灌浆结实期温度对水稻产量和品质形成的影响

灌浆结实期是水稻产量和品质形成的关键时期,该时期温度对水稻籽粒灌浆具有显著的影响.随着全球气候趋暖以及极端天气频发,温度胁迫下籽粒灌浆和稻米品质的响应特征及其生理生化机制是目前稻作研究的热点之一.本文以灌浆结实期温度为切入点,对水稻产量和品质形成的适宜温度与温度影响时段以及温度胁迫下水稻生理生化特征等方面进行了梳理.灌浆初期(齐穗后20 d)是温度影响水稻产量和品质形成的关键时期,适温(21 ～ 26℃)有利于水稻灌浆和淀粉的充实与沉积,过高或过低温度均不利于提高水稻产量和品质.温度胁迫下,水稻生理生化活性下降,光合功能降低,抗逆性减弱,干物质积累和运转受抑,从而造成产量下降及品质变劣.这些可能为水稻优质高产栽培和灌浆结实期温度研究提供一定的参考.     

水稻硅转运蛋白研究进展

硅是促进水稻生长和维持持续生产的重要营养元素,它有助于提高植物抗病虫害、抗倒伏以及抗生物和非生物胁迫的能力。硅能改善水稻的形态结构,提高产量和品质,还可以提高氮、磷利用率,减轻一些重金属的毒害作用。综述了水稻硅吸收运输有关的输入转运蛋白Lsi1、输出转运蛋白Lsi2和运输蛋白Lsi6表达和功能。同时,对这些转运蛋白的应用前景进行了展望。     

黄瓜中硅的生理功能及转运机制研究进展

硅是植物体的重要组成部分,尽管硅尚未被列为植物生长的必需元素,但它在促进植物生长发育、提高作物对非生物逆境（干旱、盐分和重金属等）和生物逆境（病虫害）抗性等方面都具有重要作用。硅不仅能改善植株对矿质营养的吸收,提高作物产量和品质,而且能沉积在叶片及叶鞘表皮细胞,形成硅化细胞和角质双硅层结构,增强寄主植物细胞壁的机械强度和稳固性,从而增强植物对真菌侵入和扩展的抵御能力,提高植物对金属离子毒害的抗性、缓解盐胁迫、增强抗高低温和抗紫外线辐射等。本文在植物硅素营养和转运机制研究的基础上,对硅素营养在黄瓜中生长发育、抗逆和吸收转运机制等方面的效应做了相关综述,并展望了黄瓜中硅研究的未来发展。     

活性硅缓解植物重金属胁迫及其生物学机制研究进展

土壤重金属污染可抑制植物的正常生长并增加其在食物链传播的风险。硅是重要的植物营养元素, 可通过多种途径调节植物生理、生化和代谢功能, 在缓解植物的重金属胁迫及促进植物生长方面发挥重要作用。论文从活性硅促进组织结构发育、调节基因表达、增强抗氧化防御系统及建立重金属内部隔离等方面进行分析, 阐述活性硅缓解植物重金属胁迫的生物学机制。建议针对硅材料的施加方式、自然条件下硅缓解复合重金属污染胁迫机制、硅材料在土壤中的老化机理等方面, 系统开展长期田间实验, 以阐明活性硅缓解植物重金属胁迫作用机制并应用于农田土壤重金属修复。     

植物硅营养的研究进展

阐述了植物吸收硅的机理、硅与其它营养元素的关系及其对非胁迫和胁迫条件下植物生长发育的有益作用 .植物吸收硅的机制目前尚不是很清楚 ,不同植物吸收硅的方式不同 .硅可影响植物中其它营养元素的含量 .在非胁迫条件下 ,硅可促进植物的生长 ;硅也参与了植物抗病、抗虫等生物胁迫 ,以及抗金属毒害、盐害、温度胁迫、干旱、抗倒伏等非生物胁迫的反应 .目前 ,应从多种植物上深入研究硅的吸收方式与机理 ;同时 ,应该改变硅在细胞壁的沉积仅仅起增强组织机械强度作用的观点 ,而应从生理代谢调控的角度进行硅作用机制的研究 ,为生产实践中硅肥的应用奠定理论基础     

