MORPHOLOGY OF FLOWERING PLANTS

Morphology is derived from the word morphos which means forms and morphology is the science which deals with the study of forms, size, colour, structure and their relative position of different organs in the organism.

Plant morphology generally includes the study of external features, forms, relative position of organs of plants and their adaptation.

Adaptation is any modification in the structure or function of an organism that results from natural selection and by which the organism becomes more suited to the environment.

Flowering plants consist of roots, stems, leaves. flowers, fruits and seeds.

The Root

The underground part of the plant developed from elongation of radicles of the embryo is Root. It helps in anchorage of plants in soil and absorption of water and minerals from soil.

Primary root: It is formed by the direct elongation of the radicle present in the majority of the dicotyledonous plants. Primary root bears lateral roots of several orders that are called secondary. tertiary, etc., roots.

Functions of root

(1) Anchorage of the plant in soil.

(2) Stores reserve food material and synthesize plant growth regulators such as cytokinins.

(3) Absorption of water and minerals from the soil.

Types of root

(1) True root: The root that develops from the radicle and grows deep inside the soil.

(2) Adventitious root: The root that develops from an organ other than the radicle and does not grow deep into the soil.

Types of root system

(Root System: Root with its branches is known as root system)

Tap root system	Fibrous root system	Adventitious root system
Develops from the radicle.	Develops from the base of the stem.	Develops from parts of the plant other than the radicle.
Found in dicotyledonous plants (e.g. gram and mango).	Found in monocotyledonous plants (e.g., wheat and paddy).	E.g. Banyan tree and Maize

Regions of the root

(1) Root Cap: The tip of the root is covered by a thimble-like structure called a root cap. Root cap is made up from a meristem called calyptrogen. It performs the function of protection of root tip against any injury.

(2) Region of meristematic activity: It is about 1 mm in length. This is a region of rapid cell division, in which the cells are small thin-walled and meristematic cells having dense cytoplasm.

(3) Region of elongation: This region is about 4-8 mm in length. Cells of this region do not divide but they undergo rapid elongation and enlargement. These cells are responsible for growth of root length. The external cells possess the power of absorption of water and mineral salts from the soil.

(4) Region of Maturation (Root hair zone): This region has differentiated and matured cells. This region does not undergo further changes. It lies adjacent to the region of elongation. The outmost Layer of this region has thick-walled or permeable cells. So this region cannot help the root in water absorption. Its only function is to anchor the plant firmly in the soil Lateral roots also arise from the interior part of this region.

Root hairs are thread-like structures present in the zone of differentiation or maturation It is about 1-6 cm in length. Most of the water and mineral absorption occurs in this region as the root hair increases the surface area of the root for better absorption.

The Stem

Stem is the aerial part of the plant body developed from plumule and epicotyl of germinating seeds. It bears nodes (region of the stem where leaves are born) and internodes (portions between two nodes). Stem branches are exogenous in origin Stems also bear buds (terminal or axillary). Stem is negatively geotropic and positively phototropic as it grows away from the soil towards sunlight. Stem performs the function of exposure of leaves, flowers and fruits. conduction of water and minerals, translocation of food.

The Leaf

It arises from the shoot apical meristem and produces food by photosynthesis. A typical leaf has three elements leaf base (hypopodium). petiole and Lamina (leaf blade).

(1) Leaf Base (Hypopodium): This is the point at which a leaf joins the stem Stipules are two little leaf-like structures at the base of the leaf. This leaf base is wide and covers the stem in monocotyledons like rice, wheat, and other monocotyledons.

(2) Petiole (Mesopodium): It is a cylindrical or subcylindrical smooth or grooved stalk of the leaf which lifts the lamina above the level of stem so as to provide it with maximum exposure. Leaf having petiole is called petiolate and sessile when petiole is absent.

(3) Lamina (Epipodium or leaf blade): It is the terminal thin, expanded, green and conspicuous part of the leaf which is specialised to perform photosynthesis. It is supported by veins and veinlets. There are two surfaces of lamina adaxial (ventral) towards the upper part of stem and abaxial (dorsal) towards the lower part of the stem.

