【作者】 蔡瑞国；

【导师】 王振林；

【作者基本信息】 山东农业大学 ， 作物学， 2008， 博士

【摘要】 本研究选用籽粒淀粉合成和特性遗传差异较大的小麦品种(系),设计花后不同强度和挑旗后不同时期遮光处理,研究了小麦籽粒发育过程中淀粉粒度分布特征、直支链淀粉积累特点、淀粉合成关键酶活性变化和完熟期籽粒提取淀粉的理化特性及其它们之间的关系,同时初步探讨了小麦籽粒的淀粉组成与其面团流变学特性之间的关系。研究结果表明,1.小麦籽粒淀粉粒度分布特征及其对弱光的响应小麦籽粒中淀粉的粒度分布因灌浆时期和基因型的不同而存在明显差异。小麦籽粒中灌浆初期形成的淀粉粒于花后15天前体积迅速增大,开花15天后淀粉粒的生成和长大同时进行,花后20-25天检测到最大粒径淀粉粒的存在。花后6天前、花后15-20天和25-30天为小麦籽粒中淀粉粒的形成高峰期。完熟期,小麦籽粒中淀粉粒的数目分布呈单峰曲线,个别品种呈双峰曲线;体积和表面积分布呈双峰曲线,个别品种呈3峰曲线。B型淀粉粒的数目和表面积比例显著高于A型的,糯小麦籽粒中A型淀粉粒的体积比例低于B型的,而非糯小麦籽粒中A型淀粉粒的体积比例高于B型的。不同基因型小麦完熟籽粒中淀粉粒度分布状况存在差异。与强筋小麦相比,糯小麦籽粒中小淀粉粒的比例较高,而弱筋小麦籽粒中大淀粉粒的比例较高。弱光对小麦籽粒中淀粉的粒度分布存在较大影响。花后持续遮光显著影响小麦籽粒中淀粉粒的生长发育,淀粉粒的生成高峰期推迟或减少。成熟期表现为,A型大淀粉粒的比例提高,B型小淀粉粒的比例降低,且此趋势的幅度随遮光程度的增大而提高。挑旗后不同时期遮光对小麦籽粒淀粉粒度分布的影响存在时期差异。挑旗～开花遮光,提高糯小麦籽粒灌浆前期较大淀粉粒的体积比例,降低灌浆中后期的体积比例,成熟期表现为,A型淀粉粒的数目比例提高,体积比例下降,而表面积比例变化不显著;强筋小麦完熟期籽粒表现为,A型淀粉粒的比例显著提高,而B型的降低。灌浆前期遮光抑制A型淀粉核的形成,完熟期表现为A型淀粉粒的比例显著下降,而B型的比例提高。灌浆中后期遮光后小麦籽粒中A型淀粉粒的比例提高,B型的降低,且变化幅度以中期遮光的大。通过分析我们发现,小麦籽粒灌浆过程中光合产物供应降低的情况下,有限的光合产物优先供给现有淀粉粒,促其体积增大,其次用于生成更多的淀粉粒。2.弱光对小麦籽粒灌浆过程中淀粉含量和积累量的变化存在显著影响花后持续遮光条件下,小麦籽粒中淀粉及其组分含量下降,积累量减少,粒重降低,且淀粉含量、积累量和粒重的降幅随遮光程度的增大而提高。持续遮光对直链淀粉和支链淀粉积累的影响存在时期差异。持续遮光条件下,籽粒灌浆前期支链淀粉含量降幅较大,后期直链淀粉降幅较大,表现为遮光前期直支比提高,后期直支比降低。花前(挑旗-开花)遮光后,强筋小麦籽粒灌浆前期的直、支链淀粉含量和直支比提高,后期的淀粉含量和直支比降低。说明,花后光合产物供应充足的情况下,有利于强筋小麦籽粒灌浆前期淀粉的积累,抑制后期的淀粉合成,且对直链淀粉合成的作用较支链淀粉大。此期遮光后强筋小麦支链淀粉的积累量增大,直链淀粉的积累量降低,粒重提高。花前遮光后,糯小麦支链淀粉含量和积累量均显著提高;直链淀粉含量表现为灌浆前期提高,中后期降低,积累量提高;粒重提高。此期遮光后糯小麦直支比降低,说明光合产物供应充足的情况下,更有利于糯小麦支链淀粉的合成。花后不同阶段遮光对小麦籽粒中的淀粉合成均存在抑制作用,且以灌浆中期遮光的影响最大,其次是灌浆后期遮光,最小的是灌浆前期遮光。灌浆前期遮光过程中,小麦淀粉含量呈下降趋势,遮光撤除后出现短时间的反弹性增长,随后低于对照;强筋小麦淀粉积累量降低,粒重下降;糯小麦直链淀粉积累量降低,支链淀粉积累量与对照差异较小,粒重略高于对照。灌浆中期遮光显著降低小麦籽粒中的直、支链淀粉含量和积累量,粒重显著下降。灌浆后期遮光过程中强筋小麦直、支链淀粉含量先提高,后降低,完熟期低于对照处理,淀粉积累量降低,粒重明显下降;此期遮光后糯小麦支链淀粉含量降低,直链淀粉含量变化不显著,直支链淀粉积累量均降低,粒重下降。遮光过程中强筋小麦直支淀粉比呈先提高后降低的趋势,说明遮光初期对非糯小麦支链淀粉的抑制作用较大,随遮光时间延长对直链淀粉合成的抑制作用加强,最终表现为对直链淀粉含量的降幅较大。遮光过程中糯小麦的直支淀粉比基本呈先下降后上升的趋势,说明遮光初期对糯小麦直链淀粉合成抑制作用较大,这与非糯小麦不同。可能与2种类型小麦淀粉的直支链淀粉组成存在较大差异有关。糯小麦和非糯小麦籽粒中的直支链淀粉积累存在显著差异。糯小麦直链淀粉含量显著低于非糯小麦,而其支链淀粉含量显著高于后者,且糯小麦支链淀粉灌浆后期的积累速率高于非糯小麦,但其直链淀粉含量于花后20天就开始降低。3.小麦籽粒淀粉形成的酶学机制及其对弱光的响应糯小麦和非糯小麦籽粒灌浆过程中淀粉合成关键酶活性变化存在显著差异。非糯小麦济南17籽粒中GBSS活性显著高于糯小麦农大糯50206。籽粒灌浆中期济南17淀粉合成所需底物的供应能力较农大糯50206强,表现为SS、UGPP和AGPP活性较高,蔗糖含量降幅较大;籽粒灌浆后期农大糯50206的供应能力较强。济南17籽粒灌浆前期和中期的SSS活性高于农大糯50206,后期低于后者,但农大糯50206的支链淀粉含量始终高于济南17,说明SSS保持一定活性就能满足支链淀粉的合成。籽粒灌浆过程中济南17籽粒中SBE活性高于农大糯50206,而其DBE活性低于后者,说明糯小麦籽粒中DBE对支链淀粉合成的作用较大。花后持续遮光造成籽粒灌浆初期蔗糖含量显著下降,说明叶片的光合同化物供应能力减弱。籽粒灌浆中期,SS、UGPP和AGPP活性下降,表明蔗糖降解和转化能力减弱,从而导致淀粉合成所需底物(主要为G-1-P)的供应能力减弱;同时籽粒中直接参与淀粉合成的关键酶(SSS、GBSS、SBE和DBE)活性均呈下降趋势,导致小麦籽粒中淀粉合成能力的减弱,表现为淀粉含量降低。研究结果表明,持续遮光情况下小麦通过上调灌浆前期和后期淀粉合成相关酶活性,从而提高有限光合同化物的利用效率,以维持较高淀粉积累量。花后持续遮光条件下籽粒中GBSS和SBE活性显著降低,据此推测GBSS和SBE是小麦籽粒中淀粉合成的光调节位点。挑旗后不同时期遮光对强筋小麦籽粒中淀粉合成关键酶活性存在较大影响,且此影响的趋势因遮光时期、酶的种类和小麦基因型而不同。挑旗-开花遮光,提高籽粒灌浆前期的蔗糖供应水平,AGPP和UGPP活性提高,转化蔗糖成为淀粉合成底物的能力增强,同时SSS和SBE活性提高,促进支链淀粉的合成,表现为籽粒灌浆前期2品种支链淀粉含量提高;籽粒灌浆后期,AGPP活性降低,DBE活性也呈下降趋势,从而抑制支链淀粉的合成。花后1-10天遮光,2强筋品种籽粒中蔗糖含量显著下降,将蔗糖转化为淀粉合成底物的能力下降(济南17AGPP活性下降,藁城8901UGPP活性下降);催化支链淀粉合成关键酶活性出现不同程度降低,从而导致小麦籽粒中支链淀粉含量下降。花后11-20天和花后21-30天遮光后,2强筋小麦品种籽粒中淀粉合成关键酶活性降低,抑制淀粉的合成,淀粉含量和积累量显著下降。不同时期遮光后均造成GBSS活性降低,这是遮光抑制直链淀粉合成的重要生理原因。挑旗后不同时期遮光对糯小麦农大糯50206籽粒中淀粉合成关键酶活性存在明显影响。挑旗-开花遮光后,农大糯50206籽粒灌浆前期和中期的SS活性增强,降解蔗糖的能力提高,蔗糖含量迅速下降;同时,此期UGPP和AGPP活性增强,淀粉合成所需底物的供应能力提高;20DAA前其SSS和SBE活性提高,DBE活性变化不显著,可见,花前遮光后提高了农大糯50206籽粒灌浆中前期的支链淀粉合成能力。