【作者】 李倩；

【导师】 崔克辉；

【作者基本信息】 华中农业大学 ， 生理学， 2012， 硕士

【摘要】 全球气候变暖同时引起白天和夜间温度升高。我国水稻在高温敏感期(幼穗分化期、抽穗开花期、灌浆期)遭受夏季高温热害的可能性越来越高。而高温对水稻生长发育影响的研究多数集中于白天高温,夜间高温下水稻的响应及基因型差异的研究还较少。水稻生长中、后期高温主要通过影响穗粒数和结实率而显著降低籽粒产量,然而其机理还不清楚。本研究以耐热性品种(汕优63、T226、N22)和热敏感品种(两优培九、T219、IR64)为材料,分别在幼穗分化期、抽穗期、灌浆期同时进行夜间高温(TN)、白天高温(TD)、全天高温(TD+N)处理,以正常温度下的植株为对照(温室对照和自然对照),观察不同时期昼夜高温对水稻产量及构成因子的影响及其基因型差异；研究根系(主要是根源激素)对不同时期昼夜高温的响应特征及其基因型差异；比较高温下根源激素与产量形成的关系。揭示根源激素高温响应影响穗粒数和结实率的内在机理,为水稻安全生产、抗(耐)高温品种选育提供理论指导。主要研究结果如下：1.幼穗分化期昼夜高温对产量形成及相关生理指标有着显著的影响。1)从产量及其构成因子来看,幼穗分化期昼夜高温处理均显著降低了水稻的产量,在品种间和处理间存在着显著差异。与对照相比,全天高温对产量的影响最大,该处理下耐高温品种降幅低于热敏感品种。幼穗分化期昼夜高温均增加了穗部颖花及枝梗的退化率并减少了枝梗及颖花的现存数,且降低了籽粒长度和宽度,影响颖花的发育,最终导致穗变小。耐高温品种SY63昼夜高温下产量均较高；夜间高温显著降低了T226枝梗及颖花退化率,T226较耐夜高温；N22较耐日高温。2)从干物质合成及根系活力来看,全天高温下SY63、IR64光合速率均显著降低,而夜间高温下各品种的响应不一致：SY63、N22的干物质量和光合速率显著降低,IR64却显著升高。该时期昼夜高温对茎鞘非结构性碳水化合物(NSC)的合成均有显著的影响,且夜间高温和全天高温下LYP9、SY63成熟期NSC残留量增加,IR64与之相反。此外,各品种夜间高温和全天高温下根系伤流量显著增加。3)从植物激素变化来看,幼穗分化期昼夜高温下根系及伤流量中细胞分裂素(Z+ZR)、生长素(IAA)、赤霉素(GA)浓度降低,脱落酸(ABA)显著增加。该时期伤流液与根系中激素含量与产量和颖花数显著正相关。SY63昼夜高温下均保持较高产的原因在于单叶光合速率、茎鞘内NSC含量较高,根系发达,根系活力较强,根系Z+ZR、IAA含量高；N22夜间高温下根系Z+ZR、IAA极低,可能是其不耐夜温的内在原因。2.抽穗期昼夜高温对产量形成及相关生理指标有着显著的影响。1)从产量及其构成因子来说,抽穗期昼夜高温处理下,各品种产量和结实率都显著低于对照。全天高温产量相对值最低,夜间高温对产量的影响最小,且热敏感品种产量相对值小于耐高温品种。花粉育性的变化趋势与结实率基本一致,昼夜高温均显著降低了各品种花粉育性,随时间延长,热害更严重,且白天高温降幅较大。N22在各高温处理下保持较高的花粉育性和结实率。2)抽穗期昼夜高温还显著减少了热敏感品种LYP9、IR64的干物质积累量,增加了成熟期茎鞘NSC的残留量,其中热敏感品种增幅高于耐高温品种,全天高温受阻最严重。除IR64外,昼夜高温显著降低了LYP9、SY63、N22的根冠比,减少了根系干物质分配的比列。各品种的根系伤流增加,全天高温增幅最明显。Ⅲ)该时期昼夜高温下激素含量变化与幼穗分化期变化趋势基本一致：Z+ZR、GA、IAA浓度低于对照,而ABA高于对照。产量、结实率与伤流液中激素浓度无显著相关性,而与根系中Z+ZR含量及其相对值呈显著正相关,与根系中ABA含量及其相对值呈显著负相关。与热敏感品种相比,全天高温下耐高温品种根系Z+ZR含量显著高于对照,且ABA低于对照,该特征有效缓解根系衰老,降低产量损失。3.灌浆期高温处理对水稻产量的影响小于前两个时期。1)夜间高温处理下产量与对照比无显著差异,白天高温和全天高温下热敏感品种结实率和粒重显著降低,从而导致产量降低,耐高温品种受高温影响程度较小。灌浆期昼夜高温对粒宽无显著影响,而对粒长的影响存在着基因型差异。2)从生理指标来看,各品种根系在该时期昼夜高温下无明显变化,而伤流量均低于对照。该时期产量、结实率、粒重与根系和籽粒Z+ZR、ABA显著正相关,与根系IAA及其相对值显著负相关。在灌浆期高温胁迫下,耐高温品种根系和籽粒中具有较高的Z+ZR、ABA含量,利于籽粒的发育充实。更多还原

