植物叶片衰老相关研究进展

植物叶片衰老是生命科学研究的热点之一。研究植物的衰老机理以及有效防止早衰具有重要的理论意义和实用价值。本文就国内外有关植物叶片衰老的影响因素、叶片衰老相关基因及其分子机制等的研究进展进行了概述,对今后的研究方向作了展望。     

VA菌根菌改善植物磷素营养的研究进展

VA菌根(Vesicular-arbuscular mycorrhizal, 简称VAM)是分布最广的一种内生菌根[1]。VAM真菌能和绝大多数农作物、园艺作物、蔬菜作物和牧草等共生,从而促进这些植物对多种矿质养分，尤其是磷（P）的吸收。笔者主要就VA菌根改善植物磷素营养的研究进展，作以简要综述，并浅谈其今后的研究。     

略论VA菌根在我国的应用

论述了ＶＡ菌根对植物生长的重要作用及在农林业中实际应用的必要性和可能性,指出当前及时开展面向生产的研究,将ＶＡ菌根真正应用于实际并取得效益,是关系到今后ＶＡ菌根研究能否继续发展的关键。在应用方法上重点提出了结合组培和工厂化育苗培育菌根化苗“借鸡下蛋”接种法,和其它在有益微生物联合接种等看法。并讨论了达到互惠共生最佳状态的调控,不同菌析的接种谱,ＶＡ真菌的防病及致病等问题。     

VA菌根改善植物磷素营养的研究进展

VA菌根(Vesicular-arbuscularmycorrhizal,简称VAM)是分布最广的一种内生菌根[1]。VAM真菌能和绝大多数农作物、园艺作物、蔬菜作物和牧草等共生,从而促进这些植物对多种矿质养分,尤其是磷(P)的吸收。笔者主要就VA菌根改善植物磷素营养的研究进展,作以简要综述,并浅谈其今后的研究。     

茶树VA菌根菌的形态学观察

菌根化植物由于扩大了对养分的吸收范围,增加根系对磷素及其它在土壤中移动缓慢的营养元素的吸收,而使植物的生长量和产量增加。从事菌根学的研究对现代生物技术的开发和应用,有重要意义。概述自然界中,普遍存在着内生菌根。萨塔奈拉耶娜(1979)发现茶树根系也有丛枝状内     

山东农业大学李刚课题组揭示植物叶片衰老调控新机制

正叶片衰老是叶片发育的最后阶段,受到多种内部因素(如年龄、发育、营养)及外部环境因素(如光照、温度、胁迫)的共同调控。在植物自然生长发育状态下,植物通过感知内部年龄的变化调控衰老进程,但遮阴环境(低比率R/FR)或延长黑暗等可提前诱发或加速叶片衰老,而高比率的R/FR光照条件显著抑制叶片衰老。植物如何整合外界环境光信号和内在年龄因素,进而调控叶片衰老的机制目前并不清晰。     

科技与产品

正脱落酸通过调控叶片衰老提高抗旱性的分子机制被揭示中国科学院上海生命科学研究院上海植物逆境研究中心以及美国普渡大学等单位的研究人员联合破译了植物激素脱落酸(ABA)通过调控植物叶片衰老,促使植物对水分养分进行源库的再分配,从而提高作物抗旱性的分子机制。该研究表明,ABA受体PYL9和经典的下游复合体PP2C/Sn RK2共同传递ABA诱导的衰老信号,通过对下游转录因子ABFs和RAV1的磷酸化激活促进衰老相关基因的表达,从而最     

植物衰老的研究进展及其在分子育种中的应用

植物衰老是植物生命科学研究领域的核心问题之一。无论是在器官水平上还是在个体水平上，衰老都是一个高度有序的被调控的过程。近年来，已发现大批衰老相关基因以及突变体，初步阐明了叶片衰老的分子机制。而在个体水平，G2豌豆以其在短日条件下无限生长的独特发育模式，提供了很好的实验材料。PPFl(Pisum sativum post—floral genel)是首次在短日条件下G2豌豆中分离出来的与衰老相关的基因，过表达PPFl基因可以显著延迟转基因拟南芥的开花时间。最新的研究表明，它可能编码一个定位于叶绿体膜上的钙离子泵，通过调节细胞质中钙离子浓度来影响植物的生长发育。PPFl还可能通过调控LFY(LEAFY)等一系列开花途径调节基因的表达水平来影响植株的整体衰老进程。关于植物衰老的研究，不仅具有理论上的重大意义，并且在分子育种中具有潜在的价值。     

