7种秋海棠叶片斑纹结构及遗传特性分析

以7种(品种)秋海棠为材料,观察叶片斑区和非斑区组织结构、测定叶绿素含量及叶绿素荧光参数F_v/F_m值,分析叶片斑纹的形成原因及银点秋海棠点状斑的遗传特性。结果显示：(1)银点秋海棠、铺地秋海棠、假厚叶秋海棠、‘皮卡’和‘非洲丛林’叶片斑区的上表皮细胞与栅栏组织细胞间存在空隙,非斑区则没有空隙,彩纹秋海棠和‘虎斑’的斑区与非斑区上表皮细胞和栅栏组织细胞间均紧密相连。(2)7种(品种)秋海棠叶片斑区和非斑区都具有完整的叶绿体超微结构,类囊体膜丰富,基质和基粒片层清晰;银点秋海棠、假厚叶秋海棠、‘皮卡’和‘非洲丛林’斑区的叶绿素a、b及总叶绿素含量均低于非斑区,而铺地秋海棠斑区和非斑区差别不大;除假厚叶秋海棠的斑区叶绿素荧光参数F_v/F_m值小于非斑区外,其余6种秋海棠均为斑区高于非斑区。(3)银点秋海棠与无斑种类杂交,杂交后代叶片有斑和无斑的植株约为1∶1,而其自交后代中有斑和无斑的植株比例近3∶1。研究发现,银点秋海棠、铺地秋海棠、假厚叶秋海棠、‘皮卡’和‘非洲丛林’的叶斑属于空隙结构型,彩纹秋海棠和‘虎斑’叶斑属于色素型。银点秋海棠点状叶斑与无斑是1对可遗传的相对性状,白色点状斑为显性性状。     

观赏植物叶斑的研究进展

斑叶植物种类丰富,其叶片上色彩各异的斑纹具有特殊的观赏性,不仅是植物重要的观赏性状,还有着一定的生物学和生态学意义,具有帮助繁衍、抵御天敌和适应环境变化等作用。本文综述了近年来观赏植物叶斑分类和形成的相关进展,根据叶片中不同的色素积累和结构区别,在微观结构上对叶斑类型进行划分并总结了叶斑形成的分子机制。现有研究表明,叶片发育过程中色素合成和代谢有关的结构基因和转录因子CHLH、DFR、CRD1等的改变、细胞器发育的受损、细胞发育和分化基因ZAT10、VAR3等的突变会通过影响色素的差异积累、改变叶片结构直接或间接的参与叶斑的形成。虽然目前已有较多对于观赏植物叶斑形成机制的研究,但观赏植物叶斑的遗传机制尚不清晰,叶斑部分的差异基因表达的原因、叶斑图案的空间分布机制等仍有待进一步研究。未来可以通过对斑叶植物中模式植物的筛选,构建泛基因组,与基因组学、蛋白组学、代谢组学等多组学技术结合,研究叶斑的起源、斑叶植物对于环境的适应等问题,探索植物的重要性状与环境适应的进化机制。     

建兰水晶艺叶片的超微结构和转录组学分析

水晶艺建兰(Cymbidium ensifolium)因其叶片上呈现出白色透明状,犹如水晶而得名,观赏价值高,但是其形成机理不明确。该研究以建兰‘铁骨水晶’为试验材料,通过对水晶叶片和绿色叶片进行显微结构和超微结构观察,并结合转录组测序等方法,探索建兰水晶艺叶片形成的原因。结果表明:(1)建兰‘铁骨水晶’水晶叶片比绿色叶片薄,叶肉细胞数量减少,形状不规则,且叶绿体含量少;水晶叶片的表皮气孔数量较绿色叶片显著减少;水晶叶片的叶肉细胞中叶绿体结构发育不良,叶绿体双膜和类囊体膜模糊,细胞中存在着大量的嗜锇颗粒。(2)转录组数据分析显示,水晶叶片中与光合作用-天线蛋白、光合作用等代谢途径相关的基因表达量显著下降,而与色素合成代谢途径相关的基因表达量上升。研究推测,建兰水晶艺叶形成的原因可能是由于与光合作用相关的基因表达量降低,导致叶绿体发育不良,叶绿素合成受阻,从而形成白色透明状叶片。     

糖-质子的共运输和韧皮部的装入T.E.汉弗莱斯(Humphreys)

