濒危藏药桃儿七对逐步失水的光合生理响应

Photosynthetic physio-response of endangered Tibetan medicine Sinopodophyllum hexandrum (Royle) Ying in the process of gradual water loss

本研究以西藏濒危藏药桃儿七为研究对象,作逐步失水处理,通过测定并分析不同水分梯度下的桃儿七叶片相对含水量、叶绿素含量、光合参数和荧光参数等来探究桃儿七对土壤干旱胁迫的光合生理响应。结果显示:随土壤水分的减少,桃儿七叶片相对含水量先上升后下降,叶绿素相对含量逐渐上升且差异不显著;桃儿七的光合气体交换参数对不同水分梯度的响应表明,在土壤相对含水量为39.68%~95.33%的条件下,桃儿七的光合作用未受显著抑制,而后随土壤水分的减少被显著抑制,且土壤相对含水量为39.68%是桃儿七光合作用气孔限制至非气孔限制的转折点;桃儿七双曲线修正模型拟合的光响应曲线、CO2响应曲线及各特征参数随土壤水分变化表现出显著的不尽相同的阈值响应特征。不同水分梯度下的叶绿素荧光参数及图像表明,随土壤水分的减少,桃儿七的光合产量严重降低,叶片光合机构受到不可逆的破坏。综合考虑各项指标得出桃儿七旱涝管理的最佳土壤相对含水量为土壤相对含水量39.68%~89.02%,过高或过低的土壤相对含水量均会影响桃儿七的光合表现。

S.hexandrum,which is a rare and endangered Tibetan medicinal plant,was taken as the object to explore photosynthesis and chlorophyll fluorescence parameters under water stress,and the relative water content of leaves,chlorophyll relative content,photosynthetic and fluorescence parameters of S.hexandrum were measured under the process of gradual water loss of soil.The results show that:With the decrease of soil water,the relative water content of leaves rose firstly and then declined,and the relative content of chlorophyll increased gradually.Response of photosynthetic gas exchange parameters of S.hexandrum to different water stress showed that the photosynthesis was not significantly inhibited under the condition of soil relative water content of 39.68%-95.33%,but significantly inhibited with the decrease of soil moisture.The photosynthetic rate of S.hexandrum changed from stomatal limitation to non-stomatal limitation,when the relative soil water content was 39.68%.The light response curve,CO2 response curve and various characteristic parameters of S.hexandrum showed significant different threshold response characteristics with soil moisture change.The chlorophyll fluorescence parameters and images under different water gradients showed that the photosynthetic yield of S.hexandrum was seriously reduced,and the leaf photosynthetic apparatus was irreversibly damaged with the decrease of soil moisture.General consideration of all respects,the optimal soil relative water content of dryland management of S.hexandrum is 39.68%~89.02%,and it will affect the photosynthetic performance of the S.hexandrum no matter the relative water content of the soil too high or too low.