籽粒灌浆后期,遮光处理的淀粉合成关键酶活性下降较快。最终表现为遮光处理的支链淀粉含量显著提高。花后1-10天遮光后,农大糯50206籽粒中SS和UGPP活性提高,AGPP活性稍有降低,SSS活性提高,15DAA前DBE活性提高,SBE活性下降,最终表现为支链淀粉含量下降。花后11-20天遮光后,SS和AGPP活性提高,UGPP活性无明显变化,蔗糖含量下降;SSS活性提高,但SBE和DBE活性下降,支链淀粉含量显著下降。花后21-30天遮光,蔗糖含量、SS、UGPP、AGPP和SSS活性均显著下降,DBE先上升后下降,SBE活性提高,但最终支链淀粉含量下降。不同时期遮光对农大糯50206籽粒中GBSS活性存在明显影响,且变化趋势与直链淀粉含量变化的趋势类似,相关性分析结果表明,糯小麦籽粒中GBSS活性和直链淀粉含量呈显著正相关。4.小麦籽粒淀粉组成与淀粉理化特性及面团流变学特性的相关性分析不同基因型小麦籽粒淀粉的膨胀特性、糊化特性、热力学特性和结晶程度存在较大差异,同时弱光对小麦淀粉的这些品质特性存在明显影响,影响趋势因遮光时期、遮光强度、基因型和粒位的不同存在较大差异。相关性分析结果表明,淀粉的直、支链淀粉组成和粒度分布与其淀粉品质特征参数间存在一定相关性。具体表现为,膨胀势与直链淀粉含量呈一定程度负相关,与B型淀粉粒的体积比例呈显著正相关。直链淀粉含量与峰值粘度、低谷粘度、稀懈值、峰值时间和糊化温度呈显著负相关,与最终粘度、反弹值和反弹比例呈显著正相关;B型淀粉粒的体积比例与峰值粘度、低谷粘度、稀懈值、峰值时间和糊化温度呈显著正相关,与最终粘度、反弹值和反弹比例呈显著负相关。T0、TP和TC与直链淀粉含量呈显著负相关,与B型淀粉粒比例呈显著正相关,⊿H与淀粉直支组成和粒度分布相关不显著。总淀粉含量与T0和⊿H呈显著负相关。直支淀粉比与TP和TC呈显著负相关。结晶度与淀粉的直支组成和粒度分布相关不显著。不同基因型小麦面团流变学特性存在较大差异,同时光照条件对其有明显影响。小麦籽粒淀粉组成与面团流变学特征参数间存在一定相关性。小麦籽粒淀粉组成与粉质仪参数中的吸水率存在显著相关性,与其它粉质参数相关不显著。吸水率与直链淀粉含量呈显著负相关,与B型淀粉粒体积比例呈显著正相关。直链淀粉含量与拉伸阻力和拉伸比例呈显著正相关,B型淀粉粒的比例与拉伸参数呈一定程度负相关。更多还原

【Abstract】 In this study, we selected more than ten wheat cultivars differing greatly in starch accumulaiton and starch characteristics, and set different-rage-shading treatments after flowering and different-stage-shading treatments beginning from flagging to study starch granule size distribution, accumulation peculiarities, changes of related enzymes activities and isolated starch physiochemical characteristics. At the same time, the realtionship between wheat starch composition and dough rheological properties was also analyzed. The main results were as follows.1. The granule size distribution characteristics of wheat grain starch and response to low lightThe granule size distribution of wheat grain starch varied with grain filling stage and genetype. The starch granules formed in the initial grain filling stage grew fastly before 15 days after anthesis (DAA). In the next time after 15 DAA, the starch granule came into being and grew in volume at the same time. And the most larger diameter starch granules were detected in the stage from 20 to 25 DAA. From analysis we deduced that there were three fastigiums of forming starch granules in wheat grain filling stage, namely, before 6 DAA, 15-20 DAA, and 25-30 DAA.At mature stage, most of wheat cultivars’ endosperms had a unimodal curve in starch granule number distribution, and a bimodal curve in starch guanule volume or surface area distribution. Few cultivars in our study showed a bimodal curve in starch granule number distribution, and a trimodal curve in starch guanule volume or surface area distribution. The number and surface area ratioes of B-type starch granules were much higher than those of A-Type starch granule in mature wheat grains. But the volume ratioes of the two types wheat starch granules were different between waxy and nonwaxy wheat cultivars. In waxy wheat cultivars, the volume ratioes of A-Type starch granules were lower than those of B-type starch granules. On the contrary, the volume ratioes of A-Type starch granules in nonwaxy wheat cultivars were higher than those of B-type starch granules. There were obvious difference in the starch granule distribution among different genetype wheat cultivars. Compared with