水稻淀粉合成对夜温变化的响应

目的 探究夜温变化对水稻淀粉形成的影响及其生理机制【方法】以优质软米浙禾香2号为材料,在灌浆初期设置31℃/20℃ (LT)、31℃/24℃ (NT)、31℃/28℃ (HT)3个夜间温度模式,测定其直链淀粉和支链淀粉含量及合成关键酶活性及相关基因的表达。结果 1)与NT相比,LT和HT处理显著降低粒重和淀粉积累,降低糊化温度和胶稠度,并影响支链淀粉链长,降低支链淀粉含量,提高直链淀粉含量,HT的影响要大于LT;2) LT和HT处理对白天叶片净光合速率的影响不显著,但显著降低籽粒中非结构性碳水化合物积累,抑制蔗糖转运基因OsSUT1、OsSUT2和OsSUT4在夜间和白天表达;3) LT 和HT处理降低夜间和白天蔗糖水解相关酶活性,增加淀粉水解酶活性,导致可溶性糖含量升高,籽粒中糖利用受阻;4)与NT相比,LT和HT处理下腺苷二磷酸葡萄糖含量呈现白天降低而夜晚升高的趋势,腺苷二磷酸葡萄糖积累及利用受到抑制,颗粒结合淀粉合酶活性随处理时间延长而显著降低,且白天酶活性也受夜间温度的影响;5)与NT相比,LT和HT处理降低了夜间支链淀粉合成相关酶活性,抑制了夜间相关基因的表达,导致支链淀粉合成受阻,但对白天酶活及相关基因表达的影响不大。结论 夜间高温对淀粉积累的影响要大于夜温降低,夜间高温/低温抑制全天蔗糖转运及代谢,进而抑制淀粉积累;支链淀粉合成受阻是导致直链淀粉相对含量升高的主要原因,直链淀粉合成相关酶活性(白天)受夜温变化影响,而支链淀粉合成相关酶活性(白天)受夜温变化的影响不显著。     

灌浆结实期冷水胁迫对寒地粳稻籽粒淀粉积累及相关酶活性的影响

采用寒地粳稻田间试验,研究灌浆结实期冷水胁迫(17℃,持续3,6,9,12,15d)对三个不同寒地粳稻品种(东农428、松粳10、龙稻7号)籽粒淀粉合成与积累、产量构成因素的影响,并探讨冷水胁迫下淀粉合成关键酶活性变化与淀粉组分及其含量的关系。结果表明,与对照相比,灌浆结实期17℃冷水胁迫下,不同寒地粳稻品种灌浆结实期可溶性淀粉合成酶(SSS)活性、淀粉分支酶(SBE)活性降低,籽粒总淀粉含量、支链淀粉含量显著下降,直链淀粉含量显著上升。相关分析表明,SSS活性、SBE活性与淀粉及其淀粉组分密切相关,对淀粉及淀粉组分含量变化均有同等重要的作用。同时,冷水胁迫下,灌浆结实期不同寒地粳稻品种的每穗实粒数、千粒重及结实率均显著降低,随着冷水胁迫时间的延长,不同寒地粳稻品种各指标的变化幅度逐渐加大。寒地粳稻产量构成因素各相关指标是不同耐冷性品种响应冷水胁迫的差异产物,可用于耐冷性鉴定。从不同寒地粳稻品种对冷水胁迫的反应指数看,松粳10受影响最大,东农428受影响最小,龙稻7号介于二者之间。     

