观赏山楂耐热性及其叶片光合与叶绿素荧光特性研究

Photosynthetic and Chlorophyll Fluorescence Characteristic of Ornamental Hawthorns under Summer Heat Stress

以引自国内外的15种观赏山楂苗木为材料,于上海夏季自然高温下对其叶片光合气体交换参数及叶绿素荧光参数进行测定,并观察它们的田间耐热性,以揭示其耐热的光合生理机制。结果显示,4种山楂表现出较强耐热性,6种较耐热,而5种耐热性较差;15种山楂叶片净光合速率(Pn)、蒸腾速率(Tr)、气孔导度(Gs)、瞬时水分利用效率(WUE)的种间差异显著(P<0.05),且耐热性强的品种Pn、Tr、Gs、WUE值较高,高温下能够维持较高的光合固碳水平;各品种山楂叶片的PSⅡ最大光能转换效率Fv/Fm、电子传递效率ΦPSⅡ和光能捕获效率Fv′/Fm′差异显著,耐热性强品种Fv/Fm保持在0.8以上,且ΦPSⅡ值与Fv′/Fm′较高。研究表明,观赏山楂主要通过加大气孔蒸腾散热、降低叶表面温度以及维持较高光能电子传递与转化效率来减轻高温对光合机构伤害,以维持植株正常光合作用;山楂叶片PSⅡ原初光能转换效率及潜在活性与其耐热性密切相关,Fv/Fm值可作为山楂耐热性鉴定指标。

To reveal photosynthetic mechanism for heat stress,the leaf gas exchange and chlorophy Ⅱ fluorescence parameters of 15 domestic or overseas hawthorns species were measured under natural high temperature stress of summer in Shanghai.And the field observation was conducted as well.The results showed that there were significant differences（P〈0.05） in the net photosynthetic rate（Pn）,transpiration rate（Tr）,stomatal conductance（Gs）,water use efficiency（WUE） among fifteen species cultivars,indicated the different photosynthetic capability and water utilization efficiency.For the chlorophy Ⅱ fluorescence parameters,the differences in maximal photochemical efficiency of PSⅡ in the dark（Fv/Fm）,quantum yield of PSⅡ electron transport in the light（ΦPSⅡ） and photochemical efficiency of PSⅡ in the light（Fv′/Fm′） is significant（P〈0.05） among the different heat-tolerant species.The adaptation mechanism under high temperature of heat-tolerant hawthorn species can be summarized of increasing heat dissipation,reducing temperature of leaf surface and holding relatively high electron transport or photochemical efficiency so as to minimize damage of photosynthetic organism and achieve a stable photosynthesis.It indicated that the efficiency of primary conversion of light energy of PSⅡ and its potential activities differed significantly among the cultivars.Fv/Fm was suggested to be index for heat tolerance of hawthorns species.