strong-gluten wheat cultivars, waxy wheat cultivars’ endosperms had much number smaller diameter starch granules, on the other side, the ratio of bigger starch granule in weak-gluten wheat cultivars’ endosperm was higher.Size distribution of starch granules in wheat endosperm were influenced markedly by low light. Reduced light density continually after wheat flowering influenced the growing and development of wheat grain starch granules significantly. Time postponed or number cut down of the forming fastigiums of wheat starch granules after continual shading. In mature wheat grains, the ratio of A-type starch granule increased markedly, the ratio of B-type starch granule decreased obviously, and the influencing range of the two type starch granules incresed with the degree of shading.Size distribution of starch granules in wheat endosperm were influenced markedly by different-stage low light after flagging stage and the influence varied with the stage of shading. After shading from flagging to anthsis, the volume ratio of larger diameter starch granules in waxy wheat grain increased in the early stage of grain filling, and decreased during the next time of grain filling. In mature waxy wheat grains, A-type starch granules’ number ratio increased, volume ratio decreaesd, and surface area ratio did not change significantly. In mature strong-gluten wheat grains, the ratioes of A-type starch granules increased markedly and those of B-type starch granules decreased obviously after shading from flagging to anthsis. Shading during the early stage of grain filling inhibitted the forming of A-type pyrenoids in wheat grains, so that the ratio of A-type starch granules in mature wheat grains decreased markedly, on the contrary, B-type starch granule ratio increased. Shading during the midterm and latter grain filling stages could increase the ratioes of A-type starch granules and decrease those of B-type starch granules. At the same time, the influencing range of shading from 11-20 DAA was much larger than that of low light from 21-30 DAA.From the results of shading’ effects on wheat starch granule distribution, we found that limited photosynthate supplied the existed starch granules firstly for growing and development, nextly afforded to come into being new starch granules during wheat grain filling.2. Low light affected the dynamic changs of starch content and accumulation during wheat grain filling markedlyUnder the low light conditions all through grain filling, wheat starch and its components contents decreased, accumulations reduced and kernel weight decreased. And those changes aggravated with the increasing of shading degree. There were stage differences for the effects of low light on amylose and amylopectin contents under shading conditions from flower to mature. The amylopectin contents decreased greatly in the early grain filling stage, but the amylose contents reduced sharply during the latter grain filling stage. Those changes appeared as the ratio of AM to AP increased in the early stage, and decreased in the latter stage during grain filling.After shading from flagging to flower, the amylsoe (AM) and amylopectin (AP)content and the ratio of AM to AP of strong-gluten