Download Morphology of Flowering Plants

Morphology Of Flowering Plants
The angiosperms are all characterised by presence of roots, stems, leaves, flowers
and fruits.
For any successful attempt at classification and at understanding any higher plant
(or for that matter any living organism) we need to know standard technical terms
and standard definitions. We also need to know about the possible variations in
different parts, found as adaptations of the plants to their environment, e.g.,
adaptions to various habitats, for protection, climbing, storage, etc.
The Root
In majority of the dicotyledonous plants (The dicotyledons, also known as dicots (or
more rarely dicotyls), were one of the two groups into which all the flowering
plants or angiosperms were formerly divided. The name refers to one of the typical
characteristics of the group, namely that the seed has two embryonic leaves or
cotyledons), the direct elongation of the radicle leads to the formation of primary
root which grows inside the soil. It bears lateral roots of several orders that are
referred to as secondary, tertiary roots. The primary roots and its branches
constitute the tap root system, as seen in the mustard plant .
In monocotyledonous plants (monocots), the primary root is short lived and is
replaced by a large number of roots. These roots originate from the base of the stem
and constitute the fibrous root system, as seen in the wheat plant .In some plants,
like grass, Monstera and the banyan tree, roots arise from parts of the plant other
than the radicle and are called adventitious roots . The main functions of the root
system are absorption of water and minerals from the soil, providing a proper
anchorage to the plant parts, storing reserve food material and synthesis of plant
growth regulators.
Regions of the Root
The root is covered at the apex (the growing point of a shoot) by a thimble (cap)-like
structure called the root cap . It protects the tender apex of the root as it makes its
way through the soil. A few millimetres above the root cap is the region of
meristematic (A meristem is the tissue in most plants containing
undifferentiated cells (meristematic cells), found in zones of the plant where
growth can take place. Meristematic cells give rise to various organs of the
plant and keep the plant growing)activity. The cells of this region are very small,
thin-walled and with dense protoplasm. They divide repeatedly. The cells proximal
to this region undergo rapid elongation and enlargement and are responsible for the
growth of the root in length. This region is called the region of elongation. The cells
of the elongation zone gradually differentiate and mature. Hence, this zone,
proximal to region of elongation, is called the region of maturation. From this
region some of the epidermal cells form very fine and delicate, thread-like
structures called root hairs. These root hairs absorb water and minerals from the
soil.
Modifications of Root
Roots in some plants change their shape and structure and become modified to
perform functions other than absorption and conduction of water and minerals.
They are modified for support storage of food and respiration .Tap roots of carrot,
turnips and adventitious roots of sweet potato, get swollen and store food. Banyan
tree roots are called prop roots. Similarly, the stems of maize and sugarcane have
supporting roots coming out of the lower nodes of the stem. These are called stilt
roots. In some plants such as Rhizophora growing in swampy areas, roots come out
of the ground and grow vertically upwards. Such roots, called pneumatophores,
help to get oxygen for respiration.
Rhizophora
THE STEM
The stem is the ascending part of the axis bearing branches, leaves, flowers and
fruits. It develops from the plumule of the embryo of a germinating seed. The stem
bears nodes and internodes. The region of the stem where leaves are born are
called nodes while internodes are the portions between two nodes. The stem bears
buds, which may be terminal or axillary
(terminal, when located at the tip of a stem (apical is equivalent but rather reserved
for the one at the top of the plant);axillary, when located in the axil of a leaf (lateral
is the equivalent but some adventitious buds may be lateral too);
).
Stem is generally green when young and later often become woody and dark brown.
The main function of the stem is spreading out branches bearing leaves, flowers and
fruits. It conducts water, minerals and photosynthates. Some stems perform the
function of storage of food, support, protection and of vegetative propagation.
Plumule
After an ovule undergoes fertilization, a seed develops, growing a protective layer
known as the testa around the developing embryo. This embryo contains the three
parts listed above. Within a short time after fertilization, the plumule becomes
visible with at least two leaves that have a growing point held between them.
While the formation of a solid root system is important, the development of the
plumule is also instrumental in the plant's eventual thriving or failure. If the
plumule develops in a normal way, the shoot emerges from the seed and works its
way up through the soil and into the atmosphere. A healthy plumule develops
cotyledons, a special type of leaf that holds seeds; this is one of the most important
ways that these plants germinate.
Because these seeds are crucial to the spread of that particular species, a plumule
that fails to thrive not only threatens the health of that particular plant but the very
existence of dozens, if not hundreds, more down the line.
Modifications of Stem
The stem may not always be typically like what they are expected to be. They are
modified to perform different functions . Underground stems of potato, ginger,
turmeric, zaminkand, Colocasia are modified to store food in them. They also act as
organs of perenation to tide over conditions unfavourable for growth. Stem tendrils
which develop from axillary buds, are slender and spirally coiled and help plants to
climb such as in gourds (cucumber, pumpkins, watermelon) and grapevines.
Axillary buds of stems may also get modified into woody, straight and pointed
thorns. Thorns are found in many plants such as Citrus, Bougainvillea. They protect
plants from browsing animals. Some plants of arid regions modify their stems into
flattened (Opuntia), or fleshy cylindrical (Euphorbia) structures. They contain
chlorophyll and carry out photosynthesis. Underground stems of some plants such
as grass and strawberry, etc., spread to new niches (a shallow recess, especially one
in a wall to display a statue or other ornament) and when older parts die new plants
are formed. In plants like mint and jasmine a slender lateral branch arises from the
base of the main axis and after growing aerially (occurring in the air)for some time
arch downwards to touch the ground. A lateral branch with short internodes and
each node bearing a rosette of leaves and a tuft of roots is found in aquatic plants
like Pistia and Eichhornia. In banana, pineapple and Chrysanthemum, the lateral
branches originate from the basal (forming or belonging to a bottom layer or
base)and underground portion of the main stem, grow horizontally beneath the soil
and then come out obliquely (not in direct way) upward giving rise to leafy shoots.
