水稻叶片衰老的分子机理及研究进展

水稻作为我国最主要的粮食作物,已知在生育期允许的范围内,适当延缓水稻叶片早衰,对产量有很大的作用。中国是最早利用水稻杂种优势的国家,杂交稻尚存在结实率偏低、空秕率较高的问题。有研究表明,叶片和根系早衰是造成这一现象的主要原因。有些杂交稻通过推迟停水期来延缓衰老,并推迟收割期,有明显的增产效果,每延迟一天,平均增产1%左右。1　叶片衰老期间基因表达的变化基因表达参与叶片衰老的调控,在转录水平上,衰老期间的基因表达存在4种模式,即基因激活、表达增强、部分抑制和完全抑制。这4种模式在衰老期间体现在ｍＲＮＡ水平上就是上…     

库源比对杂交水稻叶片衰老的影响

在水稻开花期间，通过剪去穗部部分枝梗和叶片等处理,形成不同的源库比，研究其与叶片衰老的关系，结果表明，亚种间杂交水稻赣化7号源库矛盾大，叶片衰老，降低库源比，能明显减缓其叶片中蛋白质，叶绿素含量下降和丙二醛含量的升高，说明杂交水稻叶片早衰与其为源比较大有关。     

钙对延缓杂交水稻叶片衰老的作用机理

以叶绿素、蛋白质含量为衰老的生理指标，研究了不同ｐＨ、Ｃａ２＋对杂交水稻叶片衰老的作用。结果表明，不同ｐＨ影响叶绿素和蛋白质含量，最适ｐＨ为６．０；此条件下的Ｃａ２＋浓度为０．０１～２０．００ｍｍｏｌ／ｌ，低浓度的Ｃａ２＋提高叶片中叶绿素和蛋白质含量，提高超氧化物歧化酶（ＳＯＤ）、过氧化氢酶（ＣＡＴ）、过氧化物酶（ＰＯＤ）活性，降低丙二醛（ＭＤＡ）含量；随着Ｃａ２＋浓度升高，则作用减弱；最适浓度为０．１ｍｍｏｌ／ｌ。Ｃａ２＋能延缓杂交水稻叶片的衰老，主要原因是由于Ｃａ２＋能提高叶片中活性氧防御酶的活性，降低活性氧的伤害作用。     

水稻叶片形态研究进展

水稻产量随着株型的改善而提高,其叶片形态是影响株型的主要因素。对水稻叶片构成及其功能、叶片形态的生理效应以及遗传机制等方面做出概括性的描述,为水稻高产育种提供一些理论指导。     

超高产水稻开花结实期间叶片衰老与活性氧代谢的关系

 对超高产水稻培矮64S/9311和协优9308从抽穗到籽粒成熟过程中剑叶中H2O2 、膜脂过氧化产物丙二醛（MDA）、组织自动氧化速率、脂氧合酶（LOX）及保护酶超氧物歧化酶(SOD)、过氧化氢酶(CAT)、过氧化物酶（POD）和抗坏血酸过氧化物酶（ASP）的动态变化过程进行了测定。结果表明，协优9308的剑叶衰老较慢。2个材料的剑叶叶片衰老可能原因是叶片内SOD、CAT、ASP活性过早下降，LOX活性增加，进而导致膜脂过氧化，使活性氧代谢失调，引起叶绿素和蛋白质降解，培矮64S/9311的各项生理指标比协优9308早衰老，而且乳熟期是培矮64S/9311早衰的关键时期。     

水稻属间远缘杂交种生育后期冠层叶片衰老特性的初步研究

】１９９２～１９９４年，在早晚季玻璃网房盆栽条件下对用远缘花粉诱变植物生态育种技术育成的属间杂种后代稳定品种远诱１号及其水稻亲本品种圭６３０，三系杂交水稻组合汕优６３灌浆成熟期冠层叶片的衰老特性进行了比较研究，用叶绿素含量及过氧化物酶（ＰＯＤ）的叶位间差异，对比于穗部成熟度的叶片早衰老指数（ＡＩ）为指标比较了属间远缘杂交种、品种间三系杂交组合、常规水稻品种生育后期叶片衰老特性的差异，解释了超大穗型品种远诱１号结实性良好的生理基础     