wheat cultivars increased in the early stage of grain filling, but the starch content and AM to AP ratio decreased during the latter grain filling stage. Those changes indicated that photosynthate in abundant supply could accelerate the accumulation of starch in wheat grain during early grain filling stage, inhibite the synthesis of starch in the latter grain filling stage and affect the synthesis of AM much larger than AP. Shading from flagging to flower could increase the AP accumulation, decrease the AM accumulation and raise grain weight of strong-gluten wheat. In waxy wheat cultivar, shading from flagging to flower could increase markedly the AP content and accumulation, increase the AM content in the early grain filling stage, decrease AM content in next grain filling stage, and increase AM accumulation and kernel weight. The ratio of AM to AP decreased during grain filling after shading from flagging to flower, which suggested that photosynthate in abundant supply was in favor of being used to AP synthesis.The different stage shadings after flower all inhibitated starch synthesis in wheat grain and degree of the effects varied with shading stages. Shading from 11 to 20 DAA affected the starch synthesis largestly, the effects of shading from 21-30 DAA was the next, but shading from 1-10 DAA influenced the starch synthesis slightly. Shading from 1-10 DAA could decreased the starch content during shading, after got rid of shading the starch content raised in a moment time, but in the next time the starch content of shading treatment was below as compared with the CK. At mature stage, the starch and its components accumulations and grain weight decreased in strong-gluten wheat, but in waxy wheat the AM accumulation decreaed, the AP accumulation changed slightly and grain weight raised a little. Shading from 11 to 20 DAA decreased significantly the content and accumulation of wheat starch and its components, at the same time, decreased the grain weight markedly. The AM and AP contents of strong-gluten wheat cultivars increased firstly and decreased in the next time after shading from 21 to 30 DAA, at mature wheat grains the starch contents and accumulation and grain weight were lower than those in CK. After shading from 21 to 30 DAA, the AP content in waxy wheat decreased, the AM content changed slightly, but the accumulation of AP and AM and grain weight all decreased.The ratio of AM to AP in strong-gluten wheat cultivars increased firstly and decreased subsequently during shading, which indicated that low light inhibitated the synthesis of AP more seriously during the early stage of shading, and with the prolong of shading, low light inhibitated the accumulation of AM much greatly. Finally, the decreasing percent of AM content was larger that of AP in nonwaxy wheat cultivars. The ratio of AM to AP in waxy wheat cultivars decreased firstly and increased subsequently during shading, which indicated that that low light inhibitated the synthesis of AM more seriously during the early stage of shading, which was different from that in nonwaxy wheat cultivars. Those difference might be related to the compositive ratio of AM and AP in waxy and nonwaxy wheat