植物硅营养的研究进展

阐述了植物吸收硅的机理、硅与其它营养元素的关系及其对非胁迫和胁迫条件下植物生长发育的有益作用。植物吸收硅的机制目前尚不是很清楚,不同植物吸收硅的方式不同。硅可影响植物中其它营养元素的含量。在非胁迫条件下,硅可促进植物的生长;硅也参与了植物抗病、抗虫等生物胁迫,以及抗金属毒害、盐害、温度胁迫、干旱、抗倒伏等非生物胁迫的反应。目前,应从多种植物上深入研究硅的吸收方式与机理;同时,应该改变硅在细胞壁的沉积仅仅起增强组织机械强度作用的观点．而应从生理代谢调控的角度进行硅作用机制的研究,为生产实践中硅肥的应用奠定理论基础。     

硅提高植物抗旱性的生理机制研究进展

干旱作为限制作物产量和品质的主要非生物胁迫之一,对全球社会、经济和生态造成巨大损失。在全球气候变化背景下,提高植物抗旱性的重要性日益突显。硅能够提高植物的抗旱性：外源硅的施用可以影响气孔导度,改变蒸腾速率,改善植物水分状况;通过调节气孔动力学、合成光合色素,促进光化学反应,从而改善光合作用;此外硅可通过渗透调节以平衡植物对矿质元素的吸收,以及调节抗氧化防御系统,减轻植物在干旱胁迫中的氧化损伤。总结了硅对干旱胁迫下植物水分利用、光合作用、矿质元素吸收、抗氧化系统、植物激素代谢等方面的作用及相关生理机制。建议未来从复合逆境胁迫、低硅积累植物等方面进一步揭示硅提高植物抗旱性的作用机制,从而为农林生态系统合理利用硅素来提高生产效率提供科学依据和理论基础。     

施硅对抑制植物吸收重金属镉的效应研究进展

施用化学改良剂是控制土壤重金属污染的有效手段。研究施硅对抑制植物吸收重金属镉的影响及其作用机制,对促进利用硅肥作为改良剂治理重金属污染土壤技术的发展有重要意义。近年来,以硅肥作改良剂对重金属污染的土壤进行治理的研究大量涌现。本文从施硅对抑制植物吸收镉及镉在植物体内的分布、迁移的影响;从植物细胞膜透性、抗氧化物酶系和抗氧化剂等新陈代谢或生理过程及硅-金属复合物的结构组成等方面对植物抗镉胁迫的生理生化效应及其抑制植物吸收重金属镉的机制进行综述,并对今后有待进一步研究的问题提出了建议。     

硅和干旱胁迫对水稻叶片光合特性和矿质养分吸收的影响

硅被认为是植物生长的有益元素,它能增强植物对非生物逆境和生物逆境胁迫的抗性。以抗旱性不同的一对水稻近等基因系w-14-和w-20为实验材料,采用盆栽实验,研究了干旱胁迫下硅处理对水稻生长性状、光合生理特性和矿质养分吸收的影响。结果表明,在正常水分条件下硅处理对水稻的生长及生理特性没有明显影响。干旱胁迫显著降低水稻植株的生长,叶绿素含量、叶绿素荧光参数Fv/Fm及Fv/F0值显著降低,光合作用受到明显抑制。加硅能提高干旱胁迫条件下水稻植株的生物量、水分利用效率、叶片叶绿素含量、净光合速率和蒸腾速率,而气孔导度和细胞间隙CO2浓度则下降。无论干旱与否,施硅后水稻的叶片硅含量均显著上升。两个水稻品系叶片的无机离子含量在干旱胁迫条件下均呈显著增加的趋势,而硅处理后材料w-14的叶片K+、Na+、Ca2+、Mg2+、Fe3+含量分别降低16.38%,24.50%,19.70%,21.52%,18.58%,w-20则分别降低11.64%,12.11%,16.06%,11.11%和19.15%,并使之回复到与对照更接近的水平。研究结果表明了硅提高水稻植株的抗旱性与光合作用的改善和矿质养分的调节有关。     

