MA Zhen-yu, GUO Xiu-lin, LIU Zi-hui, ZHANG Hong-mei
As a second messenger, Ca2+ plays an important role during the plant resistance to biotic or non -biotic stress.And as a carrier of Ca2+, Ca2+ -ATPase intervenes in many reactive processes of outer stimulation, so as to keep steady -state [ Ca2+] cyt level. In the report, Ca 2+ -ATPase activities of microsomal membrane system, including cytoplast membrane, mitochondrion membrane and vacuole membrane,were measured under osmotic stress with PEG6000.The re - sults showed that the Ca2+ -ATPase activities of normal plant changed with the longer light from 7: 00 AM to 7: 00 PM?In generally, the total Ca2+ -ATPase activities of three membranes were close and changed while plant subjected to osmotic stress, and it's higher in leaves than that in roots both treatment and control. In leaves, the Ca2+ -ATPase activities were decreased while treated with PEG, ABA and EGTA could reverse the effect, but it changed little in root while subjected to PEG,and were all increased by outer reagents.In detail, the Ca2+ -ATPase activities of three membranes were all in - creased by PEG in leaves, and so as to both mitochondrion membrane and vocuole membrane in root. But the Ca2+ - ATPase of cytoplast was inhibited obviously by PEG. Four outer reagents had different effects on Ca2+ -ATPase activity.In leaves, the decrease of Ca2+ -ATPase by PEG could be reversed by both ABA and EGTA, and the activities were higher than that of control at 6 h after treatment by PEG by two reagents?But the effects were different in roots.Vp could re - versed the decrease by PEG in cytoplast membrane, and increased Ca2+ -ATPase activities of mitochondrion membrane, and the vacuole membrane Ca2+ -ATPase activity were increased by ABA obviously.Different from those,TFP could pro - mote the Ca2+ -ATPase activity to raise in prophase of osmotic stress, but inhibited it after 6 h while treatment with PEG. Those indicated that three membrane both leaves and roots were all participate in the regulating process of keeping low [Ca2+ ] cyt under osmotic stress.External reagents influenced Ca2+ -ATPase activities both leaves and roots, but the re -sponse differences existed between leaves and roots.
