小麦低温种质的器官结构特征

通过对小麦冠层温度的长期观测,发现自然界存在株温持续偏低的低温种质,与其相对应,也有株温持续偏高的高温种质存在。应用光学显微镜和电子显微镜研究了小麦低温种质叶片显微和超微结构,测量统计了叶肉细胞长度、单位面积叶肉细胞数目、单个叶肉细胞中的叶绿体数目、叶肉细胞层数和叶绿体基粒片层数。结果表明,低温小麦种质较高温种质叶肉细胞小,排列紧密,叶肉细胞层数较多;叶绿体数量多,叶绿体基粒片层丰富;叶片维管束密集;随着生育期向成熟趋近,叶肉细胞、叶绿体、籽粒腹沟区有色层细胞等结构衰老缓慢。     

光周期对西葫芦185品系顶芽和叶片衰老的调控

在短日照下 ,西葫芦 (CucurbitapepoLinn .) 185品系的植株发生衰老。结构学、基因表达与系列生化分析证实 :短日照启动了顶端分生组织由营养生长锥向花芽的转化 ,进而其组成细胞发生编程性死亡 (PCD) ,导致顶端生长势的丧失 ;与长日照处理相比 ,短日照处理在发育晚期也引起大量叶肉细胞发生PCD ,进而叶片出现衰老。核酸酶活性的高度表达是PCD过程中一个非常重要的分子事件。实验证实 ,西葫芦 185品系植株衰老进程的发生与顶端分生组织和叶肉细胞中发生PCD密切相关。     

水稻衰老调控机制研究取得重要进展

正植物的衰老受发育年龄和体内信号因子精确调节。脱落酸(ABA)是植物五大激素之一,参与众多的生物学过程,如促进种子休眠、提高耐逆性、调节气孔开关、促进叶片衰老等。在植物衰老时,体内ABA含量急剧升高,外源ABA也可诱导叶片衰老,因此,ABA被认为是一重要的衰老促进激素。然而,水稻中ABA合成和信号传导相关基因的突变体并未表现出延迟衰老的表型。因此,人们一直困惑ABA是如何参与调控植物的衰老进程。     

昆虫取食和药剂熏蒸对马尾松针叶脱落酸和茉莉酸含量的影响

脱落酸(ABA)和茉莉酸(JA)在诱导植物产生抗逆性过程中具有重要作用.以马尾松为试验材料,用GC/MS检测了马尾松毛虫咬食、外源茉莉酸甲酯(MeJA)熏蒸和萜烯混合物熏蒸处理4 h后,马尾松损伤针叶、相邻姊妹针叶(处理同一轮未受损伤枝条)、系统上枝针叶(处理枝上一轮枝条)和系统下枝针叶(处理枝下一轮枝条)中ABA和JA含量的变化.结果表明,虫害4 h后,马尾松损伤针叶、相邻姊妹针叶、系统上枝针叶和系统下枝针叶的ABA和JA含量均明显升高.用10 μmol·L^-1 MeJA熏蒸和10 μmol·L^-1萜烯混合物熏蒸健康植株后,各部位枝条针叶中ABA和JA含量明显升高.说明ABA和JA是马尾松苗木伤反应信号传导途径中的重要信号分子,参与了马尾松苗木系统抗性的形成过程.     

光周期对西葫芦185品系顶芽和叶片衰老的调控

在短日照下,西葫芦(Cucurbita pepo Linn.)185品系的植株发生衰老.结构学、基因表达与系列生化分析证实:短日照启动了顶端分生组织由营养生长锥向花芽的转化,进而其组成细胞发生编程性死亡(PCD),导致顶端生长势的丧失;与长日照处理相比,短日照处理在发育晚期也引起大量叶肉细胞发生PCD,进而叶片出现衰老.核酸酶活性的高度表达是PCD过程中一个非常重要的分子事件.实验证实,西葫芦185品系植株衰老进程的发生与顶端分生组织和叶肉细胞中发生PCD密切相关.     