开放式主动增温对双季优质籼稻籽粒淀粉积累及其关键酶活性的影响

【目的】明确未来气候变暖条件下双季籼稻品质形成的淀粉积累特征。【方法】早稻以湘早籼45号(常规籼稻)和柒两优2012(杂交籼稻)，晚稻以九香粘(常规籼稻)和泰优398(杂交籼稻)为试验材料，利用开放式主动增温系统，设置全生育期增温(早稻增温1.4～1.5℃，晚稻增温2.0～2.3℃)和不增温2个处理，探明全生育期增温对双季籼稻籽粒淀粉合成及其关键酶活性的影响。【结果】开放式增温条件下，稻米中总淀粉和支链淀粉含量无显著变化，直链淀粉含量和直链淀粉占总淀粉比例降低，其中，柒两优2012和九香粘的直链淀粉含量分别显著降低了4.2%和3.4%。与不增温处理相比，增温提高了灌浆前期(抽穗后7～14 d)籽粒中总淀粉和直链淀粉积累量，但对晚稻籽粒直链淀粉积累量的影响持续时间要大于早稻，主要与淀粉合成关键酶活性不同程度升高有关。增温条件下，早稻灌浆结实期籽粒中二磷酸腺苷葡萄糖焦磷酸化酶(ADGPase)活性呈先升高后降低趋势，而晚稻呈逐渐升高趋势；增温降低了早稻抽穗后14 d和晚稻抽穗后7 d籽粒中结合态淀粉合成酶(GBSS)活性，但显著增加晚稻抽穗后期(抽穗后21、28 d)籽粒中GBSS活性；同...     

超级稻花后强、弱势粒淀粉合成相关酶活性和激素含量变化及其与籽粒灌浆的关系

 种植4个超级稻品种\[两优培九和Ⅱ优084（杂交籼稻）、淮稻9号和武粳15（粳稻）\]和2个高产对照品种\[汕优63（杂交籼稻）和扬辐粳8号（粳稻）\],观察其结实期强、弱势粒中蔗糖合酶（SuSase）、腺苷二磷酸葡萄糖焦磷酸化酶（AGPase）、淀粉合酶（StSase）和淀粉分支酶（SBE）活性及玉米素+玉米素核苷（Z+ZR）、3 吲哚乙酸（IAA）和脱落酸（ABA）含量的变化,并测定了强、弱势粒灌浆速率。结果表明,超级稻品种强势粒的最大灌浆速率、到达最大灌浆速率的时间、平均灌浆速率和糙米重与对照品种差异较小,超级稻品种弱势粒的灌浆速率和糙米重显著低于对照。灌浆期强、弱势粒的SuSase、AGPase 、StSase 和SBE活性变化及Z+ZR、IAA 和ABA 含量变化均呈单峰曲线。弱势粒的SuSase、AGPase、StSase 和SBE的峰值活性和平均活性及其Z+ZR 和IAA的峰值含量和平均含量均低于强势粒。弱势粒的ABA 峰值含量和平均含量显著高于强势粒,超级稻品种高于对照品种。籽粒灌浆速率与SuSase、AGPase和StSase 活性及Z+ZR 和IAA含量均呈显著或极显著正相关,与SBE活性及ABA含量的相关不显著。说明超级稻品种弱势粒中较低的SuSase、AGPase和StSase活性及较低的Z+ZR和IAA含量是其灌浆速率小、粒重轻的一个重要原因。     

小麦籽粒发育过程中淀粉和激素含量的变化及其关系

为给小麦籽粒生长发育的化学调控提供依据,以蛋白质含量相近、粒重和淀粉含量差异大的小麦品种川麦32和川麦107为材料,研究了籽粒发育过程中淀粉、激素含量的变化及其相互关系.结果表明,大粒品种川麦32授粉后ZR含量高,灌浆中期IAA峰值高,而小粒品种川麦107籽粒发育期间淀粉含量高,GA含量也一直高于大粒品种川麦32,因而说明ZR和IAA含量与籽粒的大小及粒重关系密切,而GA含量与淀粉含量关系更密切.     

