Anatomy and Transpiration of the Avocado Inflorescence

Structure and function of the inflorescence of cv. 'Hass' and'Fuerte' avocado (Persea americana Mill.) were examined by scanningelectron microcopy (SEM) and by porometry. Sepals and petalscould not be distinguished by their position in the flower,by visual gross morphology or by microscopic surface structureand were hence designated as tepals. These tepals were arrangedin two whorls of three, followed by two whorls of three outerand three inner stamens, each opposite a tepal. The most conspicuousfeature of tepals, developing leaves and peduncles was the densecover of hair which were most frequent on the adaxial tepalsurface (925-1200 trichomes mm^-2), followed by their abaxialsurface (625-1000 mm^-2) and peduncles (375-655 mm^-2). Stomatawere absent from the adaxial surfaces of both tepal and leaves,as well as peduncles. On the tepals, abaxial stomata appearedfunctional, small (8-9 x 11-13 µm) and scarce with 2·8-3·4stomata mm^-2, i.e. very low relative to avocado leaves (350-510stomata mm^-2) or young fruit (50-75 stomata mm^-2. However, flowersincluding tepals transpired 1·2-1·3 mmol underfield conditions in Southern California (1·6-2 kPa),i.e. in excess of leaves (0·7-1·1 mmol) and peduncles(0·6-0·8 mmolH₂O m^-2 s^-1). This situation wasattributed to the few small but functional abaxial stomata onthe tepal, in contrast to 80% closed stomata and dense epicuticularwax cover in form of rodlets on young and dendritic crystalson old leaves including the guard cells, and absence of stomatafrom the peduncle.Copyright 1993, 1999 Academic Press Persea americana Mill., avocado, bioenergetics, flower, fruit, leaf, peduncle, scanning electron microscopy, stomata, transpiration, petals, sepals, tepals     

Comparative floral ontogenies among Persoonioideae including Bellendena (Proteaceae)

Floral ontogeny is described and compared in five species and four genera of the hypothetically basal proteaceous subfamily Persoonioideae sensu Johnson and Briggs. The hypotheses surrounding the origin of the peculiar proteaceous flower and homologous structures within the flowers are examined using ontogenetic morphological techniques. Ontogenetic evidence reveals that the proteaceous flower is simple, composed of four tepals, each tepal initiated successively with the lateral tepals being initiated first and second followed by the successive initiation of the sagittal tepals. Each of four stamens is initiated opposite a tepal in a similar sequence to tepal initiation. A single carpel develops terminally from the remaining floral meristem. In taxa of Persoonieae, nectaries are initiated from a broadened receptacle in alternistamenous sites after zonal growth beneath and between the tepals and stamens has begun. The nectaries are interpreted as secondary organs, not reduced homologues of a “lost” petal or stamen series. Developmental variation is present among the examined taxa in several forms including the development of a Vorlaüferspitze (spine) on the upper portion of the tepals, adnation between the anthers and tepals, and formation of the carpel. In Placospermum the early formation of the carpel cleft extends to the floral receptacle and in the other taxa, the carpel cleft is distinctly above the receptacle. Different developmental pathways result in similar mature morphologies of the carpel in Persoonia falcata and Placospermum coriaceum. Bellendena montana is unique relative to the other taxa in having free stamens, a punctate stigma, reduced (not lost) floral bracts, and the floral and bract primordia are initiated from a common meristem. This study provides a foundation for future studies of the developmental basis of floral diversity within Proteaceae.     

Induction of Continuous Tepal Differentiation from in Vitro Regenerated Flower Buds of Hyacinthus orientalis

Continuous differentiation of tepals was successively induced from regenerated flower buds in Hyacinthus orientalis L. cv. White Pearl by controlling the exogenous hormones and explant ages. In 250 days of subculture, each flower bud differentiated an average of more than 70 tepals, with a maximum of over 140 tepals. Studies on the morphogenesis and characteristics of growth and development of the flower buds indicate that the first whorled organ of the flower bud was perianth which consisted of perianth tube and tepals grown at the top of the perianth tube, which is the same as the flower bud of the wild type in H. orentalis. The second and third whorls of the flower bud, which should be stamen and pistil in the wild type, but remained as the tepals in the regenerated flower bud. Growth of the regenerated flower bud was faster in the first several months of culture, then slowed down gradually with time. After 150 days in culture the flower bud growth and organ differentiation became very slow. Other than the tepal differentiation the regenerated flower buds also differentiated at random positions some small flower buds that also differentiated the tepals only. Histological observation revealed that the origin of the regenerated flower buds was jointly participated by some cells in the epidermal and subepidermal layers at the inner surface of the perianth explant, and the inner small flower buds were originated from the meristem which was formed by the transformation of the parenchyma at the base of the very young tepal. The authors also compared and discussed the similarities and differences of the phenotypes between the regenerated flower bud in Hyacinthus and agamous flower in Arabidopsis, from which, they have hypothesized on the role of the hormones in the promotion and termination of the gene expressions by an order of development in plant.     