棉花叶片衰老过程中激素和膜脂过氧化的关系

以陆地棉品种辽棉9号的去根幼苗为材料,对其进行暗诱导衰老培养.在培养液中分别加入6-BA、ABA、GSH、H2O2、CaCl2、A23187 和A23187 CaCl2,测定在不同培养条件下棉花去根幼苗叶片内源激素、SOD酶活性和MDA含量的变化.结果表明:棉花叶片衰老表现为细胞分裂素含量的下降和ABA含量的上升.6-BA、GSH和钙离子均延缓叶片的衰老,ABA和H2O2促进叶片的衰老.     

脱落酸和6-苄氨基嘌呤对离体小麦叶片 δ-氨基乙酰丙酸形成的调节作用

ABA能够明显地抑制Chl前体——ALA的生物合成,抑制效应随ABA浓度的提高而增强。6BA能够促进ALA的生物合成,并且能逆转ABA的抑制作用。ALA的合成在植物体内可能受ABA和细胞分裂素的调节。 在离体叶片衰老的最初阶段,6BA和ABA对Chl含量的影响可能与这两种物质通过ALA从Chl合成方面来起作用有关。     

脱落酸（ABA）在蒜苔衰老中的作用

蒜苔在切除珠蒜后可减少贮存中干物质的损失,延缓衰老,在切口处施加外源ABA可加速苔干叶绿素的破坏和组织的老化,气相色谱与色质联用法检测完整蒜苔和无珠蒜蒜苔各部分组织中ABA含量在衰老过程中的变化,发现无珠蒜苔干上,中,下各段ABA含量在衰老进程中是逐步减少的,变化幅度小,而带有珠蒜的苔干各相应段和珠蒜的ABA含量均有一迅速增加而后减少的过程,珠蒜的ABA含量最大,ABA含量高峰出现时间最早,苔干各段ABA含量按上,中,下顺序依次减少,高峰出现的时间也是由上至下依次推迟,没有发现蒜苔在衰老过程中有乙烯放出,外加乙烯对其衰老进程影响不大,本文认为珠蒜是蒜苔衰老的关键部位,能加速苔干衰老的ABA主要是在珠蒜中合成的,并自上向下极性运往苔干组织,进而动员物质的再分配,起着信息传递作用,蒜苔的衰老过程可分为“准备期”和“活跃期”两个阶段。     

脱落酸（ABA）在蒜苔衰老中的作用

蒜苔在切除珠蒜后可减少贮存中干物质的损失,延缓衰老,在切口处施加外源ABA可加速苔干叶绿素的破坏和组织的老化,气相色谱与色质联用法检测完整蒜苔和无珠蒜蒜苔各部分组织中ABA含量在衰老过程中的变化,发现无珠蒜苔干上,中,下各段ABA含量在衰老进程中是逐步减少的,变化幅度小,而带有珠蒜的苔干各相应段和珠蒜的ABA含量均有一迅速增加而后减少的过程,珠蒜的ABA含量最大,ABA含量高峰出现时间最早,苔干各段ABA含量按上,中,下顺序依次减少,高峰出现的时间也是由上至下依次推迟,没有发现蒜苔在衰老过程中有乙烯放出,外加乙烯对其衰老进程影响不大,本文认为珠蒜是蒜苔衰老的关键部位,能加速苔干衰老的ABA主要是在珠蒜中合成的,并自上向下极性运往苔干组织,进而动员物质的再分配,起着信息传递作用,蒜苔的衰老过程可分为“准备期”和“活跃期”两个阶段。     

