开放式空气CO2浓度增高对水稻颖花分化和退化的影响

在大田栽培条件下 ,研究开放式空气CO2 浓度增加 (FACE) 2 0 0 μmol·mol-1的处理对水稻每穗 1、2次枝梗及其颖花的分化数、退化数、现存数及退化率的影响 .结果表明 ,FACE处理对每穗 1、2次枝梗的分化数及 1次枝梗的退化数、退化率均无显著影响 ,但使 2次枝梗的退化数、退化率显著提高 ,使 2次枝梗现存数明显减少 ;FACE处理对每穗 1、2次颖花的分化数和 1次颖花的退化数、现存数、退化率均无显著影响 ,但使每穗 2次颖花的退化数和退化率显著提高 ;FACE处理使每穗颖花现存数显著减少主要是因为FACE处理使现存 1次枝梗上 2次枝梗大量退化引起 2次颖花退化所致 ;FACE处理使 1次颖花现存数占全穗的比率显著增加 ,使 2次颖花现存数占全穗的比率显著降低 .     

开放式空气CO2浓度增高对水稻颖花分化和退化的影响

在大田栽培条件下,研究开放式空气CO₂浓度增加(FACE)200μmol·mol^-1的处理对水稻每穗1、2次枝梗及其颖花的分化数、退化数、现存数及退化率的影响.结果表明,FACE处理对每穗1、2次枝梗的分化数及1次枝梗的退化数、退化率均无显著影响,但使2次枝梗的退化数、退化率显著提高,使2次枝梗现存数明显减少;FACE处理对每穗1、2次颖花的分化数和1次颖花的退化数、现存数、退化率均无显著影响,但使每穗2次颖花的退化数和退化率显著提高;FACE处理使每穗颖花现存数显著减少主要是因为FACE处理使现存1次枝梗上2次枝梗大量退化引起2次颖花退化所致;FACE处理使1次颖花现存数占全穗的比率显著增加,使2次颖花现存数占全穗的比率显著降低.     

籼稻颖花分化与退化对不同播期温光的响应

试验以三系杂交籼稻‘五优308’和‘天优华占’以及常规籼稻‘黄华占’为材料,在大田条件下,设置10个播期,研究田间不同温光条件对籼稻生育期天数、颖花分化和退化数的影响.结果表明: 温度对3个籼稻品种生育期的影响比日照长度大,平均温度升高1 ℃,播种-穗分化始期天数平均减少1.5 d,而穗分化历期天数与光照和温度的关系均不密切.不同播期间每穗颖花数和颖花分化数存在显著差异.穗分化期间平均温度、最高温度和最低温度升高,有效积温增加,昼夜温差扩大,光辐射增强,有利于穗分化期干物质积累和颖花分化,各品种趋势一致.穗分化期间有效积温增加50 ℃,颖花分化数增加10.5朵,昼夜温差扩大1 ℃,颖花分化增加14.3朵,总光辐射量增加50 MJ·m^-2,颖花分化数增加17.1朵.颖花退化率与温度呈现二次项相关,极端高温或极端低温的自然条件不利于颖花形成,但低温天气对颖花退化的影响大于高温.温度低于临界温度,颖花退化率大幅增加,穗分化期临界积温为550～600 ℃,日平均温度为24.0～26.0 ℃,日最高温度为32.0～34.0 ℃,日最低温度为21.0～23.0 ℃.适宜高温、昼夜温差大、光照辐射强的自然条件利于颖花分化,并减少颖花退化.     

