| Drought is one of the most important factors to limit wheat production around the world.It is reported that,ear organs of wheat performed significant physiological and biochemical advantages than leaves under drought condition.Photorespiration metabolic pathway is essential for normal growth of the plants,especially important under water stress.It is important for both theoretical and practical meanings to research physiological and molecular base of photorespiration under drought resistance involved wheat ear.In this study,drought-resistant cultivator Xinong 928 and drought-sensitive one Shaan 229 were used as the material and pot experiment were performed.Several of physiological indexes including the net photosynthetic rate,the photorespiration,the chlorophyll content,yield traits of flag leaves and ear organs were detected,and the photorespiration key enzymes activity and gene expression differences in flag leaves and spike bracts were also counted.The main results were listed as follow:1.Flag leaf net photosynthesis of both wheat cultivars were increased,and the effect of water deficit on flag leaf net photosynthetic of two varieties occur in the whole filling stage,and the plain variety is more sensitive to water deficit.The ear PN of two tested varieties increase with the growth of spike bracts organ and then drop.In flowering period(6 DAA),Xinong 928 ear PN increase by 13.5% under water deficit(P<0.05),while reduce by 26.4%(P<0.05)in Shaan 229.Spike bracts(glume and lemma)chlorophyll content and relative water content decreased slightly(P<0.05)in rainfed variety Xinong 928 during the grain filling stage under water deficit,while plain variety Shaan 229 decreased significantly(P<0.05).Results show that two varieties ear PN differences mainly occur in the early grain filling stage under water deficit,and plain variety spike PN was more sensitive to water deficit.2.The photorespiration of ear organs and flag leaves firstly increased and then decreased,reaches a peak at 12 DAA.It indicated that wheat's Pr increased under water deficit,and the drought-resistance varieties were higher than the water-sensitive varieties.In the late anthesis(day after anthesis 24,24 DAA)photorespiration in flag leaves of drought-resistant Xinong 928 increased by 105.7%(P < 0.05)and decreased by 23.6%(P < 0.05)in drought-sensitive Shaan 229.Both of their Pr are higher than the control group,and ear organs rised more than flag leaves,the ear Pr increased about 101.97% and 90.97%(P<0.05)in Xinong 928 and Shaan 229 at 12 DAA.3.The Glycolate Oxidase(GO)activity of flag leaves firstly increased and then decreased.The GO activity increase by 136.8% and 57.2%(P<0.05)in Xinong 928 and Shaan 229 at 12 DAA respectively.Spike bracts(glume and lemma)GO activity firstly increased and then decreased,Pr consistent with GO activity trends.Flag leaf Glutamine Synthetase(GS)of both wheat cultivars were increased.GS activity of flag leaves in drought-resistant Xinong 928 rise by 21.74 %(P<0.05)while fall by 36.02%(P<0.05)in Shaan 229 in the middle anthesis(12 DAA).Glume and lemma of Xinong 928 dropped by 34.2% and 27.1%(P<0.05)respectively,decrease by 44.7% and 57.8%(P<0.05),respectively in Shaan 229.GO gene expression changes earlier than GO activity.GO gene expression was significantly up-regulated in 3d and Xinong 928 was increase more than Shaan 229.The GS gene expression and enzyme activity were similar trends,down more obvious in 5d,indicating that the gene plays a major role in the enzyme activity and gene response is earlier than enzyme activity under water deficit.4.Under water deficit,the 1000-kernel weight decline by 8.14% and 11.51%(P<0.05)in Xinong 928 and Shaan 229,respectively;Yield trait and harvest index(HI)of Shaan 229 dropped strikingly by 41.4% and 16.05%(P<0.05)respectively,while slightly decreased in Xinong 928.Under water deficit,water use efficiency(WUE)in drought-resistant Xinong 928 fall by 21.74 %(P<0.05)and 36.02%(P<0.05)in Shaan 229. |
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