[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.