Ca～(2+) In Relation To Reaction And Adaptation Of Wheat Under Osmotic Stress

The effects of Ca2, EGTA, LaCh, Verapamil, CPZ and TFP on growth and POD activity and the changes of CaM level in buds and roots were studied with winter wheat (Triticum aestivuni L.) 4185 under osmotic stress of 20% PEG-6000, and the effects of LaCl3, CPZ, TFP, CaCl2 and EGTA on relative water content, relative permeability of plasma membrane and growth of seedlings during osmotic stress of 25% PEG-6000, and of osmotic stress on Ca and CaM contents with winter wheat 4185 seedlings were investigated. The results were as follows:1 Under osmotic stress, Ca2+(l 0-1 0-4mol/L) was benefit to the growth of wheat buds and roots, and Ca2 (10-102mol/L) inhibited the growth of wheat.CaCh (Immol/L) could reversed the inhibition effect of EGTA(10mmol/L) pretreatment. but CaCl2 (Smmol.'L, lOmmol/L) inhibited the growth of wheat. These data indicated that only proper Ca2 concentration was benefit to the wheat growth. In addition, the dependence of wheat on Ca was enhanced under osmotic stress, which showed that Ca2+ was very important to drought-resistance of wheat.2 Under osmotic stress, EGTA(1 , 5, lOmmol/L), LaCl3(0.5, Immol/L) and Verapamil(250, 500 u mol/L) treatment inhibited thegrowth of wheat buds and roots, but EGTA(lmmol/L) and Verapamil (250 u mol/L) had no inhibition effect on the control buds growth. The results showed that under osmotic stress, the wheat was more sensitive to deficiency of Ca2+, when extracellular Ca2+ concentration was decreased or Ca2+ transportation blocked, the growth of wheat buds and roots would be inhibited. It indicated that Ca2+ played an important role in the drought-resistance of wheat.3 Under osmotic stress, CPZ (25, 50, 100, 200 u mol/L) and TFP (10, 25, 50, 100, 200 u mol/L) inhibited the growth of wheat budsand roots, and the inhibition effect was increased with the increase of the treatment concentration, but CPZ (25 u mol/L) and TFP ( 10 U mol/L) had no inhibition effect on the control wheat. These data showed that it was disadvantage to the wheat growth when the activity of CaM was inhibited under osmotic stress, thus declined the capability of drought-resistance of wheat.4 Compared with the normal water supply, the CaM content of decreased at first 6 h, then increased slowly in wheat buds treated with 20% PEG-6000. When the CaM content was the most, the growth rate of wheat buds was the fastest. However, the CaM content of roots was lower than the control during the first 24 h. then it increased and surpassed the control. The data indicated that the CaM content decreased at the beginning of the osmotic stress might be one of the signals of drought reaction. Thus maintaining the normal CaM function was very important to sustain drought-resistance of wheat.5 Under osmotic stress, exogenous Ca +, EGTA, LaC, Verapamil, CPZ and TFP enhanced the POD activities of wheat buds and roots, and the POD activity negatively correlated with the fresh weight of wheat. So that Ca2+-CaM message system might affect thedrought-resistance of wheat by regulating the POD activity.6 After treated the wheat seedlings with different concentration PEG-6000, the results showed that 10% PEG-6000 decreased the calcium content of wheat roots, stems and leaves. The inhibited effect of Ca + absorption was enhanced with increase of the PEG treatment concentration. The calcium content of seedlings declined at 12h compared with the control, then increased from 24h to 48h,at last decreased quickly at 72h after treated with 25% PEG-6000. The decline of calcium amount of roots \vas the biggest, then stems, the leaves least.7 Compared with the control, the CaM content changes of wheat leaves and roots were different under osmotic stress. CaM content of leaves increased quickly at 12h,then decreased, however, CaM content of roots decreased at 12h,then increased during 24h to 48h,and declined again at 72...