Impacts Of ABA On Cold Resistance Of Membrane Lipid In Winter Wheat Under Cold Stress

The Triticum aestivum Dongnongdongmai1cultivar has an85%winter survival rate and is the only winter wheat variety grown in Heilongjiang Province (minimum temperature up to-30℃). The stateble of memberane plays a vital role in cold-resistance.thereby increasing the cold-resistance of winter wheat had become the focus of our research.Two winter wheat cultivars of Dongnongdongmai1(freezing-tolerant) and Jimai22(freezing-sensitive) were used to investigate the effects of exogenous ABA on lipid composition、 cell ultrastructure observation、 activity of membrane lipid oxidation enzymes and expression of fatty acid desaturase genes under cold stress. Leaves were sprayed with10-5mol· l-1ABA when seedings were at the3-trure-leaf stage to study the effect of exogenous ABA on lipid cold-resisitance.The results showed that:(1)Effect of exogenous ABA on lipid composition at low temperaturesThe contents of unsaturated fatty acids gradually decresed in the two cultivars,and the IUFA of Dongnongdongmai1were lower than Jimai22in leaves in water treatment.The linolenic acid content of Dongnongdongmai1was higher and the palmitic acid content was lower than those of Jimai22,C(16:1) and C (18:3) were determined as the reference for freezing rolerant indicators in tillering nods.The treatment under exogenous ABA have highter unsaturated fatty acids contents than the treatment of water.especially in maxmum temperature of4℃、-25℃in leaves and nods.The content of unsaturated fatty acids gradually incresed in the nods of Dongnongdongmai1,and the IUFA was higher than in Jimai22, and achieved very significant levels.(2)Effect of exogenous ABA on the system of cell membrane at low temperaturesIn contrast group,ABA increased the activity of SOD in leaves and tillering nodes of Dongnong1and Jimai22,including the contents in nods was lower than in leaves, the activity of SOD of tillering nodes was higher than in Jimai22all the time except at-10℃,.and in the ABA treatment group, the activity of SOD increased in two cultivars, especially the content in the tilling nodes and leaves of Dongnong1,and had a peak point at-25℃in the tilling nodes.and have a little effect in Jimai22; The activity of POD had a decreasing trend in the leaves of Dongnongl with water treatment,and the activity of POD in tilling nodes was higher than leaves.But with the ABA treatment,the activity of POD was increased in tilling nodes and leaves,especially in tilling nodes,and the activity of POD have peak point in-25℃,achived the60%of maximun,and in Jimai22,the acrivity of POD in leaves was higher than ABA treatment,and had no significant changes in the two groups.The treatment under exogenous ABA have lower raltive conductivity in the two cultivars in different temperature, and the decrease of MDA in Dongnongl was more than in Jimai22,and achived significant levels,it’s shows exogenous ABA can enhance the cold-resistance in the breed of cold-resistant plant.(3)Effect of exogenous ABA on cell ultrastructure observation at low temperaturesDongnongl cellular had a integral structure and lamella of proplastid cleared with water treatment at4℃by transmission electron microscopy, mitochondria has been slightly damaged in Jimai22, other membrane had a integral structure.The degreed of nucleus aggregation deeply in Dongnongl at0℃, showed vacuolation slightly; then nucleus to become smaller and severity vacuolation in Jimai22.The cell structures has been damaged both in the two cultivars at-25℃,and Jimai22showed damaged severity, nucleus collapsed completey,but the cells of Dongnongl had a completely cell structure,and nucleus membrane clearly,and a large number of heavy particles appeared.The cell ultrastructure among organelles of two cultivars were more integraller and vacuolation slighter by ABA treatment.(4)Effect of exogenous ABA on expression of TaFAD3at low temperaturesExogenous ABA affected the express of TaFAD3,and had a different trend in the two cultivars. the trend of Dongnongl was high-low, in contrast group,and trend was Increasd in the wholes,and achieved the maximun at-25℃;and in Jimai22expressed was decreased at0℃..and.The express of TaFAD3in Dongnongl significant higher than Jimai22at0℃,and insisited high level; while it expressed low at O％in Jimai22,and with a decreaced trend at-10℃,it achieved25%at the end,the results showed,ABA inhibited the express of TaFAD3in Jimai22.