Modifications of stem for : (a) storage (b) support (c) protection (d) spread and
vegetative propagation
THE LEAF
The leaf is a lateral, generally flattened structure borne on the stem. It develops at
the node and bears a bud in its axil. The axillary bud later develops into a branch.
Leaves originate from shoot apical meristems and are arranged in an acropetal
order. They are the most important vegetative organs for photosynthesis.
A typical leaf consists of three main parts: leaf base, petiole and lamina . The leaf is
attached to the stem by the leaf base and may bear two lateral small leaf like
structures called stipules. In monocotyledons, the leaf base expands into a sheath
covering the stem partially or wholly. In some leguminous plants the leafbase may
become swollen, which is called the pulvinus. The petiole help hold the blade to
light. Long thin flexible petioles allow leaf blades to flutter in wind, thereby cooling
the leaf and bringing fresh air to leaf surface. The lamina or the leaf blade is the
green expanded part of the leaf with veins and veinlets. There is, usually, a middle
prominent vein, which is known as the midrib. Veins provide rigidity to the leaf
blade and act as channels of transport for water, minerals and food materials. The
shape, margin, apex, surface and extent of incision (cut) of lamina varies in different
leaves.
Venation
The arrangement of veins and the veinlets in the lamina of leaf is termed as
venation. When the veinlets form a network, the venation is termed as reticulate
.When the veins run parallel to each other within a lamina, the venation is termed as
parallel .Leaves of dicotyledonous plants generally possess reticulate venation,
while parallel venation is the characteristic of most monocotyledons.
Types of Leaves
A leaf is said to be simple, when its lamina is entire or when incised, the incisions do
not touch the midrib.
When the incisions of the lamina reach up to the midrib breaking it into a number of
leaflets, the leaf is called compound.
A bud is present in the axil of petiole in both simple and compound leaves, but not in
the axil of leaflets of the compound leaf.
The compound leaves may be of two types : in a pinnately compound leaf a number
of leaflets are present on a common axis, the rachis, which represents the midrib of the
leaf as in neem.
In palmately compound leaves, the leaflets are attached at a common point, i.e., at
the tip of petiole, as in silk cotton.
Phyllotaxy
Phyllotaxy is the pattern of arrangement of leaves on the stem or branch. This is
usually of three types – alternate, opposite and whorled . In alternate type of
phyllotaxy, a single leaf arises at each node in alternate manner, as in china rose,
mustard and sun flower plants.
In opposite type, a pair of leaves arise at each node and lie opposite to each other as
in Calotropis and guava plants. If more than two leaves arise at a node and form a
whorl, it is called whorled, as in Alstonia.
China Rose
Calotropis
Alstonia
Modifications of Leaves
Leaves are often modified to perform functions other than photosynthesis. They are
converted into tendrils for climbing as in peas or into spines for defence as in cacti .
The fleshy leaves of onion and garlic store food .In some plants such as Australian
acacia, the leaves are small and short-lived. The petioles in these plants expand,
become green and synthesise food. Leaves of certain insectivorous plants such as
pitcher plant, venus-fly trap are also modified leaves.
THE INFLORESCENCE
A flower is a modified shoot where in the shoot: apical meristem changes to floral
meristem. Internodes do not elongate and the axis gets condensed. The apex
produces different kinds of floral appendages laterally at successive nodes instead
of leaves. When a shoot tip transforms into a flower, it is always solitary.
Depending on whether the apex gets converted into a flower or continues to grow,
two major types of inflorescences are defined – racemose and cymose. In racemose
type of inflorescences the main axis continues to grow, the flowers are borne
laterally in an acropetal succession (developing or opening in succession from
base to apex).
In cymose type of inflorescence the main axis terminates in a flower, hence is
limited in growth.The flowers are borne in a basipetal (produced in order from the
apex downwards so that the youngest are at the base)order .
In botany, a tendril is a specialized stem, leaf or petiole with a threadlike shape that
is used by climbing plants for support, attachment and cellular invasion by parasitic
plants, generally by twining around suitable hosts. They do not have a lamina or
blade, but they can photosynthesize.
THE FLOWER
The flower is the reproductive unit in the angiosperms. It is meant for sexual
reproduction. A typical flower has four different kinds of whorls arranged
successively on the swollen end of the stalk or pedicel, called thalamus or
receptacle. These are calyx, corolla, androecium and gynoecium. Calyx and corolla
are accessory organs, while androecium and gynoecium are reproductive
organs. In some flowers like lily, the calyx and
corolla are not distinct and are termed as perianth. When a flower has both
androecium and gynoecium, it is bisexual. A flower having either only stamens or
only carpels (the female reproductive organ of a flower, consisting of an ovary, a
stigma, and usually a style. It may occur singly or as one of a group) is unisexual.
