苗期玉米叶片碳氮平衡与干旱诱导的叶片衰老之关系

为了探究干旱诱导的碳氮平衡破坏与干旱诱导的叶片衰老之间的关系,该实验以8个在干旱胁迫下叶片衰老进程有明显差异的玉米品种为实验材料,采用PEG模拟干旱处理,通过测定光合速率、叶绿素含量和叶绿素荧光参数等叶片衰老指标以及非结构性碳水化合物(可溶性糖、淀粉)和全氮含量等变化,分析玉米中干旱诱导的叶片衰老与叶片中碳氮平衡(碳氮比)之间的关系。结果显示:(1)干旱胁迫下,8个玉米品种叶片净光合速率受到严重抑制,Fv/Fm大幅下降,叶绿素含量显著降低,说明干旱诱导了玉米叶片的衰老;(2)干旱诱导玉米叶片衰老的同时,8个玉米品种的叶片中可溶性糖含量显著升高,淀粉含量小幅上升,全氮含量大幅降低,碳氮比显著升高,碳氮平衡遭到了破坏;(3)8个玉米品种叶片的叶绿素含量与非结构性碳水化合物含量以及碳氮比呈极显著负相关关系,与全氮含量呈极显著正相关关系。因此,碳氮代谢与干旱诱导的叶片衰老紧密联系,碳氮平衡可能参与了干旱诱导的叶片衰老调控。     

锌对不同基因型玉米幼苗碳氮代谢的影响

选用不同耐锌玉米品种‘四单19’（低锌敏感型）和‘牡丹9’（低锌不敏感型）,采用营养液水培,研究不同锌浓度对碳酸酐酶（CA）活性、光合特性、可溶性糖含量等的影响。结果表明：玉米对锌具有选择运输的能力,当锌浓度过大对幼苗造成伤害时,根系吸收的锌向地上部运输的比例减少,以减少过量的锌对地上部造成的伤害。锌与CA活性密切相关,而CA活性与净光合速率的变化并非密切相关。低锌和高锌均显著增加了‘四单19’的可溶性糖含量,而‘牡丹9’的可溶性糖含量在缺锌与低锌处理下增加幅度并不明显,但在高锌处理下可溶性糖含量迅速增加。低锌和高锌处理都显著降低了‘四单19’叶片的蛋白质含量,而‘牡丹9’低锌处理下叶片可溶性蛋白含量下降并不明显,但在高锌处理下叶片可溶性蛋白含量大幅度下降。低锌处理下,‘四单19’的蛋白质合成受到抑制,而游离氨基酸大量积累,明显抑制了植株的生长;‘牡丹9’的蛋白质和氨基酸含量变化较小。     

玉米幼苗地下部／根间氮的循环及其基因型差异

以两个玉米（Zea mays L.）自交系原引1号（YY1）和综31（Z31）为研究材料,采用盆裁土培的培养方法,在正常供氮（HN,K0．15gN/kg干土）和低氮量供应（ON,0.038gN/kg干土）培养条件下对玉米幼苗植株体内氮的循环量及其他在地上部／根间的分配量进行了定量地测定、计算。结果表明,在玉米幼苗地上部／根间氮的循环量很高。低氮量供应使玉米幼苗植株吸氮量下降,根中氮的分配比例增加,同时地上部／根间氮的循环量也随之减少。与氮低效自交系Z31相比,氮高效自交系YY1幼苗中地上部／根间的氮循环量大、氮向根的分配量高,因而有利于其根系的生长,表现为根／地上部之比和部根长较高。这可能有利于其中后期对氮素的高效吸收与利用。     

镍对离体玉米叶片衰老的调节作用

本文研究了镍对离体玉米叶片衰老的调节作用。研究结果表明,玉米叶片在衰老过程中,超氧化物歧化酶（ＳＯＤ）、过氧化物酶（ＰＯＤ）过氧化氢酶（ＣＡＴ）、抗坏血酸过氧化物酶（ＡsＳ－ＰＯＤ）活性和抗坏血酸（ＡsA)含量显著降低,超氧阴离子自由基（Ｏ^-2)产生率显著增加,脂质过氧化作用加剧,丙二醛（ＭＤＡ）含量升高,细胞质膜透性增大。而１０^-2、１０^-3mol.L^-1Ni^2 处理能增强上述保护酶活性和抗氧化剂ＡsA的含量从而能减轻细胞膜脂过氧化使用。２０^-3、１０^-2mol.L^-1Ni^2 处理能显著延缓蛋白质和叶绿素 降解。因此镍能延缓离体玉米叶片的衰老,尤其是以１０^-2mol.L^-1Ni^2 对衰老的延缓作用更大。动态测定结果表明,１０^-2mol.L^-1Ni^2 处理能使衰老滞后２－天。     