近地层臭氧浓度升高对杂交稻颖花形成的影响

依托全球唯一的稻田开放式空气中臭氧浓度增高系统平台,以汕优63和两优培九为供试材料,设置大气背景臭氧浓度和高臭氧浓度（比大气背景臭氧浓度高50%）两个浓度水平,研究FACE条件下高O₃浓度对杂交稻颖花形成的影响.结果表明：高O₃浓度使汕优63和两优培九每穗颖花数分别减少28朵和34朵,下降幅度分别为15%和13%.从稻穗构成看,高O₃浓度胁迫下杂交稻每穗颖花数减少主要与每穗2次枝梗颖花数明显减少有关,对每穗1次枝梗颖花数的影响较小,因此高O₃浓度胁迫下水稻每穗1次枝梗颖花数占全穗的比率增加,每穗2次枝梗颖花数占全穗的比率降低.从颖花形成看,高O₃浓度胁迫下杂交稻每穗颖花数下降主要是颖花（特别是2次颖花）的分化受到抑制所致,而颖花的退化数不增反降.上述结果表明,采取相应措施削弱高O₃浓度胁迫对颖花分化的抑制作用可能是近地层高O₃浓度条件下减少杂交稻产量损失的关键.     

异季条件下稻穗枝梗和颖花分化、退化及其形成的差异性研究

以19个水稻杂交组合为试验材料,通过大田条件下的分期播种,于抽穗期调查了稻穗枝梗、颖花分化、退化及形成有关性状,分析了各性状不同季节的变异及其相互关系。结果表明,单穗一次枝梗分化数、二次枝梗分化数、颖花分化数、一次枝梗退化数、二次枝梗退化数、颖花退化数、一次枝梗退化率、二次枝梗退化率、颖花退化率、一次枝梗形成数、二次枝梗形成数、一次枝梗颖花形成数、二次枝梗颖花形成数和单穗颖花总形成数等性状均存在较大的组合间差异和季节间变异,其中19个组合单穗颖花总形成数异季差异率变幅为5.12%~93.59%,平均变异率为34.19%;总体上,不同季节下二次枝梗各性状的变异性强,颖花性状其次,一次枝梗各性状变异性最小;根据异季条件下稻穗枝梗和颖花分化、退化及其形成性状的变异性,从大穗角度讨论了杂交稻新组合育种资源选择与利用问题。     

耐热水稻品种“Nagina 22”高温胁迫下的生理响应

为研究耐热水稻品种Nagina 22(N22)开花结实期高温胁迫下的主要生理响应,采用温室盆栽试验,在各供试材料的开花期,利用人工气候室进行高温胁迫处理。研究结果表明:N22在高温胁迫下不改变开花期但表现出日开花量的转峰;与N22相比,水稻感热品种Moroberekan花药开裂显著受阻,柱头上萌发的花粉数显著减少;花粉萌发数与花药开裂状况呈极显著的相关关系,进而表现出主穗结实率与柱头上花粉萌发数呈显著的相关关系;主穗日结实率在高温下呈递减趋势,且Moroberekan较N22的下降速率显著加快,表明耐热品种与高温胁迫对结实率存在累积效应,而且高温胁迫效应发生在开花授粉之前。     

光温条件对短光低温不育水稻育性转换的影响

短光低温不育水稻是一类与长光高温不育水稻育性转换特性相反的新种质,通过对分期播种材料自然条件下的育性及人工短光处理后的育性比较分析表明,宜DIS的光敏期为第一苞分化期至第二次枝梗原基和小穗原基分化期（幼穗分化I－III期）,在常温下光敏期的短日处理可使育性趋于不育,但在高温下光敏期短日不育效应被削弱,宜DIS的花粉育性在高,低温作用下育性的均出现下降,根据高,低温影响育性的资料分析得到的敏感期基本一致,即花粉母细胞形成期至花粉内容物充实期（幼穗分化V－Ⅶ期）。     