Morphological evolution in the graminid clade: comparative floral anatomy of the grass relatives Flagellariaceae and Joinvilleaceae

New comparative data are presented on the reproductive morphology and anatomy of two genera closely related to grasses, Flagellaria and Joinvillea, in which the flowers are superficially similar, especially in stamen morphology. This investigation demonstrates some anatomical differences between the two genera. For example, both genera depart from the ‘typical’ condition of tepal vasculature (three‐traced outer tepals and one‐traced inner tepals): in Flagellaria, each tepal receives a single vascular bundle and, in Joinvillea, each tepal is supplied by three vascular bundles. Joinvillea possesses supernumerary carpel bundles, as also found in the related family Ecdeiocoleaceae, but not in Flagellaria or grasses. In the anther, the tapetum degenerates early in Flagellaria, and is relatively persistent in Joinvillea, in which the pollen grains remain closely associated with the tapetum inside the anther locule, indicating a correlation between peripheral pollen (a feature that is common in grasses) and a persistent tapetum. This study highlights the presence of a pollen‐tube transmitting tissue (PTTT) or solid style in the gynoecium of Flagellaria, as also in many Poaceae, but not in Joinvillea or Ecdeiocoleaceae. We speculate that the presence of a PTTT could represent one of the factors that facilitated the subsequent evolution of the intimately connected gynoecia that characterize grasses. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 170 , 393–404.     

蜡梅花被片表层形态观察及其意义

为探究蜡梅花被片表层蜡质的微形态结构特征和差异性,采用扫描电子显微镜对蜡梅和山蜡梅的花被片进行观察。结果表明:蜡梅花被片表层无明显蜡质覆盖物,细胞排列平滑,内表层有加厚透明状覆盖物; 山蜡梅花被片表层有厚蜡质覆盖物和表皮毛; 山蜡梅、蜡梅花被片均无气孔。以上独特的结构形态对于蜡梅花开放于寒冷季节,应对外界环境胁迫可能有一定的保护作用和生态意义。     

A kinematic analysis of tepal growth in Lilium longiflorum

Time-lapse marking experiments indicate that the growth of tepals in Lilium longiforum Thunb. from 3.7 mm to maturity is triphasic. Phase I (tepal lengths 3.7–10 mm) is characterized by spatial and temporal variation in growth rate and, in the epidermis, a random distribution of mitoses with an acropetal increase in cell area. During phase II (10–90 mm) cell elongation and (later) cell division is restricted largely to basal regions. Cell division ceases when tepals are less than one-third of their mature length of 155 mm. Phase III (90–155 mm) is characterized by the gradual transition from basal to apical growth, and a modification of epidermal cell shape. A sharp peak in growth at the extreme tip of the tepal coincides with anthesis.Abbreviations LRGR local relative growth rate - RER relative elemental rate of growth     

Leaf and tepal anatomy, plastid ultrastructure and chlorophyll content in Galanthus nivalis L. and Leucojum aestivum L.

The leaf structure of Galanthus nivalis L. (snowdrop) and Leucojum aestivum L. (snowflake) is characterized by a homogeneous mesophyll tissue. The dominant characters of the leaves are cavities with mucose substance. There is a striking difference between these plants tepal anatomy. A central cavity occurs only in snowdrop tepals. Plastids from white parts of the tepals have a poorly developed membrane system. Leaves and green parts of tepals of both species possess amoeboid chloroplasts and contain chlorophyll a and b. The chlorophyll content in tepals is lower than in leaves, but the chlorophyll a:b ratio is always 2:1. Both, snowdrop and snowflake are from the family Amaryllidaceae, but their ecology is different. This paper presents common features related to systematic relatedness and differences induced by ecological factors.     

