两种穗型冬小麦籽粒淀粉积累动态及其有关酶活性变化

花后25d内,大穗型品种豫麦66籽粒中淀粉积累比多穗型品种豫麦49慢,但花后25d后情况则相反。2个品种籽粒中淀粉积累速率的变化均呈单峰曲线,豫麦49峰值出现在花后15～20d,而豫麦66峰值则出现在花后20～25d。灌浆期豫麦66和豫麦49籽粒中蔗糖合成酶(SS)活性变化呈单峰曲线,峰值分别出现在花后20d和15d,整个灌浆期内豫麦66籽粒中SS活性高于豫麦49;2个品种籽粒中腺苷二磷酸葡萄糖焦磷酸化酶(AGPP)和淀粉分支酶(SBE)活性变化均呈单峰曲线,峰值出现在花后20d,而可溶性淀粉合成酶(SSS)活性变化则呈双峰曲线,峰值分别出现在花后10d和20d,且第二个峰值显著高于第一个。相关分析表明,SS、AGPP、SSS和SBE是影响小麦籽粒淀粉积累的关键酶。     

土壤水分亏缺对水稻茎秆贮藏碳水化合物向籽粒运转的调节

以两个茎秆贮藏物质利用效率不同的水稻(Oryza sativa)杂交组合(‘汕优63’和‘Pc311/早献党’)为材料,进行土壤水分亏缺处理(Water-deficit),以水层灌溉为对照(Well-watered),研究水分亏缺对水稻茎贮藏性碳水化合物运转及其关键酶活性的调节作用。结果表明,水分亏缺促进了水稻茎秆贮藏物质的运转和对籽粒产量的贡献,开花前茎秆贮藏的碳水化合物对产量贡献率分别提高了1.9~3.0倍(与水层灌溉相比)。土壤水分亏缺诱导了水稻茎节间α-淀粉酶、β-淀粉酶、α-葡萄糖苷酶、D-酶活性上升,但淀粉磷酸化酶受到了抑制,说明土壤水分亏缺加强水稻茎秆贮藏淀粉水解途径,而不是磷酸解途径。就蔗糖代谢而言,土壤水分亏缺提高了蔗糖磷酸合成酶的活性和活化状态,抑制蔗糖转化酶活性,促进蔗糖合成,加速贮藏物质快速降解和转移,从而调节稻株贮藏碳水化合物向籽粒的分配。     

氮素水平对冬小麦籽粒灌浆过程中淀粉合成关键酶活性的影响

小麦籽粒灌浆过程中,淀粉合成关键酶腺苷二磷酸葡萄糖焦磷酸化酶(ADPG-PPase)、可溶性淀粉合成酶(SSS)、淀粉分支酶(SBE)和束缚态淀粉合成酶(GBSS)均随着灌浆进程呈单峰曲线变化,峰值出现在花后25d;不同氮肥施用量对灌浆前期酶活性的影响较小,而在花后20d之后影响较大;随着氮肥施用量的增加,4种酶活性均呈增加趋势,但氮肥过量时酶活性下降,表明适当增加施氮量有利于淀粉合成关键酶活性的提高。     

硫营养对小麦籽粒淀粉合成及相关酶活性的影响

在田间条件下,研究了施硫对小麦籽粒淀粉合成及相关酶活性的影响.结果表明:在0～20 cm土层土壤有效硫含量为5.84 mg/kg的地块上施硫不仅提高了小麦籽粒中蔗糖的含量,而且催化蔗糖降解代谢的蔗糖合成酶(SS)活性提高,利于籽粒蔗糖的降解.施硫显著提高了灌浆期间籽粒可溶性淀粉合成酶(SSS)活性,并使腺苷二磷酸葡萄糖焦磷酸化酶(ADPGPPase)和束缚态淀粉合成酶(GBSS)活性在灌浆中、后期维持在较高水平,对直链和支链淀粉的合成都起促进作用, 使总淀粉积累增加,千粒重提高,产量增加.     

