Definition: Flower is the specialized reproductive shoot of an angiosperm plant A typical flower consists of four whorls of modified leaves viz. Calyx, Corolla, Androecium and Gynoecium.
Technical terms used in descriptionof a flower. Monoecious : A condition where both male and female flowers are borne in the same plant.
Dioecious: A condition where the male flowers are borne on male plant and female flowers on female plant.Borassus flabellifer (Toddy Palm) Borassus flabellifer (Toddy Palm)Female Plant Male Plant
Pistillate flower: Flowers having only female reproductive organ. (Gynoecium) Cucurbita Female flower Staminate flower: Flowers having only male reproductive organ. (Androecium) Cucurbita Male flower
Actinomorphic: Flowers which are symmetrical in all direction. i.e. Each whorl of the flower consisting of same size. Tribulus flower Zygomorphic: Flowers which are symmetrical in one direction only. i.e. Each whorl of the flower consisting of different sizes of petals and sepals. Cassia flower
Unisexual flower: flower having only one functional sex of the reproductive organ. (either ale or female sex organ) Castor flower Bisexual flower: Flower having both male and female functional sex organs (Gynoecium and androecium) Tribulus flower
Pedicellate flower: Flowers having a pedicel /stalk Hibiscus flowerSessile flower: Flowers without apedicel /stalk Achyranthes flower
Bracteate flower: Flowers having a bract (a small leaf like structure subtending a flower Rose BougainvilleaEbracteate flower: Flowers without abract Mimosa
Bracteolate flower: Flowers having bracteoles (Small leaf like structures on the flower stalk)Ebracteolate flower: Flowers withoutbracteoles .
Homochlamydeous flower: Flowers in which the perianth is not differentiated into calyx and corolla.Heterochlamydeous flower: Flowers inwhich the perianth is differentiated intocalyx and corolla.
Complete flower: Flowers having all the four whorls viz. Calyx, Corolla, Androecium and Gynoecium.Incomplete flower: Flowers lacking oneof the four whorls viz.Calyx, Corolla, Androecium andGynoecium.
Epigynous flower: Flowers in which the floral parts are arising above the level of the ovary.Hypogynous flower: Flowers in whichthe floral parts are arising below the levelof the ovary.
Perigynous flower: Flowers in which the floral parts are arising from the rim of the hypanthial cup of the ovary.
Parts of a flower Out of the four whorls of the flower, Calyx and Corolla are called accessory whorls as they do not directly take part in reproduction Androecium and Gynoecium are considered as essential whorls.
Calyx: 1st Whorl of the flower It is composed of sepals. Polysepalous: The sepals are free from each other. ROS E Gamosepalous: The sepals are fused with each other. HIBISCU S
COROLLA: 2nd Whorl of the flower It is composed of petals Polypetalous: The petals are free from each other ROS E Gamopetalous: The petals are fused with each other DATURA
Aestivation: The arrangement ofpetals & sepals in the flower bud Valvate: Here the floral leaves (Petals & Sepals) are arranged side by side.
Aestivation: Twisted: Here the floral leaves show regular overlapping in one direction. HIBISCU S
Aestivation: Imbricate (ascendingly imbricate): Here one floral leaf is completely in (posterior petal), one completely out (anterior petal) and remaining are overlapping in one direction.
Aestivation: Quincuncial: It is rare and found in pentamerous flower only. Here two petals are innermost, two petals are outermost and one is alternate Cassia occidentalis
Aestivation: Vexillary: It is rare and found in pentamerous flower only. Here two petals are innermost, two petals are outermost and one is alternate. Here the posterior petal is Fabaceae largest and outermost. flower
Androecium: 3rd whorl of the flower/male whorl It is composed of stamens. Each stamen has a slender stalk, at the top an anther connected by a connective. Anther Connective Filament
Adelphy: Fusion of filaments &anthers free Monadelphous: The filaments of all the stamens become fused forming a single bundle. Diadelphous: Here the filaments are fused forming two bundles. Polyadelphous: The filaments of the stamens are fused forming many bundles. Monadelphous Diadelphous Polyadelphous Pea Hibiscus Citrus
Syngeny: Fusion of anthers andfilaments free. Syngenesious stamens: The anther lobes of all the stamens become fused and filaments are free. Synandry: Here both filaments and the anthers are fused. Syngenesious stamens Synandr y Fused anthers Fused anthers and filaments Free filaments
Epipetalous stamens: Here the filaments of stamens are found attached to the petals
Anther lobes: Monothecous: The anthers have only one lobe Dithecous: The anthers have only two lobe
Gynoecium: 4th whorl of the flower/female whorl Gynoecium is composed of carpels Each carpel has three parts, Ovary with ovules, Style and Stigma.
Types of Gynoecium: Apocarpous: Here the gynoecium consists of two or more carpels and all the carpels are free. Syncarpous: Here the gynoecium consists of two or more carpels and all the carpels are fused.