花生叶片衰老与活性氧代谢

高产花生品种鲁花11号和辐8707叶片衰老研究表明，花生叶片展开至衰老过程中，超氧化物歧化酶（SOD），过氧化氢酶（CAT），过氧化物酶（POD）活性的变化趋势均可用Y＝A＋Bx Cx^2拟合；叶片丙二醛（MCA）含量，活性氧（O^-2)释放速率和质膜透性变化符合Y=Ae^Bx.叶片展开后25－30d至55－60d为叶片缓衰期，叶片展开55－60d以后为叶片速衰期，两品种相比，辐8707叶片的衰老早于鲁花11。     

稻田冬季保护性耕作条件下的土壤酶活性与水稻成熟期叶片衰老和籽粒产量之间的关系

 为研究稻田冬季保护性耕作不同种植模式对土壤酶活性以及水稻成熟期叶片衰老的影响, 设计了5种种植模式：免耕直播稻草全程覆盖马铃薯（T1）、免耕直播黑麦草（T2）、免耕直播油菜（T3）、免耕直播燕麦草（T4）和空闲（CK）,供试品种为杂交组合国稻6号。与对照（CK）相比,T1、T2和T3处理均可显著提高土壤蛋白酶、中性磷酸酶、过氧化氢酶以及转化酶活性,尤其是T1处理,其土壤酶活性明显高于其他处理,而T4处理与对照相比,差异不明显。T1、T2和T3处理均可有效延缓水稻成熟期剑叶的衰老,主要表现为成熟期剑叶中的超氧化物歧化酶、过氧化物酶活性、可溶性蛋白质和叶绿素含量下降缓慢,丙二醛含量上升的幅度较小,相对于对照（CK）,差异均达显著水平。在本试验条件下,土壤酶对水稻叶片衰老的影响程度依次为蛋白酶>过氧化氢酶>中性磷酸酶>转化酶。叶片衰老对水稻产量的影响主要表现在灌浆中后期。     

花生叶片衰老规律的研究

通过对鲁花１１ 号和辐８７０７ 两个高产花生品种叶片衰老规律的研究表明, 花生叶片展开至衰老过程中,叶绿素含量、净光合速率（Ｐｎ）、可溶性蛋白质（Ｐｒ）含量呈先升高、至最大值后缓慢下降,到衰老后期转为快速下降的抛物线变化。其变化趋势均可用函数式Ｙ＝ Ａ＋ Ｂｘ＋ Ｃｘ２（Ｙ 为上述各指标,ｘ 为叶片展开后天数）较好描述,并可分成缓降期（叶片缓衰期）和速降期（叶片速衰期）两个变化阶段。两品种相比,辐８７０７ 叶片的缓衰期和速衰期均早于鲁花１１号。     

Salinity-Induced Ultrastructural Alterations in Leaf Cells of Rice (Oryza sativa L.)

Summary

High concentrations of NaCl significantly reduced the fresh and dry weights and lengths of roots and shoots. NaCl exhibited a more rapid effect in water culture than in soil culture. In both water and solid cultures, root growth was suppressed more severely than shoot growth. Electron microscopic studies revealed that NaCl caused swelling of thylakoids, accumulation of starch grains and lipid droplets, distortion of grana stacking, increase in the size and number of plastoglobuli and vesiculation of cellular membrane. Mitochondria became deficient in cristae, swelled and the matrix appeared pale in salt-treated plants as compared with control plants. Disappearance of nucleolus and nuclear chromatin and destruction of vascular tissues were occasionally observed in salt-treated plants.     

农杆菌介导的籼稻转化研究

系统研究了影响农杆菌转化水稻的主要理化因子,以建立一个农杆菌介导法获得大量转基因籼稻植株的体系。农杆菌EHA101(pIG12Hm)感染后的籼稻Pusa Basmati 1(南亚优质米推广品种)悬浮细胞系经3周选择,其Gus阳性的抗性愈伤组织占感染细胞团总数的比例可达10%左右,最高达21.1%,转化频率有显著提高。用另外两个农杆菌菌株/质粒,EHA105(pCAMBIA1201)、EHA105(pCAMBIA1301)转化该悬浮细胞系的频率均在5%~10%之间。以转化植株的克隆数计算,Basmati 1的转化频率为1%~5%。     

Effects of Silicon on Transpiration and Leaf Conductance in Rice Plants (Oryza sativa L.)