Solute leakage, lipid peroxidation, and protein degradation during the senecence of Iris tepals

A colour change and inrolling of the tepal edges are the first symptoms of senescence of Iris flowers ( Iris x hollandica Tub., cv. Blue Magic). Tepals showed an increase in leakage of both ions and anthocyanins, prior to the visible senescence symptoms. Increased leakage occurred irrespective of the time at which the tepals were severed and placed in water, indicating that the senescence process is inherent in the tepal cells. Net loss of proteins in the tepal edges started after flower opening, and after two more days, when the first symptoms of senescence were observed, the protein level was only 20% of that at harvest. Cycloheximide delayed senescence and resulted in a lower rate of protein loss. Phenylmethylsulfony fluoride (PMSF), a protease inhibitor, had a similar effect on protein levels but did not affect the time to visible senescence, and also several other protease inhibitors did not affect the time to senescence.
During senescence the rate of respiration of the tepals remained unchanged and their rate of ethylene production decreaased. The rate of ethane production, an indicator of lipid peroxidation, was very low and remained unaltered. Antioxidants ( l ascorbic acid, benzoic acid, butylated hydroxytoluene, diphenylamine, propyl gallate, propyl- p -hydroxybenzoate and sodium benzoate) had no effect on the time to tepal senescence. It is concluded that tepal wilting is due to transfer of solutes from the symplast to the apoplast. Although net protein degradation occurs early during the senescence process, its inhibition is not correlated with a delay in the time to senescence. Furthermore, the results do not support the hypothesis that the increase in solute leakage is due to (free radical-mediated) peroxidation of membrane lipids. The present results are in contrast with the ethylene-regulated petal senescence of carnation, which is accompanied by lipid peroxidation.     

IRREGULAR FLORAL DEVELOPMENT IN CALLA PALUSTRIS (ARACEAE) AND THE CONCEPT OF HOMEOSIS

About two-thirds of the more than 100 genera in the Araceae lack tepals and their absence is considered derived. Unlike most of these atepalate genera, Calla palustris has about twice as many stamens per flower. Using epi-illumination microscopy, we studied floral development in Calla to see if the supernumerary stamens form in positions corresponding to tepal positions in perigonate Araceae. If so, this would be an example of homeosis—in this case, the replacement of tepals with stamens—in the evolution of this genus. We found the positions of stamen primordia in many floral buds too irregular to conclude that they replace tepals positionally. However, in more regular floral buds the first formed stamens do form in what correspond to tepal sites in related genera. If the immediate ancestor to Calla had tepals, as is generally assumed, stamen positions in the more regular flowers, at least, support a homeotic interpretation. There is no evidence that the supernumerary stamens arise by dédoublement, but since morphogenesis in Calla is only partly comparable to other aroids, and the phylogeny in the family is not well understood, further studies are needed to resolve the interpretation of the flower in Calla. With regard to systematics and evolution, the absence of tepals in Calla may not be homologous with atepaly in other members of the family, as has been assumed for the past century.     

海韭菜的花器官发生

运用扫描电镜（SEM）观察了海韭菜（Triglochin maritimum）的花器官发生发育过程。结果表明：海韭菜花发育是典型的单子叶植物发生模式,即两轮花被片、两轮雄蕊和两轮心皮以三基数轮状交替发生,花器官是以向心向顶的方式发生的,未发现“花被片—雄蕊复合原基”。 发育后期雄蕊和与之对生的花被片之间的共同基部可能是相继向上居间生长的结果。花被片轮和雄蕊轮二者之间在发育位置、时间和速率上存在差异,内轮花被片原基和外轮雄蕊原基的不同发育时间和发育速度使得在成熟花中内轮花被片位于外轮雄蕊的内方。观察结果不支持水麦冬属植物的花是退化（或压缩）的花序侧分枝等假花的观点。     

Floral ontogeny of <Emphasis Type="Italic">Schisandra chinensis</Emphasis> (Schisandraceae): implications for androecial evolution within <Emphasis Type="Italic">Schisandra</Emphasis> and <Emphasis Type="Italic">Kadsura</Emphasis>

The organogenesis of staminate and carpellate flowers of Schisandra chinensis (Schisandraceae) was investigated with scanning electron microscopy, with observations on the development of tepals reported for the first time. The results showed that there is no interval between the initiation of the last tepal and that of the first stamen or carpel, and that the shapes of tepal, stamen, and carpel primordia are similar. The tepals and stamens of staminate flowers are initiated acropetally in a continuous spiral Fibonacci phyllotaxis, with no carpel structures observed; the filaments are not connate. The organogenesis of the carpellate flowers is similar to that of the staminate flowers, but with no evidence of stamen development. The carpels are ascidiate without postgenital fusion. Three androecial characters of Schisandra and Kadsura are discussed in a phylogenetic context. The subglobose or obovoid androecium of Schisandra propinqua and Schisandra plena may be homologous with that in sections Kadsura and Sarcocarpon. The plesiomorphic form of the androecium within the two genera is likely to be elongate with more than ten free stamens.     