开花期低温胁迫对水稻花粉性状及剑叶理化特性的影响

以耐冷水稻品种996和冷敏感品种4628为材料,开花期在人工气候室进行7 d低温（06:00-8:00和19:00-23:00,19 ℃;08:00-10:00和16:00-19:00,21 ℃;10:00-16:00,23 ℃;23:00-06:00,17 ℃）和适温（06:00-8:00和19:00-23:00,24 ℃;08:00-10:00和16:00-19:00,26 ℃;10:00-16:00,30 ℃;23:00-06:00,22 ℃)处理,研究了低温胁迫对水稻花药开裂、花粉性状及剑叶叶绿素、可溶性糖和可溶性蛋白质含量、膜透性等理化特性的影响.结果表明：开花期低温胁迫导致水稻花药开裂系数、花粉萌发率显著下降,中部和下部颖花的不育花粉率增加.996的花药开裂系数和花粉萌发率显著高于4628,表明耐冷品种996在开花期低温胁迫下能保持较好的花粉散落特性和花粉萌发特性.低温胁迫下,996的剑叶可溶性蛋白质和游离脯氨酸含量及其增幅显著高于4628,而丙二醛含量和相对电导率及其增幅却显著低于4628,说明耐冷品种在低温胁迫下的保护性反应更迅速和强烈,其膜结构及功能更稳定.     

非生物胁迫影响水稻颖花育性机理的研究进展

本文从颖花发育的形态学和生理学角度,综述了水稻穗分化期至抽穗开花期非生物胁迫导致颖花不育的机理,旨在揭示非生物胁迫导致水稻颖花败育的关键过程及其内在联系.颖花是否可育主要与绒毡层细胞行为、花药开裂与散粉、花粉萌发、受精4个关键过程有关,胁迫通过影响这些关键过程,导致颖花不育.花药发育早期异常变化影响生殖细胞发育与授粉作用.可以通过喷施外源物质或增施硅肥等方法减缓非生物胁迫对颖花育性的伤害.今后需要加强交叉胁迫对颖花育性的影响、不同胁迫对花器官形态结构和生理特性的影响、不同水稻品种对胁迫的响应差异,以及胁迫影响花器官发育的分子生物学机制等方面的研究.     

高浓度CO2对稻穗不同位置籽粒结实和米质性状的影响

不断升高的大气CO₂浓度影响水稻颖花发育、灌浆结实和品质形成,但这种影响是否与籽粒在稻穗上的着生部位有关尚不清楚.利用稻田FACE (Free-Air CO₂ Enrichment)平台,以优质丰产粳稻‘武运粳23’为材料,CO₂处理设背景CO₂浓度(Ambient)和高CO₂浓度(增200 μmol·mol^-1, FACE)两个水平,研究开放大田条件下高浓度CO₂对水稻颖花密度、籽粒结实能力、稻米外观和食味品质的影响及其与稻穗不同着生位置的关系.结果表明:FACE处理使武运粳23籽粒产量平均增加18.3%,从产量构成因素看,穗数和饱粒重分别增加21.4%、9.4%,每穗颖花数、饱粒率平均减少9.0%、2.2%.FACE水稻饱粒率下降主要与稻穗不同部位空粒率大幅增加有关.FACE水稻每穗颖花数减少主要与稻穗上部、中部二次枝梗现存颖花大幅减少有关,而其他位置颖花数均无显著变化;稻穗不同位置饱粒重和饱粒率对FACE的响应无显著差异.FACE处理使绿粒率下降,但糙米长度和宽度均增加,稻穗不同部位趋势一致.FACE使垩白粒率(增幅59%)、垩白度(增幅55%)均极显著增加,增幅表现为稻穗一次枝梗>二次枝梗、上部>中部>下部.FACE使稻穗不同位置稻米直链淀粉含量略增,使最高粘度、热浆粘度、崩解值、最终粘度和消减值略降,但多未达显著水平.FACE使稻米糊化温度显著下降,弱势粒的降幅大于强势粒.综上,高浓度CO₂环境下武运粳23产量增加主要与穗数增多和籽粒增重有关,而稻穗明显变小;高浓度CO₂使稻米绿粒率减少,垩白增多,而对蒸煮食味品质影响较少;颖花着生位置对高浓度CO₂环境下水稻颖花发育、结实和品质的影响因不同测定指标而异.     