仅仅是在最近些年,植物生理学家才能够清楚地说明,叶子的绿色组织中合成的蔗糖是如何进入小叶脉的韧皮部并在那里浓缩的。蔗糖由绿色组织进入韧皮部的过程中,必须穿过两层膜和一个细胞间隙。首先,蔗糖在绿色组织细胞的细胞质中合成,并从那里穿过质膜进入质外体。质外体是植物无生命的细胞壁空间,它含有处于细胞壁的表面上和其间隙中的水溶液。蔗糖穿过绿色组织细胞的质膜时,就进入这个溶液。第二,蔗糖在质外体溶液中向韧皮部细胞扩散(不超过五个细胞直径的距离),并通过质膜被吸收进入这些细胞。在质外体内的蔗糖     

五种含笑属植物叶片抗寒结构指标的筛选与抗寒性评价

为筛选醉香含笑(Michelia macclurei)、‘丹霞’含笑(Michelia ‘Danxia’)、紫花含笑(M. crassipes)、‘玉霞’含笑(Michelia‘Yuxia’)和云南含笑(M. yunnanensis)的抗寒结构指标,该文从叶片解剖结构角度评价这五种含笑属植物的抗寒性,分别测定常温、自然降温和低温越冬三个温度节点五种植物的叶片厚度等9项结构指标。通过聚类分析和主成分分析这两种方法筛选抗寒结构指标,并运用隶属函数法来评价五种含笑属植物的抗寒性。结果表明:(1)不同降温阶段聚类分析筛选出的抗寒结构指标不同,常温下,栅海比、海绵组织和下表皮厚度为代表指标;自然降温阶段则是栅海比、海绵组织和角质层厚度为代表指标;而到了低温越冬时期,代表指标变为栅栏组织、海绵组织和上表皮厚度,隶属函数分析显示三个时期五种含笑属植物的抗寒性排序完全不同。(2)主成分分析筛选出的指标为上表皮厚度、栅海比与细胞结构疏松度。隶属函数评价五种含笑属植物的抗寒性排序为醉香含笑紫花含笑‘丹霞’含笑云南含笑‘玉霞’含笑,与田间观测和生理生化评价结果一致。综上结果表明,以单一时期的叶片结构指标为依据进行聚类分析来筛选抗寒结构指标评价抗寒性的方法存在一定的不足,通过主成分分析筛选指标来进行抗寒性评价的方法更具有参考价值。     

古林箐秋海棠叶斑结构对叶色的影响

该研究以古林箐秋海棠(Begonia gulinqingensis)为材料,通过分析叶片形态特征、上表皮光学特性、组织结构、叶绿素含量及叶绿素荧光参数(F_v/F_m),探讨了叶片色斑的形成原因。结果表明:(1)古林箐秋海棠叶斑发生频率和数量无明显规律,但发生部位相对稳定,叶斑主要发生在正对叶柄的两条主脉之间。(2)斑区有两种光反射模式,点状反射和多角形反射,栅栏组织细胞呈近等轴的圆形,排列疏松,与上表皮细胞间存在空隙;非斑区只有点状反射模式,栅栏组织细胞为漏斗型,排列紧密,与上表皮细胞间不存在空隙。(3)斑区和非斑区叶绿体均有密集的堆积基粒和丰富的类囊体膜,斑区叶绿素a、b及总叶绿素含量仅比非斑区分别低24.9%、25.2%、25.1%。(4)叶绿素荧光参数(F_v/F_m)值斑区为0.793,非斑区为0.790。虽然斑区叶绿素含量比非斑区略低,但叶绿体结构完整,且叶绿素荧光参数与非斑区无显著差异。斑区上表皮与栅栏组织细胞间的空隙可使光线到达绿色组织时发生二次反射,在叶片表皮细胞边缘形成白色多边形光反射使该区域相对周围正常叶片区域偏白,基于上述结果可推测古林箐秋海棠的淡绿色块斑形成与特殊的叶片结构有关。     