Discrimination of Different Parts of Saffron by Metabolomic‐Based Ultra‐Performance Liquid Chromatography Coupled with High‐Definition Mass Spectrometry

In this study, the metabolite profiling of three different parts of Crocus sativus L. was measured by using ultra‐performance liquid chromatography‐quadrupole time‐of‐flight mass spectrometry (UPLC‐QTof‐MS/MS). Multivariate statistical analysis was used to distinguish among the samples from different parts. A total of 54 compounds were identified in tepals, stigmas and stamens by UPLC‐QTof‐MS/MS. The results stated that chemical characteristics of saffron were obviously diverse in terms of the parts of flower. Through analysis, coniferin and crocin‐2 were special components in stigmas when compared to tepals and stamens. The content of flavonoids was high in tepals when compared with the stigmas. The tepal of saffron may processed as a source of flavonoids in the future. The research provided the basis for the theory that only the stigma can be used as medicine.     

Pollination function transferred: modified tepals of Albuca (Hyacinthaceae) serve as secondary stigmas

Background and Aims

The stigma, a structure which serves as a site for pollen receipt and germination, has been assumed to have evolved once, as a modification of carpels, in early angiosperms. Here it is shown that a functional stigma has evolved secondarily from modified tepals in some Albuca species (Hyacinthaceae).

Methods

Deposition of pollen on Albuca floral organs by bees was recorded. Pollen germination and fruit set was measured in flowers that had pollen deposited solely on their tepals or had their tepal tips experimentally isolated or removed after pollination.

Key Results

Leafcutter bees deposit pollen onto the papillate apices of the inner tepals of Albuca flowers. Pollen germinates in tepal-derived fluid secreted 2 or 3 d after anthesis and pollen tubes subsequently penetrate the style during flower wilting. Application of cross-pollen to the inner tepal apices of A. setosa flowers led to high fruit set. No fruits were produced in pollinated flowers in which the inner tepals were mechanically isolated or removed.

Conclusions

Pollen capture by tepals in the Albuca clade probably evolved in response to selection for floral morphology that maximizes the accuracy of pollen transfer. These findings show how pollination function can be transferred among floral organs, and shed light on how the original angiosperm stigma developed from sporophylls.     

吉祥草的花部器官发生及其系统学意义

利用扫描电镜（SEM）观察了吉祥草（Reineckia carnea）（铃兰科）的花部器官发生发育过程。吉祥草花被片、雄蕊的发生方式是由近轴端向远轴端发生的逆单向型（reversed unidirection）,花发育后期花被片合生形成花被筒,花丝与之贴生。伴随花被片、雄蕊发生,三枚心皮也由近轴向远轴方向相继发生,随后彼此合生发育。花序顶部的花易发生花器官数目变异。结合早期花原基形态以及花器官数目变异情况分析,吉祥草的花被片与雄蕊可能是由共同原基分化而成。从花部器官发生式样和花被筒形成时间两方面比较吉祥草属、白穗花属和铃兰属的特征发现,三属中,铃兰属处于相对进化的位置,而白穗花属比吉祥草属更为原始。     

ANGIOSPERM FLOWERS AND TRICOLPATE POLLEN OF BUXACEOUS AFFINITY FROM THE POTOMAC GROUP (MID-CRETACEOUS) OF EASTERN NORTH AMERICA

