Floral Nectaries of Rosmarinus officinalis L. Structure, Ultrastructure and Nectar Secretion

The nectary of Rosmarinus officinalis L. has the form of a four-lobed,asymmetrical disc situated around the base of the ovary. Thenectary lobe facing the lower flower lip is enlarged and isthe only one to have modified stomata. Vascular strands consistingof phloem only occur in the nectariferous tissue. It is suggestedthat the pre-nectar originating in the phloem accumulates primarilyas starch grains in plastids of the nectariferous cells. Thenumber of grains is very large before anthesis and decreasesconsiderably at anthesis. The transport of the pre-nectar tothe various nectariferous cells appears to be mainly via thesymplast. It could not be determined whether the process ofelimination of the nectar is solely eccrine or partly granulocrine. Rosmarinus officinalis, nectary, nectar secretion, starch grains, phloem     

新疆鼠尾草花蜜腺的发育解剖学研究

新疆鼠尾草（Salvia deserta Schang）花蜜腺位于子房基部的花托上,为盘状的花托蜜腺,其顶部裂成4片,其裂片大小不等,比例悬殊。蜜腺由产蜜组织和分泌表皮构成,又为结构蜜腺。组织化学染色显示淀粉粒动态明显,因此又属淀粉蜜腺。在发育的过程中细胞液泡化动态明显,且淀粉粒和蛋白质具有明显的消长变化,但PAS反应和苏木精脂类染色无明显变化。其泌蜜过程可能为：原蜜汁由邻近的韧皮部提供,经薄壁细胞运送至产蜜组织,在产蜜组织中进一步积聚、合成后,最终蜜汁通过变态气孔和分泌表皮细胞的角质层泌出。     

牛至花蜜腺的发育解剖学研究

牛至花蜜腺位于子房基部的花盘上,属于盘状蜜腺。蜜腺组织由分泌表皮和产蜜组织组成。分泌表皮液泡化明显,并分布有气孔器。在子房发育成熟后,由花盘表面细胞恢复分裂能力形成蜜腺原基。产蜜组织在发育过程中,液泡、淀粉粒都呈现出一定的消长规律,此种规律与蜜汁的合成和分泌有关。原蜜汁由蜜腺周围的韧皮部提供,经产蜜组织积聚合成,然后通过气孔器泌出。本文还对霜冻条件下蜜腺的结构和功能进行了初步分析。     

荔枝花蜜腺发育解剖学研究

荔枝花蜜腺呈盘状,位于子房和花萼之间的花托上。花盘蜜腺由表皮、产蜜组织、维管束组成。蜜腺的原始细胞由花托表面的2~3层细胞脱分化产生。成熟蜜腺产蜜组织细胞含有淀粉粒,为淀粉型蜜腺,表皮细胞内无淀粉粒。产蜜组织出现分化:PAS反应颜色深的细胞成网状分布,与表皮下方的1~2层细胞相连,构成蜜汁的运输通道;颜色浅的细胞分布于网眼处。蜜腺表皮上的角质层波状皱折,有泌蜜孔。表皮毛主要起保护作用,大部分蜜汁通过泌蜜孔排出。     

异株百里香花蜜腺的发育解剖学研究

异株百里香（Thymus marschallianus Willd）花蜜腺分布于子房基部的花托上,结构蜜腺盘状,成熟时膨大,环绕在花托外。蜜腺组织由分泌表皮、产蜜组织和维管束三部分组成;组织化学染色显示淀粉粒的积累是在蜜腺细胞发育的最初和最后,因此将其归为非淀粉型蜜腺。在发育的过程中细胞液泡化动态明显,而淀粉粒和多糖均不具有明显的消长变化;蜜汁是由韧皮部运转到泌蜜组织中的,再由表皮细胞的角质层渗到细胞外。     