cultivars.The accumulation of AM and AP were significantly different between waxy and nonwaxy wheat cultivars. The AM content of waxy wheat was much lower than that of nonwaxy wheat, but its AP content was significantly higher than that in nonwaxy wheat. The speed of AP accumulate in waxy wheat during the latter grain filling stage was higher than that in nonwaxy wheat, but its AM content began to decrease at 20 DAA, however, the AM content of nonwaxy wheat increased all along during grain filling.3. The enzymatic mechanism of wheat starch biosynthesis and response to low lightDynamic changes of activities of enzymes involved in starch synthesis in waxy wheat grains during grain filling were different from those in nonwaxy wheat grains. The activity of GBSS in nonwaxy wheat cultivar JN17 was significantly higher than that in waxy wheat cultivar NDN50206. The supplying ability of substrates to synthesize starch in the grains of JN17 was stronger than that in NDN50206 grains during the medium grain filling stage, which appeared as the activities of SS, UGPP, and AGPP were higher and the decreasing rang of sucrose was larger in the grains of JN17 than those in NDN50206 grains at that time. On the contrary, the supplying ability of substrates to synthesize starch in the grains of NDN50206 was stronger than that in JN17 grains during the latter grain filling stage. The activities of SSS in JN17 grains was higher than those in the grains of NDN50206 during the early and medium grain filling stages, but during the latter grain filling stage the SSS activies of JN17 were lower than NDN50206’s, meanwhile, the AP content in the grains of NDN50206 was always higher than that in JN17 grains, which suggested that the activity of SSS maintained a certain level to be enough to the synthesis of AP in wheat during grain filling. During grain filling, the activity of SBE in JN17 grains was higher than that in the grains of NDN50206, but its DBE activity was lower than the latter’s, which indicated that DBE contributed greaterly to the synthesis of AP in waxy wheat grain as compared with nonwaxy wheat cultivars.The sucrose contents of wheat grains at initial grain filling stage decreased obviously after shading throughout grain filling, which suggested that the photosynthate supplying ability of wheat leaves went down under low light conditions. During the medium grain filling stage, the activities of SS, UGPP, and AGPP all decreased under low light conditions, which indicated that the ability of degradation and transform of sucrose in wheat grains weakened. Consequently, the supplying ability of substrates for starch synthesis fell. At the same time, the activities of SSS, GBSS, SBE, and DBE all went down under low light conditions, which resulted in low starch contents. From the results in this study, we could see that, under low light conditions throughout grain filling, wheat could improve the activities of enzymes involved in starch synthesis during the early and latter grain filling stage, thereby increased the utilization efficiency of the limited photosynthate, in this way wheat could maintain a higher starch accumulation. The SBE and GBSS activities in wheat grain decreased greatly