Flower Structure

11 Key excerpts on "Flower Structure"

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  eBook - ePub

  Name that Flower: The Identification of Flowering Plants: 3rd Edition

  • Ian Clarke, Helen Lee(Authors)
  • 2019(Publication Date)
  • Melbourne University Press Digital

    (Publisher)

  2 The Structure of Flowers

  There are many ways in which the various flower parts can be arranged to make up the structure we recognise as a ‘flower’. This chapter sets out to describe the structure of a simple flower, and then discusses some of the variation commonly encountered. Chapter 8 includes some more complex examples.

  Floral structure is described under the following headings: Structure of a basic flower The perianth The reproductive organs Variation in floral structure Arrangement and union of parts The perianth The calyx The corolla Symmetry Aestivation The reproductive organs The androecium The gynoecium Placentation The style and stigma Discs and nectaries Relationships of parts in the flower The floral tube Number of parts per whorl Unisexual flowers The floral formula

  Structure of a basic flower

  A basic flower (Fig. 1 ; Pl. 1) has four series of parts arranged in concentric whorls (or rings) on the receptacle, which is the name given to the expanded end of the pedicel (flower stalk). The two outer whorls are together known as the perianth, and are not directly involved in reproduction. The reproductive structures are located in the inner whorls.

  The perianth

  The outer whorl, known as the calyx, is composed of two or more parts called sepals, which are often green in colour and enclose the rest of the flower in the bud stage. Inside the calyx is the corolla, made up of petals, which are usually white or brightly coloured. It is usual for the sepals and petals to be equal in number.

  The reproductive organs

  A whorl of stamens, called the androecium, lies inside the corolla, and is generally taken to represent the male part of the flower. Each stamen has a slender filament (stalk) and, at the top, an anther in which the pollen is produced. The pollen grains carry the male reproductive units.

  In the centre of the flower is the gynoecium, made up of carpels. Each carpel usually has three parts: an expanded basal part called the ovary, in which the ovules are produced; a central stalk-like section called the style; and a terminal stigma

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  Pollination and Floral Ecology

  • Patricia Willmer(Author)
  • 2011(Publication Date)
  • Princeton University Press

    (Publisher)

  1. Essential Flower Morphology

  Flowers are complicated assemblages of plant parts, modified originally from leaves. Repetitive patterns of units occur in series, growing centripetally and sitting upon the flower stalk. Table 2.1 shows the general patterns of floral parts, with the four main series of structures from base to tip, or outer to inner: sepals , petals , stamens , carpels . This fundamental structure can be detected in most flowers from the basic arrangement in figure 2.1 A, though the details vary enormously; these details can often be conveniently expressed in terms of a simple flower diagram of the type shown in figure 2.1 B. In particular, the numbers of each part are highly varied: primitive magnoliids have very large numbers of petals, as do cacti, but in many dicot plants there are just five petals and five sepals, whereas in most monocots these structures come in threes. Even here many exceptions occur, and some important groups, such as the crucifers (Brassicaceae) and the poppies (Papaveraceae), have their parts in multiples of two or four. These petal and sepal numbers may or may not be reflected in the inner series of stamens and carpels: in the geranium family all the parts are in fives, and in the lily and iris families all are in threes, but in some other families this numerical consistency is lost, often with fewer carpels and more stamens than there are petals and sepals.

  During flower development each part or series forms in sequence, and is in turn influenced by the initiation and growth of neighboring structures. The original apical meristem that will form the flower is protected in a bract , within which floral organs are initiated; then as floral morphogenesis progresses, the first series of structures, the sepals, grows and surrounds the bud , within which the petals and the androecium (male) and gynoecium (female) form sequentially. To add further variety, the fundamental structures may fuse into a ring as they arise or during ontogeny to form tubular organs. And sometimes parts of different floral organs may fuse, to form organ complexes. However, the basic underlying anatomy can still usually be described by a simple floral diagram as in figure 2.1

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  Floral Diagrams

  An Aid to Understanding Flower Morphology and Evolution

  • Louis P. Ronse De Craene(Author)
  • 2022(Publication Date)
  • Cambridge University Press

    (Publisher)

