L10 - Flower Structure and Inflorescences PDF

Announcements PRACTICALS Practcal – online Quizz – 18 September Submit drawing books – 19 & 20 September TEST 2 Date: 12 Sept 2024 Time: 17h00 Venues: KA & KB Format: Same as Test 1 Scope: Chapters 5,6 & part of 7 (up to fowers) Flower Structure and Inforescenc...

Announcements PRACTICALS Practcal – online Quizz – 18 September Submit drawing books – 19 & 20 September TEST 2 Date: 12 Sept 2024 Time: 17h00 Venues: KA & KB Format: Same as Test 1 Scope: Chapters 5,6 & part of 7 (up to fowers) Flower Structure and Inforescences  The Flower It is a modifed shoot - for reproducton. Made up of Four whorls: 1. Calyx consists of sepals – green, protects the young fower 2. Corolla consists of petals – coloured, atracts pollinators. 3. Androecium consists of stamens, each consistng of anther and flament – produce male gametes. 4. Gynoecium – consists of the pistl or carpels each consistng of stgma, style and the ovary (bearing ovules) Tepals: members of the perianth (calyx & corolla) – when the sepals and petals look identcal and are joined together. Flower Structure Stigma Filament Style Anther Ovary Receptacle Petal Sepal Ovule Pedicel  Male and Female reproductie foral organs Male sex organs: The stamens Stamens, composed of anther – organ that produces pollen (male gametophyte) and filament stalk that supports the anther.  Female sex organs: The carpel/pistl Oiary is the enlarged basal porton of carpel that contains the oiules (female gametophyte). The stgma is the receptve porton (stcky tp) of the carpel for pollen grains to adhere. The style is a tube connectng stgma to ovary. Male and Female parts of a fower  Non-reproductve foral organs Sepals (green) are the outermost whorl of leaf-like structures outside the corolla (whorl of petals), covering a fower bud. Petals are the inner whorl of leaf-like colorful structures of an open fower to atract pollinators. Tepals when the sepals & petals look the same or cannot be diferentated  Floral Descriptie Terms/classifcaton of fowers Complete fower – has all four whorls/incomplete - has one or more missing. Perfect fower – has both male and female parts (bisexual); imperfect fower – has either male or female parts (unisexual) - staminate and pistllate respectvely Monoecious plant/species – bear both pistllate and staminate fowers on the same plant. Dioecious plant/species bear pistllate and staminate fowers on separate plants. Actnomorphic /regular fower – can be divided into identcal halves in more than one plane. Zygomorphic/irregular fower – can only be divided into identcal halves in one plane.  Complete vs Incomplete Flower Complete fower: has all four whorls Incomplete fower: has one or more whorls missing  Perfect vs Imperfect Flower Perfect fower: has the stamen & pistl in the same fower Imperfect fower: has the male sex organs (staminate) or female sex organs (pistlate), but not both on the same fower  Monoecious vs Dioecious plants Monoecious plant/species – bear both pistllate and staminate fowers on the same plant. Dioecious plant/species bear pistllate and staminate fowers on separate plants.  Actnomorphic vs Zygomorphic fower Actnomorphic : radial symmetry fowers can be divided into 2 equal halves along any plane Zygomorphic: bilateral symmetry divided into 2 equal halves only by a medial cut through the central axis.  Coalescence and Adnaton Coalescence: Joining of members of the same whorl. Synsepaly - sepals joined; aposepaly – sepals free from one another. Synpetaly – petals joined and apopetaly – petals free from one another. Synandry – stamens joined and apoandry – stamens free from one another. Syncarpy – carpels joined and apocarpy – carpels free from one another. NB: SYN = JOINED; APO = FREE  Coalescence and Adnaton cont… Adnaton: the joining of members of one whorl to those of a diferent whorl. Hypogynous fower: sepals, petals and staments are atached at a point below the oiary and the oiary is superior. Perigynous fower: ovary lies within a hypanthium = a cup-like structure formed by sepals, petals and stamens. Epigynous fower: sepals, petals and stamens are atached aboie the oiary and the ovary is inferior. Match the following fggues I, and II and III (I) Hypogynogs (II) Peuigynogs foweu (III) Epigynogs foweu a) A-III, B-I, C-II b) A-III, B-II, C-I ovauy infeuiou, foual paut above c) A-I, B-III, C-II ovauy enclosed, foual paut same level d) A-I, B-II, C-III ovauy sgpeuiou, foual paut below  Complete, perfect, synsepalous, apopetalous, apoandrous, hypogynous and zygomorphic, pentamerous fower  Carpels Carpels are modifed leaves in which one or more leaves fold and or merge to produce one or more cavites where the midvein of the leaf becomes the dorsal suture and the point where the leaf margins merge becoming the ientral suture/s.  