水稻铅污染研究进展（综述）

铅是一种对水稻(Oryza sativa L.)生长发育毒性显著的污染物质,农田土壤中铅的存在形式和含量直接影响稻米的产量与品质.本文从土壤中铅的存在形式、水稻对铅的吸收富集规律、铅污染对水稻生长发育的影响、水稻对铅污染的生理生化效应以及抗性机制等方面进行系统地分析论述.     

Enhancement of Ultrasonic Seed Treatment on Yield,Grain Quality Characters,and 2-Acetyl-1-Pyrroline Biosynthesis in Different Fragrant Rice Genotypes

Fragrant rice is popular for the good grain quality and special aroma. The present study conducted a field experiment to investigate the effects of ultrasonic seed treatment on grain yield, quality characters, physiological properties and aroma biosynthesis of different fragrant rice genotypes. The seeds of three fragrant rice genotypes were exposed to 1 min of ultrasonic vibration and then cultivated in paddy field. The results of present study showed that ultrasonic seed treatment increased grain yield of all fragrant rice genotypes but the responses of yield formation to ultrasonic were varied with different genotypes. Compared with control, ultrasonic seed treatment increased grain 2-acetyl-1-pyrroline (2-AP, the key component of fragrant rice aroma) content by 13.40%–44.88%. Ultrasonic seed treatment also reduced the crude protein contents in grains. The head rice rate, rice length, chalky rice rate, and chalkiness degree were influenced by ultrasonic for one or two fragrant rice genotypes. The activities of peroxidase and superoxide dismutase were also enhanced due to ultrasonic seed treatment. In conclusion, ultrasonic seed treatment increased grain, regulated grain aroma and quality, and improved stress resistance of fragrant rice varieties.     

Advances in Drought Resistance of Rice

Water deficit is a serious environmental stress and the major constraint to rice productivity. Losses in rice yield due to water shortage probably exceed losses from all other causes combined and the extent of the yield loss depends on both the severity and duration of the water stress. Drought affects rice at morphological, physiological, and molecular levels such as delayed flowering, reduced dry matter accumulation and partitioning, and decreased photosynthetic capacity as a result of stomatal closure, metabolic limitations, and oxidative damage to chloroplasts. Small-statured rice plants with reduced leaf area and short growth duration are better able to tolerate drought stress, although the mechanisms are not yet fully understood. Increased water uptake by developing larger and deeper root systems, and the accumulation of osmolytes and osmoprotectants are other important mechanisms for drought resistance. Drought resistance in rice has been improved by using plant growth regulators and osmoprotectants. In addition, several enzymes have been found that act as antioxidants. Silicon has also improved drought resistance in rice by silicification of the root endodermis and improving water uptake. Seed priming improves germination and crop stand establishment under drought. Rice plants expressing HVA1, LEA proteins, MAP kinase, DREB and endo-1, 3-glucanase are better able to withstand drought stress. Polyamines and several enzymes act as antioxidants and reduce adverse effects of drought stress in rice. Drought resistance can be managed by developing and selecting drought-tolerant genotypes. Rice breeding and screening may be based on growth duration, root system, photosynthesis traits, stomatal frequency, specific leaf weight, leaf water potential, and yield in target environments. This review discusses recent developments in integrated approaches, such as genetics, breeding and resource management to increase rice yield and reduce water demand for rice production.     

