遮阴对濒危植物朝鲜崖柏光合特性的影响

【目的】分析濒危植物朝鲜崖柏(Thuja koraiensis)光合特性,探讨光合作用与环境因子的关系,为开展朝鲜崖柏的有效保育提供依据。【方法】应用Li-6400便携式光合仪器,测定朝鲜崖柏7年生扦插苗在不同光环境(L0、L1、L2、L3,即遮阴度分别为0%、25%、50%和75%)下光响应曲线、光合日变化和色素含量,并进行通径分析。【结果】随遮阴度增加,最大净光合速率(P_n,max)、暗呼吸速率(R_d)、光饱和点(L_SP)和光补偿点(L_CP)显著减小,表明朝鲜崖柏具有一定的耐阴性。随遮阴度增加光合日变化的净光合速率(P_n)、气孔导度(G_s)和蒸腾速率(T_r)随之降低,非气孔限制因素是朝鲜崖柏光合速率下降的主要原因。朝鲜崖柏通过增加叶绿素a、叶绿素b、总叶绿素和类胡萝卜素含量适应遮阴环境。在不同光环境下,空气相对湿度是影响光合日变化净光合速率的主要环境因子;根据决定系数排序,在L0和L1处理中空气相对湿度影响最大,在L2和L3处理中光合有效辐射(P_AR)影响最大。【结论】朝鲜崖柏在全光照和遮阴25%时有较好的光合性能,具有一定的耐阴性,但遮阴度过高时会因光照不足影响植株的正常生长。

Effects of shading treatments on photosynthetic characteristics of endangered plant Thuja koraiensis

【Objective】To provide scientific basis for effective conservation measures for Thuja koraiensis, the photosynthetic characteristics of endangered plant T. koraiensis were analyzed and the relationship between photosynthesis and environmental factors was discussed. 【Method】The Li-6400 portable photosynthetic system was used in the study, the photosynthetic and physiological characteristics of the 7-year-old cutting seedlings of T. koraiensis in different light environments (L0, L1, L2 and L3, shade degrees were 0%, 25%, 50% and 75%, respectively.) including light response curve,diurnal variation of photosynthesis and pigment content were analyzed, and analysis of path coefficient was carried out. 【Result】The results of light response curve fitting showed that with the increaseing of shading intensity, the maximum net photosynthetic rate, dark respiration rate, light saturation point and light compensation point decreased significantly, which indicated that T. koraiensis had a certain shade-tolerance. The results of diurnal variation curve of photosynthesis showed that with the increasing of shading intensity, the net photosynthetic rate, stomatal conductance and transpiration rate decreased, and the principal reason of the reduction in photosynthesis was attributed to non-stomatal limitation factor. The results of pigment content showed that T. koraiensis responded to the shade environment by increasing the contents of chlorophyll a, chlorophyll b, total chlorophyll and carotenoids. The results of the analysis of path coefficient showed that, air relative humidity (RH) was the main environmental factor affecting the net photosynthetic rate of diurnal variation of photosynthesis under different light environments. According to the ranking of decision coefficient, RH had the largest effet on the net photosynthetic rate in L0 and L1, and PAR had the largest in L2 and L3. 【Conclusion】T. koraiensis had better photosynthetic performance under full light and 25% shading, and had a certain shade-tolerance. However, when the shading intensity was too high, the normal growth of plants would be affected by insufficient light.