糯性和非糯性小麦灌浆期胚乳直/支链淀粉积累及其相关酶活性研究

选用3份糯性和2份非糯性小麦材料,通过田间试验在灌浆过程中分别检测了各材料的籽粒直链和支链淀粉积累量、淀粉积累速率及淀粉合成关键酶活性的动态变化过程,探讨籽粒淀粉累积与相关酶活性的关系.结果表明:(1)非糯小麦在花后7 d前均未检测到直链淀粉存在,而此时已经检测到支链淀粉含量,并且糯小麦仅含有支链淀粉,支链淀粉早于直链淀粉合成.(2)糯性和非糯性小麦灌浆期籽粒的直、支链淀粉积累速率均呈先增加后降低的趋势,且直、支链淀粉最终积累量取决于最大积累速率和平均积累速率的大小,而积累活跃期的调节作用较小;糯性和非糯性小麦在淀粉合成过程中的腺苷二磷酸葡萄糖焦磷酸化酶(AGPP)、可溶性淀粉合成酶(SSS)、颗粒结合型淀粉合成酶(GBSS)和淀粉分支酶(SEB)活性均呈单峰曲线变化,活性峰值基本上都出现在花后20～25 d左右.(3)直链淀粉积累速率与AGPP、SSS、GBSS和SBE活性变化显著或极显著正相关,而支链淀粉积累速率仅与SSS活性变化极显著正相关,总淀粉积累速率与AGPP和SSS活性变化显著或极显著正相关.     

钾对小麦旗叶蔗糖和籽粒淀粉积累的影响

 利用冬小麦品种‘鲁麦22’(Triticum aestivum cv. `Lumai 22’)在大田条件下研究了钾素对小麦旗叶蔗糖和籽粒淀粉积累及其有关酶活性的影响。结果表明,钾素有利于提高旗叶光合速率,增强开花后旗叶磷酸蔗糖合成酶活性,提高旗叶中蔗糖的含量;从而提高了灌浆期间籽粒中蔗糖的供应,增强了籽粒中蔗糖合成酶和腺苷二磷酸葡萄糖焦磷酸化酶的活性,加速了淀粉积累速率,提高了粒重和产量。     

不同穗型冬小麦品种蔗糖和淀粉合成中关键性酶的活性变化

灌浆期间的豫麦66和豫麦49旗叶中蔗糖磷酸合成酶(SPS)和籽粒中蔗糖合成酶(SS)活性均呈单峰曲线变化,峰值分别出现在花后20和15 d,整个灌浆期内豫麦66 SPS与SS活性均高于豫麦49;豫麦66籽粒中腺苷二磷酸葡萄糖焦磷酸化酶(AGPP)和淀粉分支酶(SBE)活性均呈单峰曲线变化,峰值出现在花后20 d,而可溶性淀粉合成酶(SSS)活性则呈双峰曲线变化,峰值分别出现在花后10和20 d,且第二个峰值显著高于第一个.     

淀粉含量不同的玉米自交系籽粒淀粉积累及其关键酶活性

以2个高淀粉和2个低淀粉玉米自交系为材料,分析了玉米籽粒淀粉的动态积累规律,同时对高低淀粉玉米籽粒灌浆过程中淀粉生物合成关键酶活性的动态变化及其与淀粉积累动态的相关性进行讨论分析。研究结果表明:灌浆过程中4个自交系淀粉含量变化趋势均呈sigmoid型曲线。灌浆过程中ADPG-PPase(腺苷二磷酸葡萄糖焦磷酸化酶)、SSS(可溶性淀粉合成酶)、GBSS(颗粒结合淀粉合成酶)活性均呈单峰曲线变化,峰值都出现在20～30DAP(授粉后天数)。2个高淀粉自交系的Q酶(淀粉分支酶)活性也呈单峰曲线变化,峰值也出现在20DAP,而2个低淀粉自交系的Q酶活性则呈双峰曲线变化,2个峰值分别出现在15～20DAP和30～35DAP。4个自交系籽粒淀粉的积累速率与各自交系ADPG-PPase、SSS和GBSS的活性变化呈极显著正相关。各自交系关键酶活性之间,ADPG-PPase、SSS和GBSS三者间活性变化呈极显著正相关,这3种酶活性变化与Q酶活性变化也呈不同程度的正相关。     