利用丛枝菌根真菌(AMF)提高植物抗旱性的研究进展

丛枝菌根是分布最广泛的一类内生菌根,它可以促进植物对水分的吸收和利用,提高植物的抗旱能力。丛枝菌根真菌可以通过以下几个方面增强植物抗旱性:通过菌丝增加植物对土壤水分的吸收;改善植物的磷营养及其他矿质元素营养;能显著提高蒸腾速率和气孔导度;干旱条件下降低植株叶片水势、永久凋萎点、叶片饱和亏、气孔阻力和恢复时间;改变激素平衡。     

丛枝菌根真菌(AMF)提高植物抗旱性的研究进展

丛枝菌根是分布最广泛的一类内生菌根,它可以促进植物对水分的吸收和利用,提高植物的抗旱能力。丛枝菌根真菌可以通过以下几个方面增强植物抗旱性：通过菌丝增加植物对土壤水分的吸收;改善植物的磷营养及其他矿质元素营养;能显著提高蒸腾速率和气孔导度;干旱条件下降低植株叶片水势、永久凋萎点、叶片饱和亏、气孔阻力和恢复时间;改变激素平衡。     

棉花不同叶位主茎叶衰老特征的研究

 在大田条件下,研究了棉花不同叶位主茎叶在盛铃末期的衰老状况。以转基因抗虫棉33B为材料,测定全部主茎叶的主要生理生化指标,以分析不同部位叶片衰老的差异。结果表明,（1）盛铃末期是主茎功能叶片从旺盛生理功能到衰老的转折时期;（2）从主茎上部第1叶到下部的第10叶叶绿素含量、蛋白质含量、SOD活性呈下降趋势,MDA含量、POD活性呈上升趋势;（3）盛铃期调控棉花叶片的衰老应以主茎中部轻度衰老叶片为诊断和调控主体。     

烟叶成熟过程相关基因变化及其叶绿素降解

烤烟叶片成熟过程与衰老是烟草发育的重要阶段,是一个复杂和高度调控的过程,涉及衰老相关基因的调控表达和叶绿体的分解,也是烟草质量和品质形成的关键时期,因此其成为烟草生产和研究的重要时段。介绍了烟叶衰老过程相关基因的表达变化和叶绿素分解的过程,为从分子水平定义烟叶的成熟度提供理论依据。     

Senescence of Flag Leaf and Glume in Rice: Role of Grains during Source-Sink Modification by Physical and Chemical Means

Senescence of flag leaf and glume of rice ( Oryza sativa L. cv. Ratna ) at different source sink ratios, through manipulating the plants by physical and chemical means, were analyzed. As judged from the chlorophyll retention capacity, induction of sterility deferred senescence of flag leaf and glume at both grain filling and post grain maturation period. Senescence of the glumes was promoted in the plants whose panicles were darkened. The time needed for achieving maximum 1000 grain dry weight was quickened, the harvest index (HI) was lowered and the flag leaf senescence was delayed by such manipulation. Spraying of urea deferred senescence of the flag leaf as well as increased 1000 grain dry weight and HI. The time taken for achieving maximum 1000 grain dry weight was, however, delayed. Senescence of glumes was promoted by α-HPMS spray, while the same was delayed by PMA spray on the whole plant. Both the chemicals deferred flag leaf senescence and decreased 1000 grain dry weight and HI. Senescence of the flag leaf at post grain filling period was also delayed by the above physical and chemical manipulations compared to that of control, the highest delaying effect was recorded in the flag leaf of sterile plant.
It is concluded that nutrient drainage is the primary cause of nonsequential senescence of the flag leaf of rice (cv. Ratna ). The involvement of senescence signal if any, is perhaps of secondary importance.     

