高温胁迫对华石斛幼苗的形态和生理参数的影响

摘要

华石斛为海南特有兰科植物,原产海南海拔1 000m以上的云雾林或山地雨林.为研究高温对华石斛生长的影响,本试验测定了昼/夜(10h/14h)温度梯度(25/20、30/25、35/30、40/35℃)的人工气候箱中生长1、2、4、8d以及解除胁迫15d(恢复生长)后华石斛幼苗的形态和生理生化指标.结果表明:高温30℃和35℃处理1d时,形态和各项生理生化指标变化不显著,幼苗没有受到热害.30℃和35℃处理2～4 d和40℃处理1～2 d时,细胞膜稳定性遭到破坏,导致膜脂过氧化,相对电导率、MDA含量升高,SPAD值下降,此时植物通过增加可溶性糖、可溶性蛋白含量,提高SOD、POD活性进行自我调节.30、35℃处理8d和40℃处理4d时,各项生理指标急剧下降,膜系统和抗氧化酶系统遭到破坏,植物受到严重热害.40 ℃处理8d时,95％的幼苗褐化死亡.不同处理天数下温度均与相对电导率和MDA含量呈极强正相关,与SPAD呈负相关.研究认为,相对电导率、SPAD、MDA可作为鉴定华石斛幼苗耐热性的参考指标.%High temperature is a major bottleneck in the cultivation of Dendrobium sinenese habiting the tropical cloud forest or montane rainforest with altitudes above 1 000 m in Hainan Island,China.To investigate how D.sinense responses to heat stress,morphological and physiological indices were measured for the seedlings grown under four temperatures,i.e.,25/20 (control),30/25,35/30 and 40/35 ℃ and a day/night cycles of 10h/14h for 1,2,4,8d,and recovery for 15d.Our results showed that no significant differences in morphological,physiological and biochemical changes were found in the seedlings under 30 ℃ and 35 ℃ for 1 d,while damage of cell membrane stability,resulting in membrane lipid peroxidation,increased relative conductivity and MDA content,and decreased SPAD value were observed under 30 ℃ or 35 ℃ for 2-4 d or 40 ℃ for 1-2 d.However,the damaged seedlings were still able to recover through increasing the content of soluble sugar and soluble protein,and raising the SOD,POD activities.Severe heat damages on the membrane system and antioxidant enzyme system indicated by sharply decreases in physiological indices were observed in the seedlings under 30,35 ℃ for 8 days or 40 ℃ for 4 days.When being treated at 40 ℃ for 8 days,95％ of the seedlings turned brown and died.Our studies demonstrated that the relative conductivity and MDA content were positively correlated,while the SPAD value was negatively correlated with temperatures.Therefore,these three values could be used as heat tolerance index of D.sinense seedlings.