黑麦草幼苗对NaHCO_3胁迫的生理响应

Physiological response of ryegrass seedlings to NaHCO_3 stress

采用营养液砂培方法,研究了不同浓度NaHCO3(0、50、100、150 mmol/L和200 mmol/L)胁迫对黑麦草幼苗生长、活性氧代谢和渗透溶质积累的影响。结果表明:(1)随着NaHCO3浓度增加,黑麦草幼苗鲜、干重呈降低趋势,叶片超氧阴离子(O2.)、过氧化氢(H2O2)、丙二醛(MDA)和Na+含量不断升高,过氧化氢酶(CAT)、过氧化物酶(POD)活性和抗坏血酸(AsA)、谷胱甘肽(GSH)、K+含量及K+/Na+持续下降,超氧化物歧化酶(SOD)和抗坏血酸过氧化物酶(APX)活性呈先升后降变化,液泡膜H+-ATPase和H+-PPase活性在NaHCO3浓度为50～150 mmol/L时高于对照,NaHCO3浓度为200 mmol/L时低于对照。(2)碱胁迫降低了幼苗叶片中可溶性蛋白质和游离氨基酸的含量,提高了可溶性糖和脯氨酸的含量。表明活性氧代谢和Na+、K+平衡失调及积累有机溶质进行渗透调节需更多能耗等可能是碱胁迫下黑麦草幼苗生长受抑的重要因素。

Ryegrass seedlings were exposed to Hoagland＇s nutrient solution with NaHCO3 added （0, 50, 100, 150, 200 mmol/L）, and the effects of NaHCO3 stress on the plant growth, metabolism of reactive oxygen species （ROS） and osmotica accumulation in leaves were studied by a sandy culture. The results showed （ 1 ） With the increasing of NaHCO3 concentration, the fresh and dry weights of the seedlings decreased, the contents of 02-, H202, MDA and Na＋ in leaves increased gradually, and the activities of CAT and POD, the contents of AsA, GSH and K＋ as well as K ＋/Na＋ decreased continually, and the activities of SOD and APX exhibited a humped-curve, while the activities of V - H＋ - AT- Pase and V - H＋ - PPase were higher than the control at 50 - 150 mmol/L NaHCO3 but lower than the control at 200 mmol/L NaHCO3. （2） Alkali-stress decreased the contents of soluble protein and free amino acid while increased the contents of soluble sugar and proline in the seedling leaves. It was concluded that the imbalances of ROS metabolism and Na＋ to K ＋ in the seedling leaves were possibly caused by alkaline stress, and consumed more energy for osmotic adjustment by accumulating organic solutes, which might be an important reason that the growth of ryegrass seedlings under alkaline stress was inhibited.