Indel polymorphism in sugar translocation and transport genes associated with grain filling of rice (Oryza sativa L.)

Molecular Breeding - Depending on the position on the panicle, grain filling differs for spikelets on primary branches and secondary branches of upper and lower portions in rice (Oryza sativa L.)....     

Ethylene inhibitors promote male gametophyte survival in rice

Rice (Oryza sativa L. cv. Lalat) was grown in pots under open field conditions during the wet season of 1997. Attempts were made to manipulate the growth and development of the male gametophyte, located on the basal region of the panicle, by exogenous application of chemicals regulating formation/action of ethylene and compare grain setting in the spikelets bearing few grain. Application of ethylene action (AgNO₃) and synthesis inhibitor (Co(NO₃)₂; paclobutrazol and uniconazole) improved grain setting in the spikelets and the ethylene releasing substance 2-chloroethyle phosphonic acid (CEPA) depressed it compared to the control. The ethylene inhibitors promoted dry mass accumulation and concentrations of starch and reducing sugars in the anthers of the basal spikelets, while CEPA reduced the level of these carbohydrates significantly. The ethylene inhibitors helped in the survival of more numbers of pollen in these anthers, but CEPA depressed their number significantly. Promotion of growth of the basal anthers was accompanied by a concomitant reduction in the concentration of nonreducing sugars and enhanced activities of acid invertase and sucrose synthase enzymes. It is concluded that male gametophyte development of the basal spikelets of rice is susceptible to ethylene at the stage of pollen mitosis. The possibility of the hormone interfering in carbohydrate metabolism of the anther during this stage of development is discussed.     

High ethylene production slackens seed filling in compact panicled rice cultivar

Change of plant type in rice resulting in increased compactness of the panicle, allows space for accommodation of a larger number of spikelets, but grain yield does not increase proportionately because of limitations in grain filling. The objective of this study was to evaluate potential causes of poor filling of spikelets by comparing the physiological processes that influence source and sink activities between a compact- (OR-1920-7) and a loose-panicled (Lalat) rice cultivars growing in the open field conditions in the farm of Regional Research and Technology Transfer Station, Orissa University of Agriculture and Technology, Chiplima, India during dry season of 2007. Although grain number per unit length of the branches was higher in the compact-panicled cultivar than the loose-panicled cultivar, average grain weight was lower on the primary and secondary branches at top, middle and basal positions of the panicle in the former compared to the corresponding positions of the panicle in the latter. Compared to Lalat, ethylene production rate was considerably higher in the boot of the flag leaf sheath of OR-1920-7 during the pre-anthesis period. Ethylene evolution rate correlated negatively with growth and cell division rates and starch concentration of the juvenile endosperm. Because spikelet growth was slower in OR-1920-7 than in Lalat, unused carbohydrates accumulated in the endosperm. The stomatal conductance of the flag leaf during this period was also lower in the former than that of the latter and it correlated negatively with ethylene evolution rate of the boot. It is concluded that high ethylene production slackened grain filling of compact-panicled rice cultivar OR-1920-7 because of its adverse influence on both source and sink activities.     

Hormones in the grains in relation to sink strength and postanthesis development of spikelets in rice

Inferior spikelets usually exhibit a slower grain filling rate and lower grain weight than superior spikelets in a rice (Oryza sativa L.) panicle. This study investigated whether the variations in grain filling between the two kinds of spikelets were attributed to their sink strength and whether the sink strength was regulated by the hormonal levels in the grains. Using two field-grown rice genotypes, the division rate of endosperm cells, hormonal levels in the grains, and grain weight of both superior and inferior spikelets were determined during the grain filling period. The results showed that superior spikelets had dominance over inferior spikelets in endosperm cell division rate and cell number, grain filling and grain weight. Changes in zeatin (Z) and zeatin riboside (ZR) contents paralleled and were very significantly correlated with the cell division rate and cell number. Cell division rate and the content of indole-3-acetic acid (IAA) in the grains were also significantly correlated. Gibberellin (GAs; GA₁+ GA₄) content of the grains was high but ABA levels were low at the early grain filling stage. ABA increased substantially during the linear phase of grain growth and was very significantly correlated with grain dry weight during this period. Application of kinetin at 2 through 6 days post anthesis (DPA) significantly increased cell number, while spraying ABA at 11 through 15 DPA significantly increased the grain filling rate. The results suggest that differences in sink strength are responsible for variations in grain filling between superior and inferior spikelets. Both cytokinins and IAA in the grains may mediate cell division in rice endosperm at early grain filling stages, and therefore regulate the sink size of the grain, whereas ABA content correlates with sink activity during the linear period of grain growth.     