Involvement of polyamines in the drought resistance of rice

This study investigated whether and how polyamines (PAs) in rice (Oryza sativa L.) plants are involved in drought resistance. Six rice cultivars differing in drought resistance were used and subjected to well-watered and water-stressed treatments during their reproductive period. The activities of arginine decarboxylase, S-adenosyl-L-methionine decarboxylase, and spermidine (Spd) synthase in the leaves were significantly enhanced by water stress, in good agreement with the increase in putrescine (Put), Spd, and spermine (Spm) contents there. The increased contents of free Spd, free Spm, and insoluble-conjugated Put under water stress were significantly correlated with the yield maintenance ratio (the ratio of grain yield under water-stressed conditions to grain yield under well-watered conditions) of the cultivars. Free Put at an early stage of water stress positively, whereas at a later stage negatively, correlated with the yield maintenance ratio. No significant differences were observed in soluble-conjugated PAs and insoluble-conjugated Spd and Spm among the cultivars. Free PAs showed significant accumulation when leaf water potentials reached -0.51 MPa to -0.62 MPa for the drought-resistant cultivars and -0.70 MPa to -0.84 MPa for the drought-susceptible ones. The results suggest that rice has a large capacity to enhance PA biosynthesis in leaves in response to water stress. The role of PAs in plant defence to water stress varies with PA forms and stress stages. In adapting to drought it would be good for rice to have the physiological traits of higher levels of free Spd/free Spm and insoluble-conjugated Put, as well as early accumulation of free PAs, under water stress.     

Recent progress on molecular breeding of rice in China

Molecular breeding of rice for high yield, superior grain quality, and strong environmental adaptability is crucial for feeding the world’s rapidly growing population. The increasingly cloned quantitative trait loci and genes, genome variations, and haplotype blocks related to agronomically important traits in rice have provided a solid foundation for direct selection and molecular breeding, and a number of genes have been successfully introgressed into mega varieties of rice. Here we summarize China’s great achievements in molecular breeding of rice in the following five traits: high yield, biotic stress resistance, abiotic stress resistance, quality and physiology. Further, the prospect of rice breeding by molecular design is discussed.     

水稻籽粒灌浆速率的分子机制与遗传调控研究进展

水稻(Oryza sativa)的高产优质是我国粮食安全的重要保障, 也是育种家一直追求的目标。水稻籽粒灌浆速率(GFR)是一个重要而复杂的农艺性状, 直接影响籽粒充实度、粒重和米质。目前, 快速灌浆的优良水稻品种缺乏, 可供育种利用的相关优异基因资源有限, 已成为制约水稻产量和品质进一步提高的瓶颈。相对于水稻的其它农艺性状, GFR具有复杂的时空动态和环境可变性, 相关研究长期围绕灌浆过程的生理生化特性和栽培措施展开, 而分子机制和遗传调控研究启动较晚。该文以近年来国内外发现的水稻GFR相关基因为主线, 从糖类代谢和运输相关基因对GFR的影响、转录和翻译调控基因对GFR的调节、粒型和粒重等相关数量性状位点(QTL)对GFR的作用, 以及GFR相关QTL的分析和克隆4个方面, 对GFR分子机制与遗传调控进行综述; 并对GFR的研究策略特别是表型组学相关技术的应用前景进行展望, 以期推动该领域的基础研究和育种应用。     

Research on the adaptive mechanism of photosynthetic apparatus under salt stress: New directions to increase crop yield in saline soils

Photosynthesis is the largest organic synthesis on Earth, salinity limits crop yield and quality worldwide directly or indirectly related to the decrease in photosynthetic efficiency. The mechanism by which photosynthetic apparatus responds to salt stress is extremely complex and varies with plant genotype, developmental stage, the history of the plant cell and duration of stress imposed. Recent studies have partially revealed the mechanisms from different levels: molecular, physiological and biochemical, morphological; but there is currently no unified mechanism to explain the effect of stress on photosynthesis. This study comprehensively reviews the adaptive mechanism of photosynthetic apparatus under salt stress, summarises methods for increasing the resistance and provides a practical way to increase grain yield in saline soils.     

Post‐flowering night respiration and altered sink activity account for high night temperature‐induced grain yield and quality loss in rice (Oryza sativa L.)

