Abstract:

Drought stress often affects plant growth and development, and the plant will change their metabolic system to cope with drought stress. In order to understand the drought resistance mechanism of Brachypodium sylvaticum, physiological responses to PEG-6000 simulated drought stress for three B. sylvaticum (BsL, BsD and BsB) were studied. The result showed that, in three B.sylvaticum, the Peroxidase (POD) and Catalase (CAT) activity and Malondialdehyde (MDA) content were positively correlated with drought stress and processing time. While, the content of chlorophyll were negatively correlated with drought stress and processing time. The Ascorbate peroxidase (APX) activity of BsB and BsD increased with drought stress and processing time, but the APX activity of BsL increased at first, reached maximum value at 5% PEG-6000 (2 day), and then decreased. Photosynthetic parameters of three B. sylvaticum were also measured. Net photosynthesis (P_n), transpiration rate (T_r) and stomatal conductance (G_s) of three B.sylvaticum decreased with increasing processing time and drought stress intensity, and intercellular CO₂ concentration (C_i) of BsL and BsD also had the same change trend. Conversely, C_i of BsB increased with the increase of processing time and drought stress intensity. In su mmary, when the concentration of PEG-6000 was more than 10%, B. sylvaticum would be injured,and need to be watered.

Key words: Brachypodium sylvaticum, Drought stress, Antioxidant enzymes, Osmotic substance, Photosynthesis

摘要：

本研究以3个不同生态型的小颖短柄草（Brachypodium sylvaticum）为试验材料（分别简称为BsL，BsD，BsB），研究不同浓度的聚乙二醇（PEG-6000）模拟干旱胁迫对其抗氧化酶活性、渗透物质、叶绿素含量及光合参数的影响。结果表明：BsL，BsD，BsB的过氧化物酶（Peroxidase，POD）及过氧化氢酶（Catalase，CAT）的活性和丙二醛（Malondialdehyde，MDA）的含量均随胁迫强度和处理时间增加而增加，叶绿素含量呈相反趋势。BsD，BsB的抗坏血酸过氧化物酶（Ascorbate peroxidase，APX）的活性均随胁迫强度和处理时间的增加而增加，BsL则先增后减。BsL，BsD的净光合速率（P_n）、蒸腾速率（T_r）、气孔导度（G_s）和胞间CO₂浓度（C_i）均随处理时间和胁迫强度的增强而减小，BsB的P_n，T_r和G_s呈相同趋势，而C_i在轻度胁迫下降低，中度和重度胁迫处理2 d时却升高。综上所述，BsL，BsD和BsB小颖短柄草均能耐受一定程度的干旱，但BsB较耐旱。当PEG-6000超过10%时会对小颖短柄草造成伤害，需及时补充水分。

关键词: 小颖短柄草, 干旱胁迫, 抗氧化酶, 渗透物质, 光合作用