In symmetry, the flower may be actinomorphic (radial symmetry) or zygomorphic
(bilateral symmetry). When a flower can be divided into two equal radial halves in
any radial plane passing through the centre, it is said to be actinomorphic, e.g.,
mustard, datura, chilli. When it can be divided into two similar halves only in one
particular vertical plane, it is zygomorphic, e.g., pea, gulmohur, bean, Cassia
(cinnamon). A flower is
asymmetric (irregular) if it cannot be divided into two similar halves by any
vertical plane passing through the centre, as in canna.
A flower may be trimerous, tetramerous or pentamerous when the floral
appendages are in multiple of 3, 4 or 5, respectively. Flowers with bracts, reduced
leaf found at the base of the pedicel, are called bracteate and those without bracts,
ebracteate.
Based on the position of calyx, corolla and androecium in respect of the ovary on
thalamus, the flowers are described as hypogynous perigynous and epigynous . In
the hypogynous flower the gynoecium (the female part of a flower, consisting of
one or more carpels)occupies the highest position while the other parts are situated
below it. The ovary in such flowers is said to be superior, e.g., mustard, china rose
and brinjal. If gynoecium is situated in the centre and other parts of the flower are
located on the rim of the thalamus almost at the same level, it is called perigynous.
The ovary here is said to be half inferior, e.g., plum, rose, peach. In epigynous
flowers, the margin of thalamus grows upward enclosing the ovary completely and
getting fused with it, the other parts of flower arise above the ovary. Hence, the
ovary is said to be inferior as in flowers of guava and cucumber, and the ray florets
of sunflower.
Thalamus: Insertion of Floral Leaves on Thalamus
In the below mentioned article, we will discuss about the insertion of floral
leaves on thalamus.
Thalamus (also called torus) is the axis of the floral shoot which is the direct
pro-longation of the pedicel and bears four sets of floral members.
Usually, it is a slightly swollen knob-like structure but sometimes it may be
somewhat elongated and conical bearing floral leaves spirally as in Artabotrys
, Michelia , etc., or like an inverted cone with a spongy flat top as in lotus , or it may
be slightly convex as in brinjal, etc. In perigynous and epigynous flowers the
thalamus becomes flat or cup-shaped as explained under leaf insertion.
The thalamus of most flowers has three internodes which are very much condensed.
But, in certain flowers these internodes are elongated. The first inter-node (between
calyx and corolla) is called the anthophore (anthos=flower), the second internode
(between corolla and androecium) is the androphore (also called gynandrophore)
and the third internode (between androecium and gynoecium) is called the
gynophore.
Cleome gynandra shows both androphore and gynophore (gynandrophore).
Capparis sepiaria and Pterospermum acerifolium show gynophores only. Passionflower (Passiflora suberosa of Passifloraceae) shows an androphore .
The thalamus is terminated by the pistil except in cases of monstrous development.
But, in the family Umbelliferae the thalamus normally projects into the ovary and
the carpels remain attached to it separating at maturity.
This prolongation of the thalamus is called the carpophore. This is seen in the fruits
of anise, Foeniculum, Coriandrum, etc.
Any portion of the thalamus may be modified in certain flowers into characteristic
structures called discs. The discs often bear nectar glands. Thus, the family Rutaceae
(orange, lemon, etc.) has fleshy annular discs surrounding the bases of the pistils .
In grape vine (Vitis sp. of Vitaceae) the disc is formed of some scaly structures . The
disc may be hypogynous, perigynous or epigynous according as it is below, around
or on the top of the ovary.
Insertion of Floral Leaves on the Thalamus:
In a typical flower the thalamus is a slightly swollen (conical, convex, etc.) struc-ture
with the calyx, corolla, androecium and gynoecium developed successively on it. It is
terminated by the pistil so that the gynoecium is on the top .
Such a flower is hypogynous (i.e., other members below gynoecium). The ovary here
is superior and other members inferior. This condition may be seen in many
common flowers like magnolia, mustard, brinjal, etc.
If the thalamus be flattened out to form a flat or a cup-shaped concave top, the
gynoecium will be placed not on the top of the flower but at the centre. The other
three whorls are usually inserted on the rim of the flat or the concave halamus.
Such an ovary may also be partially sunken in the thalamus. This is called the
perigynous condition as the other members surround the gynoecium. Examples of
the first (i.e., thalamus more or less flat) type may be found in the peas, strawberry,
etc., while the second type (thalamus forming a concave receptacle) is found in rose,
etc.
Here also the gynoecium is usually described as superior although it is not actually
on the top of the flower. Sometimes, the term half-inferior is used instead of
superior.
In a third type the cup-shaped thalamus as seen may fuse with the wall of the ovary
giving the appearance as in . It now appears that the gynoecium is the lowest or the
inferior whorl of the flower while all other members are superior, i.e., the condition
is epigynous.
Epigyny may be seen in the unisexual female flowers of cucurbits and in plants like
banana, guava, sunflower, etc. It should be noted that in an epigynous flower the
wall of the ovary has also got the thalamus fused with it.
Thus, any fruit developed out of this ovary has this thalamus tissue on the outside.
This statement is further strengthened by the fact that in some gooseberry one or
two foliage leaves are sometimes seen to develop on the fruit wall. This is possible
because of the stem nature of the thalamus.
Flower Anotomy
Lily
Datura: Jimson weed or Devil's snare
Plum
Peach
is used for extracting cinnamon
Cassia or Cinnamon , bark
Parts of a Flower
Calyx
The calyx is the outermost whorl of the flower and the members are called sepals.
Generally, sepals are green, leaf like and protect the flower in the bud stage. The
calyx may be gamosepalous (sepals united) or polysepalous (sepals free).