中国秋海棠属植物叶片斑纹多样性研究

通过对野生和引种栽培植物的观察,结合文献和标本的查阅,对中国秋海棠属植物斑叶类资源及叶斑多样性进行了研究.发现中国分布的203种(含变种和亚种)秋海棠属植物中有斑纹的种类达84种,叶斑色彩多表现为淡绿色、银绿色、银白色、白色.从园艺学角度出发,根据中国秋海棠属植物斑纹在叶片的分布位置,首次提出了中国秋海棠属植物叶斑分类标准,并对观察到的斑叶类秋海棠进行了分类,方便人们选择利用.根据斑纹与叶脉的关系分为叶脉相关类型(Ⅰ)和非叶脉相关类型(Ⅱ),前者细分为脉间斑纹类(Ⅰ A)、沿脉斑纹类(Ⅰ B)、中脉及脉间斑纹类(ⅠC)3种,后者细分为环状面斑类(ⅡA)、掌状面斑类(ⅡB)、近完全面斑类(ⅡC)、完全面斑类(ⅡD)、混合面斑类(ⅡE)和不规则面斑类(ⅡF)6种.中国产野生秋海棠属植物中较常见的叶斑类型为Ⅰ A1、ⅠA2、Ⅰ B1、Ⅰ B2和ⅡA.同时对叶斑的产生机理和遗传特性进行了讨论和展望.中国斑叶类秋海棠属植物种质资源及其叶斑类型的多样性极其丰富,有望通过研究摸清其遗传特性,实现特定观赏性状新品种的定向选育.     

中国假鹰爪属和皂帽花属植物叶的形态结构及其分类学意义

利用扫描电镜技术、叶片离析法和石蜡切片法研究了假鹰爪属Desmos 4种植物和皂帽花属Dasy-maschalon 3种植物叶片的形态结构。结果表明：假鹰爪属植物叶片近轴面表皮具大型球状含晶簇细胞和不含晶簇的表皮细胞两种类型,远轴面表皮细胞均具一较小的晶簇;叶肉组织明显分化为栅栏组织细胞和海绵组织细胞,油细胞分布于第2层的栅栏组织和海绵组织内,单位毫米叶宽油细胞数为4～6个;主脉维管组织被薄壁细胞分隔成束状。皂帽花属植物叶片近轴面表皮细胞形状相同,均具一晶簇,远轴面表皮细胞的晶簇和近轴面表皮细胞的晶簇相似;靠近上、下表皮的叶肉组织均分化为栅栏组织细胞,在两层栅栏组织细胞之间分化为一至几层海绵组织细胞,油细胞分布于海绵组织内,单位毫米叶宽油细胞数为2～3个;主脉维管组织形成连续的环状。由此可见两属叶的结构具有明显的差异,因而支持假鹰爪属和皂帽花属为两个独立属的观点。     

低温和PEG预处理对小麦愈伤组织形成及IAA氧化的影响

研究了低温和PEG预处理对小麦成熟胚愈伤组织形成及IAA氧化的影响。结果表明,低温和PEG预处理促进两种小麦成熟胚愈伤组织形成,但对其IAA氧化的影响不同;其中低温引起‘郑引1号’IAA氧化酶活性降低,但对‘保7059’的影响不大;而PEG使‘保7059’的IAA氧化酶活性增加,但对‘郑引1号’无明显影响;两种处理均使两种小麦IAA过氧化物酶活性降低。     

附生兰科植物根被组织研究概述

植物根被组织是指存在于附生兰科植物、地生兰科植物、一些石蒜科、天南星科、薯蓣科以及百合科植物根部的典型适应性结构特征;成熟根被组织是由1～25层左右死细胞构成的白色鞘,其细胞壁多有螺旋式增厚,呈天鹅绒状或网状、羽毛状结构,具有海绵质地.该组织有六种应用于分类学特征的形态,依据这六种形态可将其分为12种类型;根被组织具有...     

Impaired Chloroplast Biogenesis in Immutans,an Arabidopsis Variegation Mutant,Modifies Developmental Programming,Cell Wall Composition and Resistance to Pseudomonas syringae

