| The experiments were carried out in greenhouse and experimental farm of ShandongAgricultural University in20092011growth seasons of wheat. Five wheat cultivarsincluding Yannong19, Lumai21, Zimai12, Yumai34and Wennong6were taken asexperimental material, the effects of interactions between nitrogen and sulfur on grain yieldand nitrogen, sulfur use efficiency in wheat and their physiological basis were studied inhydroponic and field trials.1Effects of interactions between nitrogen and sulfur on seedling growth,uptake and utilization of nitrogen and sulfur in wheatUnder the condition of hydroponics，four wheat cultivars including Lumai21, Yannong19,Yumai34and Zimai12were taken as experimental material. Six fertilization treatments weredesigned, two nitrogen application levels:4mmol·L-1（N4） and8mmol·L-1（N8）, and threesulphur application rates:0.15mmol·L-1（S0.15）、0.60mmol·L-1（S0.60）、2.40mmol·L-1（S2.40）,using the randomized complete block experiment design. The results were as follows：Underthe same nitrogen level, the root activity of wheat was decreased significantly as the sulfurrate increased from0.15mmol·L-1to2.40mmol·L-1. Under the4mmol·L-1of nitrogen level,the contents of sulfur and nitrogen in shoots of seedlings are increased with the increase of Srates, the photosynthetic rates of leaves are increased, the development of leaves andsecondary roots are promoted, and the dry matter accumulations in shoots and roots areincreased, while the use efficiencies of sulfur and conducive to the development of seedlings,and the accumulations of dry nitrogen are decreased. Under the8mmol·L-1of nitrogen level,the sulfur contents of wheat shoots are increased with the increase of S rates, while there arenot significant changes in the nitrogen contents, and the excessive sulfur application can result in the reduce of the ability of photosynthesis. It is also not matter and nitrogen andsulfur in shoots and roots. Under the0.15mmol·L-1of sulfur rate, it is conducive to improvethe contents of nitrogen in shoots and roots with the increase of nitrogen levels. Under the2.40mmol·L-1of sulfur rate, there are no significant differences in the contents of nitrogen inshoots and roots. These results indicate that at certain levels of nitrogen and sulfur application,there is mutual promotion between nitrogen and sulfur, at too high levels of nitrogen andsulfur application, there is mutual inhibition between them, which is not conducive to theabsorptions and uses of nitrogen and sulfur in wheat. The responses of different cultivars tothe nitrogen and sulfur fertilization are different. Under the4mmol·L-1nitrogen level, higherrate of sulfur is more conducive to the accumulations of sulfur and nitrogen in differentorgans of Yumai34and Zimai12compared to those of Lumai21and Yannong19, andunder the8mmol/L nitrogen level, the tolerance abilities of Yumai34and Zimai12againstexcessive sulfur are higher.2Effects of interactions between nitrogen and sulfur on nitrogen, sulfurmetabolism, grain yield and nitrogen, sulfur use efficiency in wheatUnder the condition of field experiments, two wheat cultivars including Yannong19andWennong6were taken as experimental material during20092010and20102011wheatgrowth seasons. The experiment was studied using the split block experiment design, wheatcultivars were as main area, nitrogen levels were as deputy director area and sulphurapplication rates were as duputy area. In20092010wheat growth season, four fertilizationtreatments were designed, two nitrogen application levels0kg·hm-2（N0） and240kg·hm-2（N240） and two sulphur application rates0kg·hm-2（S0） and60kg·hm-2（S60）; In20102011wheat growth season, twelve fertilization treatments were designed, three nitrogenapplication levels:0kg·hm-2（N0）,120kg·hm-2（N120） and240kg·hm-2（N240） and foursulphur application rates:0kg·hm-2（S0）,20kg·hm-2（S20）,40kg·hm-2（S40） and60kg·hm-2（S60）. The results were as follows：2.1Effects of sulphur rates on nitrogen metabolism of wheat under different nitrogenfertilizer application levels Under the0kg·hm-2of nitrogen level, the activity of nitrate reductase （NR） in flag leaf ofYannong19and Wennong6was a trend of rise first, then fall with the increasing of sulphurapplication rate, the NR activity of S40treatment was higher than that of the other Streatments; sulphur application could improve the activity of proteases and the content of totalfree amino, the amount of nitrogen accumulation in vegetative organs at anthesis and maturityand that in grain at maturity, the amount and the efficiency of nitrogen translocation fromvegetative organs to grain. Under the120kg·hm-2and240kg·hm-2of nitrogen level, theactivity of NR, proteases and the content of total free amino in flag leaf of Yannong19were atrend of rise first, then fall with the increasing of sulphur application rate. The amount ofnitrogen accumulation in vegetative organs at anthesis and maturity and that in grain atmaturity, the amount and the efficiency of nitrogen translocation from vegetative organs tograin were a trend of rise first, then fall with the increasing of sulphur application rate. Theactivity of NR in flag leaf on7d and14d after anthesis in Wennnong6was