玉米密植群体下部叶片衰老对植株碳氮分配与产量形成的影响

玉米密植会造成花后下部叶片早衰, 为探明其对植株根系性能、碳氮积累分配及产量形成的影响, 采用大田与土柱栽培相结合的方式, 以登海661和郑单958为试材, 分析了密植条件下两品种花后碳氮分配、根系性能和植株干物质积累量的变化。两年结果表明, 玉米密植群体下部叶片早衰导致两品种花后穗位叶叶绿素含量和净光合速率显著降低, 向根系转运的光合产物数量显著减少, 成熟期(R6)的根系生物量、根长密度和根系表面积较CK显著减少。根系性能的下降导致花后氮素吸收量显著降低, 叶片光合速率降低、整株叶片衰老进程加快, 单株籽粒产量显著下降, 登海661较CK低7.61%, 郑单958较CK低8.35%。郑单958的花后叶片衰老要早于登海661, 且叶面积和净光合速率比登海661低, 导致花后干物质积累量和产量较登海661显著降低。可见玉米密植群体花后下部叶片衰老加速了根系衰老, 降低了氮素吸收量, 影响整株绿叶面积和光合持续期, 最终导致花后干物质积累量和籽粒产量降低。     

Regulation of Correlative Senescence in Arachis hypogaea L. by Source-Sink Alteration through Physical and Hormonal Means

Amongst the plants ( Arachis hypogaea ) subjected to differential reproductive manipulations, the leaf levels of chlorophyll and sugar and the dry weight of the aerial plants increased more (except sugar level in defruited plant) in the deflorated plants than either in the defruited or control plants, and the order of senescence was: control > defruited > deflorated. Seed yield per plant increased in deflorated plants as a result of increase in the number of pods (sink size) and reduction in the sink strength (seed wt per pod). While 75 % defoliation caused a decrease in all the parameters relating to senescence (chlorophyll, protein, reduced nitrogen, sugar and dry wt), 25% defoliation caused a slight decrease of chlorophyll level of leaf and aerial plant weight. However, the level of protein and reduced nitrogen in the leaf and sugar in the stem increased by the latter (through 25% defoliation). Defoliation up to 25% reduced seed yield by only 2%. Whereas the level of chlorophyll and aerial plant dry weight were not significantly changed by either kinetin or ABA, the level of protein and reduced nitrogen in the leaf and sugar level in both leaf and stem increased by kinetin. GA₃ increased almost all the parameters studied. All the three phytohormones increased the yield, mainly by increasing the sink size rather than the sink strength. It is concluded that the aerial flowers are more lethal than the underground fruits in inducing whole plant senescence where the leaf senescence is uncoupled from fruit maturation in normal condition possibly due to sink limitation.     

Effects of Soil Salinity and Plant Density on Yield and Leaf Senescence of Field‐Grown Cotton

The response of cotton to constant salinity has been well documented under controlled conditions, but its response to changing salinity under field conditions is poorly understood. Using a split‐plot design, we conducted a 2‐year field experiment to determine the effects of soil salinity and plant density on plant biomass, boll load, harvest index and leaf senescence in relation to cotton yield in three fields with similar fertility but varying salinity. The main plots were assigned to weak (electrical conductivity of soil saturated paste extract, ECe = 5.5 dS m^?1), moderate (ECe = 10.1 dS m^?1) and strong (ECe = 15.0 dS m^?1) soil salinity levels, while plant density (3.0, 4.5 and 7.5 plants m^?2) was assigned to the subplots. Soil salinity had a negative effect on seedcotton yield, but the negative effect was compensated for by increased plant density under strong‐salinity conditions. Seedcotton yield under weak salinity changed little with varying plant density, but the medium plant density yielded better than the low or high plant density under moderate salinity. Plants accumulated 49 and 112 % more Na⁺ in leaves under moderate and strong salinity than under weak salinity. Strong salinity also led to higher boll load and early leaf senescence. Plant density had no effect on Na⁺ accumulation in leaves, but greatly reduced boll load and delayed leaf senescence. Plant biomass, maximum leaf area index and harvest index were greatly affected by salinity, plant density and their interaction. Accelerated leaf senescence under strong salinity was attributed to the high boll load and increased accumulation of toxic ions like Na⁺ in leaves, while delayed leaf senescence with increased plant density was attributed to the reduced boll load. Optimal yield can only be obtained with proper coordination of total biomass and harvest index by modification of plant density based on salinity levels.     