【Abstract】 Both the daytime and nighttime temperatures are increasing as a result of global warming. The possibility of occurrence of high temperature at the heat-sensitive stages (panicle initiation, heading and grain filling stage) for rice is increasing. Most of the studies on the effects of high temperature on rice are concentrated in the high day temperature. Little is known about how high night temperature affects rice production. High temperature during heading and maturity stages of rice growth decrease grain yield by reducing the number of spikelets per panicle and grain filling percentage. However, its mechanism is still unclear. In this study, three heat-tolerant cultivars (Shanyou63, T226, N22) and three heat-sensitive cultivars (Liangyoupeijiu, T219, IR64) were cultivated and subjected to high temperature during panicle initiation, heading and grain filling periods, respectively. The natural temperature and the optimum day and night temperature combination were taken as controls (CK and NT), and three high temperature treatments included high night temperature (TN), high day temperature (TD) and the whole day of high temperature (TD+N).The aims of this study were to observe the effects of high night and day temperature during different stages on yield and its genotypic variation; to study the responses of roots morphology and hormones under different forms of heat treatments; to analyze the relationship between hormones changes and the yield formation by high temperature, with the purpose to reveal the mechanism for changes of hormones in roots affecting the number of spikelets per panicle and grain filling percentage, and provide theoretical guidance for rice production and breed of heat-tolerant cultivar. The main results are as follows:1. High temperature during panicle initiation affected grain yield and other physiological indices significantly.1) Analyzing of the yield and its component factors, day and night high temperature during panicle initiation both remarkably reduced grain yield. Compared to control, the influence of TD+N on yield was greater than other two high temperature treatments, and the reduction for heat-tolerant cultivars under TD+N was less than that for heat-sensitive cultivars. To be specific, both day and night high temperature promoted the branchs and spikelets degeneration and reduced their survived number. On the other hand, the high temperature decreased grain length, grain width and finally reduced the grain weight, especially in TD+N.At this stage, SY63achieved a higher yield under all high temperature treatments; The lower degeneration of T226under TN lead to its resistant to high night temperature; and N22was more resistant to high day temperature. Interestingly, IR64showed some thermostability at this stage.2) In addition, TD+N reduced the photosynthesis of SY63and IR64, while TN decreased both dry matter accumulation and photosynthesis of SY63and N22, but increased for IR64. High temperature also impeded the synthesis of non-structural carbohydrate (NSC) in stem. And there is a higher content NSC residual in stem at mature for LYP9, SY63under TN and TD+N, while a lower content for IR64. The xylem sap was significantly increased in all varieties by TN and TD+N.3) Moreover, the high temperature obviously decreased the concentration of zeatin+zeatin riboside (Z+ZR), indole-3-acetic acid (IAA) and gibberellins (GA), and increased the concentration of abscisic acid (ABA) in xylem sap and roots. The relationships of hormones in xylem sap to both yield and spikelets per panicle are significant and positive, respectively. Similar correlations were observed between hormones in roots and both yield and spikelets per panicle.The possible reasons that SY63could keep high yield under high temperature treatments were attributed to higher leaf photosynthetic rate, higher content of NSC in stem, well developed roots system, higher vigorous roots activity and higher contents of Z+ZR and IAA in roots. N22was sensitive to high night temperature, possibly because it had an extremely low content of Z+ZR and IAA in roots by TN.2. High temperature during heading also affected grain yield and other physiologicalindices significantly.1) High temperature at heading significantly reduced grain filling percentage and yield of all cultivars. The relative yield was less for the heat-sensitive cultivars than for the heat-tolerant cultivars, with a more reduction under TD+N treatment and a less reduction under TN. The changes of pollen fertility and grain filling under high temperature were similar. The pollen fertility was decreased by high temperature both day and night, while more pronounced decline by TD.The heat damage increased with time.2) High temperature also decreased the dry matter accumulation of LYP9and IR64, and increased NSC content in stem at mature, the increase amplitude was higher for heat-sensitive cultivars. Except for IR64, the roots/shoot ratio of LYP9, SY63and N22got smaller by high temperature. In addition, the increase of xylem sap was observed in all cultivars, especially in TD+N. 3) The variation trends of hormones under high temperature were basically similar between heading stage and panicle initiation stage:the mean concentrations of Z+ZR, GA, IAA were lower in high temperature treatments than in CK, while ABA was higher. The results of the correlation analysis between yield and grain filling percentage and hormones showed that:the yield and grain filling percentage had no significant correlation with the hormones concentration in xylem sap, but was significantly positive correlated with Z+ZR concentration in roots and significantly negative correlated with ABA concentration in roots. The relationship of their relative values was same. Under TD+N, the Z+ZR content in roots of tolerant cultivars was significantly higher than control, and the ABA content was significantly lower than control, which contributed to remission root senescence and yield loss.3. The effects of high temperature during grain filling on yield were less than the othertwo stages mentioned above.1) Compared to control, the TN treatment did not reduce yield significantly, but the TD and TD+N treatments significantly reduced grain filling percentage, grain weight and yield. The reduction was less for the heat-tolerant cultivars than for the heat-sensitive cultivars. High temperature had significant effects on grain length, depended in genotypes, whereas no significant effects on grain width.2) Compared to other two stages, the roots morphological indices had no remarkable changes among treatments during grain filling, and the bleeding content was lower by high temperatures. The high temperature treatments also obviously decreased Z+ZR and IAA contents in roots and spikelets during grain filling, and heat-tolerant cultivar had a higher relative IAA concentration in spikelets. The yield, grain filling and grain weight were significantly positive correlated with Z+ZR and ABA concentration in roots and spikelets, and significantly negative correlated with IAA concentration in roots. The results suggested that high contents of Z+ZR and ABA in roots and grains may be an important factor for stable grain yield for heat-tolerant cultivars during grain filling.更多还原