【作者】 李华伟；

【导师】 姜东；

【作者基本信息】 南京农业大学 ， 生态学， 2011， 博士

【摘要】 随着全球气候变化加剧,全球变暗、持续性降雨等极端气候增加。黄淮海麦区和长江中下游麦区(30～42°N)是我国主要的小麦产区,气象资料表明,过去的五十年内,该区的日照时数在小麦灌浆期下降2.98～3.67 hrs；而连续降雨大于5天次数达到了的每年0.92次(国家气象局气象中心资料室)。为阐明全球变暗造成的弱光或持续降雨带来的弱光和渍水双重胁迫对小麦生长发育以及籽粒产量和品质的形成的影响,我们分别在2006～2008和2008～2009年进行了以下两个试验,为对该区小麦的高产优质栽培和抗性品种选育提供理论依据。试验一：2006～2008年期间,选用耐弱光性不同的品种扬麦158(耐弱光)和扬麦11(弱光敏感)为材料,从拔节至成熟期对小麦进行遮光处理：分别遮去冠层上部自然光强的8%(S1)、15%(S2)和23%(S3),不遮光为对照(SO),以模拟全球变暗造成的弱光对小麦产量和品质造成的影响；试验二：在2008～2009年期间,选用扬麦158,在0～7 DAA(花后天数,WS1)、8～15 DAA(WS2).16～23 DAA(WS3)和24～31 DAA(WS4)对小麦进行遮光和渍水处理,遮去自然光强的75%,保持土壤表层1～2 cm的水层,以模拟在小麦灌浆期间不定期发生的持续性降雨给小麦产量和品质带来的影响,获得的主要研究结果如下：1.拔节至成熟期遮光对小麦产量和品质形成的影响及其生理机制适度的遮光对小麦产量形成有促进作用(S1和S2提高了扬麦158产量,S1对扬麦11的产量无显著影响),对于籽粒中淀粉及其组分含量无影响；重度遮光(扬麦158的S3,扬麦11的S2和S3)降低了小麦产量,同时也降低了籽粒中总淀粉及支链淀粉的含量。随着遮光程度的增加,小麦籽粒总蛋白,清蛋白,球蛋白及其谷蛋白含量对遮光强度的增加而增加。适度的遮光降低了扬麦158的降落值,但对于湿面筋含量、面筋指数和沉降值,淀粉的糊化参数和粉质参数都无显著影响,但重度遮光却显著提高了面粉的降落质,降低了面粉峰值粘度、低谷粘度和最终粘度,延长了面团形成时间,稳定时间,但降低了面团弱化度。但是重度遮光下产量的降低远低于光照强度的降低(15%和22%)(扬麦11产量在S2下降低了2.3%,扬麦158和扬麦11在S3下分别降低5.9%和6.7%),小麦在长期的弱光环境中形成了以下的适应和补偿效应来减缓弱光对其造成的伤害：(1).植株形态和LAI的改善：随着遮光程度的增加,小麦叶片变大变薄,节问变长,叶面积指数(LAI)增加,提高了小麦群体对光能的截获率,从而部分补偿了光合有效辐射的降低；同时小麦叶片叶绿素含量增加,尤其是叶绿素b的含量,更有利于植物对弱光中占优势的蓝光的利用。(2).叶片光合功能的改善：小麦上3叶Pn在适度遮光(S1和S2)下升高；在重度(S3)遮光下两小麦旗叶Pn降低,但下降的47.25%和61.40%被倒二叶和倒三叶补偿。弱光下叶片最大光化学效率(Fv/Fm)和实际光化学效率(ΦPSⅡ)提高,电子传递效率(ETR)增加,非光化学淬灭系数(NPQ)降低,表明弱光条件下天线色素吸收的光能通过热量散射的形式散失的比例减少,而通过叶片光反应中心Ⅱ比率增加,从而也部分补偿了光合有效辐射的降低。(3).花前贮藏物质转运率的提高：适度遮光条件下,小麦叶片和茎节内蔗糖含量提高,蔗糖：蔗糖果糖基转移酶(SST)和果聚糖：果聚糖果糖基转移酶(FFT)活性提高,有利于果聚糖的积累,最终向籽粒转运量增加,但对籽粒贡献率下降；而重度遮光条件下花后碳同化降低,花前贮藏干物质得到有效利用,在一定程度上补偿了弱光对小麦产量的影响。2.花后遮光和渍水对小麦产量和品质形成的影响及其生理机制花后不同时期遮光和渍水都可显著降低小麦产量,籽粒产量的降低主要由于花后光合同化量的降低造成；WS降低了小麦的总淀粉含量,支链淀粉含量和支/直；WS导致淀粉粒平均粒径下降,主要是小粒径淀粉粒体积百分比增加(B型)造成的；单位重量淀粉粒数目和表面积增大；WS使小麦籽粒蛋白质含量降低,清蛋白、球蛋白和麦谷蛋白含量降低,但醇溶蛋白含量增加；WS2对产量、淀粉和蛋白质品质的影响大于WS3,其次大于WS1和WS4。WS使旗叶净光合速率(Pn)、实际光化学效率((?)PSⅡ)、最大光化学效率(Fv/Fm)和光化学淬灭系数(qP)降低,非光化学淬灭系数((?)NPQ)升高；小麦旗叶组织及叶绿体内活性氧浓度(H2O2浓度和O2-释放速率)以及膜透性增加(MDA含量增加)；旗叶和叶绿体抗氧化酶SOD及叶片CAT活性在WS处理后4天(DAT)升高,在8 DAT却下降；抗坏血酸-谷胱甘肽循环相关酶APX、GR、DHAR和MDHAR活性随胁迫时间延长而增强；WS1移除后,旗叶功能已完全恢复,WS2只有部分恢复；光合参数和抗逆境酶活性的变化与相关编码基因的表达量变化一致。WS激活了花前贮藏物质向籽粒中转运,WS处理越早,茎秆中贮藏干物质向籽粒中转运越早,下部茎节中的干物质的转运时期要早于上部茎秆,并具有较高的转运速率。WS降低了蔗糖：蔗糖果糖基转移酶(SST)和果聚糖：果聚糖果糖基转酶(FFT)的活性,但提高了果聚糖外水解酶(FEH)活性；果聚糖的分解早于茎秆可溶性糖含量的降低。WS抑制了小麦籽粒氮素的积累,但是却提高了花前贮存氮素转运对籽粒的转运,表明小麦籽粒中氮素积累对花前贮藏氮素的依赖性增强。WS使小麦各营养器官花前贮存氮素的转运量(RANP)显著升高,导致总转运量的升高,从而提高了其对籽粒氮素的贡献率(CRNP)。但是WS处理下RANP对NAP的补偿只有5%～14%,最终WS籽粒氮素积累量仍显著低于对照。综上所述,拔节至成熟期重度的遮光和花后遮光和渍水显著抑制了小麦的光合同化能力,减少了光合产物的积累,最终导致小麦籽粒产量及淀粉和蛋白质积累量显著下降。遮光和花后遮光和渍水改变了淀粉、蛋白质及其组分含量,导致最终籽粒品质与面粉品质发生显著变化。但适度的遮光却对籽粒产量和品质的形成有促进作用。花后0～7天遮光和渍水处理之后小麦叶片功能可以完全恢复,但其他时期处理移除后小麦旗叶功能无法恢复。更多还原

【Abstract】 The Huang-Huai-Hai (3-H) plain and the downstream plain of the Yangtze River are main wheat production areas in China. As a consequence of increases in aerosols, air pollutants and population density, dimming or shading (decrease in global radiation, i.e. the sum of the direct solar radiation and of the diffuse radiation scattered by the atmosphere) have become major challenges to crop production in many areas of the world. Furthermore, persistent heavy rainfall event occurs frequently in this