The immutans (im) variegation mutation of Arabidopsis has green- and white- sectored leaves due to action of a nuclear recessive gene. IM codes for PTOX, a plastoquinol oxidase in plastid membranes. Previous studies have revealed that the green and white sectors develop into sources (green tissues) and sinks (white tissues) early in leaf development. In this report we focus on white sectors, and show that their transformation into effective sinks involves a sharp reduction in plastid number and size. Despite these reductions, cells in the white sectors have near-normal amounts of plastid RNA and protein, and surprisingly, a marked amplification of chloroplast DNA. The maintenance of protein synthesis capacity in the white sectors might poise plastids for their development into other plastid types. The green and white im sectors have different cell wall compositions: whereas cell walls in the green sectors resemble those in wild type, cell walls in the white sectors have reduced lignin and cellulose microfibrils, as well as alterations in galactomannans and the decoration of xyloglucan. These changes promote susceptibility to the pathogen Pseudomonas syringae. Enhanced susceptibility can also be explained by repressed expression of some, but not all, defense genes. We suggest that differences in morphology, physiology and biochemistry between the green and white sectors is caused by a reprogramming of leaf development that is coordinated, in part, by mechanisms of retrograde (plastid-to-nucleus) signaling, perhaps mediated by ROS. We conclude that variegation mutants offer a novel system to study leaf developmental programming, cell wall metabolism and host-pathogen interactions.     

家蚕消化管内桑叶的银染法研究

通过银染法对家蚕整体染色,结果表明:家蚕消化管内的桑叶由叶表皮、叶肉和叶脉组成。叶表皮包括上表皮和下表皮。上表皮细胞可分为三种:钟乳体细胞、绿色表皮细胞和黄色表皮细胞;下表皮内含有气孔;叶肉组织内含有晶体,其中海绵组织内的最多。家蚕消化管由前向后可分为前肠、中肠和后肠,由外向内依次为肌层、底膜、上皮细胞层、内膜。中肠最为发达,其发达的上皮细胞向内表面突起形成许多大的指突形皱褶;上皮细胞层内有圆筒形细胞、杯形细胞两种细胞,两者在形状、功能以及嗜银性等方面有所差异。家蚕消化管对桑叶不同组织的消化吸收效率有差异,上表皮吸收效率最高,下表皮和栅栏组织次之,最低的是海绵组织。采用动物细胞染色方法对植物细胞进行染色,并与常规植物学染色方法进行了比较;依据细胞嗜银性的不同,可将桑叶的上表皮细胞分为两种亚型。     

Cell Lineage of Vein Formation in Variegated Leaves of the C4Grass Stenotaphrum secundatum

Clonal analysis of variegated leaves of the C₄grass, Stenotaphrumsecundatum, indicates that invasions among meristematic layersoccur during the organogenetic stage of leaf development, resultingin long, broad white and green stripes. These layer invasionscease prior to the second phase of leaf development when delimitationof leaf regions occurs. Vein precursors mostly arise duringthe second phase, so that procambial strand formation is superimposedon the lineage makeup of earlier-formed tissue. Anatomical evidenceindicates that procambium arises through formative divisionswithin ground tissue of leaf primordia and that each strandis derived from a variable number (one–four) of groundmeristem precursors. If a developing vein straddles the boundarybetween previously-formed green and white sectors, then themature vein is half green and half white, reflecting its mixedcell lineage. In Stenotaphrum, 24.8% of the sectors observedwere bounded by such ‘half veins’. The temporalrelationship of layer invasion and tissue system delimitationin this species supports the view that positional signals aremore important than lineage history in the determination oftissue type. However, analysis of planes of cell division indeveloping veins indicates, that, once formed, procambial strandsare discrete lineage units that extend longitudinally by proliferativedivisions. Thus, lineage restrictions may play an importantrole in the third stage of leaf development, differentiationof tissues and cells, which also includes the maintenance ofcell identity.Copyright 2000 Annals of Botany Company C₄photosynthesis, cell lineage, clonal analysis, leaf development, St. Augustine’s grass,Stenotaphrum secundatum , variegation, vein formation     

Arabidopsis Chloroplast FtsH,vat2 and Suppressors of var2 Leaf Variegation: a Review

Variegation mutants are ideal model systems to study chloroplast biogenesis.We are interested in variegations whose green and whitesectored leaves arise as a consequence of the action of nuclear recessive genes.In this review,we focus on the Arabidopsis var2 variegation mutant,and discuss recent progress toward understanding the function of VAR2 and the mechanism of var2-mediated variegation.VAR2 is a subunit of the chloroplast FtsH complex,which is involved in turnover of the Photosystem Ⅱ reaction center D1 protein,as well as in other processes required for the development and maintenance of the photosynthetic apparatus.The cells in green sectors of var2have normal-appearing chloroplasts whereas cells in the white sectors have abnormal plastids that lack pigments and organized lameliae.To explain the mechanism of var2 variegation,we have proposed a threshold model in which the formation of chloroplasts is due to the presence of activities/processes that are able to compensate for a lack of VAR2.To gain insight into these activities,second-site suppressor screens have been carried out to obtain mutants with nonvariegation phenotypes.Cloning and characterization of several var2 suppressor lines have uncovered several mechanisms of variegation suppression,including an unexpected link between var2 variegation and chloroplast translation.     