结实期低温胁迫对水稻强、弱势粒淀粉形成与积累的影响

【目的】研究结实期低温胁迫对水稻强、弱势粒淀粉组分含量、积累速率及关键酶活性的影响，明确淀粉合成关键酶活性变化对淀粉积累速率的调控效应，探究强、弱势粒淀粉形成积累差异对水稻产量的影响。【方法】以耐冷型品种东农428和冷敏型品种松粳10为试验材料，设置1个常温处理(白天温度28℃，14h/夜间温度22℃，10 h，7 d)和4个低温处理(17℃，低温处理时间分别为1、3、5、7 d)，分析了结实期低温胁迫对强、弱势粒淀粉组分积累、合成关键酶活性、水稻产量及构成因素的影响，并探讨了灌浆期各阶段淀粉积累差异与酶活性变化的关系。【结果】与对照相比，结实期低温胁迫降低了两个品种水稻强、弱势粒中腺苷二磷酸葡萄糖焦磷酸化酶(AGPase)、可溶性淀粉合成酶(SSS)、淀粉分支酶(SBE)的峰值活性以及支链淀粉和总淀粉含量，提高了齐穗后28~38 d 低温处理3、5、7 d的颗粒结合型淀粉合成酶(GBSS)活性和直链淀粉含量。与对照相比，各低温处理酶活性最高和淀粉积累最快的时间均有不同程度的推迟，低温处理7 d的影响最大，强、弱势粒低温处理7 d的支链淀粉和总淀粉含量分别在齐穗后13、18 d降幅最大，直链淀粉含量在28 d增幅最大。相关分析表明，强、弱势粒直链淀粉含量及强势粒支链淀粉、总淀粉含量与其最大积累速率呈极显著正相关，弱势粒支链淀粉、总淀粉含量还受到其最大积累速率出现时间的影响。AGPase、GBSS、SSS、SBE活性变化与淀粉积累速率和积累时间早晚密切相关，对淀粉及淀粉组分含量的变化有着明显的影响。同时，结实期低温胁迫显著降低了水稻的千粒重、结实率和产量，且随低温处理天数的增加降幅逐渐增大。结实期低温胁迫对弱势粒中淀粉合成关键酶活性变化影响大于强势粒，弱势粒淀粉合成积累减慢，含量降低，导致水稻千粒重显著下降，产量降低。【结论】就品种而言，耐冷型东农428具有较高的淀粉合成关键酶活性，淀粉及其组分含量较高，在低温胁迫下产量能维持在较高的水平。因此，强、弱势粒淀粉合成关键酶活性对淀粉合成起着非常关键的调控作用，淀粉组分和含量及其变化对产量有着十分重要的影响。     

优良食味水稻品种籽粒蛋白质积累特征及其对氮素水平的响应

【目的】探讨优良食味水稻品种的籽粒蛋白质积累特征及其对氮素水平的响应。【方法】以食味值不同的常规粳稻和杂交稻为材料,在结实期设置不同氮素施用水平处理,分析不同类型品种在不同氮素水平下的蒸煮食味品质及其与稻米蛋白质及其组分含量的关系。进一步分析各品种在不同氮素水平下稻穗不同部位的氨基酸含量及籽粒蛋白质含量在结实期的动态变化,总结优良食味水稻品种的籽粒蛋白质积累特征及其对氮素水平的响应特征。【结果】优良食味水稻品种籽粒蛋白质含量较低,且随着氮素水平的增加而上升;优良食味水稻崩解值较高,消减值较低;蒸煮食味品质受氮素水平影响较小。优良食味水稻品种蛋白组分含量较低,且稻米蛋白质含量与食味品质呈显著负相关。在常规粳稻中,稻米食味值与清蛋白、球蛋白和醇溶蛋白含量均显著负相关;在杂交稻中,稻米食味值与醇溶蛋白和谷蛋白含量显著负相关。优良食味水稻品种籽粒充实过程中游离氨基酸含量较低,并呈现较低水平的蛋白质积累。而食味较差品种灌浆期籽粒的氨基酸含量较高,成熟籽粒蛋白质含量也较高,且氮素供应水平提升其籽粒蛋白质含量的效应更为显著。【结论】优良食味水稻品种的籽粒蛋白质含量较低,与其充实过程中蛋白质积累水平较低有紧密关系,且受氮素水平影响较小。     