Summary

To characterize the protection effect of silicon against excessive transpiration in rice plants (Oryza sativa L.), we investigated the factors responsible for transpiration, such as cuticular conductance (gc), leaf surface wax content (WC), and stomatal movement in response to environmental stimuli, using leaves of plants grown in nutrient solution with silicon (+Si) and without silicon (–Si). The rate of transpiration of whole plants (E) under field conditions was clearly reduced by application of silica. The gc of –Si leaves under precisely regulated conditions was 33% higher than that of +Si leaves, reflecting higher adaxial gc. Silicon has little effect on WC, a factor responsible for regulation of cuticular resistance to water flux in rice leaves. These results suggest that silicon is one of the main factors responsible for regulation of gc, but that its effect was not due to an increase in the WG. Leaf conductance (gl) of –Si leaves tended to decrease more slowly than that of +Si leaves over time after changes from high to low light intensity. Moreover, it was always higher over the entire duration of the experiment, irrespective of irradiation intensity. The gl of –Si leaves was higher at lower relative humidity (RH) and the initial response to a subsequent increase in RH was slower than that of +Si leaves. A comparison of gl and gc between +Si and –Si leaves showed that the higher gl of –Si leaves was due to higher stomatal conductance. These results indicated that the reduction in E by application of silica was mainly attributable to reduction in the rate of transpiration through stomatal pores.     

Characteristics of Gas Exchange and Chlorophyll Fluorescence during Senescence of Flag Leaf in Different Rice (Oryza sativa L.) Cultivars Grown under Nitrogen-Deficient Condition

Abstract

Effects of nitrogen (N) deficiency on photosynthetic gas exchange and photosystem II (PSII) photochemistry of flag leaves during grain-filling stage were investigated in six rice cultivars, Kasalath (a conventional indica), IR36 (an improved indica), Shirobeniya (a conventional japonica), Nipponbare (an improved japonica), Akenohoshi (an improved japonica-indica intermediate type) and BSI429 (an improved tropical japonica, a new plant type line) grown hydroponically in N-sufficient (NS) and N-deficient (ND) solution. From 3 to 24 days after heading (DAH), net photosynthetic rate (P_n), maximum quantum yield of photosystem II (PSII) (F_v/F_m), quantum yield of PSII electron transport ( Φ_psii), and contents of chlorophyll (Chl) and ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) in the flag leaves decreased, particularly under the ND condition in all six cultivars. A substantial difference was observed among the ND plants for the sustainability index (SI, the ratio of the value at 24 DAH to that at 3 DAH) of P_n, F_v/F_m, Φ_psii, Chl content and Rubisco content; SIs of those parameters of Akenohoshi, BSI429, Nipponbare and Shirobeniya were higher than those of IR36 and Kasalath. The SI of P_n showed significant positive correlations with those of F_v/F_m, Φ_psii, and the contents of Chl and Rubisco under the ND condition. It was concluded that the sustainability of photosynthesis in the flag leaves was mainly due to those of PSII photochemistry and electron transport, which was associated with the maintenance of Chl and Rubisco under the ND condition.     

水稻矮生性突变体的应用及研究进展

水稻矮化育种是20世纪以来中国水稻育种所取得的重大成就之一,对中国粮食增产以及保障粮食安全至关重要。综述水稻矮生性状的遗传、矮化植株的特征特性、矮化机理及矮秆基因定位克隆等方面的研究进展,并进一步分析了当前在利用水稻矮秆突变体育种中存在的问题及发展前景。     

Spatial and Temporal Variation in Photon Flux Density on Rice (Oryza sativa L.) Leaf Surface

Abstract

Spatial and temporal variations of photosynthetic photon flux density (PFD) measured using small photodiodes (Hamamatsu, model G1118) attached on the leaf surface of rice (Oryza sativa L.) differed with the orientation and inclination even at the same height of the canopy. Under sunny conditions, the fluctuation pattern of PFD was mainly determined by the orientation and inclination of the leaf surface, and not by the daily change of PFD in the open, e. g., high peaks of PFD were observed in the morning on east-oriented leaves, but only low peaks on north-oriented leaves. Under overcast conditions, however, the PFD on the leaf surface depended highly on the PFD in the open irrespective of the leaf orientation and inclination. The present study suggests that the orientation and inclination should be considered as the major factors influencing the PFD regime (spatial variation and daily total PFD) within the rice canopy. To determine the effects of spatial and temporal variations of PFD on crop productivity, the daily net assimilation of each leaf was estimated from the obtained data and the light-photosynthesis curve.     