荆条花蜜腺发育解剖学研究

荆条（Ｖｉｔｅｘ ｃｈｉｎｅｎｓｉｓ Ｍｉｌｌ．）花蜜腺属于淀粉型子房蜜腺,呈圆筒状环绕于子房的基部。蜜腺外观上无特殊结构,表面有。由分泌表皮和泌蜜组织组成,包括分泌表皮、气孔器、泌蜜薄壁组织和维管束。密腺和子房壁起源相同。花蕾膨大期,泌蜜组织细胞中产生大液泡;露冠期,泌蜜组织中形成维管束;花蕾初放期,分泌表皮细胞分化形成气孔器,无气孔下室,淀粉粒的积累在此期达到高峰;盛花期,蜜腺中已无淀粉粒,密     

刺五加雌花蜜腺的显微形态和超微结构观察

利用光学显微镜、扫描电镜及透射电镜对刺五加雌花蜜腺结构进行了观察,结果表明:(1)刺五加雌花蜜腺为花盘蜜腺,由表皮和泌蜜组织构成;(2)蜜腺表面几乎均匀地分布着大量变态的气孔,蜜汁从气孔泌出;(3)蜜腺发育过程中有淀粉粒的积累和水解过程,液泡也伴随规律性变化;(4)蜜腺分泌方式为渗透型,或者以渗透型为主胞吐型为辅的分泌方式;(5)金胺O染色说明蜜腺表面具有角质层,可观察到微通道从中穿过,可能是蜜汁向外界分泌的通道之一.     

鹅掌柴花蜜腺的发育解剖学研究

对鹅掌柴(Scheffler octophylla Harms．)花蜜腺的发育进行解剖结构观察。鹅掌柴花盘蜜腺位于下位子房上方环绕花柱基部。蜜腺由分泌表皮、产蜜组织组成,心皮维管束与其相邻并发出一些伸入蜜腺基部的短分枝。蜜腺起源于心皮原基基部外侧的几层细胞。鹅掌柴花蜜腺为淀粉型蜜腺,淀粉粒为许多微小颗粒聚集成的复粒。原蜜汁由蜜腺基部维管束的筛管提供,达产蜜组织细胞和表皮细胞后以淀粉粒的形式贮藏。泌出的蜜汁一部分来自淀粉粒的降解,一部分来自泌蜜期输入的原蜜汁。表皮和产蜜组织细胞均具泌蜜功能。泌出的蜜汁大部分通过气孔排出,还有部分由角质层渗出。     

On the mechanisms of nectar secretion: revisited

Background and Scope

Models of nectar formation and exudation in multilayered nectaries with modified stomata or permeable cuticle are evaluated. In the current symplasmic model the pre-nectar moves from terminal phloem through the symplasm into the apoplasm (cell walls and intercellular spaces) with nectar formation by either granulocrine or eccrine secretion and its diffusion outwards. It is concluded, however, that no secretory granules are actually produced by the endoplasmic reticulum, and that secretory Golgi vesicles are not involved in the transport of nectar sugar. Therefore, the concept of granulocrine secretion of nectar should be discarded. The specific function of the endomembrane system in nectary cells remains unknown. According to the apoplasmic model, the pre-nectar moves from the terminal phloem in the apoplasm and, on the way, is transformed from phloem sap into nectar. However, viewed ultrastructurally, the unloading (terminal) phloem of nectaries appears to be less active than that of the leaf minor veins, and is therefore not actively involved in the secretion of pre-nectar components into the apoplasm. This invalidates the apoplasmic model. Neither model provides an explanation for the origin of the driving force for nectar discharge.

Proposal

A new model is proposed in which nectar moves by a pressure-driven mass flow in the nectary apoplasm while pre-nectar sugars diffuse from the sieve tubes through the symplasm to the secretory cells, where nectar is formed and sugars cross the plasma membrane by active transport (‘eccrine secretion’). The pressure originates as the result of water influx in the apoplasm from the symplasm along the sugar concentration gradient. It follows from this model that there can be no combinations of apoplasmic and symplasmic pre-nectar movements. The mass-flow mechanism of nectar exudation appears to be universal and applicable to all nectaries irrespective of their type, morphology and anatomy, presence or absence of modified stomata, and their own vascular system.     