不同冠温特征小麦的籽粒灌浆特性及内源激素的变化

为阐明小麦冠层温度与其籽粒灌浆特性、内源激素变化的关系,2001~2003年对黄淮麦区及河南省推广的30个小麦品种冠温特征、籽粒灌浆特性和籽粒发育过程中内源激素(玉米素ZR、赤霉素GA3、生长素IAA、脱落酸ABA)含量及比值的变化进行了研究。结果表明,豫麦50在灌浆后期冠层温度明显降低,表现为冷尾型;豫麦34和豫麦70在灌浆后期冠层温度有上升的趋势,表现为暖尾型。在灌浆末期冷尾型与暖尾型小麦冠层温度相差超过2.5℃。冷尾型豫麦50强、弱势粒的最大灌浆速率、平均灌浆速率和渐增期、快增期、缓增期的灌浆速率均大于暖尾型豫麦34、豫麦70;强势粒的激素含量变化及其比值变化规律性明显,弱势粒表现的规律性不如强势粒。冷尾型豫麦50强势粒ZR、IAA、GA3含量峰值均高于豫麦34、豫麦70,其ZR/ABA、GA3/ABA、IAA/ABA峰值亦高于暖尾型豫麦70和豫麦34,而ABA含量在灌浆中期上升快,且高峰值大于豫麦70和豫麦34,达到高峰后下降较快;在弱势粒中,豫麦50上述各种激素含量仍保持较高状态。     

氮肥对水稻胚乳淀粉品质、相关酶活性及基因表达量的影响

【目的】旨在为阐明灌浆成熟期氮素营养对水稻淀粉品质影响机理以及建立优质高产水稻栽培技术提供理论依据。【方法】选用4个籽粒直链淀粉含量差异显著的粳稻品种,通过盆栽试验研究氮素营养对稻米淀粉组分和蛋白质含量及稻米蛋白质水解对淀粉黏滞特性的影响,并分析氮素营养对灌浆过程中籽粒蔗糖合酶(SuSy)、蔗糖磷酸合酶(SPS)、蔗糖酸性转化酶(AI)活性及OsGBSSⅠ、OsISAⅠ、OsSBEⅠ、OsSBEⅡ基因转录表达量的影响。【结果】结果表明,籽粒支链淀粉含量对氮素营养很敏感,灌浆成熟期氮素营养能改变籽粒淀粉组分含量;施氮条件下,高直链淀粉含量品种蒸煮食味品质下降更加明显,去除稻米蛋白质可明显提高稻米黏滞特性,蛋白质对淀粉黏滞特性的影响很大;增加灌浆成熟期氮素营养能显著或极显著提高籽粒SuSy和AI活性,显著抑制籽粒SPS活性;灌浆成熟期氮素营养能改变灌浆不同时期籽粒OsGBSSⅠ、OsISAⅠ和OsSBEⅡ基因转录表达量,以致灌浆过程中这些基因的转录表达量变化动态发生改变,但OsSBEⅠ基因转录表达量不因氮素营养而发生改变;受氮素营养的影响,灌浆起始期籽粒OsGBSSⅠ基因表达量明显上调,而灌浆中后期明显下调;氮素营养明显抑制灌浆成熟期籽粒OsISAⅠ基因和灌浆中后期的OsSBEⅠ基因转录表达,显著提高灌浆前期和中期的籽粒OsSBEⅠ基因转录表达量;氮素营养能抑制灌浆起始期籽粒OsSBEⅡ基因的转录表达,而提高灌浆中后期的基因转录表达。【结论】灌浆成熟期氮素营养除了通过蛋白质含量对淀粉品质产生影响外,还通过调控淀粉合成相关的酶活性和基因表达量等生理环节对淀粉含量和精细结构起作用,最终改变稻米黏滞特性和食味品质。     