Corolla
Corolla is composed of petals. Petals are usually brightly coloured to attract insects
for pollination. Like calyx, corolla may be also free (gamopetalous) or united
(polypetalous). The shape and colour of corolla vary greatly in plants. Corolla may
be tubular, bell-shaped, funnel-shaped or wheel-shaped.
Aestivation: The mode of arrangement of sepals or petals in floral bud with respect
to the other members of the same whorl is known as aestivation. The main types of
aestivation are valvate, twisted, imbricate and vexillary. When sepals or petals in a
whorl just touch one another at the margin, without overlapping, as in Calotropis, it
is said to be valvate. If one margin of the appendage overlaps that of the next one
and so on as in china rose, lady’s finger and cotton, it is called twisted. If the
margins of sepals or petals overlap one another but not in any particular direction
as in Cassia and gulmohur, the aestivation is called imbricate. In pea and bean
flowers, there are five petals, the largest (standard) overlaps the two lateral petals
(wings) which in turn overlap the two smallest anterior petals (keel); this type of
aestivation is known as vexillary or papilionaceous.
Calotropis
Pea Flower
Androecium
Androecium is composed of stamens. Each stamen which represents
the male reproductive organ consists of a stalk or a filament and an
anther. Each anther is usually bilobed and each lobe has two chambers,
the pollen-sacs. The pollen grains are produced in pollen-sacs. A sterile
stamen is called staminode.
Stamens of flower may be united with other members such as petals or
among themselves. When stamens are attached to the petals, they are
epipetalous as in brinjal, or epiphyllous when attached to the perianth
(the outer part of a flower, consisting of the calyx (sepals) and
corolla (petals))as in the flowers of lily. The stamens in a flower may
either remain free (polyandrous) or may be united in varying degrees.
The stamens may be united into one bunch or one bundle
(monoadelphous) as in china rose, or two bundles (diadelphous) as in
pea, or into more than two bundles (polyadelphous) as in citrus. There
may be a variation in the length of filaments within a flower, as in Salvia
and mustard.
Gynoecium
Gynoecium is the female reproductive part of the flower and is made up of one or
more carpels. A carpel consists of three parts namely stigma, style and ovary.
Ovary is the enlarged basal part, on which lies the elongated tube, the style. The
style connects the ovary to the stigma.
The stigma is usually at the tip of the style and is the receptive surface for pollen
grains. Each ovary bears one or more ovules attached to a flattened, cushion-like
placenta. When more than one carpel is present, they may be free (as in lotus and
rose) and are called apocarpous. They are termed syncarpous when carpels are
fused, as in mustard and tomato. After fertilisation, the ovules develop into seeds
and the ovary matures into a fruit.
Placentation: The arrangement of ovules within the ovary is known
as placentation. The placentation are of different types namely,
marginal, axile, parietal, basal, central and free central .
In marginal placentation the placenta forms a ridge along the
ventral suture of the ovary and the ovules are borne on this ridge
forming two rows, as in pea.
When the placenta is axial and the
ovules are attached to it in a multilocular ovary, the placentaion is
said to be axile, as in china rose, tomato and lemon. In parietal placentation, the
ovules develop on the inner wall of the ovary or
on peripheral part. Ovary is one-chambered but it becomes two- chambered due to
the formation of the false septum (a partition separating two chambers, such as that
between the nostrils or the chambers of the heart), e.g., mustard and Argemone.
When the ovules are borne on central axis and septa are absent, as in Dianthus and
Primrose the placentation is called free central. In basal placentation, the placenta
develops at the base of ovary and a single ovule is attached to it, as in sunflower,
marigold.
Brinjal Flower
Lily Flower
Citrus
Salvia
Lemon Placentation
Tomato Placentation
Marigold Placentation
THE FRUIT
The fruit is a characteristic feature of the flowering plants. It is a mature or
ripened ovary, developed after fertilisation.
If a fruit is formed without fertilisation of the ovary, it is called a parthenocarpic
fruit.
Generally, the fruit consists of a wall or pericarp and seeds.
The pericarp may be dry or fleshy. When pericarp is thick and fleshy, it is
differentiated into the outer epicarp, the middle mesocarp and the inner
endocarp.
In mango and coconut, the fruit is known as a drupe. They develop from
monocarpellary (consisting of a single carpe) superior ovaries and are one
seeded. In mango the pericarp is well differentiated into an outer thin epicarp, a
middle fleshy edible mesocarp and an inner stony hard endocarp. In coconut
which is also a drupe, the mesocarp is fibrous.
The Seed
The ovules after fertilisation, develop into seeds. A seed is made up of a seed coat
and an embryo. The embryo is made up of a radicle, an embryonal axis (The embryo,
or immature plant, is divided into regions by an embryonic axis region that
eventually becomes the stem) and one (as in wheat, maize) or two cotyledons (as in
gram or chana and pea).
Structure of a Dicotyledonous Seed
The outermost covering of a seed is the seed coat. The seed coat has two layers, the
outer testa and the inner tegmen. The hilum is a scar on the seed coat through
which the developing seeds were attached to the fruit. Above the hilum is a small
pore called the micropyle. Within the seed coat is the embryo, consisting of an
embryonal axis and two cotyledons. The cotyledons are often fleshy and full of
reserve food materials. At the two ends of the embryonal axis are present the radicle
and the plumule. In some seeds such as castor the endosperm formed as a result
of double fertilisation, is a food storing tissue. In plants such as bean, gram and
pea, the endosperm is not present in mature seeds and such seeds are called nonendospermous.
