Effects Of Exogenous ABA And6-BA On Flag Leaf Senescence And Grain Filling In Different Types Of Stay-Green Wheat

The purpose of this study was to test the hypothesis that whether and how exogenousabscisic acid (ABA) and6-Benzylaminopurine (6-BA) may be involved in mediating flag leafsenescence and accumulation of grain starch and redistribution of carbohydrates during grainfilling of two different stay-green wheat varieties. A stay-green wheat (Wennong6) and anon-stay-green wheat (Jimai20) were grown in the experimental plots with sprayingexogenous ABA and6-BA at10mg L-1for4days in full-bloom stage. The main results wereas follows:1Effects of exogenous ABA and6-BA on Flag leaf Senescence1.1Effects of exogenous hormones on content of chlorophyll in wheat leavesThe chlorophyll content of ABA-treated and6-BA-treated plants in stay-green flagleaves were dramatically increased by15.44and27.78%on7DAA, respectively, over thecontrols, meanwhile these in Jimai20increased by13.26and17.16%.1.2Effects of exogenous hormones on content of soluble protein in wheat leavesAlthough there were no significant differences of both cultivars with ABA application in7-21DAA, significantly increased soluble protein concentrations of Wennong6and Jimai20by18.78%and22.80%separately.6-BA treatment increased soluble protein concentrations ofWennong6and Jimai20in7-35DAA. Treatment with on28DAA increased proteinconcentrations of Wennong6and Jimai20by33.68%and30.10%, respectively, comparedwith the control values.1.3Effects of exogenous hormones on content of MDA in wheat leavesThe ABA-treated and6-BA treated plants had lower leaf MDA content, which werereduced significantly on35DAA,10.86%and26.28%of Wennong6,17.70%4and14.98% of Jimai20, respectively, relative to the controls.2Effects of exogenous hormones on grain filling process2.1Effects of exogenous hormones on ehe grain filling parametersThe maximum rate, mean grain filling rate and duration of ABA-treated Jimai20weresignificantly increased, however, the two kind of rate of Wennong6were increased and itsgrain filling duration was reduced (Table2), implying that the ABA-treated stay-green wheatgain from increased higher grain filling rate compensated the loss of a shortened grain fillingperiod. ABA application markedly extended the active grain filling period2.39d and6.53dfor superior and inferior grains of Jimai20, respectively, but such differences of Wennong6(-0.12d for superior grains and-0.2d for inferior grains) were rather small.2.2Effects of exogenous ABA on dry matter distribution in different organs at maturity inwheatABA improved dry matter translocation amount and raises contribution of dry mattertranslocation amount after anthesis to grain in Jimai20and Wennong6(18.18%up to22.22%,9.43%up to10.42%, respectively). There was no significant difference in dry matteraccumulation amount after anthesis in Jimai20, but that of stay-green Wennong6wasobviously increased through spraying exogenous ABA.2.3Effects of exogenous ABA on starch content, accumulation and accumulation rateStarch accumulation and starch accumulation rate of two types of grains (superior grainsand inferior grains) of the two different types of stay-green wheat. At flourishing floweringstage, we applied exogenous ABA so as to study the differences of different types of grainsand various genotypes in starch content. The results showed that final starch content in bothsuperior and inferior grains of the two wheat were significantly increased, as the values ofJimai20increased by10.2%and9.6%, and the content improved by10.9%and2.6%ofWennong6respectively, contrast to their respective controls.Starch accumulation of Jimai20and Wennong6changed slightly at7DAA and increased rapidly from7DAA to28DAA.ABA application increased starch accumulation rate, in comparison with control treatment.This could explain ABA-treated grains which had the higher starch content. Protein content ofthe two cultivars decreased firstly and increased subsequently. Jimai20revealed higher grain protein at all the stages of grain filling process. Protein content of superior and inferior grainsof Jimai20were17.33%and23.82%higher than that of Wennong6respectively, at35DAA.Compared to the control, application of ABA observably increased protein content of superiorand inferior grains, as the content on days35increased4.64%and5.10%in Jimai20compareto2.80%and13.15%in Wennong6.