Floral nectary structure and nectar composition in Eccremocarpus scaber (Bignoniaceae), a hummingbird-pollinated plant of central Chile

Surface features, anatomy, and ultrastructure of the floral nectary of Eccremocarpus scaber (Bignoniaceae), pollinated predominantly by the largest-known hummingbird (Patagona gigas gigas), were studied together with nectar sugar content and secretion rate. The annular disk nectary comprises epidermis, secretory and ground parenchyma with intercellular spaces, and branched vascular bundles terminating in the secretory parenchyma where only phloem is found. Amyloplasts and vacuoles increase in size throughout development, the latter becoming sites of organelle degradation. Transferlike cells in nectary phloem and P-proteinlike fibrillar material in phloem parenchyma were observed. Flowers produced around 32 μl of nectar (mostly after anthesis) with 11 mg of sugar composed of fructose, glucose, sucrose, and maltose in a ratio of 0.34:0.32:0.17:0.17. Morphological studies as well as the presence of maltose and glucose in nectar suggest storage of the originally phloem-derived sugars as starch with its subsequent hydrolysis. The low sucrose/hexose ratio (0.25) and high nectary secretion force (nectar per flower biomass) observed places E. scaber close to large-bodied bat-pollinated plants. A hypothesis based on nectar origin and nectar secretion is advanced to explain pollinator-correlated variation in sucrose/hexose ratio.     

芝麻菜花蜜腺的结构和发育研究

通过解剖镜观察、石蜡切片和薄切片等方法,对芝麻菜的花蜜腺的位置、形态、结构、发育过程及泌蜜前后组织化学变化进行了研究。芝麻菜花蜜腺4枚,分成两对,其中一对侧蜜腺较大,棱柱状,分别着生在外轮2个短雄蕊基部内侧的花托上,结构上由表皮、产蜜组织和维管组织构成;另一对中蜜腺较小,近棒状,分别着生在内轮4个长雄蕊外侧的花托上,结构上仅由表皮和产蜜组织构成。二者表皮细胞外都具角质层,且蜜腺产蜜组织细胞中只含少量的多糖物质。两类蜜腺的蜜汁均由变态气孔泌出体外。无论侧蜜腺还是中蜜腺,蜜腺原基皆是在雌、雄蕊已分化后,由花托相应位置表皮下的1～2层细胞分裂形成的。在蜜腺发育中,产蜜组织细胞在泌蜜前后不具明显的液泡变化。     

Developmental and Anatomical Studies on the Floral Nectaries of Capsella bursa-pastoris

The development and structure of the floral nectaries of Capsella bursa-pastoris (L.) Medic. were examined. The nectaries consisted of four separated parts which were semiorbicular and were morphologically and anatomically similar to one another. They were located at the receptacle between stamens, and each part was composed of secretory epidermis, nectariferous tissue and vascular bundles, belonging to structural nectary. When the various floral organs were developed, 2--3 superficial layer cells of the receptacle between stamens became meristemoid and contributed to primordia the formation of nectary. By intercalary meristematic activity, the four nectaries formed synchronously. During the different stages of nectary differentiation, the content of starch gra ins and vacuolation in the cells of epidermis and nectariferous tissue changed regularly. According to the structural and histochemical changes the pre-nectar might be supplied by phloem. The nectar formed in nectariferous tissue was then secreted to the sub-stomatal chamber and where it was finally excreted from the stoma.     