兴安落叶松针叶解剖结构变化及其光合能力对气候变化的适应性

叶片易受环境因子影响,其形态解剖结构特征不但与叶片的生理功能密切相关,而且反映树木对环境变化的响应和适应。叶片结构的改变势必会改变树木的生理功能。同一树种长期生长在异质环境条件下,经过自然选择和适应,会在形态和生理特性等方面产生变异,形成特定的地理种群。另外,母体所经受的环境胁迫也会影响到其子代的生长、发育和生理等特征。因此,了解植物叶片形态结构对环境变化的响应与适应是探索植物对环境变化的响应适应机制的基础。兴安落叶松(Larix gmelinii Rupr.)是我国北方森林的优势树种,主要分布在我国东北地区,但日益加剧的气候变化可能会改变其现有的分布区。为了区分叶片对气候变化的可塑性和适应性,本研究采用同质园法比较测定了6个不同气候条件下的兴安落叶松种源的32年生树木的针叶解剖结构和光合生理相关因子,利用石蜡切片方法分析了针叶的解剖结构特征、光合能力（Pmax-a）、水分利用效率（WUE）之间的关系及其对气候变化的适应性。结果表明：表皮细胞厚度、叶肉细胞厚度、传输组织厚度、维管束厚度、内皮层厚度以及叶片总厚度均存在显著的种源间差异（P < 0.05）。叶肉细胞厚度与Pmax-a、气孔导度和WUE之间均存在显著的正相关关系（P < 0.05）。叶肉细胞厚度、表皮细胞厚度、叶片总厚度以及叶肉细胞厚度和表皮细胞厚度在叶片总厚度中所占比例均与种源地的干燥度指数（即年蒸发量与年降水量之比）呈正线性关系。这些结果说明：不同种源兴安落叶松针叶解剖结构因对种源原地气候条件的长期适应而产生显著的差异,从而引起其针叶光合作用、水分利用等生理功能发生相应的变化,从而有利于该树种在气候变化的情景下得以生存和繁衍。     

Microscopic structure of Scots pine (<Emphasis Type="Italic">Pinus sylvestris</Emphasis> (L.)) needles during ageing and autumnal senescence

Needle ageing and senescence were studied in Scots pine (Pinus sylvestris) trees growing in natural conditions with minimal anthropogenic influence. The four existing needle generations were analyzed by light and transmission electron microscopy before and during autumnal yellowing of the oldest needle generation. The change from green to yellow occurred within less than 4 days in central Finland. The structure of the oldest needles remained largely intact as long as they were green. Increase in mitochondrion size and hypertrophy of the phloem parenchyma were the only changes, probably related to the approaching senescence. In the yellow needles, the structure of the mesophyll tissue varied from nearly intact with reduced chloroplasts and higher numbers of plastoglobuli, to totally disintegrated cells. In the disintegrated cells, peroxisomes were absent, and chloroplasts were smaller with a patchy appearance and degraded, eventually empty-looking stroma. Mitochondria were enlarged, but retained integrity until the last stages of deterioration, and lipids increased. At the light microscopic level, vacuolar volume in mesophyll cells and cavity formation in transfusion tissue increased. Ageing was characterized by increases in the vacuolar volume and cytoplasmic lipids, altered appearance of vacuolar tannin from homogenous ‘sandy’, to large spherical drops and finally to a large mass in the mesophyll, and by hypertrophy and tannin accumulation in the phloem parenchyma. Changes related to needle ageing, senescence and cell location in the mesophyll tissue were discussed relative to findings with stress by strong light, weather conditions and ozone.     

RING-box proteins regulate leaf senescence and stomatal closure via repression of ABA transporter gene ABCG40

Plant hormone abscisic acid (ABA) plays an indispensable role in the control of leaf senescence, during which ABA signaling depends on its biosynthesis. Nevertheless, the role of ABA transport in leaf senescence remains unknown. Here, we identified two novel RING-box protein-encoding genes UBIQUITIN LIGASE of SENESCENCE 1 and 2 (ULS1 and ULS2) involved in leaf senescence. Lack of ULS1 and ULS2 accelerates leaf senescence, which is specifically promoted by ABA treatment. Furthermore, the expression of senescence-related genes is significantly affected in mature leaves of uls1/uls2 double mutant (versus wild type (WT)) in an ABA-dependent manner, and the ABA content is substantially increased. ULS1 and ULS2 are mainly expressed in the guard cells and aging leaves, and the expression is induced by ABA. Further RNA-seq and quantitative proteomics of ubiquitination reveal that ABA transporter ABCG40 is highly expressed in uls1/uls2 mutant versus WT, though it is not the direct target of ULS1/2. Finally, we show that the acceleration of leaf senescence, the increase of leaf ABA content, and the promotion of stomatal closure in uls1/usl2 mutant are suppressed by abcg40 loss-of-function mutation. These results indicate that ULS1 and ULS2 function in feedback inhibition of ABCG40-dependent ABA transport during ABA-induced leaf senescence and stomatal closure.     

