Using automatic weighing and irrigation system ,three-years-old pear-jujube tree were exposed to suitable soil water condition ,medium drought and severe drought , corresponding to 75% ± 5% ,60% ± 5% ,45% ± 5% of field water capacity ,respectively ,to examine effects of soil water availability on leaf photosynthetic and drought-resis-tant parameters .Results showed that:(1 ) Medium drought did not have significant effect on leaf photosynthetic parame-ters ,while severe drought significantly reduced leaf net photosynthetic rate ( Pn ) ,transpiration rate ( Tr ) ,stomatal con-ductance (Gs) ,intercellular CO2 concentration (Ci) ,and light use efficiency (LUE) ,but increased the water use effi-ciency (WUE ) and the stomatal limitation value ( Ls ) . (2 ) Medium drought did not influence leaf malonaldehyde (MDA ) content ,but significantly increased catalase (CAT ) activity ,whereas severe drought significantly increased MDA content ,the activity of superoxide dismutase (SOD ) and peroxidase (POD ) ,and increased the contents of ascorbic acid (ASA) and glutathione (GSH) .However ,the increases in activities of SOD and POD and contents of ASA and GSH could not repair the damage of membrane system by severe drought . Hence ,medium drought did not cause an abiotic stress for pear-jujube leaves ,but severe drought had significant impacts on leaf photosynthetic parameters and membrane system ,indicating the necessity of irrigation when severe drought occurs .%利用自动称量和补水系统，对三年生梨枣树进行适宜水分、轻度和重度干旱三种土壤水分处理（土壤含水量分别为田间持水量的75％±5％、60％±5％和45％±5％），旨在探究不同土壤水分对梨枣叶片光合参数和抗旱性的影响。结果表明：（1）轻度干旱对梨枣叶片的光合参数没有显著影响，但重度干旱引起净光合速率（ Pn）、蒸腾速率（Tr）、气孔导度（Gs）、胞间CO2浓度（Ci）和光能利用率（LUE）明显降低，而水分利用效率（WUE）和气孔限制值（Ls）增加。（2）轻度干旱对梨枣叶片丙二醛（MDA）含量影响不大，过氧化氢酶（CAT）活性则显著上升；而重度干旱下MDA含量显著上升，同时超氧化物歧化酶（SOD ）和过氧化物酶（POD ）活性以及抗坏血酸（ASA ）和还原型谷胱甘肽（GSH ）含量明显升高，但仍不能消除重度干旱对梨枣叶片膜系统造成的严重伤害。因此，轻度干旱并未引发梨枣叶片显著的生物学胁迫，而在重度干旱条件下梨枣叶片的光合能力和膜系统均受到严重影响。
展开▼