region due to increasing climatic variability under global climate. To evaluate the long term low radiation or combined stress of shading and waterlogging impact on crop yield and quality formation, two experiment were done during 2006～2009. Experiment 1:Shading tolerant wheat cultivar Yangmai 158 (YM 158) and sensitive cultivar Yangmai 11 (YM 11) were planted in a field experiment. Four treatments were designed from jointing to maturity, as non-shading (S0),8%,15% and 23% less intercept radiation (S1, S2 and S3); Experiment 2:winter wheat was subjected to simultaneous waterlogging and shading stress (WS) at 0-7 days after anthesis (DAA, WS1), 8-15 DAA (WS2),16-23 DAA (WS3) and 24-31 DAA (WS4), respectively, with no waterlogging and shading was set as the control (WS0); wheat canopy living environment, grain yield and quality, and accumulation and redistribution of carbohydrate and nitrogen were elucidated. Here are the main results:1 Effect of long term low radiation on wheat yield and quality formationCompared with S0, the observed grain yield increased under light shading (S1 and S2 to YM 158 and S1 to YM 11). and lose under heavy shading (S3 to YM 158, S2 and S3 to YM 11). Shading between jointing and maturity showed no effect on amylose content while significantly reduced amylopectin content, which resulted in the significant decrease in total starch content. Heavy shading reduced starch peak viscosity, starch through viscosity and also pasting temperature, prolonged dough development time (DDT) and dough stability time (DST), enhanced falling-number, wet-gluten concentration and SDS-sedimentation volume. However, light shading reduced the falling-number and final viscosity, but had no effect on other quality parameters. Under long-term low radiation conditions, grain protein content and its components increased with increasing in the contents of gliadin, glutinin and GMP (glutenin macropolymer). The initial formation of HMW-GS was predated by shading. The rapid HMW-GS accumulation duration was prolonged by S1. Long-term shading increased falling-number, wet-gluten concentration and SDS-sedimentation volume. In addition, the fluctuations in accumulations quality traits due to shading in Yangmai 158 were less than Yangmai 11. The yield loss of YM 11 was 2.3% and 6.7% in S2 and S3, respectively, and 5.9% in S3 of YM 158, which was much less than the corresponding reduction in radiation. Tree composition effects were found in winter wheat under long term shading to mitigate radiation decrease as below:(1). The enhancement of leaf area, internodes length and LAI. The reduction in PAR via shading was accompanied by an increase in the fraction of diffusion light and blue light. Stem was found to be longer, and leaf to be thinner and bigger. Thus, PAR was intercepted much more than the control in shading treatments, which could partially compensate for the reduction in PAR. Furthermore, an enhancement of chlorophyll content was found in the leaves under shading, especially Ch1 b. The increase in Ch1 b content would improve the proportion of the antenna pigments in light-harvesting complexⅡ, and enable the leaves to effectively catch light, especially the blue light fraction.