不同生长时期羊草大针茅光合速率与光照强度关系的比较研究

本文对不同生长时期羊草、大针茅的光合速率与光照强度的关系进行了比较研究。在从营养生长初期到生长后期,研究结果表明:光补偿点都有增加,但羊草增加很少,大针茅增加一倍;高的饱光强出现在营养生长的高峰期、其变动幅度,大针茅大于羊草;高的净光合速率的光强系数,羊草普遍高于大针茅,并且都以营养生长高峰期最高;在10千勒光强下,相对光合速率羊草大于大针茅;羊草、大针茅的光合速率与饱和光强的变化,跟它们的叶片含水率的变化有着广泛的一致性。     

Ultrastructure of Mesophyll Cells and Pigment Content in Senescing Leaves of Maize and Barley

Leaf senescence is a genetically regulated stage in the plant life cycle leading to death. Ultrastructural analysis of a particular region of the leaf and even of a particular mesophyll cell can give a clear picture of the time development of the process. In this study we found relations between changes in mesophyll cell ultrastructure and pigment concentration in every region of the leaf during leaf senescence in maize and barley. Our observations demonstrated that each mesophyll cell undergoes a similar senescence sequence of events: a) chromatin condensation, b) degradation of thylakoid membranes and an increase in the number of plastoglobules, c) damage to internal mitochondrial membrane and chloroplast destruction. Degradation of chloroplast structure is not fully correlated with changes in photosynthetic pigment content; chlorophyll and carotenoid content remained at a rather high level in the final stage of chloroplast destruction. We also compared the dynamics of leaf senescence between maize and barley. We showed that changes to the mesophyll cells do not occur at the same time in different parts of the leaf. The senescence damage begins at the base and moves to the top of the leaf. The dynamics of mesophyll cell senescence is different in leaves of both analyzed plant species; in the initial stages, the process was faster in barley whereas in the later stages the process occurred more quickly in maize. At the final stage, the oldest barley mesophyll cells were more damaged than maize cells of the same age.     

甘蓝热胁迫叶片细胞的超微结构研究

高温胁迫引起植物体损伤是很常见的,人们已从多方面探讨高温胁迫对植物的影响,主要工作集中在生理生化、膜结构、热激蛋白及作物产量等方面［１—４］,超微结构的变化也有少量报道［５—７］。但目前要建立一个高温对植物体影响的模式还比较困难。本文探讨了甘蓝不同耐热品种叶片细胞超微结构在热胁迫后的差异,目的是建立植物耐热程度的细胞学指标,为育种工作者选育耐热性品种提供细胞学依据。材料和方法试验材料为甘蓝（Ｂｒａｓｓｉｃａｏｌｅｒａｃｅａｖａｒ．ｃａｐｉｔａｔａＬ．）耐热品种“夏光甘蓝”和感热品种“京丰甘蓝”。…     

Fluorescence Microscopy of Fresh Tissue as a Rapid Technique for Assessing Early Injury to Mesophyll

A technique was developed for sectioning fresh red spruce foliage (Picea rubens Sarg.) for use in fluorescence microscopy. This allowed rapid examination of mesophyll in 3-5 mm needle sections. Healthy, ozone treated and cold stressed needles were examined to assess the utility of this technique for early detection of damage. Healthy mesophyll cells fluoresced bright red, while injured cells fluoresced yellow-green in ozone treated needles, and yellow-orange in frozen needles. Shifts in fluorescence wavelengths may be useful for early detection of injury to mesophyll before it is evident by standard light or electron microscopy.     