氮素穗肥对杂交籼稻籽粒灌浆影响及其与淀粉合成关键酶活性间关系

【目的】为明确氮素穗肥对杂交稻籽粒灌浆和淀粉合成关键酶活性的影响。【方法】选用两个直链淀粉含量差异较大的杂交稻品种锦优1319(高直链淀粉)和蓉优702(低直链淀粉),在不同的氮素穗肥处理下(设0、60、90和120 kg/hm² 4个纯氮水平,分别用CK、N1、N2、N3表示)研究氮素穗肥水平对籽粒灌浆和淀粉合成关键酶活性的影响。【结果】不同穗肥处理下杂交稻籽粒灌浆特性差异显著,且不同类型品种表现各异,其中氮素穗肥的施用显著降低了稻米的直链淀粉含量。锦优1319的G_max和G_mean随氮素穗肥水平的变化均表现为N2>CK>N1>N3,而蓉优702则表现为N3>N2>CK>N1;施用氮素穗肥显著增加了花后5～25 d籽粒腺苷二磷酸焦磷酸化酶(ADPG)和淀粉分支酶(DBE)的活性,降低了花后5～15 d籽粒GBSS活性,降低了花后5～25 d籽粒淀粉合成酶(SSS)和SBE活性。【结论】高直链淀粉品种锦优1319籽粒灌浆的最佳氮素穗肥施用量低于低直链淀粉品种蓉优702：其中锦优1319...     

灌浆期不同时段高温对稻米淀粉理化特性的影响

【目的】研究灌浆期不同时段高温对稻米淀粉组成、结构和理化特性的影响,揭示高温对稻米淀粉理化特性影响的时段效应,阐明高温、结构和功能之间的关系。【方法】以耐热水稻品种黄华占和热敏感的9311近等位基因系为实验材料,利用人工气候箱设置高温[38℃(昼)/30℃(夜)]和对照[28℃(昼)/22℃(夜)],研究灌浆前期(齐穗期后1－15 d)和后期(齐穗期后16 d至成熟)高温对稻米的加工品质、外观品质、淀粉组成、支链淀粉链长分布、粒度分布、胶稠度、黏度特性、糊化特性、结晶特性和颗粒形态的影响。【结果】灌浆期高温使糙米率、精米率、整精米率显著下降,使垩白粒率和垩白度显著升高,导致加工品质和外观品质变差。灌浆期高温使总淀粉含量、直链淀粉含量、短支链淀粉含量、大淀粉粒占比、直/支链淀粉比显著下降,而中等支链淀粉含量、小中淀粉粒占比、糊化温度和糊化焓显著上升,黏度特性显著改变,结晶类型不变但结晶度显著改变,淀粉颗粒表面出现小孔,表面变得凹凸不平,导致淀粉颗粒更加碎片化和蒸煮食味品质变劣。灌浆期不同时段高温对稻米品质的影响不同,灌浆前期高温对稻米淀粉的影响大于灌浆后期,耐热品种受影响小于热敏感品种。灌浆前期高温处理下供试材料具有较高的消减值和较低的崩解值,黏度特性变差;灌浆后期高温处理下供试材料具有较低的消减值和较高的崩解值,黏度特性变好。【结论】灌浆前期高温对淀粉理化特性的影响最大,进而导致稻米的加工品质、外观品质和蒸煮食味品质变劣,灌浆后期高温提升了黏度特性。     

花后不同时段低温对籼粳杂交稻稻米品质性状的影响

【目的】花后低温是影响米质的首要生态因子。为明确花后低温对甬优品种稻米品质性状及淀粉RVA谱特性的影响,【方法】以籼粳杂交稻甬优17号、甬优538和杂交籼稻中浙优1号、常规粳稻浙粳88为材料,采用盆栽试验,通过人工气候箱于水稻花后0-15d(前期)、15-30d(中期)和30d-成熟(后期)分别进行20℃、17℃和14℃的低温处理。【结果】花后低温显著影响供试品种整精米率、垩白度、胶稠度、直链淀粉含量及蛋白质,使甬优品种淀粉RVA谱特征值峰值黏度、热浆黏度、冷胶黏度、崩解值降低,回复值和消减值升高。花后前期低温对稻米加工品质影响最大,而花后中、后期低温对外观品质、蒸煮食味品质和营养品质影响最大,且甬优17号比甬优538对低温更敏感。花后低温对稻米品质影响明显,低温处理影响因品种类型、品质指标及处理时段而异。【结论】生产中应基于品种特性综合考虑稻米各品质指标,在结实期采取相应的米质调优栽培措施,充分发挥籼粳杂交稻品种的品质潜力。     

