Data_Sheet_1_Drought Tolerance of Soybean (Glycine max L. Merr.) by Improved Photosynthetic Characteristics and an Efficient Antioxidant Enzyme Activities Under a Split-Root System.pdf

Water deficiency significantly affects photosynthetic characteristics. However, there is little information about variations in antioxidant enzyme activities and photosynthetic characteristics of soybean under imbalanced water deficit conditions (WDC). We therefore investigated the changes in photosynthetic and chlorophyll fluorescence characteristics, total soluble protein, Rubisco activity (RA), and enzymatic activities of two soybean varieties subjected to four different types of imbalanced WDC under a split-root system. The results indicated that the response of both cultivars was significant for all the measured parameters and the degree of response differed between cultivars under imbalanced WDC. The maximum values of enzymatic activities (SOD, CAT, GR, APX, and POD), chlorophyll fluorescence (Fv/Fm, qP, ɸPSII, and ETR), proline, RA, and total soluble protein were obtained with a drought-tolerant cultivar (ND-12). Among imbalanced WDC, the enhanced net photosynthesis, transpiration, and stomatal conductance rates in T2 allowed the production of higher total soluble protein after 5 days of stress, which compensated for the negative effects of imbalanced WDC. Treatment T4 exhibited greater potential for proline accumulation than treatment T1 at 0, 1, 3, and 5 days after treatment, thus showing the severity of the water stress conditions. In addition, the chlorophyll fluorescence values of FvFm, ɸPSII, qP, and ETR decreased as the imbalanced WDC increased, with lower values noted under treatment T4. Soybean plants grown in imbalanced WDC (T2, T3, and T4) exhibited signs of oxidative stress such as decreased chlorophyll content. Nevertheless, soybean plants developed their antioxidative defense-mechanisms, including the accelerated activities of these enzymes. Comparatively, the leaves of soybean plants in T2 displayed lower antioxidative enzymes activities than the leaves of T4 plants showing that soybean plants experienced less WDC in T2 compared to in T4. We therefore suggest that appropriate soybean cultivars and T2 treatments could mitigate abiotic stresses under imbalanced WDC, especially in intercropping.

水分亏缺可显著影响植物光合特性，但目前关于非均匀水分亏缺（imbalanced Water Deficit Condition, WDC）条件下大豆抗氧化酶活性与光合特性变化的相关研究仍较为匮乏。本研究依托分根系统，探究了两个大豆品种在四种不同类型非均匀水分亏缺处理下，其光合与叶绿素荧光特性、总可溶性蛋白含量、核酮糖-1,5-二磷酸羧化酶/加氧酶（Rubisco）活性（RA）以及抗氧化酶活性的变化规律。结果显示，两个供试品种的所有被测参数均表现出显著响应，且不同品种在非均匀水分亏缺下的响应程度存在差异。耐旱品种ND-12的抗氧化酶活性（超氧化物歧化酶（Superoxide Dismutase, SOD）、过氧化氢酶（Catalase, CAT）、谷胱甘肽还原酶（Glutathione Reductase, GR）、抗坏血酸过氧化物酶（Ascorbate Peroxidase, APX）以及过氧化物酶（Peroxidase, POD））、叶绿素荧光参数（最大光化学效率（Fv/Fm）、光化学淬灭（qP）、PSII实际量子效率（ɸPSII）以及电子传递速率（ETR））、脯氨酸含量、Rubisco活性及总可溶性蛋白含量均达到峰值。在四种非均匀水分亏缺处理中，T2处理组在胁迫5天后的净光合速率、蒸腾速率与气孔导度均得到提升，进而使得总可溶性蛋白含量更高，这可抵消非均匀水分亏缺带来的负面影响。在处理后的0、1、3、5天，T4处理组的脯氨酸积累潜力均高于T1处理组，由此反映出T4处理的水分胁迫程度更为严重。此外，随着非均匀水分亏缺程度加剧，叶绿素荧光参数Fv/Fm、ɸPSII、qP及ETR均呈下降趋势，其中T4处理组的参数值最低。经受非均匀水分亏缺（T2、T3、T4）的大豆植株均出现了氧化应激迹象，如叶绿素含量下降。但大豆植株可启动抗氧化防御机制，包括加速上述抗氧化酶的活性。相较而言，T2处理组大豆叶片的抗氧化酶活性低于T4处理组，这表明T2处理下大豆受到的水分亏缺程度轻于T4处理。综上，选用适宜的大豆品种并采用T2处理方式，可缓解非均匀水分亏缺下的非生物胁迫，在间作系统中应用效果尤为突出。