Carbon and nitrogen allocation and grain filling in three maize hybrids differing in leaf senescence

Between flowering and maturity, leaf senescence reduces green leaf area while grains are filled from photosynthesis, nitrogen (N) uptake by roots and remobilisation from shoots. The question arises of possible effects of leaf senescence on photosynthesis, N uptake and remobilisation and their modification through genetic variations in senescence. To address this question, we compared three cultivars showing different behaviours. Tarro and Nicco are two modern hybrids presenting the same important grain sink but showing different time course of senescence, the former being normally senescent the latter “stay-green”. Déa hybrid, very well known by many previous experiments was the reference hybrid.The purpose was to monitor precisely the carbon (C) and N repartition in the main organs of the plant in connection with the progress of leaf senescence (experiment 1) and to measure the changes created by variations of N supply and soil-climate conditions (experiment 2).In experiment 1, time course of leaf senescence of the different leaf stages and weight of leaves, shoots and grains and N concentration of shoots and grain were measured weekly. In experiment 2, the same three cultivars were grown at limiting and non-limiting N supply in four locations in France during 2 years. At flowering, silage and harvest stage, dry matter and N concentration were measured in the main parts of the plant, and leaf senescence was evaluated at silage stage.On soil well supplied with N, Tarro had an identical rate of leaf senescence than Nicco for leaves below the ear, but higher for leaves above the ear. After flowering, Nicco accumulated more biomass than Tarro, but kept a larger part of this total biomass in the stem. In contrast, Tarro accumulated a larger part of total biomass in the grain.After flowering, N uptake was larger in Nicco than Tarro. Shoot N concentration decreased earlier and more completely in Tarro than Nicco, indicating a larger remobilisation to the grain. Though Tarro began and finished grain filling simultaneously with Nicco, it reached 70% of final grain weight 25 °C d sooner than Nicco.The senescence due to N stress differed from the physiological senescence of a senescent hybrid. The time course of the reproductive phase and the N repartition in the plant suggest that a threshold in grain filling or in shoot nitrogen decrease could be the internal signal triggering senescence of uppermost leaves.     

水稻叶片保绿性的分子遗传研究进展

植物叶片的衰老是植物在长期进化过程中形成的适应机制,与收获器官的形成及营养转运密切相关,受植物内部因素调节,属于不可逆转的过程。作物叶片过早衰老将导致同化能力降低,影响作物的产量和品质。加强植物叶片功能研究将有助于改善我国农作物品质、增加产量。水稻作为我国的第一大粮食作物,延缓水稻叶片衰老,延长其光合功能期对提高产量有着重要的意义。本文将从水稻叶片保绿性的概念和分类、叶片保绿过程中叶绿素的功能及其降解等生理生化特点、叶片保绿性的表型遗传和基因效应等遗传特性以及叶片保绿性分子调控等几个方面的进行综述。理清水稻叶片保绿性的分子遗传机制,对具高保绿能力叶片的高产水稻品种选育及高产潜力水稻种质资源的挖掘都具有重要指导意义。     

棉花叶片早衰的诊断及遗传效应分析

比较了利用活体叶片快速、无损害诊断棉花叶片早衰的SPAD差值法和绿色叶面积分级诊断方法,并分析了棉花叶片早衰的数量遗传行为。选用不同叶形和早衰类型的9个棉花品种(系),比较开花当天倒4叶及以后每5 d一次的SPAD值表明, 早衰棉花品种在开花35 d后SPAD值明显降低,因此,将开花后35 d和开花当天倒4叶的SPAD的差值作为诊断棉花叶片早衰的指标。构建持绿亲本33B和早衰亲本CJ463的6个世代(P₁、F₁、P₂、F₂、BC₁和BC₂),用联合尺度检验法对其叶片早衰的数据进行世代均值分析,结果表明棉花叶片早衰主要受加性遗传效应控制,至少是一对加性效应的主基因控制陆地棉叶片早衰遗传,且遗传力较高,说明对持绿材料的早代选择是有效的。总之,用SPAD差值和绿色叶面积分级两种诊断叶片早衰的方法来分析叶片早衰遗传及其与叶面积关系的结果基本一致。     

Monocarpk Senescence in Relation to Yield of Sesamum indicum During Source-Sink Alteration

Defoliation hastens senescence of the capsule wall, increased seed weight/capsule and harvest index, promotes seed filling and decreased the post-flowering contribution and yield/plant. Defruiting delayed senescence of the subtending leaf. Treatment of kinetin on the capsule wall increased its chlorophyll, sugar and dry weight and also increased yield by increasing harvest index, seed weight/capsule compared to seed treatment as well as control, although post-flowering contribution reduced significantly. When treated on the capsule wall ABA defers senescence of both leaf and capsule wall and also increased the yield parameters but seed treatment although defers senescence of both the source organs, decreased the yield parameters. Treatment of urea defers senescence of the source organs and also increased yield and capsule number though harvest index was reduced.
It is concluded that contribution from the capsule wall and deferment of senescence of this organ at the post capsule development period determines yield and in normal condition contribution of source is limited by the sink size.