玉米灌浆期水分差异供应对籽粒淀粉积累及其酶活性的影响

利用普通玉米(Zay mays)‘掖单22’和高油玉米‘高油115’,研究了灌浆期水分差异供应对籽粒淀粉及其组分积累、相关酶活性动态变化的影响。结果表明,两种类型玉米淀粉积累和酶活性动态变化趋势基本一致,但对水分的反应有差异。缺水提高了‘掖单22’籽粒中淀粉、支链淀粉含量,而直链淀粉含量下降,‘高油115’则是籽粒中的淀粉含量、支链淀粉和直链淀粉含量提高;充分供水使淀粉及其组分产量提高;叶片中蔗糖合成酶(SS)、磷酸蔗糖合成酶(SPS)活性随水分供应水平而提高,尤其在授粉后10~30 d增幅更加明显。充分供水明显提高籽粒中腺苷二磷酸葡萄糖焦磷酸化酶(ADPG-PPase)、尿苷二磷酸葡萄糖焦磷酸化酶(UDPG-PPase)、可溶性淀粉合成酶(SSS)和淀粉粒结合淀粉合成酶(GBSS)活性,缺水使籽粒中酶活性下降较早且迅速;SPS、ADPG-PPase、SSS酶活性对缺水反应比较敏感。     

水稻淀粉胚乳程序性细胞死亡中的去核化

对水稻品种中籼8836淀粉胚乳细胞的去核化发育阶段的细胞超微结构变化和同期籽粒灌浆速率及相关酶活性的动态进行了观察和分析。开花受精后约在第3天胚乳完成细胞化,花后第5天少数淀粉胚乳细胞启动去核发育过程。核消亡是淀粉胚乳细胞程序性细胞死亡(PCD)的第一步。同一籽粒淀粉胚乳细胞的去核进程是不同步的。花后第13天所有淀粉胚乳细胞都已完成去核过程。在去核过程中,胚乳核的形态变化特征既有动植物PCD的共性又有其特殊性。伴随核降解过程,一部分线粒体解体,表明去核化与线粒体解体有一定联系。在去核化发育阶段,与PCD有关的酶类,如超氧化物歧化酶(SOD)过氧化氢酶(CAT)活性非常高;与淀粉合成有关的酶类,如ADPG焦磷酸化酶、可溶性淀粉合成酶(SSS酶)、淀粉分支酶(或Q酶)也表现出很高的活性。去核化发育阶段籽粒灌浆速率最高,籽粒增重亦最快。淀粉胚乳细胞去核之后,细胞并未立即死亡,这些无核的细胞仍维持正常有序的代谢活动,继续进行淀粉和贮藏蛋白的合成与积累,但上述酶类的活性明显降低,灌浆速率也明显趋缓。淀粉胚乳细胞最终被贮藏物质充满时成为死细胞,完成其程序性死亡过程。Evan’s blue染色鉴定表明淀粉胚乳细胞死亡不同步,细胞死亡在淀粉胚乳组织中是随机发生的。     

Post-anthesis alternate wetting and moderate soil drying enhances activities of key enzymes in sucrose-to-starch conversion in inferior spikelets of rice