High night temperature (HNT) is a major constraint to sustaining global rice production under future climate. Physiological and biochemical mechanisms were elucidated for HNT‐induced grain yield and quality loss in rice. Contrasting rice cultivars (N22, tolerant; Gharib, susceptible; IR64, high yielding with superior grain quality) were tested under control (23°C) and HNT (29°C) using unique field‐based tents from panicle initiation till physiological maturity. HNT affected 1000 grain weight, grain yield, grain chalk and amylose content in Gharib and IR64. HNT increased night respiration (Rn) accounted for higher carbon losses during post‐flowering phase. Gharib and IR64 recorded 16 and 9% yield reduction with a 63 and 35% increase in average post‐flowering Rn under HNT, respectively. HNT altered sugar accumulation in the rachis and spikelets across the cultivars with Gharib and IR64 recording higher sugar accumulation in the rachis. HNT reduced panicle starch content in Gharib (22%) and IR64 (11%) at physiological maturity, but not in the tolerant N22. At the enzymatic level, HNT reduced sink strength with lower cell wall invertase and sucrose synthase activity in Gharib and IR64, which affected starch accumulation in the developing grain, thereby reducing grain weight and quality. Interestingly, N22 recorded lower Rn‐mediated carbon losses and minimum impact on sink strength under HNT. Mechanistic responses identified will facilitate crop models to precisely estimate HNT‐induced damage under future warming scenarios.     

Engineering OsBAK1 gene as a molecular tool to improve rice architecture for high yield

Generating a new variety of plant with erect-leaf is a critical strategy to improve rice grain yield, as plants with this trait can be dense-planted. The erect-leaf is a significant morphological trait partially regulated by Brassinosteroids (BRs) in rice plants. So far, only a few genes can be used for molecular breeding in rice. Here, we identified OsBAK1 as a potential gene to alter rice architecture. Based on rice genome sequences, four closely related homologs of Arabidopsis BAK1 ( AtBAK1 ) gene were amplified. Phylogenetic analysis and suppression of a weak Arabidopsis mutant bri1-5 indicated that OsBAK1 (Os08g0174700) is the closest relative of AtBAK1. Genetic, physiological, and biochemical analyses all suggest that the function of OsBAK1 is conserved with AtBAK1 . Overexpression of a truncated intracellular domain of OsBAK1 , but not the extracellular domain of OsBAK1 , resulted in a dwarfed phenotype, similar to the rice BR-insensitive mutant plants. The expression of OsBAK1 changed important agricultural traits of rice such as plant height, leaf erectness, grain morphologic features, and disease resistance responses. Our results suggested that a new rice variety with erect-leaf and normal reproduction can be generated simply by suppressing the expression level of OsBAK1 . Therefore, OsBAK1 is a potential molecular breeding tool for improving rice grain yield by modifying rice architecture.     

Comprehensive metabolomic,proteomic and physiological analyses of grain yield reduction in rice under abrupt drought–flood alternation stress

Abrupt drought–flood alternation (T1) is a meteorological disaster that frequently occurs during summer in southern China and the Yangtze river basin, often causing a significant loss of rice production. In this study, the response mechanism of yield decline under abrupt drought–flood alternation stress at the panicle differentiation stage was analyzed by looking at the metabolome, proteome as well as yield and physiological and biochemical indexes. The results showed that drought and flood stress caused a decrease in the yield of rice at the panicle differentiation stage, and abrupt drought–flood alternation stress created a synergistic effect for the reduction of yield. The main reason for the decrease of yield per plant under abrupt drought–flood alternation was the decrease of seed setting rate. Compared with CK0 (no drought and no flood), the net photosynthetic rate and soluble sugar content of T1 decreased significantly and its hydrogen peroxidase, superoxide dismutase, peroxidase activity increased significantly. The identified differential metabolites and differentially expressed proteins indicated that photosynthesis metabolism, energy metabolism pathway and reactive oxygen species response have changed strongly under abrupt drought–flood alteration stress, which are factors that leads to the rice grain yield reduction.