Important

Some legume plants develop swollen leaf bases which are known as pulvinus.

Venation An arrangement of veins and veinlets within a leaf lamina is called venation. There are two types of venation:

Reticulate Venation	Parallel Venation
Veins are arranged as a network or web-like structure.	Veins run parallel to one another.
Found In leaves of dicotyledonous plants.	Found in leaves of monocotyledonous plants.
Examples: China rose and Peepal.	Examples: Grass, Maize and Sugarcane

Types of Leaf

(1) Simple leaves: Those leaves that have single undivided lamina are known as simple leaves.

The lobes of a simple leaf may be pinnately arranged (such as the Brassica) or palmately arranged (such as the Gossypium, Passiflora. and Ricinus).

(2) Compound leaves: Compound leaves are those in which the lamina or leaf blade is entirely divided into many units called leaflets or pinnae.

Pinnately compound leaves and palmately compound leaves are two types of compound leaves.

(1) Pinnately compound leaves: A common type of compound leaf in which the leaflets are divided into two rows and the rachis is long and elongated. E.g. Neem and rose.

(2) Palmately compound leaves: At the tip of the petiole, the leaflets are arranged palmately in accordance with the number of leaflets present. Leaflets are attached to common points at the petiole tip. E.g. Silk and cotton.

Phyllotaxy

Leaves are arranged in a pattern on the stem or branch known as phyllotaxy. Following are the different types of phyllotaxy:

(1) Alternate: In this type of phyllotaxy, leaves originate alternately at each node. E.g. China rose and Mustard.

(2) Opposite: At each node of opposite type, there are two leaves arranged oppositely. E.g. Calotropis and Guava.

(3) Whorled: When a node has more than two leaves that arise at the same time and form a whorl E.g. Nerium and Alstonia.

INFLORESCENCЕ

It is the arrangement of flowers on the floral axis (Peduncle). There are two main types of Inflorescence:

Racemose	Cymose
It shows unlimited growth in the axis.	It shows limited growth in the axis.
Order of opening of flower is centripetal.	Order of opening of flower is centrifugal.
Main axis continues to grow.	Main axis terminates into a flower.
E.g., Radish, Mustard and Amaranthus.	E.g., Cotton, Jasmine and Calotropis.

THE FLOWER

Flower is a specialised condensed shoot of an angiospermic plant in which the shoot apical meristem gets transformed into a floral meristem and it is also known as the reproductive unit of plant. There are four types of organs found in a flower - sepals (green in colour), petals (colourful structure), stamen (male reproductive part of flower) also known as androecium and lastly, carpels (female reproductive part of flower) also known as gynoecium.

Flowers have short or long flower stalks which are called pedicels. Thalamus/Receptacle is the conical or spherical upper part of the pedicel.

Types of Flowers

Flowers are classified under different categories depending on their symmetry, number of appendages and ovary position.

On the basis of symmetry

(1) Actinomorphic (Radial symmetry): An actinomorphic flower is a flower with two equal radial halves when cut from any plane that passes through its centre. E.g. Mustard and Datura.

(2) Zygomorphic (Bilateral symmetry): When a flower can be divided into two similar halves only in one vertical plane, it is called a zygomorphic flower. E.g. Pea, Bean and Gulmohar.

(3) Asymmetric (Irregular): When a flower cannot be divided into two identical halves by any vertical plane passing through the middle, it is asymmetric (irregular). E.g., Canna.

On the basis of floral appendages

(1) Trimerous flower: Floral appendages in multiple of three.

(2) Tetramerous flower: Floral appendages in multiple of four.

(3) Pentamerous flower: Floral appendages in multiple of five.

On the basis of position of calyx, corolla and androecium with respect to ovary

(1) Hypogynous: Here, Ovary is superior and petals. sepals and stamens are located below the ovary. E.g., Mustard and China rose.