CO2浓度倍增对红松幼苗根尖和叶解剖结构及生理功能的影响

大气CO₂浓度升高对植物的影响是目前植物生态学研究中普遍关注的问题。以往的研究主要关注植物地上部分叶解剖结构及生理功能的改变, 而对根解剖结构和生理功能变化以及根与叶变化之间潜在联系的研究较少。该文以三年生红松(Pinus koraiensis)幼苗为研究对象, 通过CO₂浓度倍增(从350 µmol·mol^-1增加到700 µmol·mol^-1)试验, 研究当年生针叶和根尖解剖结构及生理功能的变化。结果表明: (1) CO₂浓度倍增处理的红松幼苗, 气孔密度显著降低, 叶肉组织面积、木质部及韧皮部面积明显增加; (2) CO₂浓度倍增导致红松幼苗根尖直径增粗, 皮层厚度和层数显著增加, 管胞直径变小; (3)高CO₂浓度处理下, 叶气孔导度和蒸腾速率降低, 光合速率和水分利用效率提高, 同时根尖的导水率显著下降, 但管胞的抗栓塞能力显著提高。这些结果显示, 叶和根解剖结构及生理功能在CO₂浓度升高条件下具有一致的响应。未来研究中应该同时关注全球气候变化对植物地上和地下器官结构与功能的影响。     

Quantitative Determination of Changes in the Number and Size of Chloroplasts in Naturally Senescing Leaves of Rice Seedlings

Changes in the number and size of chloroplasts in senescingleaves of rice seedlings were determined. The method employedinvolves electron microscopic examination of large numbers ofcells and chloroplasts in the mesophyll of leaves at differentstages of senescence with the aid of a microcomputer. Analysisshowed that, once leaves had been fully expanded, the numberand size of the mesophyll cells remained unaltered throughoutthe course of senescence. By contrast, the quantity of chloroplastspresent in leaves decreased with advancing senescence. Whencompared with the newly expanded 6th leaves, the chloroplastnumber per unit area of mesophyll section was reduced by 40%and the mean cross section area of chloroplasts by 23% in theoldest leaves (3rd leaves) of seedlings. Chloroplasts occupied33% of the mesophyll section area in the 6th leaves and thepercentage decreased slightly in the 5th leaves and markedlyin lower leaves to reach 17% in the 3rd leaves. The rate ofoxygen evolution decreased approximately in parallel to thedecline in the chloroplast content. Thus, sequential decreasein the amount of chloroplasts is a main cause of loss of photosynthesisduring foliar senescence of rice seedlings. (Received May 31, 1989; Accepted October 17, 1989)     

Changes in cell ultrastructure and endogenous abscisic acid and indole-3-actic acid concentrations in Fatsia japonica leaves under polyethylene glycol-induced water stress

Ultrastructural alterations in epidermal and mesophyll cells as well as variations in bulk leaf endogenous ABA and IAA concentrations were studied in PEG-treated plants of Fatsia japonica Decne & Plank. Under stress induced by PEG vesicles containing fibrous material and electron-dense bodies associated with plasma membranes were observed. Cytochemical examination indicated that electron-dense bodies corresponded to lipids and the fibrous material of the vesicles were polysaccharides. Chloroplasts, mitochondria, nuclei and Golgi apparatus also showed modifications. A strong relationship was found between increasing PEG-induced water stress, increasing endogenous ABA and ultrastructural changes. In relation with leaf ontogeny and ABA concentration a higher ABA level was observed in younger than in older leaves. The differences in the endogenous concentrations of indole-3-acetic acid are unclear, except after 7 days of PEG-treatment. The increase in the endogenous abscisic acid concentration could be related with the ultrastructural changes.Abbreviations ABA = abscisic acid - IAA = indole-3-acetic acid - PEG = polyethylene glycol - = leaf water potential - TEM = transmission electron microscope     

长白松的木材解剖及其分类问题

关于长白松的分类问题一直有争议^[6-11],根据作者对吉林省安图县二道白河产的长白松的木材解剖研究,发现其木材的射线管胞内壁具深锯齿,颇与欧洲赤松(Pinus sylvestris Linn.)相近^{[14] [15]},但以其木射线薄壁组织细胞水平壁无纹孔和晚材最后数列管胞弦壁上存在着排列成轴向单行小形具缘纹孔来看,这又显属赤松(Pinus densiflora Sieb.et Zucc.)的特征。因此,作者认为长白松的木材结构是处于欧洲赤松与赤松之间而更偏于赤松^[10],故确认其当归属于赤松的种群范围。