  PART I INTRODUCTION TO FLORAL DIAGRAMS 1 Introduction to Flower Morphology 1.1 Definition of Flowers There is no general agreement nor any rule about how a flower should be defined. Since the end of the nineteenth century two main contrasting hypotheses have been provided and the discussion is still ongoing (reviewed in Bateman, Hilton and Rudall, 2006). The pseudanthial hypothesis accepts that flowers evolved from a branched, multiaxial structure – that is, a condensed compound inflorescence (e.g. Eichler, 1875; Eames, 1961). This means that a flower is an assemblage of separately functioning entities that became grouped together. The euanthium hypothesis states that the flower evolved from a simple uniaxial (euanthial) structure – that is, a condensed sporophyll- bearing axis with proximal microsporophylls and distal megasporophylls (e.g. Arber and Parkin, 1907). However, reconstructions of the early angiosperm flower (e.g. Sauquet et al., 2017) suffer from the absence of clear transitional forms between ancestral prototypes and angiosperms. Floral organs all have attributes of leaves, and leaf-like elements, such as stipules, leaf bases, petioles and blades, occasionally appear in flowers (e.g. Arber, 1925; Gue ´de `s, 1979). The stamen is recognized as equivalent to a microsporangiophore (an axis) or micro- sporophyll (a leaf) bearing microsporangia (the pollen sacs), while the ovary is described as a grouping of folded megasporophylls (the carpels) enclosing the megasporangia (ovules) (Endress, 2006). However, the origin of stamens is unclear, with a greater diversity of stamen structures in other seed plants (Endress, 2006). Developmental and genetic evidence supports the fertile organs of flowers to be a combination of axes and subtending leaves (at least for the ovary: e.g. Endress, 2019), reflecting a modular vegetative system of a main axis with lateral branches arising in the axil of leaves. However, not all researchers 3

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  Biology Workbook For Dummies

  • Rene Fester Kratz(Author)
  • 2022(Publication Date)
  • For Dummies

    (Publisher)

  • Roots contain a core of vascular tissue that carries water away from the roots and toward the shoots and brings sugars from the shoots toward the roots. Like those of a carrot, some roots specialize in storing extra sugars for later use by the plant. » Reproductive structures like flowers and cones produce egg and sperm and may create pro- tective structures around the young embryo. Flower Structure (see Figure 18-2) also helps with pollination, the distribution of pollen (which contains sperm) to the plant’s female parts. • Stamens are the male parts of flowers. They consist of the anther, which makes pollen, and a thin stalk called a filament. Scientists call the ring of male parts within the flower the androecium. • The flower’s female parts are the carpels, which may be joined together to form a pistil. The part of the carpel that catches pollen is the stigma, and the swollen base that contains eggs in ovules is the ovary. Many flowers have an elongated tube, the style, between the stigma and the ovary. Scientists call the ring of female parts within the flower the gynoecium. • The pretty parts of flowers are often showy petals, which help attract animals to flowers so they can help distribute pollen. Scientists call the ring of petals in the flower the corolla. • Flowers may also have a ring of green, leaf-like structures called sepals. Sepals help protect the flower when it’s still in the bud. In some flowers, the sepals look just like the petals and help attract pollinators. Scientists call the ring of sepals in the flower the calyx. CHAPTER 18 Studying Plant Structures 323 • After the fertilization of the eggs by sperm, the ovules within a flower become seeds, and the ovary becomes a fruit. Seeds protect the embryo, and fruits help scatter the seeds away from the parent plant. • A stalk called the peduncle supports the flower, which may also have a swollen base called the receptacle.