Arabidopsis Chloroplast FtsH,var2 and Suppressors of var2 Leaf Variegation:a Review

Variegation mutants are ideal model systems to study chloroplast biogenesis. We are interested in variegations whose green and whitesectored leaves arise as a consequence of the action of nuclear recessive genes. In this review, we focus on the Arabidopsis var2 variegation mutant, and discuss recent progress toward understanding the function of VAR2 and the mechanism of var2-mediated variegation. VAR2 is a subunit of the chloroplast FtsH complex, which is involved in turnover of the Photosystem II reaction center D1 protein, as well as in other processes required for the development and maintenance of the photosynthetic apparatus. The cells in green sectors of var2 have normal-appearing chloroplasts whereas cells in the white sectors have abnormal plastids that lack pigments and organized lamellae. To explain the mechanism of var2 variegation, we have proposed a threshold model in which the formation of chloroplasts is due to the presence of activities/processes that are able to compensate for a lack of VAR2. To gain insight into these activities, second-site suppressor screens have been carried out to obtain mutants with nonvariegation phenotypes. Cloning and characterization of several var2 suppressor lines have uncovered several mechanisms of variegation suppression, including an unexpected link between var2 variegation and chloroplast translation.     

Nuclear—organelle interactions: the immutans variegation mutant of Arabidopsis is plastid autonomous and impaired in carotenoid biosynthesis

The immutans (im) variegation mutant of Arabidopsis thaliana contains green- and white-sectored leaves due to the action of a nuclear recessive gene. The mutation is somatically unstable, and the degree of sectoring is influenced by light and temperature. Whereas the cells in the green sectors contain normal chloroplasts, the cells in the white sectors are heteroplastidic and contain non-pigmented plastids that lack organized lamellar structures, as well as small pigmented plastids and/or rare normal chloroplasts. This indicates that the plastids in im white cells are not affected equally by the nuclear mutation and that the expression of immutans is ‘plastid autonomous’. In contrast to other variegation mutants with heteroplastidic cells, the defect in im is not maternally inherited. immutans thus represents a novel type of nuclear gene-induced variegation mutant. It has also been found that the white tissues of immutans accumulate phytoene, a non-colored C₄₀ carotenoid intermediate. This suggests that immutans controls, either directly or indirectly, the activity of phytoene desaturase (PDS), the enzyme that converts phytoene to zeta-carotene in higher plants. However, im is not the structural gene for PDS. A secondary effect of carotenoid deficiency, both in immutans and in wild-type plants treated with a herbicide that blocks carotenoid synthesis, is an increase in acid ribonuclease activity in white tissue. It is concluded that the novel variegation generated by the immutans mutation should offer great insight into the complex circuitry that regulates nuclear—organelle interactions.     

INDEPENDENCE OF TISSUES DERIVED FROM APICAL LAYERS IN ONTOGENY OF THE TOBACCO LEAF AND OVARY

Six different homoplastidic periclinal chimeras of tobacco carrying the plastogene DP₁ were selected after somatic segregation in heteroplastidic seedlings. Direct observation of the plane of division in epidermal cells of young leaves, and the number and size of sub-epidermal green spots on leaves with the Green-White-White (G-W-W) pattern of variegation, indicated that the ratio of periclinal to anticlinal divisions in L-I during development of the lamina was 1:3100. The number of green and white seedlings obtained from the different chimeral branches indicated a similar frequency of periclinal divisions in development of the ovary. The arrangement of green and white tissue in mature leaves of the various chimeral types indicated the extent of participation by the three apical layers in the initiation of the buttress, development of the axis, and formation of the lamina. During development of the lamina there must be three independent initial-groups present. L-I and L-II initials remain marginal, but early in the growth of the lamina the leading edge of tissue derived from L-III becomes separated from the submarginal (L-II) initials by the products of frequent periclinal divisions of the L-II initials.