利用叶色特征监测小麦叶片的碳氮状况

研究了不同土壤水氮条件下小麦 (Triticumaestivum) 抽穗后叶片碳氮状况及其比例与叶片叶色 (SPAD值 ) 的关系。结果表明, 小麦中后期叶片氮含量和可溶性糖含量与顶部 3张叶片叶色 (SPAD值 ) 均呈显著的指数正相关, 其相关程度大小为L1>L2 >L3, 但与不同叶位叶色间的差值或比值相关并不显著 ;而叶片碳氮比与各叶位叶色相关不显著, 但与顶 1叶和顶 3叶的叶色差值呈极显著直线相关, 据此建立了基于叶色特征的叶片氮含量、可溶性糖含量和碳氮比监测模型, 检验结果显示, 顶 1叶叶色和顶 1叶与顶 3叶叶色的差值可用来有效地评估小麦叶片的碳、氮含量及碳氮比状况。     

植物叶片衰老过程中基因的表达与调控

从衰老相关基因的分离、克隆、表达、调控及叶片衰老延缓几个方面,介绍叶片衰老过程中基因表达调控的研究进展。     

不同水分条件下控释尿素对夏玉米产量和叶片衰老特性的影响

采用旱棚土柱试验,以郑单958为材料,研究不同水分处理(重度干旱胁迫W₁、轻度干旱胁迫W₂、正常水分条件W₃)和不同控释尿素施氮处理(N₀:不施氮肥;低氮N₁:施纯氮150 kg·hm^-2;中氮N₂:施纯氮225 kg·hm^-2;高氮N₃:施纯氮300 kg·hm^-2)对夏玉米产量及叶片衰老特性的影响.结果表明: 控释尿素与水分耦合对延缓叶片衰老、提高功能叶作用时间和效率以及提高产量方面存在显著互作效应.相同氮素条件下,随着土壤水分含量的增加,夏玉米叶面积指数(LAI)、穗位叶叶绿素含量及超氧化物歧化酶(SOD)活性、过氧化氢酶(CAT)活性、过氧化物酶(POD)活性均显著提高,可溶性蛋白含量增加,而丙二醛(MDA)含量显著降低,产量增加;相同水分条件下,随着施氮量的增加,夏玉米LAI、穗位叶叶绿素含量及各种保护酶活性均显著提高,可溶性蛋白含量增加,而MDA含量显著降低,产量也呈增加趋势.但处理W₃N₃、W₃N₂和W₂N₃之间差异不显著,且相对于其他处理,各项指标(MDA除外)均保持较高水平,MDA含量较低,表明控释尿素与水分的耦合效应有利于维持穗位叶功能,延缓叶片衰老,促进光合产物的生产,进而提高夏玉米产量.综合产量、叶面积指数、叶绿素含量和各种保护酶活性及MDA、可溶性蛋白含量,在土壤含水量为(75±5)%的田间持水量条件下(正常水分),控释尿素施氮量超过225 kg N·hm^-2后,继续增施氮肥不能持续提高花后叶片的保护酶活性,且导致保护酶活性下降加快,MDA含量显著升高,加速植株衰老,不利于氮素的高效利用;在土壤含水量为(55±5)%的田间持水量条件下,控释尿素施氮量在300 kg N·hm^-2条件下水氮耦合效应最佳.     