(2). The present study found that slight shadings (S1 and S2 for the shading-tolerant cultivar YM 158, and S1 for the intolerant YM 11) even increased Pn of the flag leaf, while Pn of flag leaf was depressed when radiation reduction exceeded 15% for YM 11 or 23% for YM 158. Pn of the penultimate and third leaves increased with increasing shading intensity. Thus, in both YM 158 and in YM 11 under S3, about 61.40% and 47.25% of the reduction in flag leaf Pn was compensated by the increase in Pn of the lower leaves. Here, the PSⅡsystem centre was not essentially damaged, and even became more active in the penultimate and third leaves under shading conditions as exemplified by increased Fv/Fm andΦPSⅡ. The relative quantity of electrons passing through PSⅡin dark-adapted leaves was improved (as indicated by increased ETR). Low NPO in shaded leaves indicated that less light-energy absorbed by the antenna pigments in PSⅡwas dispersed via heat.(3). Light shading between jointing and maturity enhanced the sugar stored in vegetative organs during 0-20 DAA (Days after anthesis). and the activity of SST (sucrose: sucrose fructosyltransferase) and FFT (fructan:fructan fruc-tosyltransferase), however. which led to fructans accumulated and then more water soluble carbohydrates (WSC) stored in stem, stored matte Shading had no significant effect on FEH (fructan exohydrolase) activity. Finally, the account of remobilized of post-anthesis stored matter enhanced. Severe shading had the opposite effect on the accumulation of the carbohydrate, and the account of remobilized of post-anthesis reduced while that of pre-anthesis stored enhanced, party compensated the decrease of post-anthesis assimilation. Redistribution amount of nitrogen stored pre-anthesis (RANP) and its account for the final grain protein decreased under low radiation. Grain protein accumulation relied on more from the nitrogen accumulation after anthesis with severer shading.2 Effect of post-anthesis combined shading and waterlongging on grain yield and quality formationCompared with the control (WSO), WS onset at anytime of grain-filling reduced grain yield and changed grain quality significantly; WS reduced amylopectin content, which resulted in the significant decrease in total starch content. And WS also reduced the mean diameters by valume, number, and surface area, enhanced the radio of B type starch. WS reduced grain protein content with a decrease in albumin, globulin and glutinin contents and increasing in the contents of gliadin. WS2 had more severe effect on the grain yield and starch, protein quality traits than WS3, and followed by WS1 and WS4.Depressed flag leaf net photosynthetic rate (Pn) and chlorophyll fluorescence parameters of Fv/Fm,ΦPSⅡand qL, while enhancedΦNPQ were observed in the WS1, WS2 and WS3 leaves. The concentrations of malondialdehyde (MDA) and H2O2, and O2-release rate were increased in the flag leaf and the chloroplasts. The activities of superoxide dismutase (SOD) and