垂柳花蜜腺的发育解剖学研究

垂柳雌花蜜腺一枚,位于于房与花序轴之间,多呈扁平广卵形,由分泌表皮、泌蜜组织和维管束组成。雄花蜜腺呈基部相连的两枚突起,一枚位于花丝与花序轴之间,基部宽扁,上部棒状;另一枚位于花丝与苞片之间,棒状,仅由分泌表皮和泌蜜组织组成。雌、雄花蜜腺均起源于花托表面2—3层细胞。在蜜腺发育过程中,雌、雄花蜜腺泌蜜组织细胞的液泡发生规律性变化．雌花蜜腺为淀粉型蜜腺,而雄花蜜腺为非淀粉型蜜腺。雌、雄花蜜腺的原宜汁分别由蜜腺维管束韧应部或花丝维管束韧皮部提供,其蜜计最后均由分泌表皮细胞和变态气孔排出。     

葡萄两性花花蜜腺的发育解剖学研究

葡萄两性花的花蜜腺位于子房基部的花盘上,共5枚,呈椭圆形,与雄蕊相间排列,属于花盘蜜腺,蜜腺由表皮和泌蜜组织组成,缺乏维管束,表皮具薄的角质层,无气孔器,蜜腺原基由子房基部表层细胞恢复分裂能力形成,在蜜腺发育过程中,泌蜜组织的液泡规律 性变化和多糖动态变化均不明显,原蜜汁由子房维管束的韧皮部提供,蜜汁通过表皮细胞排出。     

The Floral Nectary ofDigitalis purpureaL., Structure and Nectar Secretion

The floral nectary of the foxglove (Digitalis purpureaL.), locatedat the base of the ovary, was examined by: scanning electronmicroscopy; quantitative bright-field microscopy via computer-aided3-D reconstruction from serial sections; morphometric procedures;transmission electron microscopy and measurement of nectar effluxunder different experimental conditions. Time-lapse video recordingvia a microscope with incident light clearly showed that thenectar escaped from the apertures of modified stomata. The volumeflux via individual stomatal apertures was 0.31±0.1 nlmin^-1; therefore only a fraction of the total number of stomataper nectary (115±8) would be sufficient to dischargethe amount of nectar reported in previous publications. Thestomatal apertures are continuous with intercellular spacestraversing the small-celled nectariferous tissue. The latteris vascularized only by phloem, whose termini consists of rowsof slender cells. These sieve-like cells are surrounded by moreor less isodiametrical sheath cells with dimensions similarto the secretory cells. Details of nectary functioning are basedon enhanced structural information, complementary data on nectardischarge after experimental manipulations and the nature ofthe effluence.Copyright 1998 Annals of Botany Company Digitalis purpureaL.; foxglove; floral nectary; (ultra-)structure; 3-D reconstruction; morphometry; nectar flow; time-lapse video recording.     

油菜花蜜腺发育过程的超微结构变化与泌蜜机理的研究

油菜花蜜腺由２枚侧蜜腺和２枝中蜜腺组成,其基本结构类似。在蜜腺发育过程中,产蜜组织细胞内的内质网、高尔基体、质体和线粒体以及液泡都发生有规律变化。泌蜜前,细胞器的数量增加。其中,质体内积累淀粉,此过程与蜜腺内初皮部的分化并和线粒体的增加相关。泌蜜时,内质网数量增多,并产生小泡．小泡向质膜移动。泌蜜后,细胞液泡化,细胞器数量减少,细胞萎缩。根据观察结果分析,其原蜜汁来源于韧皮部,转运至产蜜组织细胞的质体、内质网和高尔基体内加工成蜜汁,最后通过胞吐和渗透相结合的方式泌出。     

Anatomy and ultrastructure of the floral nectary in Peganum harmala L. (Nitrariaceae)

Anatomy and ultrastructure of the floral nectary of Peganum harmala L. were studied using light and transmission electron microscopy. The floral nectary was visible as a glabrous, regularly five‐lobed circular disc encircling the base of the ovary. Anatomically, it comprised a single layered epidermis and 15–20 layers of small, subepidermal secretory cells overlying several layers of large, ground parenchyma cells. The floral nectary was supplied by phloem and both sieve tubes and companion cells were found adjacent to the ground parenchyma. Based on our ultrastructural observations, plastids of secretory cells during the early stages of development were rich in starch grains and/or osmiophilic plastoglobuli, but these disappeared as nectar secretion progressed. The nectar appeared to exude through the modified stomata along symplastic and apoplastic routes. The abundant plastids and mitochondria suggest an eccrine mechanism of nectar secretion in P. harmala.     

