The Role Of Exogenous Nitric Oxide In Grain Quality And Endogenous In Leaves Senescence Of Tillers In Wheat

Nitric oxide (NO) is a key signaling molecule in different physiological processes ofplants, including adapting stress and senescence. The objective of this study was to determinethe effects of NO in wheat growing period. Field-experiments were conducted in2009-2011growing seasons used exogenous and endogenous two kinds of methods to certain:1.Theeffect of exogenous NO on photosynthetic characteristics, chlorophyll fluorescence in leavesand protein components, GMP content and particle size distribution in grains under droughtstress.2. The effect of endogenous NO on senescence of tillers in leaves in wheat. The firstexperiment was carried out in water stress condition which depending on raining entirely,with different concentrations on NO at different spraying time (jointing stage, heading stageand anthesis) was conducted. The second experiment was carried out under different nitrogenlevels using two wheat cultivars with different panicle-type. The main results were as follows:1. The adjustment of exogenous nitric oxide to leaves photosynthetic characteristicsand grain protein composition under drought stress in winter wheat1.1The adjustment of exogenous nitric oxide to leaves photosynthetic characteristics andChlorophyll fluorescence properties under drought stress in winter wheatExogenous NO improved the leaf photosynthetic rate under drought stress significantly,and with concentration increasing, photosynthetic rate rose at first and then declined. Lowconcentration NO increased leaf photosynthetic rate significantly and made it keep higherlevel. Transpiration rate was influenced by period, variety and NO concentration. In generallyspeaking, with increasing of concentration, it first increased and then trends dropped.However, exogenous treatment was not same at different wheat varieties. Low NOconcentration promoted the stomata conductance and high concentration was suppressed. Ithad a positive meaning for NO to maintain suitable stomata opening wheat under droughtstress. NO improved instantaneous water use efficiency of leaves under drought stress, andC2(0.4mmol L-1) improved significantly. Different effects showed as different periodprocessing, jointing stage>heading stage>anthesis. NO improved the chlorophyll content buthad no significantly effect on carotenoid content. It increased Fv/Fm most significantly spraying at jointing stage. Because of increasing the ratio of photosynthetic electron transferenergy to total absorption of light energy, the utilization rate of light energy improved.1.2The adjustment of exogenous nitric oxide to protein composition under drought stress inwinter wheatUnder drought stress condition, we researched different wheat types for grain protein,GMP content and particle size distribution. It showed that, exogenous NO treatment improvedproportion in glutenin, but to albumin, globulin and gliadin, it influenced differently betweenthe varieties. More storage protein in the cereal was the form of glutenin with the NOspraying. NO increased the strong gluten varieties of albumin content type and reducedgliadin content but had no obviously effect on globulin. It increased in the weak glutencultivars type of globulin content, declined albumin content and was not sensitive to gliadin.In conclusion, it was known that NO adjusted the ratio of glutenin and gliadin to influence thegluten type of wheat. While for the structure protein, it regulated albumin or globulinbasically to suit the function of their metabolic activity.2The effect of endogenous NO on senescence of tillers in leaves in wheat2.1The adjustment of endogenous nitric oxide to senescence of tillers in leaves in wheatThe changes of NO content influenced senescence. NO content in main stem andprimary tiller was produced plentifully at heading and then fallen sharply at anthesis. It was atheading that the cell of main stem and primary tiller leaves going active apoptosis began toproduced the DNA fragmentation (except for the primary tiller under N3treatment). Inaddition, the shift induced by NO content changes accompanying with the aging of leaves.NO content in secondary tiller were much higher than main stem and primary tiller duringjointing to heading, and the earliest DNA degradation happened at secondary tiller sincebooting stage, when NO was found to accumulate rapidly. The present results had shown thatthe aging of leaves could be significantly influenced by NO, and it was also suggested thatsenescence were more sensitive relation to the marked changes of NO content than NOcontent itself.2.2The adjustment of N supplying to both endogenous nitric oxide content and NR activity inwheat leavesAn apparent positive correlation existed in both cultivars leaves between NO content andNR activity among main stem, primary tiller and secondary tiller at early stage. Higher Napplications produced higher NR activity and higher NO content. With the progress ofgrowing period, it was weakened for the relationship between NR activity and NO content in leaves, or even with no correlation at heading stage. And with N application levels increasing,both NR activity and NO content reached the maximum and then decreased. There wassaturability for both the NR activity and the NO content in vivo as the N applicationincreasing.2.3The adjustment of endogenous nitric oxide to both tillers senescence and yield and proteincontentThere was an increase in the survival of productive tillers with increase of nitrogen leveluntil N2treatment. Number of live tillers per plant in wheat increased to a peak of3.84(or1.94) for JN17(or TN18) at240-N treatment as more N application supplied. The maximumgrain yield reached at240-N application as the tillers increasing. Thus, grain production wasclosely related to the number of ears producing by primary tiller, which had much more effectupon by N-fertilizer. The aging happened later for primary tiller than main stem under thesame N level. Unlike the other N treatment, the360-N treatment resulted in later aging forprimary tiller till anthesis, however, the largest numbers of ears were not obtained under theN-360application level at maturity. Numbers of tillers died at anthesis. Too late dying fornumbers of ineffective primary tiller had consumed lots of nutrients which caused thereduction of grain yield comparing with240-N application. Nitrogen level influenced kernelprotein content. Compared with main stem, it was decreased by15.8to2.4%for primary tillerin JN17, and by15.7to3.7%in TN18, respectively. Supplied with more N-fertilizer, itbecame more less for the difference between main stem and primary tiller. Overall, these dataindicated that N-fertilizer regulated the ears number of primary tiller and reduced thedifference of protein content between main stem and primary tiller, in other words, it was aneffective ways to regulate the number and quality of primary tiller by N application in order tobalance the yield and uniformity of ears.