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  Cambial Growth, Root Growth, and Reproductive Growth

  • T.T. Kozlowski(Author)
  • 1971(Publication Date)
  • Academic Press

    (Publisher)

  Chapter 7 FLOWERING As outlined by Matthews (1963), the processes leading to development of mature seeds and fruits display several sequential stages including (1) enlarge-ment of the inflorescence in the flower bud, (2) flowering, (3) pollination (transfer of pollen from anther to stigma), (4) fertilization (fusion of male and female gametes), (5) growth and differentiation of the embryo, (6) growth of the seed and fruit to maturity, and (7) ripening of fruits and cones. The first three of these phases will be discussed in the present chapter and the others in Chapter 8. Floral Structure and Arrangement As Kramer and Kozlowski (1960) emphasized, many botanists often restrict the term flower to angiosperms. However, this volume will use the term more broadly, in line with common usage of horticulturists and foresters, and treat the young cones or strobili of gymnosperms as flowers also. ANGIOSPERMS Typical complete flowers of angiosperms bear four types of organs in their receptacles (Fig. 7.1). The outermost of these are the sepals which together make up the calyx. Above the sepals are the petals, collectively called the corolla. The sepals and petals together comprise the perianth. Most flowers have a regular or actinomorphic corolla, with petals similar in shape and size and the flower showing radial symmetry. Some flowers, as in the Leguminosae, have an irregular or zygomorphic corolla and exhibit bilateral symmetry. Inside the perianth are two kinds of reproductive organs. These are the pollen-producing stamens, collectively called the androecium, and the carpels which comprise the gynoecium. Typically the mature carpel resembles a folded or rolled leaf blade with appressed or fused margins. A flower may have a single carpel or more than one. The carpel usually consists of a lower, 306 7. Floral Structure and Arrangement Anther Filament Pollen Stigma Petal Style Sepal Antipodais Ovule Polar nuclei Egg nucleus Synergids Micropyle Sperm nuclei Pollen tube FIG.

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  Biology Today and Tomorrow with Physiology

  • Cecie Starr, Christine Evers, Lisa Starr, , Cecie Starr, Cecie Starr, Christine Evers, Lisa Starr(Authors)
  • 2020(Publication Date)
  • Cengage Learning EMEA

    (Publisher)

  Floral form and composition vary among species, but a typical flower has four concentric rings (whorls) of modified leaves. The outermost ring is the calyx, and it consists of leaflike sepals 2 . Sepals, which are photosynthetic and inconspicuous, enclose and protect the flower’s internal tissues before it opens. Just inside the calyx is the corolla, a ring of petals 3 . Petals are the largest and most brightly colored parts of a typical flower. Inside the corolla is a ring of stamens, the reproductive organs that produce the plant’s male gametophytes (gamete-making structures, Section 15.2). A sta- men is a thin filament with an anther at the tip 4 ; a typical anther consists of four pouches called pollen sacs. Pollen grains, which are immature male gametophytes, form inside pollen sacs. The innermost ring of modified leaves folds and fuses into one or more carpels: reproductive organs that produce female gametophytes 5 . A flower may have one carpel or several, depending on the species. A carpel (or a compound structure that consists of multiple fused carpels) is commonly called a pistil. The upper region of a carpel is a sticky or hairy stigma that is specialized to receive pollen grains. Typically, the stigma sits on top of a slender stalk called a style. The lower, swollen region of a carpel is the ovary, which contains one or more ovules. In seed plants, an ovule 6 is the structure in an ovary that gives rise to the female gametophyte. As you will see in Section 29.4, seeds are mature ovules. Variation in Form Flowers vary widely in form. Some flowers are single blos- soms (Figure 29.4A); others occur in clusters called inflorescences (Figure 29.4B). Figure 29.2 Sharing pollen, nectar, pests, and pathogens. Varroa mites and deformed wing virus spread from one insect pollinator to another on shared flowers.

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  Anatomy of Flowering Plants

  An Introduction to Plant Structure and Development

  • Paula J. Rudall(Author)
  • 2020(Publication Date)
  • Cambridge University Press

    (Publisher)