This study tested the hypothesis that a post-anthesis moderate soil drying can improve grain filling through regulating the key enzymes in the sucrose-to-starch pathway in the grains of rice (Oryza sativa L.). Two rice cultivars were field grown and two irrigation regimes, alternate wetting and moderate soil drying (WMD) and conventional irrigation (CI, continuously flooded), were imposed during the grain-filling period. The grain-filling rate and activities of four key enzymes in sucrose-to-starch conversion, sucrose synthase (SuSase), adenosine diphosphate-glucose pyrophosphorylase (AGPase), starch synthase (StSase), and starch branching enzyme (SBE), showed no significant difference between WMD and CI regimes for the earlier flowering superior spikelets. However, they were significantly enhanced by the WMD for the later flowering inferior spikelets. The activities of both soluble and insoluble acid invertase in the grains were little affected by the WMD. The two cultivars showed the same tendencies. The activities of SuSase, AGPase, StSase, and SBE in grains were very significantly correlated with the grain-filling rate. The abscisic acid (ABA) concentration in inferior spikelets was remarkably increased in the WMD and very significantly correlated with activities of SuSase, AGPase, StSase, and SBE. Application of ABA on plants under CI produced similar results to those seen in plants receiving WMD. Applying fluridone, an indirect inhibitor of ABA synthesis, produced the opposite effect. The results suggest that post-anthesis WMD could enhance sink strength by regulating the key enzymes involved, and consequently, increase the grain-filling rate and grain weight of inferior spikelets. ABA plays an important role in this process.     

Short-term effects of experimental warming and enhanced ultraviolet-B radiation on photosynthesis and antioxidant defense of <Emphasis Type="Italic">Picea asperata</Emphasis> seedlings

It is generally accepted that sucrose synthase (SuSy), ADP-glucose pyrophosphorylase (AGPase), soluble starch synthase (SSS), granule-bound starch synthases (GBSS) and starch branching enzyme (SBE) play a key role in starch synthesis in wheat grains. Starch synthesis in wheat grains is influenced by genotype and environment. However, what is not known is the degree of variation in enzyme activity during starch accumulation of wheat cultivars differing in kernel types. The present study was carried out to characterize the changing activities of key enzymes during grain filling in two kernel type winter wheat cultivars. Results showed that starch accumulation rate (SAR) and activities of SuSy, AGPase, SSS, GBSS and SBE in large kernel types were significantly higher than those in small kernel types. The soil water deficit experienced during the course of the experiment led to an increase at early grain-filling period and decrease during late grain-filling, respectively, in SAR and activities of key enzymes involved in starch synthesis, especially SuSy, AGPase, SSS, and SBE. Water deficit enhanced grain starch accumulation in small kernel types. It suggests that rainfed treatment increase physiological activities during early grain-filling and promote starch accumulation in small kernel types. The simulation with Richards’ equation showed that it was accumulation duration and SAR that determined the starch accumulation in large kernel types. Compared with small kernel types, plants of large kernel types maintained longer filling duration, higher SAR and greater activities of related enzymes during mid and late grain-filling. These observations suggest stronger sink activities in large kernel types at a later stage of development. Consequently, large kernel types have advantages over the small kernel types in terms of the amount of starch accumulation at mid and late stage, but are sensitive to water deficit.     

Activities of key enzymes in sucrose-to-starch conversion in wheat grains subjected to water deficit during grain filling

This study tested the hypothesis that a controlled water deficit during grain filling of wheat (Triticum aestivum) could accelerate grain-filling rate through regulating the key enzymes involved in Suc-to-starch pathway in the grains. Two high lodging-resistant wheat cultivars were field grown. Well-watered and water-deficit (WD) treatments were imposed from 9 DPA until maturity. The WD promoted the reallocation of prefixed 14C from the stems to grains, shortened the grain-filling period, and increased grain-filling rate or starch accumulation rate (SAR) in the grains. Activities of Suc synthase (SuSase), soluble starch synthase (SSS), and starch branching enzyme (SBE) in the grains were substantially enhanced by WD and positively correlated with the SAR. ADP Glc pyrophosphorylase activity was also enhanced in WD grains initially and correlated with SAR with a smaller coefficient. Activities of granule-bound starch synthase and soluble and insoluble acid invertase in the grains were less affected by WD. Abscisic acid (ABA) content in the grains was remarkably enhanced by WD and very significantly correlated with activities of SuSase, SSS, and SBE. Application of ABA on well-watered plants showed similar results as those by WD. Spraying with fluridone, an ABA synthesis inhibitor, had the opposite effect. The results suggest that increased grain-filling rate is mainly attributed to the enhanced sink activity by regulating key enzymes involved in Suc-to-starch conversion, especially SuSase, SSS, and SBE, in wheat grains when subjected to a mild water deficit during grain filling, and ABA plays a vital role in the regulation of this process.     