a trend of rise first,then fall with the increasing of sulphur application rate, but higher sulphur application rateimproved the activity of NR on21d and28d after anthesis. The activity of proteases and thecontent of total free amino of flag leaf increased with the increasing of sulphur applicationrate, and the amount of nitrogen accumulation in vegetative organs at anthesis and maturityand that in grain at maturity, the amount and the efficiency of nitrogen translocation fromvegetative organs to grain were increased.The results indicated that under the low nitrogen level, sulphur application could improvethe nitrogen assimilation capacity and accelerate flag leaf protein degradation in the rates ofsulphur from0kg·hm-2to60kg·hm-2, it is conducive to improve the amount of nitrogenaccumulation in all organs and the distribution ratio of nitrogen in grain; under the middle andhigh nitrogen levels, appropriate sulphur application rates could improve the amount ofnitrogen accumulation and the distribution ratio of nitrogen in grain,60kg·hm-2of sulfurapplication rate was not conducive to improve nitrogen metabolism of Yannong19, but wasbeneficial to improve nitrogen metabolism of Wennong6.2.2Effects of sulphur rates on sulphur metabolism of wheat under different nitrogenapplication levelsUnder the same nitrogen level, the activities of O-Acetylserine thiollyase （OASS） andSerine acetyltransferase （SAT） in flag leaf of Yannong19decreased significantly with60kgS hm-2applied; the activities of OASS and SAT in flag leaf of Wennong6decreased on0d,5d and15d after anthesis, but increased significantly on25d after anthesis. Under the low nitrogen level, sulphur application could improve the sulphur accumulation amount inorgans aboveground and sulfur absorption amount after anthesis, and the amount and theefficiency of sulphur translocation from vegetative organs to grain, in the rates of sulphurfrom0kg·hm-2to60kg·hm-2. Under the middle and high levels, appropriate amount of sulfurapplication improved the sulphur accumulation and the amount of sulphur translocation fromvegetative organs to grains in Yannong19and Wennong6,60kg·hm-2of sulfur rate was notconducive to improve the amount of sulphur assimilation and the amount of sulphurtranslocation from vegetative organs to grains in Yannong19, but was still beneficial toimprove the sulphur metabolism of Wennong6.2.3Effects of sulphur application rates on wheat senescence characteristics underdifferent nitrogen application levelsUnder the0kg·hm-2of nitrogen level, the superoxide dismutase（SOD） activity and thesoluble protein content in flag leaf of Yannong19and Wennong6increased and thecontent of malondialdehyde （MDA） in flag leaf decreased with the increasing rates of sulphur,it is conducive to delay the flag leaf senescence. Under the120kg·hm-2of nitrogen level, theSOD activity and the content of soluble protein in flag leaf of Yannong19were a trend ofrise first, then fall with the increasing rates of sulphur, the SOD activity of S20treatment washigher than that of the other S treatments, the content of MDA was a trend of fall first, thenrise with the increasing rates of sulphur; the SOD activity and soluble protein contents in flagleaf of Wennong6increased with the increasing rates of sulphur, the content of MDAdecreased significantly. Under the240kg·hm-2of nitrogen level, the SOD activity andsoluble protein contents in flag leaf of Yannong19were a trend of rise first, then fall with theincreasing rates of sulphur, and the MDA content was a trend of fall first, then rise; the SODactivity and soluble protein contents in flag leaf of Wennong6increased with the increasingrates of sulphur, and the MDA content decreased gradually, but there were no significantdifference among sulfur treatments after14days after anthesis.The results indicate that under low nitrogen level, sulphur application could increase theSOD activity and soluble protein contents in flag leaf of Yannong19and Wennong6anddecrease the MDA content in the rates of sulphur from0kg·hm-2to60kg·hm-2, it is conducive to delay the flag leaf senescence; Under the middle and high nitrogen levels,appropriate amount of sulphur application was beneficial to delay the senescence of flag leafin both cultivars, but the amount of sulphur application exceed to20kg·hm-2was useless toYannong19.2.4Effects of sulphur rates on photosynthetic carbon metabolism under differentnitrogen application levelsUnder the0kg·hm-2of nitrogen level, the photosynthesis rate of flag leaf in Yannong19and Wennong6on0day,7days and14days after anthesis was a trend of rise first, then fallwith the increasing of sulphur application rate, but the photosynthesis rate of flag leaf on21days and28days after anthesis increased with the increasing of sulphur application rate;Sucrose phosphate synthase （SPS） activity of flag leaf, the amount of dry matteraccumulation after anthesis and its contribution to grain of both cultivars increased with theincreasing of sulphur application rate. Under the120kg·hm-2of nitrogen level, thephotosynthesis rate and sucrose phosphate synthase （SPS） activity of flag leaf and the amountof dry matter accumulation after