Structure of Monocotyledonous Seed
Generally, monocotyledonous seeds are endospermic but some as in orchids are
non-endospermic. In the seeds of cereals such as maize the seed coat is
membranous and generally fused with the fruit wall. The endosperm is bulky and
stores food. The outer covering of endosperm separates the embryo by a proteinous
layer called aleurone layer. The embryo is small and situated in a groove at one end
of the endosperm. It consists of one large and shield shaped cotyledon known as
scutellum and a short axis with a plumule and a radicle. The plumule and radicle
are enclosed in sheaths which are called coleoptile and coleorhiza respectively.
Orchid
Maize or Corn
Wheat
Gram or Chana
Castor use for extracting oil
MORE ABOUT MONOCOTS AND DICOTS
Monocots and Dicots
Chart showing Differences
Monocot
Dicot
SEED
Monocots have only one seed leaf inside the seed coat. It is often only a thin leaf,
because the endosperm to feed the new plant is not inside the seed leaf.
Dicots have two seed leaves inside the seed coat. They are usually rounded and fat,
because they contain the endosperm to feed the embryo plant.
GERMINATION
Homeria
Lilium
Gloriosa
When a monocot seed germinates, it produces a single leaf. It is usually long and
narrow, like the adult leaf. Even when it is quite a round shape, there is only one
seed leaf in a monocot.
Eryngium
Sanguisorba
Cladanthus
When a dicot germinates, it produces two seedleaves. They contain the food for the
new plant, so they are usually fatter than the true leaves. The first true leaves are
often a different shape.
LEAVES
Washingtonia
Clivia
Canna
The leaves of monocots are often long and narrow, with their veins in straight lines
up and down the leaf. Sometimes, the veins run from the centre of the leaf to the
edge, parallel to one another.
Malva
Rosa
Campanula
Leaves of dicots come in many different shapes and sizes. The veins go from the
central midrib to the edge of the leaf, crossing and joining to form a netted pattern
all over the leaf.
STEM & ROOTS
Stem
Sheath
Root
The stems of monocots are usually unbranched and fleshy. They do not grow thicker
from year to year. New leaves often grow wrapped in a protective sheath formed by
the older leaf. The roots of dicots are usually short and stringy. Dicots often have
bulbs.
Stem
Stipule
Root
The stems of dicots are usually tough. They can grow wider each year and are often
branched. They sometimes have stipules at the base of the leaf. The root is often a
single long tap root with smaller roots growing from it.
FLOWER
Cyrtanthus
Pleione
Agapanthus
The parts of the flower of monocots are in threes. The sepals are often the same
colour as the petals, making it look as if the flower has six petals. There are usually
the same number of stamens as petals.
Oenothera
Epilobium
Geranium
The flowers of dicots usually have flower parts in fours or fives. The calyx is a
separate ring of sepals under the corolla, and is usually green.
SEEDPOD
Iris
Anthericum
Hedychium
The seed pods or fruits of monocots usually have three parts. The seeds are often
large and fleshy. The largest seed in the world, the Coco-de-Mer, and the smallest
seeds in the world, Orchid seeds, are both monocot seeds.
Lychnis
Erigeron
Clitoria
The seedpods or fruits and the seeds of dicots are very variable in shape, size and
texture. The seedpod can have any number of chambers, from none to many. There
are often more seeds in a seedpod than in a monocot seedpod.
SEMI-TECHNICAL DESCRIPTION OF A TYPICAL FLOWERING PLANT
Various morphological features are used to describe a flowering plant. The
description has to be brief, in a simple and scientific language and presented in a
proper sequence. The plant is described beginning with its habit, vegetative
characters – roots, stem and leaves and then floral characters inflorescence and
flower parts. After describing various parts of plant, a floral diagram and a floral
formula are presented. The floral formula is represented by some symbols. In the
floral formula, Br stands for bracteate K stands for calyx , C for corolla, P for
perianth, A for androecium and G for Gynoecium, G for superior ovary and G for
inferior ovary, for male, for female , for bisexual plants, ⊕ for actinomorphic and
for zygomorphic nature of flower. Fusion is indicated by enclosing the figure within
bracket and adhesion by a line drawn above the symbols of the floral parts. A floral
diagram provides information about the number of parts of a flower, their
arrangement and the relation they have with one another . The position of the
mother axis with respect to the flower is represented by a dot on the top of the floral
diagram. Calyx, corolla, androecium and gynoecium are drawn in successive whorls,
calyx being the outermost and the gynoecium being in the centre. Floral formula
also shows cohesion and adhesion within parts of whorls and in between whorls.
The floral diagram and floral formula in represents the mustard plant (Family:
Brassicaceae)
Floral formula is a means to represent the structure of a flower using numbers,
letters and various symbols, presenting substantial information about the flower in
a compact form. It can represent particular species, or can be generalized to
characterize higher taxa, usually giving ranges of organ numbers. Floral formulae
are one of the two ways of describing flower structure developed during the 19th
century, the other being floral diagrams.[2] The format of floral formulae differs
between authors, yet they tend to convey the same information.
Meaning of Floral Formula:
It is a symbolic and numerical representation of various floral parts. It also furnishes
information regarding symmetry, sexuality and interrelationship of various floral
parts viz., calyx, corolla, androecium and gynoecium.
Numerology of Symbols:
A number put just after the symbol represents the number of parts in that particular
whorl. If the parts of a whorl are united then the number is bracketed e.g.
If five free sepals are present the whorl is represented by K5 and if united it is
represented by K(5).