catalase (CAT) were stimulated at the 4th day after onset WS (DAT), while were depressed at DAT. The activities of the ascorbate-glutathione cycle enzymes of ascorbate peroxidase (APX), glutathione reductase (GR), dehy-droascorb atereductase (DHAR) and monode hydroascorbate reductase (MDAR) in the flag leaf and the chloroplasts were increased with the prolonged WS stresses. The expression of genes encoding Rubisco activase B (RcaB), major chlorophyll a/b-binding protein (Cab) and antioxidative enzymes-related genes encoding mitochondrial manganese superoxide dismutase (Mn-SOD), chloroplast Cu/Zn superoxide dismutase (Cu/Zn-SOD) and catalase (CAT), and gene encoding a cytosolic glutathione reductase (GR) were well coincided with the activities of these enzymes. The function of flag leaf was fully recovered in WS1, while were only partially recovered in WS2 after WS removed.Reserve stored in stem was activated to remobilize to grains to alleviate the depression in photosynthate accumulation caused by WS. And the earlier WS onset, the more stored reeves was remobilized from stems to grains. The remobilization of stored reserves was activated earlier in the lower internodes than the upper internodes, and had a higher remobilization rate in the lower internodes than upper internodes. Before a significant drop in the total stem WSC, fructans was hydrolyzed and fructose and source began to accumulate. With the prolonged WS stress, fructose, source, glucose together with fructans reduced, caused significant drop in stem WSC. The acceleration of fructans loss was together with an enhancement of the activity of FEH, however an inhibited activity of SST and FFT. The gain from the enhanced remobilization still could not balance the loss of photosynthesi under WS, and the finial grain weight and starch accumulation were lower than control.Redistribution amount of nitrogen stored pre-anthesis (RANP) and its account for the final grain protein enhaced by WS. Redistribution amount of nitrogen stored pre-anthesis (RANP) in the vegetative organs increased under WS and resulted in a enhancement of total RANP. However, only 5%～14% of reduction in NAP was compensated by the the increase in RENP of the vegetative organs, thus, the final grain protein was still lower under WS than control.In conclusion, heavy shading between jointing and maturity, combined shading and waterlogging during grain filling reduced wheat photosynthetic capacity and then carbon assimilation. The reductions in amount of photosynthetic assimilates after anthesis and amount of pre-anthesis stored photosynthetic assimilates and nitrogen in vegetative organs which transferred to grain after anthesis were involved in the depressed grain yield, and accumulations of protein and starch in wheat under low radiation and waterlogging. The starch and protein content were affected, and then resulted in significant changes in qualities of grain and flour. But slight low radiation could enhance wheat production. The flag leaf function could recover after the remove of WS1, but can not after the remove of WS2 and WS3.更多还原