棉 花 学 报 Cotton Science 2005，17(3)：141-145

Effects of Abscisic Acid on Water Relationship and Defensive Enzymes Activities in Cotton Seedling under Water Stress
YAO Man-sheng, YANG Xiao-huan,GUO Ping-yi
(Chemical Regulation Cente，Shanxi Agricultural University，Taigu 030801，China)

Abstract：The variations of relative water content (RWC)，osmotic potential，activlties of superoxide dismutase (SOD)，catalase (CAT) and peroxidase (POD) of Jin-mian 21 and 99 B cotton seedling were studied under the condition of PEG6000 osmotic stress and abscisic acid (ABA). The content of malondiadehyde (MDA) , metabolite of membrane lipid peroxidation, and the drought resistance under water stress of two cotton cultivars were also tested and compared.
     Cotton seeds sterilized with 0.l% Hgcl₂ for 5 min, rinsed with tap water, were germinated under 28℃ in culture chamber. After germinated, the seeds were sown in plastic pots containing sands and incubated in room. After emergence, seedlings were irrigated with 1/2 Hoagland nutrition solution, incubated with 14 h/d, 5000 Lx, and a day/night temperature of 28℃/20℃. After the third leaf fullyelongated, the seedlings were separated to two groups, one irrigated with 1/2 Hoagland nutrition solution and the other with the same solution containing O.2×10^-5 mol•L^-l ABA for one week. Each treatment consisting of ten plants was duplicated three times. Then seedlings were treated with three different polyethylene glycol (PEG) water potential solutions of Hoagland (-0.5 MPa, -0.8 MPa, -1.1MPa). After 24 hours, physiological indexes of the third leaf of two cultivars were tested. The results showed that ABA could slow down the reduction of RWC and increased osmotic potential under PEG different osmotic stress (-0.5 MPa, -0.8 MPa, -1.1MPa) in cotton seedlings. When PEG osmotic potential was -1.l MPa, RWC of Jin-mian 21 and 99B were 86% and 74% , separately; osmotic potential of two cultivars were separately -l.28 Mpa and -1.69 Mpa, the result showed that ABA could increase water content of cotton leaves, therefore Jin-mai 21 was higher drought resistant than 99B. After treated with ABA, the defensive enzyme activities of SOD, CAT and POD were higherthan the untreated, and there were significant difference between the two cultivars. Function of membrane lipid peroxidation in Jin-mian 21 was lower than that in 99B. In addition, the accumulation of MDA of Jin-mian 21 decreased in comparison with 99B. Our results demonstrated that ABA could protect the intactness of membrane structure and decreased the hurt of water stress. The experimental results also indicated that the anti-insect ability of 99B and the drought resistance of Jin-mian 21 had no common physiological foundations.
Key words：ABA；cotton；water stress；defensive enzymes    [Full Text,581KB]