Locules and placentaton Locules: Cavites within the ovary where ovules occur – formed by fusion of one or more carpels (pistl). Unilocular ovary - one locule Bilocular ovary - two locules Trilocular ovary - three locules Placenta: the point in the ovary where the ovule is atached – by the funiculus. Placentaton: the patern in which ovules are atached to the placentae  Placentation The way or pattern in which the ovules are attached to placentae is called placentation. Parietal placentaton: occur in unilocular ovaries in which ovules are atached to the side walls of the ovary. Marginal placentaton: Occurs in simple unilocular pistl where ovules occur in a row on one side of the ovary. Axile placentaton: Occurs in multlocular pistls with the placenta at the central axis.  Free/central placentaton: Occur in unilocular compound pistl with the placenta on the central axis. Apical placentaton: the atachment of the ovules is at the apex. Basal placentaton: the atachment of ovules to the botom of the ovary. Inforescences  Inforescences Flowers are borne solitary on the plant or occur in a cluster on an axis called the rachis. The way in which fowers are atached to the rachis in an inforescence difers among diferent plants. The rachis may be branched or non-branched. These lead to inforescences being described in diferent terms.  There are many types of inforescences. Each type of inforescence is determined by how the fowers are arranged. Inforescences are a useful plant ID tool. Determinate and indeterminate growth.  Parts of Inforescence Peduncle: central axis on which fowers are produced Pedicel: stalk of single fower, pedicillate or sessile Bract: reduced leaf at the base of fower Receptacle: fat disc like peduncle axis  Types of Inforescences Simple monopodial inforescences: 1. Raceme: Of indeterminate growth, pedicels of equal lengths, oldest fower at the base. 2. Spike: Of indeterminate growth; fowers sessile. 3. Catkin/amentum: Of indeterminate growth; fowers sessile and imperfect. 4. Spadix: Fleshy, of indeterminate growth, fowers sessile; staminate and pistllate (at base) fowers separate. 5. Umbel: Of determinate growth; fowers originate at the same point; pedicels of equal length. 6. Corymb: Of determinate growth; oldest fowers with long pedicels at the base; fowers carried on the same plane. 7. Capitulum/head: of determinate growth; main axis a fat receptacle; fowers sessile; staminate ray forets and bisexual disc forets.  Raceme Individual fowers have pedicels. Pedicels can vary in length from species to species. Lower fowers open frst. peduncle Indeterminate growth. pedice l raceme  Spike Unbranched inforescence form consistng of a main stalk with stemless forets atached along its length  Catkin Elongated inforescence of unisexual fower on a woody plant.  Spadix Fleshy spike which carries numerous minute fowers embedded on its surface, usually surrounded by a colorful bract called a spathe  Umbel Individual fower pedicels all originate from the same spot on the peduncle. Outer fowers open frst. pedicel determinate. peduncl e  Corymb Somewhat similar to the umbel. Individual fower pedicels are atached to the peduncle at diferent points. Often fat-topped. Outer fowers open frst. peduncl pedicel e Determinate.  Composite Head A highly advance disk inforescence flower Consists of separate ray & disc fowers Bracts may be green , buy can also be colored ray bract Petal-like foret atached at flower the perimeter dense inforescence of small, often stalkless fowers  Compound monopodial inforescences 1. Panicle/ Compound raceme: 2. Compound spike 3. Compound corymb: peduncle is branched and each branch bear corymb like inforescence 4. Compound umbel: shortened prim axis with fowers on the branches 5. Cyme: main axis ends in a fower; two lateral buds contnue growth in turn each ends in a fower; oldest fower at base.  Panicle/Compound raceme A highly branched inforescence consistng of many, repeatng units. Panicles can be made of many spikes, racemes, corymbs, or umbels. A panicle of racemes  Compound spike AKA the spike of spikelet The fowers are sessile  Compound corymb The main axis is branched, each branch has corymbs (fowers) All fowers on same level  Cyme In real life, cymes tend to be fat or convex shaped. The inner fowers open frst. Determinate growth.  Sympodial inforescences Monochasium: stem axis ends in a fower; growth contnues from one lateral bud. 1) Helicoid monochasium: growth contnues from a lateral bud on the same side of the stem. 2) Scopioid monochasium: growth contnues on lateral buds alternately forming a zigzag patern Dichasium: stem axis ends in a fower, growth contnues from two opposite buds. 1) Simple/single dichasium: terminal bud transformed into a fower; two axillary buds grow out. Process happens once. 2) Compound dichasium: terminal bud transformed into a fower and two axillary buds grow out; process happens more than once.