Rice SIZ1, a SUMO E3 ligase, controls spikelet fertility through regulation of anther dehiscence

? Sumoylation, a post-translational modification, has important functions in both animals and plants. However, the biological function of the SUMO E3 ligase, SIZ1, in rice (Oryza sativa) is still under investigation. ? In this study, we employed two different genetic approaches, the use of siz1 T-DNA mutant and SIZ1-RNAi transgenic plants, to characterize the function of rice SIZ1. ? Genetic results revealed the co-segregation of single T-DNA insertional recessive mutation with the observed phenotypes in siz1. In addition to showing reduced plant height, tiller number and seed set percentage, both the siz1 mutant and SIZ1-RNAi transgenic plants showed obvious defects in anther dehiscence, but not pollen viability. The anther indehiscence in siz1 was probably a result of defects in endothecium development before anthesis. Interestingly, rice orthologs of AtIRX and ZmMADS2, which are essential for endothecium development during anther dehiscence, were significantly down-regulated in siz1. Compared with the wild-type, the sumoylation profile of high-molecular-weight proteins in mature spikelets was reduced significantly in siz1 and the SIZ1-RNAi line with notably reduced SIZ1 expression. The nuclear localization signal located in the SIZ1 C-terminus was sufficient for its nuclear targeting in bombarded onion epidermis. ? The results suggest the functional role of SIZ1, a SUMO E3 ligase, in regulating rice anther dehiscence.     

Apoplasmic assimilates and grain growth of contrasting rice cultivars differing in grain dry mass and size

Apical dominance in assimilate filling impacts grain growth in basal spikelets of rice panicle. In this study, organic materials of the pericarp, apoplasmic space and endosperm of the apical and basal caryopses, and photosynthesis of the flag leaf were measured during early part of grain development in three types of rice cultivars with similar phenology, but difference in grain weight and size in the dry and wet seasons of 2006 and 2007, respectively. Photosynthetic activity of the flag leaf was consistently low in small-seeded cultivars. Rates of grain filling and cell division of endosperm and concentration of assimilates, starch, proteins and chlorophylls of the caryopsis were lower, but spikelet ethylene production and peroxidase activity were higher in a small-seeded cultivar compared to a big-seeded cultivar. Similar disparities in grain filling and other attributes were noticed for the inferior basal spikelets of the panicle compared to the superior apical spikelets, except the assimilate concentration of the pericarp and endosperm. Temporal fluctuation in assimilate concentration of the organs were similar between the cultivars. Concentration of apoplasmic assimilates mostly exhibited negative correlation with that of pericarp and endosperm. Compared to the apical spikelets, correlation was more negative for the basal spikelets. Conversely, correlation was positive between the concentration of apoplasmic assimilates and endosperm cell number and grain weight of the cultivars. Ethylene released from the spikelets at anthesis affected growth and cell division rates of endosperm and enhanced protein and chlorophyll degradation and peroxidase activity of the caryopsis. It was concluded that variation in spikelet ethylene production may be responsible for differences in size or weight of grains among rice cultivars and spikelets at different locations of the panicle. The concentration of apoplasmic assimilates could be an indicator for grain filling capacity, and ethylene regulated the concentration by affecting pericarp activity for assimilate unloading.