Photosynthesis Characteristics and Antioxidant Enzyme Activity in Periploca sepium Seedlings under Drought Stress

In order to provide countermeasures for species cultivation and planting about vegetation recovery of shell islands in Yellow River Delta.With Periploca sepium seedlings as materials,the effects of different drought stress on gas exchange and systems of anti-oxidation were conducted.Four treatments were arranged:control,light drought,moderate drought and heavy drought.Results showed:(1)With the drought stress increasing,net photosynthesis rate first increased and then decreased,transpiration rate and stomatal conductance decreased,intercellular CO2 concentration first decreased and then increased.Under light stress,the decline of netphotosynthetic rate of P.sepium seedlings was caused by stomatal conductance decreasing.However,it is mainly by non-stomatal factors under heavy stress.(2)With the drought stress increasing,instantaneous water use efficiency,apparent light use efficiency and carboxylation efficiency of P.sepium seedlings showed the tendency of increase-decrease.Instantaneous water use efficiency decreased by 39% under heavy stress,apparent light use efficiency(apparent CO2 use efficiency)decreased by 48%(33%),71%(69%) under moderate stress and heavy stress.(3)With the drought stress increasing,the activity of superoxide dismutase(SOD) of P.sepium first increased and then decreased,peroxidase(POD),catalase(CAT),the content of malondialdehyde(MDA) always increased.The effect of POD,CAT to prevent lipid peroxidation is not significant,SOD is significant.The content of shell sand moisture at 12.8% was the limit of the activity of SOD,the content of malondialdehyde(MDA) of P.sepium in the leaves increased by 153%.