If there are more than one whorl of an organ, they are represented by the some of
their representative parts. If a flower has three whorls of five stamens each, then the
androecium is represented by A5+5+5.
If one organ is united with other organ then an arrow is made. It starts from the top
of one symbol and ends on the top of the symbol for the other organ with which
united e.g., if each of the five petals bears the stamens the union of two organs is
represented as below;
The epigenous condition of a flower is represented by a line placed above the
number of carpels. While its hypogenous condition is represented by under-lining
the number of its carpels e.g. The epigenous flower with five carpels is written G5
and the same type of hypogenous flower with five carpels is written as G5.
The missing organ is represented by putting a zero or 0 after its symbol. If the
number of organs in a whorl is more than ten its symbol is followed by the mark of
infinity or ∞.
Symbols Used in Construction of Floral Formula:
Symbols used in construction of floral formulae are as below:
How to Write Floral Formula?
The writing of floral formula one should start from bract and bracteole then
symmetry and sex of flower, calyx, corolla, androecium and gynoecium. The number
of parts of each organ is indicated in figures (1, …… 4, 5) after the relevant symbol
(K, C, A, G).
If the parts are free, the figure numeral is placed as such but if they are united, the
numeral figure is placed inside bracket (see numerology of symbols). In bilabiate
structure, the number of parts broken into two figures depending upon the number
of parts in the upper and lower lip.
Adnation of members of different whorls is shown by joining the top of their
symbols by a curved line
A break in the alternation of parts of any two successive floral cycles is indicated by
inserting a vertical line between the symbols of the two floral cycles. The position of
ovary whether, it is superior, half inferior or inferior is shown by placing a
horizontal line below in front and above the symbol of gynoecium respectively.
How to Read Floral Formula?
The following examples illustrate the methods of reading and constructing the
floral formulae:
The formulae read as follows:
Lathyrus:
Flower zygomorphic, hermaphrodite, gamosepalous, calyx with five sepals;
polypetalous, corolla with five petals; androecium with ten stamens, diadelphous;
gynoecium superior of one carpel.
Ipomoea:
Flower actinomorphic, hermaphrodite; calyx polysepalous with five sepals; corolla
gamopetalous with five petals; androecium with five free epipetalous stamens;
gynoecium syncarpous with two superior carpels.
The floral diagram is always drawn circular in outline. The different floral whorls
are represented in concentric circles, the sepals on the outermost circle, then the
petals, the stamens and carpels towards the inner side (Fig. 11.2 & 11.3).
The first step to draw a floral diagram is to examine mature floral buds which are
due to open shortly but have not yet opened.
Pluck the floral bud from the mother axis only after you have noted down the
anterior and posterior sides. Floral parts are drawn in a floral diagram as they
would be seen in their transverse sections below the mother axis.
Make the floral diagram in the following sequential stages:
1. A very small circle is drawn above the floral diagram. This circle represents the
mother axis. In actinomorphic flowers, the mother axis circle may be denoted as but
in zygomorphic flowers it is drawn as. If the flowers are terminal, the mother axis is
not drawn.
2. In bracteate flowers, a section of bract is drawn below the floral diagram. In
flowers without any bract, such a section is not drawn.
3. In bracteolate flowers, bracteoles are drawn in section on the left and right sides
of the diagram.
4. Note the number of sepals, their arrangement in relation to the mother axis and
their aestivation. Draw transverse sections of sepals between the mother axis and
the bract, keeping all these points in view. In case of odd number of sepals, the odd
sepal would be drawn either posterior or anterior to the flower, i.e., opposite the
mother axis or opposite the bract, respectively.
5. The same procedure is repeated for petals as for sepals. However petals should be
drawn alternate with the sepals.
6. If the flower is zygomorphic, petals are drawn of unequal sizes. Same may be the
case with the sepals also in zygomorphic flowers.
7. If any sepal or petal is spurred, it is shown by drawing a loop at the back of that
particular part in the floral diagram.
8. If parts of sepals or of petals are fused, draw lines to connect their edges together
in the floral diagram.
9. In the epipetalous condition (i.e. when stamens are joined with petals), link the
stamens and petals with small radial lines.
10. In case of bilabiate calyx or corolla, the two lips are joined by bulging lines.
11. Count the number of stamens, the number of whorls in which they are arranged,
their cohesion and agnation to other floral parts, their position in relation to petals,
their introse or extrose position, and draw them inside the petals in the floral
diagram. Stamens are represented through transverse sections of the anthers. In the
obdiplostemonous condition, the stamens of the outer whorl are drawn opposite to
the petals. Introse stamens face towards the centre whereas the extrose towards the
petals. Staminodes are represented either by an asterisk (*) or by a cross (x).
12. The gynoecium is represented by a transverse section of the ovary. Also draw
the number of locules and the number of ovules in each loculus in the ovary. Type of
placentation is also drawn.
Actinomorphic: characterized by radial symmetry, such as a starfish or the flower of
a daisy.
Floral symmetry describes whether, and how, a flower, in particular its perianth,
can be divided into two or more identical or mirror-image parts.
Uncommonly, flowers may have no axis of symmetry at all, typically because their
parts are spirally arranged.
Actinomorphic[edit]
Further information: Merosity
Wurmbea stricta, its tepals in actinomorphic arrangement
Most flowers are actinomorphic ("star shaped", "radial"), meaning they can be
divided into 3 or more identical sectors which are related to each other by rotation
about the centre of the flower. Typically, each sector might contain one tepal or one
petal and one sepal and so on. It may or may not be possible to divide the flower
into symmetrical halves by the same number of longitudinal planes passing through
the axis: Oleander is an example of a flower without such mirror planes.