Monocarpellary Gynoecium: A gynoecium with a single carpel Bicarpellary Gynoecium: A gynoecium with two carpels Tricarpellary Gynoecium: A gynoecium with three carpels Tetracarpellary Gynoecium: A gynoecium with four carpels Pentacarpellary Gynoecium: A gynoecium with five carpels Polycarpellary Gynoecium: A gynoecium with more than five carpels
Types of gynoecium based onlocules Unilocular ovary: Ovary having single chamber Eg. Pea Bilocular ovary: Ovary having two chambers Eg. Brinjal Trilocular ovary: Ovary having three chambers Eg. Castor Tetralocular ovary: Ovary having four chambers Eg. Ocimum Pentalocular ovary: Ovary having five chambers Eg. Hibiscus
Placentation: The arrangement ofovules on the placenta inside theovary is called placentation. Thereare several types of placentation. a. Marginal placentation In this type, the ovary is monocarpellary, monolocular and the placenta is on the ventral suture. The ovules are attached to the placenta which is on the margin. e.g. Beans, Pea, etc.
b. Axile placentation : In this type, the ovary has two or more carpels, syncarpous, and has two or more locules. The ovules are borne at or near the centre on the axis formed by the union and fusion of the septa (partitions) and usually in vertical rows. e.g., Apple, Hibiscus etc. c. Parietal Placentation: In this type, the ovary has two or more carpels, and is syncarpous, and monolocular. Here there are as many placentae as the number ofcarpels and the ovules are attached to those placentae at the periphery. e.g., Cucurbita, Argemone.
d. Free Central placentation: In this type the ovary is monolocular, wherein the ovules are borne on a central axis that reaches the top of the ovary. e.g., Primula, Sandal Wood. e. Free basal placentation: Similar to free central but the placental column does not reach the top of the ovary. e.g., Portulaca, Celosia
Structure of mature anther: Anther Wall Layers : Anther wall consist of following layers : (1) Epidermis : Outermost, single layered and protective in function. The epidermis of Arceuthobium develops some fibrous thickenings and is called exothecium. (2) Endothecium : Cells of this layer have a-cellulosic fibrous bands arising from inner tangential wall which help in dehiscence of anther due to their hygroscopic nature. (3) Middle layer : Cells of this layer are ephemeral and are one-three layered. It degenerates at maturity. (4) Tapetum : This is the innermost layer of anther wall which surrounds the sporogenous tissue. Tapetal cells are nutritive. The tapetum has two types of cells: (a) Secretory or glandular tapetum : These cells secrete sporopollenin which help in the ornamentation of exine. (b) Amoeboid or plasmodial or invasive tapetum : Cells undergo breakdown and their entire protoplasts move in the centre to nourish microspores.
Structure of mature anther: Pollen sac (Microsporangium): an anther consists of two lobes. Each lobe has two cavities called pollen sac or microsporangia. A matured microsporangia consists of large number of pollen grains.
Structure of pollen grain: The branch of science that deals with the study of the characteristics of the pollen grains is called palynology. Each pollen grain is a haploid, unicellular mass of protoplast with a single nucleus. It is surrounded by a thick wall differentiated into two layers; the outer thick exine and the inner thin intine. The pollen grains reveal a wide range of microsculpturing of the exine. At one or more places, the exine is very thin or absent. These spots are called germ pores
Ovule: Ovule: It is defined as integumented megasporangium present within the ovary that develops into a seed. Funicle is the stalk that attaches ovule at maturity to the placenta. The place of attachment is Hilium. The mass of parenchyma cells forming the main body of ovule is the Nucellus. The basal part of the nucellus is called chalaza.
Ovules The nucellus is covered by one or two envelopes called integuments. At the tip the integuments leave an opening called Micropyle. Embeded in the nucellus is embryo sac or female gametophyte containing eight nuclei. They are egg nucleus with two synergids towards micropyle, three antipodals near chalazal end and two polar nuclei at the center.
Types of Ovules: (1) Orthotropous : The micropyle, chalaza and funicle are in a straight line. This is the most primitive type of ovule e.g., Piper, Polygonum, Cycas. (2) Anatropous : The ovule turns at 1800 angle. Thus it is inverted ovule. Micropyle lies close to hilum or at side of hilum e.g, found in 82% of angiosperm families. (3) Campylotropous : Ovule is curved more or less at right angle to funicle. Micropylar end is bend down slightly e.g., in members of Leguminosae, Cruciferae. (4) Hemianatropous : Ovule turns at 900 angle upon the funicle or body of ovule and is at right angle to the funicle e.g., Ranunculus. (5) Amphitropous : Ovule as well as embryo sac is curved like horse shoe e.g, Lemna, Poppy, Alisma. (6) Circinotropous : The ovule turns at more than 3600 angle, so funicle becomes coiled around the ovule e.g., Opuntia (Cactaceae), Plumbaginaceae.