Effects Of Cold Acclimation And ABA On Chlorophyll Fluorescence And Antioxidant Enzyme Activities Of Winter Wheat

‘Dongnongdongmai 1' is the only one winter wheat cultivar that can be grown in cold area of Heilongjiang Province,‘Jimai 22'is a winter wheat cultivar which can safely overwinter in Shandong and other areas.At present,there are few studies on the chlorophyll fluorescence characteristics of the two winter wheat cultivars under the cold acclimation period.In order to investigate the effects of cold acclimation and exogenous ABA on chlorophyll fluorescence characteristics and antioxidant enzyme activities of different cold-tolerant winter wheat cultivars,In this study,the foliage was sprayed with moderate concentration of ABA at three-true leaf stage,the chlorophyll fluorescence parameters,pigment content,antioxidant enzyme activity and other physiological indexes of two winter wheat cultivars were determined,and the gene expression patterns of photosynthetic related proteins under natural growth conditions were analyzed according to temperature changes.In order to fully understand the impact cold acclimation on the two wheat varieties,we also conducted an indoor simulation of cold acclimation treatment test,and the determination of the relevant indicators.The results of the tests are as follows:1.In the field of cold acclimation test,it was found that the ‘DN1'compared with the 'JM22'had higher NPQ value,pigment content,antioxidant enzyme activity and lower MDA content to adapt to the temperature change.‘JM22' is not sensitive to the low temperature of the cold acclimation period,Its pigment content,SOD,POD,APX activity and MDA content remained s Tab.and did not appear a large ups and downs,therefore,the chlorophyll fluorescence parameters such as ?PSII,q P and ETR of ‘JM22' during the detection period are higher than ‘DN1' in more time.Simultaneously,it was found that ‘DN1' could reduce the actual photochemical quantum yield(?PSII),PSII maximum photochemical efficiency(FV/FM),photochemical quenching coefficient(q P),and relative electron transport rate(ETR)substantial decline;And ‘JM22' the parameters of the decline is more obvious,when the temperature suddenly drops below 0?.qPCR results show: chlorophyll a/b-binding protein gene(TaCP3,TaCP5)have a higher expression of two wheat in each period,and corresponding changes of pigments;TaNPQ4 involved in photochemical quenching have maintained a relatively high expression levels with the corresponding of higher NPQ in ‘DN1'.2.Our study found that 'DN1' parameters are similar with the field of natural cold acclimation results under indoor simulated cold acclimation,and Compared with ‘JM22',‘DN1' had higher chlorophyll fluorescence parameters,pigment content and antioxidant enzyme activity under moretemperature conditions.Compared with ‘JM22',the decrease of chlorophyll fluorescence parameters was smaller,POD and APX had higher activity and lower MDA content of ‘DN1',after a relatively low temperature(-4 ? /-10 ?)treatment.At the same time,we found that ‘DN1'was more acclimatized at(4 ? /0 ?)day and night,and that ‘DN1' was more able to adapt to lower temperatures after acclimatized at4?/0?.3.The effect of exogenous ABA on chlorophyll fluorescence and antioxidant enzyme activities of two winter wheat cultivars showed that the effect of exogenous ABA on the short-term effects of two winter wheat was more clear.In the spraying ABA the next day(September 24)two winter wheat's ?PSII,q P,ETR,chlorophyll a,chlorophyll b and carotenoids content have asignificant decline and NPQ,POD,APX,etc are Significant increase compared with the control.At the same time,we found that the effect of exogenous ABA on the two winter wheat cultivars was more significant at the temperature below 0?.When the average temperature was about-3?on October29,ABA can effectively improve the chlorophyll fluorescence parameters,the content of each pigment,antioxidant enzyme activity and can upregulate the expression of TaCBP3,TaCBP5,TaNPQ4 and can significantly reduce the MDA content;In other testing periods,the two wheat varieties showed different responses to ABA,and the response of ‘DN1' to ABA was closer to the latter part of the detection period,but ‘DN1' response to ABA was at lower temperature.The results of the tests show that ‘DN1'can adjust the temperature changes earlier to maintain the stability of its photosynthetic system and antioxidant system through the changes in gene expression and related physiological and biochemical changes,and as well as to avoid damage caused by a sudden cooling later.Exogenous ABA treatment can play a positive role in the two wheat varieties,but the response of the two cultivars to ABA is different in the cold acclimation period...