Abstract: This paper studied the effects of short and long term abscisic acid (ABA) treatments on the CO₂ assimilation (P_n),carboxylation efficiency(CE),response of P_n to CO₂,and antioxidant enzyme activities of wheat seedlings exposed to UV-C.The results showed that under no UV-C,short-and long term ABA treatments increased P_n by 14.69% and 20.46%,and decreased stomatal conductance (G_s) by 14.74% and 17.31%,respectively,compared to the control,while no effects were observed on intercellular CO₂ concentration (C_i) and CE.Under UV-C,the P_n,CE,G_s and C_i decreased,with the least decrease in long term ABA treatment,less in short term ABA treatment,and the most in control.ABA could increase the response of P_n to CO₂,while UV-C inhibited it.In ABA treatments,antioxidant enzyme activities were enhanced,while MDA content was decreased.Under UV-C,CAT activity increased first,reached its maximum after 1 h,and decreased then.The activities of SOD and POD in ABA treatments increased first and decreased then,with the greater increase in long term ABA treatment than in short term ABA treatment,while those in the control decreased.It was suggested that through enhancing P_n and antioxidant enzyme activities,ABA could enhance the resistance of wheat to UV-C,and long term ABA treatment had better effects than short term ABA treatment.

Key words: Rice, Cultivating fish in rice field, Symbiotic effect