缺镁胁迫对龙眼叶片衰老的影响

选用苗龄为 180d的龙眼 (DimocarpuslonganaLour.cv .Wulongling)幼苗 ,采用水培实验方法 ,设正常供Mg(4mmol·L-1)、低Mg(0 .4mmol·L-1)和缺Mg 3个处理 ,并在移栽后 12 0d和 15 0d取样测定 .结果表明 ,随着缺Mg程度的加重 ,龙眼叶片的叶绿素含量、PSⅡ活性、光合作用速率降低 ;蛋白质和核酸含量减少 ;O-·2 产生速率、H2 O2 含量提高 ,膜脂过氧化加剧 ;CTK类物质 (ZR、DHZR、iPA)含量下降 ,ABA含量提高 ,说明缺Mg对龙眼叶片的衰老有明显影响     

植物叶片衰老过程中叶绿素降解代谢研究进展

本文对近年来植物叶片衰老过程中叶绿素降解代谢研究进展作一介绍,包括叶绿素降解产物分离、检测和命名;叶绿素降解途径及降解酶系。此外,对叶绿素降解意义及今后研究趋势进行了评述。     

Antioxidative protection in a drought-resistant maize strain during leaf senescence

Leaves of 7- and 18-day-old plants of two maize strains, one resistant (LIZA) and one sensitive (LG11) to water stress, were floated in 1 m M paraquat and 1 m M H₂O₂ for 12 h in light and in darkness. The aim of this work was to analyse the effects of these substances on the activities of enzymes involved in the scavenging of active oxygen species during senescence. Three senescence parameters; chlorophyll loss, lipid peroxidation and conductivity; showed a general cell damage caused by both oxidative treatments and revealed a higher tolerance of LIZA than LG11 to paraquat and H₂O₂ both in light and in darkness. Activities of antioxidative enzymes increased by the effect of oxidative treatments in young and senescent leaves of the drought-resistant maize strain LIZA. These increases were about 3-to 6-fold in glutathione reductase. 3-to 4-fold in superoxide dismutase and 2-fold in ascorbate peroxidase activities. The possible correlation between water stress resistance. senescence and the potential of antioxidant enzymes was analysed.     

Protein degradation and nitrogen remobilization during leaf senescence

Leaf senescence, a type of programmed cell death, is a complex and highly regulated process that involves the degradation of macromolecules, including proteins, nucleic acids, and lipids. Nutrients, especially nitrogen, are re-mobilized from senescing leaves to newly developing tissues or reserve organs. Our review focuses on three pathways for protein breakdown and the resorption of N during this process: the ubiquitin/proteosome system, the chloroplast degradation pathway, and the vacuolar and autophagic pathway. We propose that two relative biochemical cycles exist for amino acid recycling and N-export — the GS/GOGAT cycle and the PPDK-GS/GOGAT cycle.     

The timing of maize leaf senescence and characterisation of senescence-related cDNAs

Leaf senescence was characterised in two Zea mays lines, earlier senescence (ES) and later senescence (LS). Loss of chlorophyll was delayed in LS compared with ES, but the decline in photosynthesis occurred simultaneously in the two lines. Western analysis detected transition points during senescence of both lines when major quantitative and qualitative changes occurred in a number of leaf proteins. Differences in the pattern of translatable mRNAs were apparent earlier than alterations in pigment or protein levels. A cDNA library was constructed using mRNA from ES leaves early in senescence and differential screening was employed to isolate senescence-related clones. Two senescence-enhanced cDNAs showed sequence homology with cDNAs for seed proteins - a cysteine protease and a protein-processing enzyme. These findings suggest that there are similarities between gene expression during seed maturation, germination and leaf senescence. Other senescence-enhanced cDNAs were related to genes implicated in gluconeogenesis and chlorophyll breakdown.     

冬小麦-夏玉米播前耕作对夏玉米叶片衰老特性的影响

以‘郑单958(ZD958)’为试验材料,设置冬小麦播前旋耕夏玉米播前免耕(RN)、冬小麦播前翻耕夏玉米播前免耕(MN)和冬小麦播前翻耕夏玉米播前旋耕(MR)3个处理,研究冬小麦-夏玉米播前耕作条件下夏玉米叶面积、叶片光合色素含量、可溶性蛋白含量、叶片保护酶活性及丙二醛(MDA)含量的变化.结果表明:从抽雄期(VT)到抽雄后40 d(VT+40),MN与MR的叶面积显著高于RN;从VT+40到成熟期(R6),MR的叶面积下降幅度显著高于其他处理.叶片光合色素含量呈单峰曲线变化,抽雄后20 d(VT+20)达最高值,之后逐渐下降;与RN相比,MR和MN的叶绿素a含量分别提高11.4％和9.7％,叶绿素b含量分别提高14.9％和15.9％.随着生育进程的推进,各处理的穗位叶可溶性蛋白含量呈下降趋势,MR与MN处理VT～VT+40维持较高水平,较RN分别提高11.5％和24.4％;超氧化物歧化酶(SOD)、过氧化氢酶(CAT)和过氧化物酶(POD)活性均呈单峰曲线变化,VT+20时期达到最大值,之后逐渐下降,MR与MN的SOD、CAT和POD活性从VT到VT+40维持较高水平;MDA含量均呈上升趋势,RN始终高于MN和MR.与RN相比,MN和MR平均增产24.0％和30.6％;与MN相比,MR平均增产5.2％.MN可有效延缓叶片衰老,有利于产量提高.     