Actinomorphic flowers are also called radially symmetrical or regular flowers. Other
examples of actinomorphic flowers are the lily (Lilium, Liliaceae) and the buttercup
(Ranunculus, Ranunculaceae).
Zygomorphic[edit]
Satyrium carneum. Ground orchid with typical zygomorphic floral anatomy
Zygomorphic ("yoke shaped", "bilateral" - from the Greek ζυγόν, zygon, yoke, and
μορφή, morphe, shape) flowers can be divided by only a single plane into two
mirror-image halves, much like a yoke or a person's face. Examples are orchids and
the flowers of most members of the Lamiales (e.g., Scrophulariaceae and
Gesneriaceae). Some authors prefer the term monosymmetry or bilateral
symmetry.[1]
Asymmetric[edit]
A few plant species have flowers lacking any symmetry, and therefore having a
"handedness". Examples are Valeriana officinalis and Canna indica.[2]
Differences[edit]
Actinomorphic flowers are a basal angiosperm character; zygomorphic flowers are a
derived character that has evolved many times.[3]
Some familiar and seemingly actinomorphic so-called flowers, such as those of
daisies and dandelions (Asteraceae), and most species of Protea, are actually
clusters of tiny (not necessarily actinomorphic) flowers arranged into a roughly
radially symmetric inflorescence of the form known as a head, capitulum, or
pseudanthium.
Peloria[edit]
Digitalis purpurea (common foxglove) displaying an aberrant peloric terminal
flower and normal zygomorphic flowers
Peloria or a peloric flower refers to an aberration in which a plant that normally
produces zygomorphic flowers produces actinomorphic flowers instead. This
aberration can be developmental, or it can have a genetic basis: the CYCLOIDEA
gene controls floral symmetry. Peloric Antirrhinum plants have been produced by
knocking out this gene.[3] Many modern cultivars of Sinningia speciosa ("gloxinia")
have been bred to have peloric flowers as they are larger and showier than the
normally zygomorphic flowers of this species.
Charles Darwin explored peloria in Antirrhinum (snapdragon) while researching the
inheritance of floral characteristics for his The Variation of Animals and Plants under
Domestication.[4] Later research, using Digitalis purpurea, showed that his results[5]
were largely in line with Mendelian theory.[6]
Floral symmetry groups[edit]
If we consider only those flowers which consist in a single flower, rather than a
flower head or inflorescence, we can group the flowers into a relatively small
number of 2D symmetry groups. Monocots are identifiable by their trimerous petals,
thus monocots often have rotational symmetry of order 3. If the flower also has 3
lines of mirror symmetry the group it belongs to is the dihedral group D3. If not,
then it belongs to the cyclic group C3. Eudicots with tetramerous or pentamerous
petals may have rotational symmetry of order 4 or 5. Again, whether they also have
mirror planes decides whether they belong to dihedral (D4 and D5) or cyclic groups
(C4 or C5). The sepals of some monocot flowers develop to replicate the petals, thus,
superficially, certain monocots can appear to have rotational symmetry of order 6
and belong to either symmetry group D6 or C6. It must be remembered however,
that flower symmetry is rarely perfect in the way that geometric symmetry is. The
general layout of a flower belongs to the above symmetry groups, but an individual
flower will not show exact symmetry.
The Brassicaceae are a medium-sized and economically important family of
flowering plants (angiosperms), informally known as the mustards, the mustard
flowers, the crucifers, or the cabbage family.
The name Brassicaceae is derived from the included genus Brassica. An older name,
Cruciferae (English /kruːˈsɪfəri/), meaning "cross-bearing", describes the four
petals of mustard flowers, which resemble a cross; it is one of eight plant family
names without the suffix -aceae that are authorized alternative names (according to
ICBN Art. 18.5 and 18.6 Vienna Code); thus both Cruciferae and Brassicaceae are
used.
The family contains 372 genera and 4060 accepted species.[2] The largest genera are
Draba (440 species), Erysimum (261 species), Lepidium (234 species), Cardamine
(233 species), and Alyssum (207 species).
The family contains the cruciferous vegetables, including species such as Brassica
oleracea (e.g., broccoli, cabbage, cauliflower, kale, collards), Brassica rapa (turnip,
Chinese cabbage, etc.), Brassica napus (rapeseed, etc.), Raphanus sativus (common
radish), Armoracia rusticana (horseradish), Matthiola (stock) and the model
organism Arabidopsis thaliana (thale cress).
Pieris rapae and other butterflies of the family Pieridae are some of the best-known
pests of Brassicaceae species planted as commercial crops.
The Fabaceae, Leguminosae or Papilionaceae,[6] commonly known as the legume,
pea, or bean family, are a large and economically important family of flowering
plants. It includes trees, shrubs, and perennial or annual herbaceous plants, which
are easily recognized by their fruit (legume) and their compound, stipulated leaves.