A new genus of fossil angiosperms (Spanomera gen. nov.) is established for flowers from two localities in the mid-Cretaceous Potomac Group of Maryland, eastern North America. The type species, Spanomera mauldinensis sp. nov., from the early Cenomanian Elk Neck beds, has inflorescence units with terminal pistillate, and lateral staminate flowers. The organization of inflorescences and flowers is opposite and decussate. Staminate flowers typically have five tepals: two lateral, one posterior, and two in the anterior position. Each tepal is opposed to a stamen with a short filament, dorsifixed anther, and two pairs of pollen sacs. Stamens contain pollen comparable to the dispersed pollen species Striatopollis paraneus (Norris) Singh. Pistillate flowers have two lateral tepals and two anterior-posterior tepals that are opposed to two carpels. Carpels are slightly fused basally along their ventral margins and are semicircular in outline with a long, decurrent, papillate ventral stigma. Frequently this stigmatic surface has abundant attached pollen of the Striatopollis paraneus type. Spanomera marylandensis sp. nov., from the late Albian Patapsco Formation, is similar to S. mauldinensis but is known only from isolated flowers and floral parts. Staminate flowers have four stamens with dorsifixed anthers and each is opposed to a tepal. Stamens contain pollen comparable to the dispersed pollen species Striatopollis vermimurus (Brenner) Srivastava. Carpels have pollen of S. vermimurus on the stigma. Spanomera provides further evidence of unisexual but probably insect-pollinated flowers among mid-Cretaceous, early nonmagnoliid (“higher”) dicotyledons, and is interpreted as closely related to extant Buxaceae. Characters that Spanomera shares with other taxa suggest that the Buxaceae themselves may be closely related to Myrothamnaceae and other “lower” Hamamelididae.     

Expression of AODEF,a B-functional MADS-box gene,in stamens and inner tepals of the dioecious species Asparagus officinalis L.

Garden asparagus (Asparagus officinalis L.) is a dioecious species with male and female flowers on separate unisexual individuals. Since B- and C-functional MADS-box genes specify male and female reproductive organs, it is important to characterize these genes to clarify the mechanism of sex determination in monoecious and dioecious species. In this study, we isolated and characterized AODEF gene, a B-functional gene in the development of male and female flowers of A. officinalis. Southern hybridization identified a single copy of AODEF gene in asparagus genome. Northern blot analysis showed that this gene was specifically expressed in flower buds and not in vegetative tissues. In situ hybridization showed that during early hermaphrodite stages, AODEFgene was expressed in the inner tepal and stamen whorls (whorls 2 and 3, respectively), but not in the outer tepals (whorl 1), in both male and female flowers. In late unisexual developmental stages, the expression of AODEF gene was still detected in the inner tepals and stamens of male flowers, but the expression was reduced in whorls 2 and 3 of female flowers. Our results suggest that AODEF gene is probably not involved in tepal development in asparagus and that the expression of AODEF gene is probably controlled directly or indirectly by sex determination gene in the late developmental stages.     

Biosystematic studies onDisporum (Liliaceae-Polygonatae)

Both the floral biology and morphometrics of two Japanese species of AsianDisporum (sectionEudisporum) are presented. These two species,D. sessile andD. smilacinum, represent extremes in both floral morphology and divergence in pollination within the section. The inverted flowers ofD. sessile have an elongate floral tube formed by the imbrication of the oblanceolate tepals. The tepal bases are modified into well developed, saccate nectaries. The stamens have rigid, vertical filaments which tightly encircle the ovary-style axis, and extrorse anthers located within a floral cavity which can accommodate a large pollinator (cross-pollination). The stigma is exserted and the depth of its cleft formation constant.D. smilacinum, in contrast, has an open, nodding campanulate flower with lanceolate tepals which have only shallow nectaries at their bases. The stamens have widely divergent filaments with versatile anthers that have laterally introrse dehiscence (wind and/or self-pollination). The depth of the stigma cleft is variable. For both species, the pattern of differential UV absorption and reflectance is similar. It is suggested on morphological grounds and by pollinator observation, thatD. sessile with a high energy flower requiring specialized visitors represents a more advanced condition than that observed inD. smilacinum, which is more generalized and primitive. Seasonal herbivore pressure on the tepal nectaries ofD. sessile is discussed in relation to its pollination.     

Embryogenesis and seed development in Sinomanglietia glauca (Magnoliaceae)

The development of the floral bud, especially the ovule and seed coat, of Sinomanglietia glauca was observed. Floral buds were covered by eight to nine hypsophyll pieces. The hypsophyll nearest the tepal was closed completely and characterized by two arrays of densely stained cells with dense cytoplasm, which split longitudinally at flowering. The perianth consisted of 16 tepals arranged in three whorls. The gynoecium was composed of numerous apocarpous carpels; the ovule was anatropous with two integuments. Embryogenesis was of the Polygonum type, and the endosperm was nuclear. The inner integument degenerated during seed development. The seed of S. glauca had an endotestal seed coat comprised of a sclerotic layer derived from the inner adaxial epidermis of the outer integument and a sarcotesta derived mainly from the middle cells between the inner and outer epidermis of the outer integument. The embryo developed normally, so embryogenesis is not the cause of difficult regeneration.