6-苄（基）腺嘌呤和抗坏血酸对渗透胁迫时杨树光合作用光抑制的影响

研究了6-BA和A5A对渗透胁迫时杨树幼苗叶片光合作用光抑制和活性氧代谢的影响．结果表明，渗透胁迫时杨树叶片净光合速率(Pn)和表观量子效率(AQY)降低，光合作用光抑制加剧，超氧化物歧化酶(SOD)活性升高，抗坏血酸过氧化物酶(APX)活性降低，O2产生加快，H2O2和膜脂过氧化产物丙二醛(MDA)含量升高．6-BA和A5A预处理使胁迫时叶片SOD和APx活性升高。O2生成减少。H2O22和MDA含量降低，同时缓解了光合作用的光抑制．相关分析表明，杨树叶片活性氧水平和MDA含量与Pn和AQY呈负相关．胁迫时杨树叶片活性氧的积累与光合作用光抑制有一定关系，6-BA和A5A对光抑制的缓解作用与其对活性氧清除系统的促进作用有关。

Effects of 6-BA and AsA on photosynthesis photoinhibition of attached poplar leaves under osmotic stress of root

In order to know more about the relationships between photosynthesis photoinhibition and reactive oxygen species metabolism, the effects of 6-benzyladenine (6-BA) and ascorbate (AsA) on net photosynthetic rate (Pn), apparent quantum yield (AQY), superoxide dismutase (SOD) and ascorbate peroxidase (APX) activities, O2-* generation rate, and H2O2 and malondialdehyde (MDA) contents were studied with attached leaves of poplar clone seedlings under osmotic stress of root. Under osmotic stress, the photosynthesis photoinhibition of attached poplar leaves, judged by the significant decrease of Pn and AQY, was aggravated, and the balance of reactive oxygen species metabolism was destroyed. The superoxide dismutase (SOD) activity increased, but ascorbate peroxidase (APX) activity decreased. In the meantime, the O2-* generation rate and the contents of H2O2 and malondialdehyde (MDA) increased. When osmotic stressed poplar seedlings were pretreated with 6-BA and AsA, the activities of SOD and APX increased, O2-* generation rate and H2O2 and MDA contents decreased, and photosynthesis photoinhibition was alleviated. The contents of reactive oxygen species and MDA in poplar leaves were negatively correlated with net photosynthetic rate and apparent quantum yield. It's indicated that the photosynthesis photoinhibition of attached leaves of poplar clone seedlings had intrinsic relations with the accumulation of reactive oxygen species under osmotic stress of root, and the alleviation effects of 6-BA and AsA on photosynthesis photoinhibition were related to their promotion effects to the scavenging system of reactive oxygen species.