不同类型土壤上种植的小麦籽粒中与淀粉合成相关的酶活性变化

测定池栽条件下灰潮土、水稻土、砂姜黑土上种植的强筋小麦‘郑麦9023’籽粒灌浆过程中腺苷二磷酸葡萄糖焦磷酸化酶（AGPP）、尿苷二磷酸葡萄糖焦磷酸化酶（UGPP）、可溶性淀粉合成酶（SSS）、淀粉粒结合淀粉合成酶（GBSS）、淀粉分支酶（SBE）5个与淀粉合成有关的酶活性变化的结果表明,不同类型土壤上种植的小麦籽粒中AGPP、UGPP、SSS、GBSS、SBE活性均呈单峰曲线变化,花后18d,AGPP、UGPP、SSS和SBE活性达到峰值,而GBSS则在花后24d达到峰值。AGPP、SSS、SBE活性峰值表现为灰潮土〉水稻土〉砂姜黑土,UGPP峰值表现为灰潮土〉砂姜黑土〉水稻土,GBSS峰值则表现为水稻土〉灰潮土〉砂姜黑土。     

Abscisic acid and cytokinins in the root exudates and leaves and their relationship to senescence and remobilization of carbon reserves in rice subjected to water stress during grain filling

The possible regulation of senescence-initiated remobilization of carbon reserves in rice (Oryza sativa L.) by abscisic acid (ABA) and cytokinins was studied using two rice cultivars with high lodging resistance and slow remobilization. The plants were grown in pots and either well-watered (WW, soil water potential = 0 MPa) or water-stressed (WS, soil water potential = -0.05 MPa) from 9 days after anthesis until they reached maturity. Leaf water potentials of both cultivars markedly decreased at midday as a result of water stress but completely recovered by early morning. Chlorophyll (Chl) and photosynthetic rate (Pr) of the flag leaves declined faster in WS plants than in WW plants, indicating that the water deficit enhanced senescence. Water stress accelerated starch remobilization in the stems, promoted the re-allocation of pre-fixed (14)C from the stems to grains, shortened the grain-filling period and increased the grain-filling rate. Sucrose phosphate synthase (SPS, EC 2.4.1.14) activity was enhanced by water stress and positively correlated with sucrose accumulation in both the stem and leaves. Water stress substantially increased ABA but reduced zeatin (Z) + zeatin riboside (ZR) concentrations in the root exudates and leaves. ABA significantly and negatively, while Z+ZR positively, correlated with Pr and Chl of the flag leaves. ABA, not Z+ZR, was positively and significantly correlated with SPS activity and remobilization of pre-stored carbon. Spraying ABA reduced Chl in the flag leaves, and enhanced SPS activity and remobilization of carbon reserves. Spraying kinetin had the opposite effect. The results suggest that both ABA and cytokinins are involved in controlling plant senescence, and an enhanced carbon remobilization is attributed to an elevated ABA level in rice plants subjected to water stress.     

水分胁迫对水稻籽粒蛋白质积累及营养品质的影响

以生产上广泛使用的水稻(Oryza sativa)品种‘汕优63’、‘扬稻6号’和‘武育粳3号’为材料,研究了水分胁迫对结实期水稻籽粒蛋白质积累及营养品质的影响。结果表明:正常施氮水平下,花后10~20 d的水分胁迫提高了谷氨酰胺合成酶(Glutamine synthetase,GS)和谷氨酸合酶(Glutamate synthase,GOGAT)活性,提高了籽粒自身利用无机氮合成氨基酸的能力,从而利于籽粒内蛋白质的积累,而高氮水平下,水分胁迫降低了籽粒自身合成氨基酸的能力。以重量为基数的蛋白质含有率在整个灌浆过程中呈“V”型消长,正常施氮水平下,水分胁迫明显提高了花后15 d至成熟期蛋白质含有率,而高氮水平下,水分胁迫处理的蛋白质含有率明显低于水层灌溉。与水层灌溉相比,水分胁迫提高了正常施氮水平下精米中醇溶蛋白和谷蛋白含量,但却明显降低了高氮水平下精米中醇溶蛋白和谷蛋白含量。水分胁迫对稻米中赖氨酸含量的影响因品种、植株的氮营养水平的不同而不同,水分胁迫显著降低了两种氮肥水平下‘汕优63’中赖氨酸含量,但却明显提高‘扬稻6号’中赖氨酸含量;而‘武育粳3号’于两种氮肥水平下表现恰好相反,正常施氮水平下赖氨酸含量略有升高;而高氮水平下赖氨酸含量明显降低。     