  5 Flower Flowers are borne on reproductive axes, either as solitary struc- tures or on inflorescences, which can be unbranched or variously branched (Figure 5.1). In a determinate inflorescence, the inflor- escence apex is terminated by a flower, whereas in an indetermi- nate inflorescence it maintains growth until the apical meristem becomes exhausted 32, 152 . Each flower is often subtended by one or two modified leaf-like sterile bracts borne on the inflorescence axis, though bracts are entirely absent from some species. Some species also possess one or more leaf-like bracteoles on the flower axis. At the onset of flowering, the shoot apical meristem under- goes structural modification that transforms it from a vegetative apex to a reproductive apex. 5.1 Flower Structure The floral axis (receptacle) is unbranched, determinate and highly condensed. It bears several distinct organ regions in a consistent radial sequence 10, 32, 107, 152 . The densely crowded floral organs are arranged either in distinct whorls or in a spiral pattern on the axis. Each organ series consists of one or more whorls. In a typical flower bud, an outer region of sterile organs (either tepals, or sepals and petals) encloses the pollen-bearing organs (stamens), which in turn are outside the ovule-enclosing organs (carpels). The outer sterile organs represent the perianth, and the stamens and carpels form the androecium and gynoecium respectively. In species with a syncarpous ovary, the gynoecium terminates the short floral axis, though a residual floral axis exists in some species with free carpels (Figure 5.2). Different organ arrangements characterize different angiosperm lineages. For example, some species possess unisexual flowers, in which one of the reproductive organ types is either absent or sterile: female flowers lack functional stamens and male flowers lack carpels.

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  Flowers on the Tree of Life

  • Livia Wanntorp, Louis P. Ronse De Craene(Authors)
  • 2011(Publication Date)
  • Cambridge University Press

    (Publisher)

  His focus is primarily on organization, and not architecture. It includes the reconstruction of the entire primary morphological surface, i.e. the surface that is derived from the floral apex. Thus the information content is greater than in Troll’s approach. Concomitantly, Leinfellner’s approach requires a more detailed mor- phological analysis with transverse microtome section series, and sometimes also study of younger developmental stages. In general, if we don’t know what happens with the primary morphological sur- face, we don’t know a crucial aspect of development. Unfortunately, in many publi- cations on gynoecium and other floral structures this aspect is not studied. It is also useful to distinguish between morphology, anatomy and histology. Morphology is related to the development of the primary morphological surface. Histology deals with all the kinds of tissues in the organs. Anatomy is related to the patterns of distribution of the tissues in the organs and organ complexes, especially the architecture of the vasculature. For the analysis of all three levels, histology, anatomy and morphology, anatomical techniques are necessary. In the studies on rosids in my lab, Merran Matthews and Julien Bachelier made detailed analyses of the gynoecium structure in larger clades and showed that all these aspects just mentioned, the topography of the inner morphological sur- face, anatomy and histology, are of systematic interest (Matthews et al., 2001; Matthews and Endress, 2002, 2004, 2005a, b, 2006, 2008; Bachelier and Endress, 2007, 2008, 2009). For related studies on other angiosperms, see, e.g. Remizowa et al. (2006). 5.6 Concept of sepals and petals The concept of sepals and petals in angiosperms has been tackled from different perspectives, and new aspects have been discussed, but it is still not convincingly resolved how sepals and petals should be distinguished and where in the phylo- genetic tree petals originated.

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  Tropical Plant Types

  Pergamon International Library of Science, Technology, Engineering and Social Studies

  • B. G. M. Jamieson, J. F. Reynolds(Authors)
  • 2016(Publication Date)
  • Pergamon

    (Publisher)

  C H A P T E R 11 Morphology of the Flower THE flower is a shoot of limited growth, with much-shortened internodes, which bears typically four types of organs. These, from the apex down-wards, are the carpels (collectively the gynaecium), the stamens (collec-tively the androecium), the petals (collectively the corolla) and the sepals (collectively the calyx). A study of the vascular anatomy of these organs suggests that they are ultimately homologous with leaves. The carpels are apparently megasporophylls and the stamens microsporophylls (see p. 125). The petals appear to be sterilized microsporophylls (and it is a fact that increase in numbers of petals in cultivated flowers is associated with decrease in the number of stamens) while the sepals appear to be morphologically bracts. A bract is a small leaf with relatively undeveloped lamina in the axil of which a flower or inflorescence branch arises. Those parts of the flower which are concerned directly with reproduc-tion, the carpels and stamens, are termed the essential floral organs while the perianth members, the petals and sepals, which play an indirect part in reproduction, are termed the inessential or accessory floral organs. The stalk of an individual flower is a pedicel and the stalk of an inflores-cence, i.e. an axis with more than one flower, is a peduncle. Each pedicel normally arises in the axil of a bract which may be indistinguishable from a normal leaf of the species or may be much-reduced or absent. Minute bracts, known as bracteoles, may occur on the pedicel. The bracteoles may be closely adpressed around the flower as an involucre, the upper bracteoles of which may be indistinguishable from the sepals. The position of the bract is used to orientate its axillary flower in descriptions. The side of the flower towards the bract is said to be anterior or ventral and the side towards the main axis is said to be posterior or dorsal.

