水分胁迫下, 柚〔Citrus maxima ( Burm.) Merr.〕树苗叶片相对含水量( RWC) 、水势( ΧW) 、净光合速率( Pn) 、可
溶性蛋白质和叶绿素( Chl) 含量下降, 丙二醛( MDA) 、脯氨酸( Pro) 含量和超氧化物歧化酶( SOD) 活性升高, 过氧化氢
酶( CAT) 活性先上升后下降, 抗坏血酸过氧化物酶( APX) 活性、抗坏血酸( AsA) 和还原型谷胱甘肽( GSH) 含量明显降
低。 叶绿素荧光参数中光系统Ⅱ光化学原初效率( Fv/Fm) 、光系统Ⅱ电子传递量子效率( ΥPS Ⅱ) 和光化学猝灭( qp)
下降, 非光化学猝灭( qN) 和热能耗散系数( KD) 升高。 显示膜系统和 PSⅡ是水分胁迫的主要抑制位点。 抗旱性强的
品种具有较高的活性氧清除能力。 长期紫外线-B( UV-B) 增强辐射能缓解水分胁迫下柚树苗叶片 RWC 、ΧW、APX 活
性和 GSH、AsA 含量下降, 但对水分胁迫下的 Pro 含量、Pn 和叶绿素荧光特性作用不明显。 初步推测:UV-B 和水分
胁迫对植物有部分相同的作用机制, 都导致植株膜脂过氧化程度加剧和 PS Ⅱ的失活, 同时存在各自作用方式的特
异性.
 

Under water stress, relative water content, water potential, net photosynthesis rate, soluble protein and chlorophyll contents in leaves of pomelo 〔Citrus maxima ( Burm .) Merr.〕 seedlings were decreased, MDA and free proline contents, SOD activity were increased, CAT activity increased at first, then decreased . The activity of APX , the contents of AsA and GSH were declined .Chlorophyll fluorescence parameters Fv / Fm, ΦPS Ⅱ and qp were decreased, qN and KD were raised .It demonstrated that membrane and photosystem PS Ⅱ were the important target of water stress .The capacity of getting rid of activated oxygen was higher in the drought-resistant variety than in the drought-sensitive one.Long-term enhanced UV-B radiation could delay the decrease of relative water content, water potential, APX activity and GSH, AsA contents in leaves of pomelo seedlings under water stress, but had no obvious effects on Pn, free proline content and chlorophyll fluorescence parameters .The results suggested that UV-B and water stress owned partial same functional model to plants with leading to membrane lipid peroxidation aggravation and PS Ⅱ inactivation,meanwhile there were specific properties of individual action model were existed .