花后土壤水分状况对小麦籽粒淀粉和蛋白质积累关键调控酶活性的影响

在温室盆栽条件下,以2个不同蛋白质含量的冬小麦(Triticum aestivum L．)品种皖麦38和扬麦9为材料,研究了花后第4天开始的土壤干旱(SRWC=45％～50％)和渍水对籽粒蛋白质和淀粉积累关键调控酶活性的影响。小麦叶片和籽粒的测定结果均表明,小麦源库器官中籽粒蛋白质和淀粉积累的关键调控酶活性变化趋势在2个品种间基本一致。与对照(SRWC=75％～80％)相比,干旱和渍水均明显降低了花后旗叶中蔗糖含量和磷酸蔗糖合成酶(SPS)活性,而氨基酸含量和谷氨酰胺合成酶(GS)活性略有下降。干旱和渍水均降低了籽粒库蔗糖合成酶(SS)和结合态淀粉合成酶(GBSS)活性,可溶性淀粉合成酶(SSS)活性降低尤甚。其中干旱处理下SS的下降比渍水更为明显。与对照相比,渍水明显降低了籽粒谷丙转氨酶(GPT)和GS活性,而干旱的影响较小。相关性分析结果表明籽粒淀粉产量和含量与SPS,SSS和GBSS活性的关系比与SS活性的关系更为密切,籽粒蛋白质产量和含量与叶中GS和籽粒中GPT活性的关系比与籽粒中GS关系活性更为密切。这些结果表明小麦源库器官中调控籽粒蛋白质和淀粉积累的关键酶活性变化是花后不同水分状况影响籽粒淀粉和蛋白质特性的重要因素。     

Activities of starch hydrolytic enzymes and sucrose-phosphate synthase in the stems of rice subjected to water stress during grain filling

To understand the effect of water stress on the remobilization of prestored carbon reserves, the changes in the activities of starch hydrolytic enzymes and sucrose-phosphate synthase (SPS) in the stems of rice (Oryza sativa L.) during grain filling were investigated. Two rice cultivars, showing high lodging-resistance and slow remobilization, were grown in the field and subjected to well-watered (WW, psi(soil)=0) and water-stressed (WS, psi(soil)=-0.05 MPa) treatments 9 d after anthesis (DAA) till maturity. Leaf water potentials of both cultivars markedly decreased during the day as a result of WS treatment, but completely recovered by early morning. WS treatment accelerated the reduction of starch in the stems, promoted the reallocation of prefixed (14)C from the stems to grains, shortened the grain filling period, and increased the grain filling rate. More soluble sugars including sucrose were accumulated in the stems under WS than under WW treatments. Both alpha- and beta-amylase activities were enhanced by the WS, with the former enhanced more than the latter, and were significantly correlated with the concentrations of soluble sugars in the stems. The other two possible starch-breaking enzymes, alpha-glucosidase and starch phosphorylase, showed no significant differences in the activities between the WW and WS treatments. Water stress also increased the SPS activity that is responsible for sucrose production. Both V(limit) and V(max), the activities of the enzyme at limiting and saturating substrate concentrations, were enhanced and the activation state (V(limit)/V(max)) was also increased as a result of the more significant enhancement of V(limit). The enhanced SPS activity was closely correlated with an increase of sucrose accumulation in the stems. The results suggest that the fast hydrolysis of starch and increased carbon remobilization were attributed to the enhanced alpha-amylase activity and the high activation state of SPS when the rice was subjected to water stress.