after shading, which suggested that the SBE and GBSS were the regulatory sites of light in the biosynthesis of starch in wheat grains.The activities of key enzymes involved in starch synthesis of strong-gluten wheat grains were influenced greatly by different stage shading after wheat flagging stage and the effects varied with the shading stage, enzyme kind, and wheat genotype. After shading from flagging to flower, the supply level of sucrose increased during the early grain filling stage. At the same time the activities of AGPP and UGPP in wheat grains improved, so that the ability of sucrose-transform in wheat grains increased. Meanwhile, the activities of SSS and SBE in wheat grains enhanced, which facilitated the biosynthesis of AP. As a result, the AP contents of the two strong-gluten wheat cultivars increased obviously in the early grain filling stage. At the latter grain filling stage, the activities of AGPP and DBE decreased, which inhibited the biosynthesis of AP in the two wheat cultivars. After shading from 1 to 10 DAA, the sucrose contents in the grains of the two strong-gluten wheat culticars decreased, the ability of translating sucrose to substrate of starch synthesis went down, and the key enzymes involved in the biosynthesis of AP appeared different extent decrease, which resulted in the decrease of AP contents in strong-gluten wheat cultivars. After shading from 11 to 20 DAA and shading from 21 to 30 DAA, the key enzymes involved in the biosynthesis of starch of the two strong-gluten wheat cultivars all decreased, so that the biosynthesis of starch were inhibited after shading. As a result, the starch content and accumulation decreased. The activities of GBSS in strong-gluten wheat cultivars decreased after different-stage shading, which was the important physiological reason for the decrease of AM content under low light conditions.The activities of key enzymes involved in starch synthesis of waxy wheat grains were influenced greatly by different stage shading after wheat flagging. After shading from flagging to flower, the activities of SS in waxy wheat cultivar NDN50206 increased during the early and medium grain filling stage, so that the ability of sucrose degradation improved, as a result, the sucrose content decreased rapidly. At the same time, the activities of UGPP and AGPP increased, so that the supplying ability of substrate for starch biosynthesis improved. Before 20 DAA, the activities of SSS and SBE in waxy wheat grains enhanced and the activities of DBE did not change significantly. In this way, shading from flagging to flower could improve the ability of AP synthesis in waxy wheat grains during the early and medium grain filling stage. During the latter grain filling stage, the activities of enzymes involved in waxy wheat starch biosynthesis of shading treatment went down much quickly than CK. In mature waxy wheat grains, the AP content increased after shading from flagging to flower. After shading from 1 to 10 DAA, the activities of SS and UGPP in waxy wheat grains increased, AGPP activity decreased slightly, SSS activity enhanced, DBE activity improved before 15 DAA, and the activity of SBE went down. As a result, the AP content of