀ was between - 4 and - 5℃. The activity of SOD increased at the beginning of cold treatment at LT50 then decreased afterwards. Concentrations of MDA and the Pro gradually increased with time of low temperature exposure. 12~ 24 h was considered to be a critical period for cold injury of C. medica under the LT50.