Response of Rice Starch Synthesis to Night Temperature Changes

【Objective】To clarify the effect of night temperature changes on rice starch accumulation, and to explore circadian changes of physiological characteristics of rice amylose/amylopectin formation at various night temperatures.【Method】High-quality japonica rice ‘Zhehexiang 2’ was subjected to three night temperature gradients of 31℃/20℃ (LT), 31℃/24℃ (NT), and 31℃/28℃ (HT) at the beginning of grain ripening stage, and the amylose and amylopectin contents, the key enzyme activities involved in amylose and amylopectin formation and the expression of related genes were measured at noon and midnight. 【Result】 The results showed that 1) compared with NT, LT and HT treatments significantly reduced grain weight and starch accumulation, LT and HT both reduced amylopectin content and increased amylose content, meanwhile the effect of HT was greater than LT. LT and HT treatments decreased grain pasting temperature and gel consistency, and had a significant influence on branched chain length. 2) The net photosynthetic rate of leaves under LT and HT presented no significant difference compared to NT, but LT and HT significantly reduced the accumulation of non-structural carbohydrates, meanwhile down-regulated the expression level of sucrose transporter genes OsSUT1, OsSUT2, and OsSUT4 both at noon and midnight. 3) LT and HT treatment reduced sucrose hydrolysis-related enzyme activities, meanwhile promoted starch hydrolase activities, resulting in increased soluble sugar contents, sugar utilization in grain was blocked. 4) Compared with NT, the adenosine diphosphate glucose content showed a downward tendency during the day and a rising trend at night under the treatment of LT and HT, which presented that the accumulation and utilization of adenosine diphosphate glucose were inhibited. And the granules bound starch synthetase activity were significantly reduced under LT and HT compared to NT with the prolongation of the treatment, and the enzyme activity at daytime was significantly influenced by temperature changing at night. 5) Compared with NT, LT and HT reduced the activities of night-time amylopectin synthesis-related enzymes and inhibited the expression of night-time related genes, which retarded formation of amylopectin, but the enzyme activities related to amylopectin synthesis was not significantly influenced by night temperature changing. 【Conclusion】High night temperature had a less effect on starch accumulation than low night temperature. High or low night temperature inhibited sucrose transport and metabolism, resulting in declined starch accumulation. The retarding of amylopectin formation was the main reason for the increase of relative content of amylose at high or low night temperature. Night temperature changes directly affected the metabolic process of starch formation at night, but the daytime activities of amylose-related enzymes were affected by night temperature changes, while the daytime activities of amylopectin-related enzymes were not significantly affected by night temperature changes.     

Changes in Enzyme Activities Involved in Starch Synthesis and Hormone Concentrations in Superior and Inferior Spikelets and Their Association with Grain Filling of Super Rice

The changes in activities of key enzymes involved in sucrose-to-starch conversion and concentrations of hormones in superior and inferior spikelets of super rice were investigated and their association with grain filling was analyzed.Four super rice cultivars,Liangyoupeijiu,IIyou 084,Huaidao 9 and Wujing 15,and two high-yielding and elite check cultivars,Shanyou 63 and Yangfujing 8,were used.The activities of sucrose synthase (SuSase),adenosine diphosphoglucose pyrophosphorylase (AGPase),starch synthase (StSase) and starch branching enzyme (SBE),and the concentrations of zeatin + zeatin riboside (Z + ZR),indole-3-acetic acid (IAA) and abscisic acid (ABA) in superior and inferior spikelets were determined during the grain filling period and their relationships with grain filling rate were analyzed.Maximum grain filling rate,the time reaching the maximum grain-filling rate,mean grain filling rate and brown rice weight for superior spikelets showed a slight difference between the super and check rice cultivars,but were significantly lower in the super rice than in the check rice for inferior spikelets.Changes of enzyme activities and hormone concentrations in grains exhibited single peak curves during the grain filling period.The peak values and the mean activities of SuSase,AGPase,StSase and SBE were lower in inferior spikelets than in superior ones,as well as the peak values and the mean concentrations of Z + ZR and IAA.However,the peak value and the mean concentration of ABA were significantly higher in inferior spikelets than in superior ones and greater in the super rice than in the check rice.The grain filling rate was positively and significantly correlated with the activities of SuSase,AGPase and StSase and the concentrations of Z + ZR and IAA.The results suggested that the low activities of SuSase,AGPase and StSase and the low concentrations of Z + ZR and IAA might be important physiological reasons for the slow grain filling rate and light grain weight of inferior spikelets in super rice.     