Modification of nitrogen remobilization, grain fill and leaf senescence in maize (Zea mays) by transposon insertional mutagenesis in a protease gene

A maize (Zea mays) senescence-associated legumain gene, See2beta, was characterized at the physiological and molecular levels to determine its role in senescence and resource allocation. A reverse-genetics screen of a maize Mutator (Mu) population identified a Mu insertion in See2beta. Maize plants homozygous for the insertion were produced. These See2 mutant and sibling wild-type plants were grown under high or low quantities of nitrogen (N). The early development of both genotypes was similar; however, tassel tip and collar emergence occurred earlier in the mutant. Senescence of the mutant leaves followed a similar pattern to that of wild-type leaves, but at later sampling points mutant plants contained more chlorophyll than wild-type plants and showed a small extension in photosynthetic activity. Total plant weight was higher in the wild-type than in the mutant, and there was a genotype x N interaction. Mutant plants under low N maintained cob weight, in contrast to wild-type plants under the same treatment. It is concluded, on the basis of transposon mutagenesis, that See2beta has an important role in N-use and resource allocation under N-limited conditions, and a minor but significant function in the later stages of senescence.     

大田淹水对夏玉米叶片衰老特性的影响

选用登海605(DH605)和郑单958(ZD958)为试验材料,在大田条件下研究了不同淹水时期(三叶期、拔节期和开花后10 d)和持续时间(3 d、6 d)淹水对夏玉米叶片衰老特性的影响.研究表明: 淹水胁迫后超氧化物歧化酶(SOD)、过氧化氢酶(CAT)和过氧化物酶(POD)等保护酶活性以及可溶性蛋白含量较不淹水对照显著下降,而丙二醛(MDA)含量显著升高,三叶期淹水6 d后DH605和ZD958的含量较对照分别升高35.3%和34.1%.淹水胁迫后叶片叶绿素含量降低,产量显著下降.三叶期淹水6 d对夏玉米产量的影响最大,DH605和ZD958较对照分别减产32.1%和35.2%.不同生育期中,三叶期淹水造成的影响最大,拔节期次之,开花后10 d淹水造成的影响较小,且影响程度随淹水持续时间的延长而加剧.     

Water stress, ammonium, and leaf senescence in detached rice leaves

Ammonium accumulation in relation to water stress-promoted senescence of detached rice leaves was investigated. The effect of water stress on the senescence of detached rice leaves is associated with the accumulation of ammonium. The accumulation of ammonium in detached rice leaves by water stress is attributed to a decrease in glutamine synthetase activity. Ammonium accumulation in detached rice leaves, induced by water stress, was accompanied by an increase in tissue sensitivity to ethylene which, in turn, accelerated leaf senescence.     

富氮营养对枫香幼苗弱光碳平衡能力的影响

采用室内模拟典型林型光环境和土壤氮素供给的方法,研究了不同光氮处理对枫香幼苗的存活率、叶功能性状、生物量分配和气体交换的影响;应用数学模型估算了不同光氮处理下全株的光补偿点,并与典型林型的林下光合有效辐射加以比较.结果表明： 富氮营养导致3.0%、6.0%透光率时枫香幼苗存活率(耐荫性)和比叶面积下降,而对幼苗生物量分配的影响不明显;富氮营养时光强对叶片最大光合速率影响显著,而弱光下增加氮素供给导致基于质量的叶片暗呼吸速率增加;光、氮对茎呼吸速率有显著影响,而光氮互作对叶呼吸速率有影响;3.0%、6.0%和12.0%透光率时,增加氮素供给使整株补偿点上升,而25.0%透光率下则使其下降.增加氮素供给导致的弱光下枫香幼苗的耐荫性下降与其碳平衡能力变化相关联.在大气氮沉降增加背景下,我国枫香种群的维持可能更加依赖于干扰和林隙更新,进而对其动态产生深刻的影响.