anthesis and its contribution to grain of Yannong19were atrend of rise first, then fall with the increasing of sulphur application rate, S20treatment washigher than the other treatments; the photosynthesis rate and sucrose phosphate synthase （SPS）activity in flag leaf and the amount of dry matter accumulation after anthesis and itscontribution to grain of Wennong6were increased with the increasing of sulphur applicationrate. Under the240kg·hm-2of nitrogen level, the photosynthesis rate of flag leaf on0day and7days after anthesis in Yannong19was a trend of rise first, then fall with the increasing ofsulphur application rate, but the photosynthesis rate of flag leaf on14days,21days and28days after anthesis decreased; The SPS activity and sucrose content in flag leaf of Yannong19decreased with the increasing of sulphur application rate, but the amount of dry matteraccumulation after anthesis and its contribution to grain were a trend of increase first, thenfall; The photosynthesis rate, SPS activity and sucrose content of flag leaf in Wennong6ingrain filling stage increased with the increasing of sulphur application rate, the amount of drymatter accumulation after anthesis and its contribution to grain increased, but there were nosignificant difference between S40and S60treatment. The results indicated that under the low nitrogen level, sulphur application could improvethe photosynthetic carbon assimilation capability and sucrose synthesis capability in flag leafof Yannong19and Wennong6in the rates of sulphur from0kg·hm-2to60kg·hm-2, theamount of dry matter accumulation after anthesis and its contribution to grain also increased;under the middle nitrogen level, appropriate amount of sulphur application could improve thephotosynthetic carbon assimilation capability and the amount of dry matter accumulation,more than20kg·hm-2of sulphur application rate was not conducive to the photosyntheticcarbon metabolism of Yannong19; under the high nitrogen level,60kg·hm-2of sulphurapplication rate was not conducive to the photosynthetic carbon assimilation capability andthe amount of dry matter accumulation both in Yannong19and Wennong6.2.5Effects of sulphur application rates on grain yield and nitrogen, sulphur useefficiency in wheat under different nitrogen application levelsNitrogen use efficiency and sulphur use efficiency of Wennong6is significantly higherthan those of Yannong19.Under the0kg·hm-2of nitrogen level, the grain yield of Yannong19and Wennong6increased with the increasing of sulphur application rate, but sulphur use efficiency decreased;nitrogen use efficiency of Yannong19was a trend of rise first, then fall, S20treatment washigher than the other S treatments, nitrogen use efficiency of Wennong6decreased. Underthe120kg·hm-2and240kg·hm-2of nitrogen levels, the grain yield of Yannong19was atrend of rise first, then fall with the increasing of sulphur application rate, S20treatment washigher than the other S treatments, the grain yield of Wennong6increased; nitrogen useefficiency and sulphur use efficiency of Yannong19were a trend of fall first, then rise,nitrogen use efficiency and sulphur use efficiency of Wennong6significantly decreased.The results indicated that nitrogen use efficiency and sulphur use efficiency of Wennong6were higher, the higher nitrogen application and sulphur application was beneficial toimprove the grain yield of Wennong6; nitrogen use efficiency and sulphur use efficiency ofYannong19were lower, under the middle and high nitrogen application levels, more than20kg·hm-2of sulphur application rate could decrease the grain yield of Yannong19.2.6Effects of sulphur application rate on grain quality of wheat under different nitrogen application levelsUnder the0kg·hm-2of nitrogen level, protein contents and the amount of proteinaccumulation in grains of Yannong19and Wennong6increased with the increasing of sulfurapplication rate; Under the120kg·hm-2and240kg·hm-2of nitrogen levels, protein contentsand the amount of protein accumulation in grains of Yannong19were a trend of rise first,then fall with the increasing of sulfur application rate, N120S40treatment was higher than theother treatments, protein contents and the amount of protein in accumulation in grain ofWennong6increased.Under the0kg·hm-2of nitrogen level, water absorption rate, dough developing time anddough stability time of Yannong19were a trend of rise first, then fall with the increasing ofsulphur application rate, the water absorption rate of Wennong6increased, dough developingtime and dough stability time of Wennong6were extended; Under the120kg·hm-2ofnitrogen level, dough developing time of both cultivars and dough stability time of Yannong19were a trend of rise first, then fall with the increasing of sulphur application rate, doughstability time of Wennong6was shortened, there were no significant difference among Streatments in water absorption rate of both cultivars; Under the240kg·hm-2of nitrogen level,sulphur application decreased water absorption rate, shortened dough developing time anddough stability time, so deteriorate the processing quality of wheat. |
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