屋顶绿化植物佛甲草对温度梯度的生理生态适应

Ecophysiological adaptation of green roof plant Sedum lineare to temperature variation

以屋顶生长的佛甲草为材料,通过光照培养箱进行不同温度条件处理,分别测量了叶片的CO2交换、叶绿素含量、叶绿素荧光参数以及植株不同部位的碳同位素比率变化(δ13C)。结果表明:持续高温/低温、较大的昼夜温差和叶表面风力的条件下,佛甲草为适应环境变化,光合会由C3代谢途径转变成景天酸代谢途径(CAM),是兼性CAM植物。短期降温会使叶片光系统Ⅱ(PSⅡ)发生不可逆失活,光合能力下降;复水后有助于PSⅡ的恢复和重建,而干旱天气会减缓恢复过程;在不利温度环境中生长的佛甲草老叶掉落较多,剩余叶片的叶绿素含量和Fv/Fm值增高,光合能力提高。δ13C测定结果显示,高温使嫩叶气孔导度降低,对成熟叶片气孔导度影响小,佛甲草茎杆虽然含有叶绿素,但没有明显的光合作用。

To investigate physiology of S. lineare planted in adverse environment, we conducted measurements of gas exchange and chlorophyll fluorescence parameters in leaves of S. lineare that grew in roof and was cultivated in a light incubator for temperature experiment. We also measured carbon isotope ratio （δ13C） in different organs of S. lineare grown in the incubator under different temperatures for 30 days. Main results were as follows：Long term treatment of high/low temperature, high diurnal temperature difference between day and night and high leaf boundary layer conductance altered by wind force could lead to inactivation of photosystem II in leaves of S. lineare and to the switch of C3 photosynthetic pathway to CAM,indicating that S. lineare＇was a facultative CAM plant;Short term chilling caused irreversible inactivation of photosystem II in leaves of S. lineare;Rehydration would help the recovery of photosystem U,but such recovery would be delayed under dry condition. Planted in an adverse temperature environment would bring about defoliation, and the chlorophyll contents and chlorophyll fluorescence parameters would increase in the remaining leaves of S. lineare. When planted with sufficient water supply, mature leaves of S. lineare did not show a temperature-sensitivity, but the young leaves would;The measured δ13C showed decrease of leaf stomatal conductance of young leaves, but no effect on that of old leaves caused by high temperature. The stems, though containing chlorophyll, did present significant photosynthetic capacity.