长药景天花蜜腺的发育解剖学研究

长药景天花蜜腺５枚,呈侧向扁平的舌形或弯月形,分别位于５株离生心皮的外侧,两者的基部相连,属于子房蜜腺。蜜腺由分泌表皮、产蜜组织和仅含韧皮部的维管束组成。长药景天花蜜腺起源于心皮外侧基部的表层结构。产蜜组织在发育过程中,细胞中的液泡体积及淀粉粒呈现有规律的消长变化。泌蜜后期,蜜腺组织从上往下液泡化,具明显的方向性。根据其结构及多糖变化分析,来自韧皮部的原蜜汁以淀粉粒形式贮存于产蜜组织中,泌蜜期水解     

Floral nectar production and nectary anatomy and ultrastructure of Echinacea purpurea (Asteraceae)

BACKGROUND AND AIMS: In spite of the impressive species diversity in the Asteraceae and their widespread appeal to many generalist pollinators, floral-nectary ultrastructure in the family has rarely been investigated. To redress this, a study using Echinacea purpurea, a plant of horticultural and nutraceutical value, was undertaken. Nectar secretion of disc florets was compared with floral nectary ultrastructure taking into account nectar's potential impact upon the reproductive success of this outcrossing species. METHODS: Micropipette collections of nectar in conjunction with refractometry were used to determine the volume and nectar-sugar quantities of disc florets throughout their phenology, from commencement of its production to cessation of secretion. Light, scanning-electron and transmission-electron microscopy were utilized to examine morphology, anatomy and ultrastructure of nectaries of the disc florets. KEY RESULTS: Florets were protandrous with nectar being secreted from anthesis until the third day of the pistillate phase. Nectar production per floret peaked on the first day of stigma receptivity, making the two innermost whorls of open florets most attractive to foraging visitors. Modified stomata were situated along the apical rim of the collar-like nectary, which surrounds the style base and sits on top of the inferior ovary. The floral nectary was supplied by phloem only, and both sieve elements and companion cells were found adjacent to the epidermis; the latter participated in the origin of some of the precursor cells that yielded these specialized cells of phloem. Companion cells possessed wall ingrowths (transfer cells). Lobed nuclei were a key feature of secretory parenchyma cells. CONCLUSIONS: The abundance of mitochondria suggests an eccrine mechanism of secretion, although dictyosomal vesicles may contribute to a granulocrine process. Phloem sap evidently is the main contributor of nectar carbohydrates. From the sieve elements and companion cells, an apoplastic route via intercellular spaces and cell walls, leading to the pores of modified stomata, is available. A symplastic pathway, via plasmodesmata connecting sieve elements to companion, parenchyma and epidermal cells, is also feasible. Uncollected nectar was reabsorbed, and the direct innervation of the nectary by sieve tubes potentially serves a second important route for nectar-sugar reclamation. Microchannels in the outer cuticle may facilitate both secretion and reabsorption.     

地椒花蜜腺发育的解剖学观察

通过显微和亚显微观察对地椒花蜜腺的发育进行了研究。地椒花蜜腺位于子房基部的花盘上,属于盘状蜜腺,新鲜时呈绿色。蜜腺由分泌表皮和泌蜜组织组成,分泌表皮为一层细胞,表皮细胞角质膜较厚,表皮上分布着大量的气孔器,气孔器突出于表面;泌蜜组织细胞多层。花盘中央有维管束通向子房,在维管束和泌蜜组织之间有４￣５层大型的薄壁细胞。蜜腺由花盘的表皮及其内侧相邻的细胞发育而来,在发育过程中,其细胞中的液泡和贮藏的淀粉