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  Early Flowers and Angiosperm Evolution

  • Else Marie Friis, Peter R. Crane, Kaj Raunsgaard Pedersen(Authors)
  • 2011(Publication Date)
  • Cambridge University Press

    (Publisher)

  16 Patterns of structural diversification in angiosperm reproductive organs This chapter provides an overview of the main patterns of structural diversification in angiosperm flowers as inferred from the occurrence of floral features in the fossil record in the context of phylogenetic analyses of angiosperm rela- tionships (Chapter 7). The systematic chapters (Chapters 8–15) provide descriptions of the individual fossils and cite the relevant literature. Here we focus on broader patterns, the appearance of major structural novelties and, where possible, what these imply about floral innovation among angiosperms as a whole. In part these large-scale patterns in the evolution of floral structure reflect the successive diver- sification of different lineages of angiosperms at different times in the past. The consequences of floral innovation for angiosperm pollination and dispersal biology are con- sidered in Chapters 17 and 18. Aspects of the diversifica- tion of reproductive structure in specific angiosperm lineages are addressed in Chapter 20. Building on earlier work by Brenner (1963), Muller (1970) and others, studies in the 1970s on early angio- sperms from the Potomac Group of eastern North America were the first to demonstrate a coordinated increase in the diversity and ‘advancement’ of pollen and leaves through the Early and mid-Cretaceous (Doyle and Hickey, 1976; Hickey and Doyle, 1977; Hickey, 1978). This work con- firmed that monoaperturate angiosperm pollen appeared first in the fossil record, an observation that was (and remains) consistent with phylogenetic concepts based on extant plants. A parallel increase in the structural complex- ity of fossil angiosperm leaves was also broadly consistent with interpretations of the evolution of leaf architecture among extant taxa (Hickey and Wolfe, 1975; Doyle and Hickey, 1976; Hickey and Doyle, 1977).

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  Bioinspired Actuators and Sensors

  • Minoru Taya, Elizabeth Van Volkenburgh, Makoto Mizunami, Shûhei Nomura(Authors)
  • 2016(Publication Date)
  • Cambridge University Press

    (Publisher)

  2 Principles of structural organization and functions in biological species 2.1 Plant structures from elementary units and motor cells 2.1.1 Plant cells Plants can perform four functions (Niklas, 1992): (i) photosynthesis, (ii) hydraulics, (iii) mechanics, and (iv) reproduction. We will discuss photosynthesis in Section 3.1.6, the combined subject of the second and third will be re-examined in terms of morphing structures in plants, in Sections 3.2.1. A part of reproduction will be reviewed only in the area of seed dispersals in Section 3.2.6. The combination of hydraulics and mechanics will be examined here in terms of their building blocks (cells) all the way to the assembled structure of the tree-trunk. Cells are certainly the starting building block of all plants and animals. But it is primarily the cell walls that differentiate plants from animals, that is, rigid cell walls exist only in plants, not animals. A typical cell wall structure in a plant is composed of middle lamella (the boundary adjacent to the neighboring cells), primary and secondary walls, Fig. 2.1. The secondary walls are deposited on the primary cell wall by secretion from the protoplast, but each lamella so deposited has microfibrils with different orientations (Fig. 2.1(b)). The boundaries between the middle lamella, primary and secondary walls are not distinct, but smoothly graded where polymer adhesive “lignin” is used as a seamless adhesion agent. If we zoom in on the nanostructure of the primary wall, we will see the hierarchical structure composed of macrofibrils, microstructure (microfi- brils, glycoprotein, acidic pectin, hemi-cellulose molecule), and finally nanostructure (micelle composed of cellulose molecules), see Fig.

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