外源2,4表油菜素内酯对越夏期高温与弱光胁迫下紫花苜蓿生长和光合性能的影响

doi:10.11686/cyxb2019511

摘要/Abstract

摘要： 为探讨外源2,4表油菜素内酯(EBR)对高温与弱光胁迫下紫花苜蓿生长与光合性能的调节作用,采用绿色遮阳网模拟遮荫条件,设置3种光环境[全光照(L₀)、46.30%透光率(L₁)和28.63%透光率]和4种EBR浓度[蒸馏水(CK)、0.01、0.1和1 mg·L^-1],研究越夏期弱光胁迫下叶面喷施EBR对紫花苜蓿幼苗的形态、生长、光合色素含量、光合参数和光合-光响应曲线的影响。结果表明:越夏期随遮荫程度增加,紫花苜蓿冠层光合有效辐射(PAR)、红光与远红光比值(R/FR)、红光和紫外光波段占PAR的比例明显下降,绿光波段占PAR的比例明显上升;遮荫及EBR处理下,与对照相比,紫花苜蓿叶面积,叶重比,节间长,茎叶夹角,叶绿素a、b含量和胞间CO₂浓度明显增加,叶面温度(T_leaf)和类胡萝卜素含量明显降低。轻度遮荫及1 mg·L^-1 EBR处理下紫花苜蓿净光合速率和最大净光合速率与L₀无显著差异。Pearson相关分析结果表明,越夏期遮荫条件下,紫花苜蓿冠层PAR、R/FR和紫外光波段占PAR的比例与光强显著正相关。遮荫及EBR处理下,紫花苜蓿根重比与光强显著正相关,主茎节数与光强无明显相关性。综合上述结果,越夏期遮荫条件下,外源EBR可调整紫花苜蓿植株结构,降低叶面温度,促进光合色素的合成,提高光合效率,缓解高温与弱光对紫花苜蓿生长的抑制作用。L₁条件下,外源1 mg·L^-1 EBR对紫花苜蓿生长的促进作用最明显。

关键词: 紫花苜蓿, 越夏期, 遮荫, 光合色素, 光合-光响应曲线

Abstract: This study investigated the regulatory effects of exogenous 2, 4-epibrassinolide (EBR) on the growth and photosynthesis of alfalfa under high temperature and low light stress in summer. A simulated shade experiment with green shade mesh was conducted by setting up three light environments [full sunlight (L₀), 46.30% sunlight (L₁), and 28.63% sunlight] and four EBR concentrations [distilled water (CK), 0.01, 0.1, and 1 mg·L^-1]. The effects of EBR on the morphology, growth, photosynthetic pigment content, photosynthetic parameters and photosynthetic light-response curve were assessed. Results showed that the photosynthetically active radiation (PAR), red to far-red (R∶FR) ratio and percentages of the red and violet bands in PAR on the alfalfa canopy significantly decreased and that the percentage of the green band significantly increased with increasing shade in summer. Compared with CK, the leaf area, leaf mass rate, internode length, acropetal angles between leaf and mainstem, chlorophyll a and b contents, and intercellular CO₂ concentration significantly increased, and temperature of the leaf thermocouple (T_leaf) and carotenoid content significantly decreased under shaded conditions. Compared with L₀, the net photosynthetic rate and maximum net photosynthetic rate did not show distinct changes with 1 mg·L^-1 EBR treatment under L₁ in summer. The results of Pearson correlation analysis showed that PAR, R∶FR, and the percentage of the violet band on the alfalfa canopy had significant positive correlations with light intensity under shaded conditions. The root mass rate had a distinctly negative correlation, and the node number of the mainstem had no significant correlation with light intensity under EBR or shade treatments. The above results indicate that exogenous EBR can regulate the plant structure, decrease T_leaf, promote the synthesis of photosynthetic pigments, and improve the photosynthetic efficiency, and in this way alleviate high temperature and low light stress in alfalfa. Among the rates tested, 1 mg·L^-1of EBR was the optimal concentration to improve the growth of alfalfa under slight shading (L₁) during the summer period.

Key words: alfalfa, summer, shading, photosynthetic pigment, photosynthetic light-response curve

覃凤飞, 李志华, 刘信宝, 渠晖, 平措卓玛, 洛松群措, 苏梦涵. 外源2,4表油菜素内酯对越夏期高温与弱光胁迫下紫花苜蓿生长和光合性能的影响[J]. 草业学报, 2020, 29(9): 146-160.

QIN Feng-fei, LI Zhi-hua, LIU Xin-bao, QU Hui, PINGCUO Zhuo-ma, LUOSONG Qun-cuo, SU Meng-han. Effects of exogenous 2, 4-epibrassinolide on the growth and photosynthesis of alfalfa under high temperature and low light stress in summer[J]. Acta Prataculturae Sinica, 2020, 29(9): 146-160.

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