this shading treatment in waxy wheat grains decreased. After shading from 11 to 20 DAA, the activities of SS and AGPP in waxy wheat grains increased, UGPP activity did not change obviously, sucrose content decreased, SSS activity enhanced, but the activities of SBE and DBE decreased markedly. As a result, the AP content of this shading treatment in waxy wheat grains decreased significantly. After shading from 21 to 30 DAA, the sucrose content and activities of SS, UGPP, AGPP, and SSS all decreased markedly, DBE activity increased firstly and then decreased during shading, and SBE activity increased. As a result, the AP content of this shading treatment in waxy wheat grains also decreased. The activities of GBSS in waxy wheat grains were influenced greatly by different stage shading after flagging and its changing trend was similar to the changes of AM. The correlative analysis results indicitated that AM content was in significantly positive correlation with the acticity of GBSS in waxy wheat grain.4. Relationships of wheat starch composition and starch physiochemical characteristics or dough rheological propertiesThere were greater difference among different genotype wheat cultivars in swelling, pasting, thermic, and crystal characteristics. The above characteristics of wheat starch could be influenced by low light and the effects varied with the shading stage, shading rage, wheat genotype and kernel position. The correlative analysis results indicitated that there were close correlations between wheat starch composition, which included AM or AP content and granule size distribution, and starch physicochemical characteristics. The swelling power of wheat starch was negatively correlated with AM content (AMC) to a certain extent and significant positively correlated with the B-type starch granule volume ratio (BV). AMC was significant negatively correlated with peak viscosity (PV), through viscosity (TV), breakdown (BD), peak time (PT), or pasting temperature (PT). On the contrary, AMC was significant positively correlated with final viscosity (FV), setback (ST), or setback ratio (SR). BV was significant positively correlated with PV, TV, BD, peak time(PT), or PT, and significant negatively correlated with FV, ST, or SR. T0, TP, or TC was significant negatively correlated with AMC, and positively correlated with BV. There was not a significant correlation between starch composition and⊿H or craystal raio of wheat starch.The dough rheological properties of wheat were different among wheat cultivars and they could be affected by low light. From the results in our study, we found that there were a certain correation between wheat starch compositon and wheat dough rheological properties. Wheat starch composition were significant correlated with water absorption, but they were not significant correlated with other farinograph parameters. The water absorption parameter was significant positively correlated with BV, but negatively correlated with AM. At the same time, we found that AM was significant positively correlated with resistance or ratio of the extensograph parameters. BV was negatively correlated with the extensograph parameters, but they were not significant.更多还原