The family is widely distributed, and is the third-largest land plant family in terms of
number of species, behind only the Orchidaceae and Asteraceae, with about 751
genera and some 19,000 known species[7][8][9] . The five largest of the genera are
Astragalus (over 3,000 species), Acacia (over 1000 species), Indigofera (around 700
species), Crotalaria (around 700 species) and Mimosa (around 500 species), which
constitute about a quarter of all legume species. The ca. 19,000 known legume
species amount to about 7% of flowering plant species.[8][10] Fabaceae is the most
common family found in tropical rainforests and in dry forests in the Americas and
Africa.[11]
Recent molecular and morphological evidence supports the fact that the Fabaceae is
a single monophyletic family.[12] This point of view has been supported not only by
the degree of interrelation shown by different groups within the family compared
with that found among the Leguminosae and their closest relations, but also by all
the recent phylogenetic studies based on DNA sequences.[13][14][15] These studies
confirm that the Fabaceae are a monophyletic group that is closely related to the
Polygalaceae, Surianaceae and Quillajaceae families and that they belong to the
order Fabales.[16]
Along with the cereals, some fruits and tropical roots a number of Leguminosae
have been a staple human food for millennia and their use is closely related to
human evolution.[17]
A number are important agricultural and food plants, including Glycine max
(soybean), Phaseolus (beans), Pisum sativum (pea), Cicer arietinum (chickpeas),
Medicago sativa (alfalfa), Arachis hypogaea (peanut), Lathyrus odoratus (sweet pea),
Ceratonia siliqua (carob), and Glycyrrhiza glabra (liquorice). A number of species are
also weedy pests in different parts of the world, including: Cytisus scoparius
(broom), Robinia pseudoacacia (black locust), Ulex europaeus (gorse), Pueraria
lobata (kudzu), and a number of Lupinus species.
In botany, a bract is a modified or specialized leaf, especially one associated with a
reproductive structure such as a flower, inflorescence axis, or cone scale. Bracts are
often (but not always) different from foliage leaves. They may be smaller, larger, or
of a different color, shape, or texture. Typically, they also look different from the
parts of the flower, such as the petals and/or sepals. The state of having bracts is
referred to as bracteate or bracteolate, and conversely the state of lacking them is
referred to as ebracteate and ebracteolate, without bracts.
DESCRIPTION OF SOME IMPORTANT FAMILIES
Fabaceae
This family was earlier called Papilonoideae, a subfamily of family Leguminosae. It is
distributed all over the world.
Vegetative Characters
Trees, shrubs, herbs; root with root nodules
Stem: erect or climber
Leaves: alternate, pinnately compound or simple; leaf base, pulvinate; stipulate;
venation reticulate.
Floral characters
Inflorescence: racemose
Flower: bisexual, zygomorphic
Calyx: sepals five, gamosepalous; imbricate aestivation
Corolla: petals five, polypetalous, papilionaceous, consisting of a posterior standard,
two lateral wings, two anterior ones forming a keel (enclosing stamens and pistil),
vexillary aestivation
Androecium: ten, diadelphous, anther dithecous
Gynoecium: ovary superior, mono carpellary, unilocular with many ovules, style
single
Fruit: legume; seed: one to many, non-endospermic Floral Formula: ⊕ K(5)
C1+2+(2) A(9)+1 G1
Economic importance
Many plants belonging to the family are sources of pulses (gram, arhar, sem, moong,
soyabean; edible oil (soyabean, groundnut); dye (indigofera); fibres (sunhemp);
fodder (Sesbania, Trifolium), ornamentals (lupin, sweet pea); medicine (muliathi).
Solanaceae
It is a large family, commonly called as the ‘potato family’. It is widely distributed in
tropics, subtropics and even temperate zones (Figure 5.22).
Vegetative Characters
Plants mostly, herbs, shrubs and small trees
Stem: herbaceous rarely woody, aerial; erect, cylindrical, branched, solid
or hollow, hairy or glabrous, underground stem in potato (Solanum tuberosum)
Leaves: alternate, simple, rarely pinnately compound, exstipulate; venation
reticulate
Floral Characters
Inflorescence : Solitary, axillary or cymose as in Solanum Flower: bisexual,
actinomorphic
Calyx: sepals five, united, persistent, valvate aestivation Corolla: petals five, united;
valvate aestivation Androecium: stamens five, epipetalous
Gynoecium: bicarpellary, syncarpous; ovary superior, bilocular, placenta swollen
with many ovules
Fruits: berry or capsule
Seeds: many, endospermous
Floral Formula: (refer to the book)
Economic Importance
Many plants belonging to this family are source of food (tomato, brinjal, potato),
spice (chilli); medicine (belladonna, ashwagandha); fumigatory (tobacco);
ornamentals (petunia).
Lilaceae
Commonly called the ‘Lily family’ is a characteristic representative of
monocotyledonous plants. It is distributed world wide (Figure 5.23).
Vegetative characters: Perennial herbs with underground bulbs/corms/ rhizomes
Leaves mostly basal, alternate, linear, exstipulate with parallel venation Floral
characters
Inflorescence: solitary / cymose; often umbellate clusters
Flower: bisexual; actinomorphic
Perianth tepal six (3+3), often united into tube; valvate aestivation Androcium:
stamen six, (3+3)
Gynoecium: tricarpellary, syncarpous, ovary superior, trilocular with many ovules;
axile placentation
Fruit: capsule, rarely berry
Seed: endospermous
Floral Formula: ⊕ P3+3 A3+3 G(3)
Economic Importance
Many plants belonging to this family are good ornamentals (tulip, Gloriosa), source
of medicine (Aloe), vegetables (Asparagus), and colchicine (Colchicum autumnale).
Pisum sativum (pea) plant : (a) Flowering twig (b) Flower (c) Petals (d)
Reproductive parts (e) L.S.carpel (f) Floral diagram
Allium cepa (onion) plant : (a) Plant (b) Inflorescence (c) Flower (d) Floral diagram