Hormonal changes are related to the poor grain filling in the inferior spikelets of rice cultivated under non-flooded and mulched condition

Non-flooded plastic mulching cultivation (PM) of rice can save much irrigation but usually exhibits a poor grain filling and low grain weight when compared to traditional flooding cultivation (TF). This study measured the variations of plant hormones during grain filling and investigated whether they were related to the grain-filling problem under mulching in a field experiment. Hormonal levels in the grains and the grain development of both superior (early flowered) and inferior spikelets (later flowered) were monitored continuously during the grain filling period. The contents of indole-3-acetic acid (IAA), zeatin riboside (ZR) and abscisic acid (ABA) were higher in superior grains than in inferior ones at early grain-filling stage. For individual spikelets, the peaks of IAA and ZR contents appeared just before the peak grain-filling rate but the peak ABA content matched it. The earlier flowered superior spikelets did not show much difference in grain filling characteristics and hormonal changes under the two cultivation treatments. Distinctively with the inferior spikelets in a panicle, PM led to lower grain weight, higher grain-filling rate at early stage and shorter active grain-filling period than the TF. PM also resulted in less IAA and ZR but more ABA contents in the grains than TF at early and middle grain filling stages in these inferior spikelets. Peaks of these hormone contents in the PM inferior grains usually appeared earlier and also disappeared more quickly than those in TF inferior grains. When exogenous IAA was applied to plants at the initial grain-filling stage, IAA and ZR were increased and ABA was reduced in the inferior grains. The treatment prolonged the active grain-filing period and reduced the peak grain-filling rate of inferior grains, similarly as the case with TF. As a result, IAA spraying enhanced the weight of PM inferior grains but reduced that of TF ones. Exogenous ABA spraying led to the opposite effects to those of IAA. The results suggest that the shortened grain-filling period in the inferior grains under PM is related to the increased ABA and reduced IAA and ZR in the grains. Regulation of the ratio of ABA to IAA in grains could potentially increase the weight of inferior grains under the water-saving cultivation with film mulching.     

灌浆成熟期温度对水稻籽粒淀粉合成关键酶活性及品质的影响

 选用蒸煮食味品质不同的3个粳稻品种，利用温室高温和自然常温，研究了灌浆成熟期温度对水稻籽粒淀粉合成关键酶活性及蒸煮食味品质的影响。结果表明，灌浆成熟期高温条件下，水稻籽粒蛋白质含量提高，直链淀粉含量和味度值降低，劣质品种提高或降低的程度大于优质品种；RVA谱特性对灌浆成熟期温度的反应因品种和特性而异；灌浆过程中，籽粒ADPG焦磷酸化酶、可溶性淀粉合成酶和淀粉分支酶活性随灌浆进程，酶活性逐渐增加，达到峰值以后，酶活性又逐渐下降，呈单峰曲线，但不同品种酶活性达到峰值的时间和同一时期的酶活性大小有差异；ADPG焦磷酸化酶和可溶性淀粉合成酶的活性表现对温度的影响反应较为迟钝，而淀粉分支酶活性表现对温度变化的反应较为敏感，温度过高过低都降低该酶活性。