Genetic Analysis of Water Use Efficiency in Rice (Oryza sativa L.) at the Leaf Level

Carbon isotope discrimination (?¹³C) is considered as an index of leaf-level water use efficiency, an important objective for plant breeders seeking to conserve water resources. We report in rice a genetic analysis for ?¹³C, leaf structural parameters, gas exchange, stomatal conductance, and leaf abscisic acid (ABA) concentrations. Doubled haploid and recombinant inbred populations, both derived from the cross IR64 × Azucena, were used for quantitative trait locus (QTL) analysis following greenhouse experiments. ?¹³C QTLs on the long arms of chromosomes 4 and 5 were colocalized with QTLs associated with leaf blade width, length, and flatness, while a QTL cluster for ?¹³C, photosynthesis parameters, and ABA was observed in the near-centromeric region of chromosome 4. These results are consistent with phenotypic correlations and suggest that genetic variation in carbon assimilation and stomatal conductance contribute to the genetic variation for ?¹³C in this population.     

Spotted-Leaf Mutants of Rice(Oryza sativa)

Many rice spotted-leaf(spl) mutants are ideal sources for understanding the mechanisms involved in blast resistance,bacterial blight resistance and programmed cell death in plants.The genetic controls of 50 spotted-leaf mutants in rice have been characterized and a few spotted-leaf genes have been isolated as well.This article reviews the origin,genetic modes,isolation and characterization of spotted-leaf genes responsible for their phenotypes,and their resistance responses to main rice diseases.     

Response of Leaf Photosynthesis to Vapor Pressure Difference in Rice (Oryza sativa L) Varieties in Relation to Stomatal and Leaf Internal Conductance

Abstract

In the afternoon when air humidity decreases, leaf photosynthetic rate (P_n) often declines in rice grown under irrigated conditions. To clarify the genotypic difference of P_n in response to humidity, we measured P_n and stomatal conductance (g_s) for nine rice varieties with diverse genetic backgrounds, at various vapor pressure differences (VPD) and developmental stages. P_n and g_s of all the varieties decreased with VPD increase from 1.0 to 2.3 kPa of VPD. The variety with high g_s at low VPD exhibited a greater decline of g_s with VPD increase than the variety with low g_s, but cv. Takanari showed the highest g_s under altered VPD conditions. Significant logarithmic relations were found between the decreased P_n and g_s at the respective developmental stages, suggesting that g_s is the dominant factor determining P_n and its response to VPD change. To explicate the effect of decreased g_s on P_n, we analyzed the relations by using the model that accurately estimated the genotypic difference in P_n at a low VPD with g_s and leaf nitrogen content per unit leaf area in the previous study. The model assuming that leaf internal conductance (g_w) remains unchanged well explained the decreased P_n at high VPDs by g_s change alone. The analysis also suggested the constancy of g_w and carboxylation capacity at high VPD. It is concluded that the genotypic difference in the decrease of P_n at a high VPD is brought mainly by that in decreased g_s, and the varieties with a high g_s always exhibit a high P_n owing to their relatively high g_s at either high or low VPD environments.     

水稻叶片衰老基因LPS1的克隆与功能研究

【目的】早衰突变体是研究早衰机制的良好载体,对于探究早衰的遗传机理与作用机制及提高水稻的产量和品质具有重要作用。【方法】本研究利用EMS诱变获得了一个早衰突变体lps1,并对该突变体及其野生型进行表型观察、细胞学及组织化学分析、生理生化分析、遗传分析、基因定位和激素处理。【结果】lps1的叶片从3叶期开始发黄,成熟期株高、有效分蘖数、结实率、千粒重等极显著降低。电镜观察发现lps1叶表面光滑,硅质化突起和叶绿体数目减少、片层结构紊乱。生理生化分析表明lps1中有大量的活性氧积累,同时伴有蛋白质的降解、细胞膜的损伤以及大规模的细胞死亡。遗传分析表明该早衰表型受单隐性核基因控制,并且其在第5染色体上编码了一个泛素结合酶。亚细胞定位结果证明LPS1蛋白在细胞质与核中均有表达。外源激素处理发现,lps1对外源激素的处理更为敏感,且LPS1突变促进了ABA合成相关基因的表达。【结论】LPS1 突变使水稻ABA合成信号途径异常,进而引发H₂O₂等一系列与衰老相关生理指标的异常变动,导致lps1过早衰老,最终造成水稻产量严重降低。