(2) Perigynous: The thalamus grows upwards into a cup-shaped structure, such that the gynoecium is positioned in the centre and other parts of the flower are positioned on the rim of the thalamus almost at the same level. The ovary will be half inferior or half superior. E.g., Plum, Peach and Rose.

(3) Epigynous: The ovary is enclosed completely by the thalamus and is fused with it, while the rest of the flower parts grows above the ovary, and thus the ovary is said to be inferior. E.g. Guava and Cucumber.

Important

Flower can be bisexual if have both androecium and gynoecium or it may be unisexual if it has only androecium/ stamen or only gynoecium/carpel.

Aestivation

Aestivation is the arrangement of accessory floral organs (sepals or petals) in relation to one another in the floral bud. Following are the four different types of aestivation found in flowers.

(1) Valvate: There is no gap between the petals or sepals of the same whorl and they just touch each other end when they are adjacent but do not overlap. E.g., Calotropis

(2) Twisted: A petal has two parts, one of which is covered by the adjacent petals and the other by the posterior petals. E.g. China rose, cotton and lady finger.

(3) Imbricate: A sepal or a petal is overlapping. but not in a definite direction. E.g. Cassia and Gulmohar.

(4) Vexillary or papilionaceous: Out of the five petals the largest petal (standard) overlaps the two lateral petals (wings), which overlap the two smallest anterior petals (keels). E.g., Bean and Pea.

Parts of a Flower

Calyx

In most flowers, the calyx is the outermost whorl of the flower, and the individual calyx is known as sepal Generally, sepals are green and leaf-like and they protect the flower during the bud stage. The calyx can be gamopetalous (sepals united) or polysepalous (sepals free).

Corolla

Corolla is composed of petals and is the second whorl They are usually brightly coloured and help in attracting insects for pollination. Corolla can be tubular-shaped, bell-shaped, funnel-shaped or wheel-shaped. Corolla can be gamopetalous (petals united) or polypetalous (petals free).

Important

When there is no distinction between sepals and petals. then there is perianth. They may be sepaloid (greenish) or petaloid (colourful) The individual parts of the perianth are known as tepals. Examples: Onion, lily, etc.

Androecium

Androecium is a male reproductive organ composed of stamens. It is the third whorl of flower part. Each stamen consists of a stalk or a filament and an anther lobes which contain pollen grains. A sterile stamen is called staminode.

Stamen can be:

(1) Epipetalous: Stamens are attached to the petals., e.g., Brinjal.

(2) Epiphyllous: Stamens attached to the perianth. e.g., Lily flowers.

(3) Monadelphous: Stamens united into one bundle. e.g., China rose.

(4) Diadelphous: Stamens united into two bundles. e.g. Pea.

(5) Polyadelphous: Stamens united into more than two bundles, e.g. Citrus.

Anther: Anther is a pollen-producing part. Each anther has two lobes (bilobed) containing pollen sacs (also known as microsporangia). The pollen grains (male gametophyte) are produced inside the pollen sacs.

Filament: Stalk-like structure that attaches to the base of the flower.

Gynoecium

Gynoecium is a female reproductive organ composed of carpels. Carpels consist of stigma, style and ovary. It is the third or innermost whorl and is also called pistil.

Ovary: It is an enlarged basal part on which lies in the elongated tube, the style. This style connects to the ovary to the stigma. Each ovary has ovules attached to the placenta.

Stigma: Sticky part present on the tip of the style. Stigma is a receptive surface for pollen grains.

Placentation

Placenta is a parenchymatous cushion present inside the ovary where ovules are borne. An ovary may have one or more placentae. The number, position and distribution or arrangement of placentae inside the ovary is known as placentation.

Types of Placentation:

(1) Marginal: A marginal placenta is found in the unilocular ovary. It forms a ridge along the ventral suture of the ovary, and the ovules are borne in two rows along this ridge. E.g. Pea.

(2) Axile: Axile placentation, in which the ovules are attached to the axial placenta in a multilocular ovary. E.g., Lemon.

(3) Parietal: This kind of placentation is found in the unilocular syncarpous ovary. In it the ovule originates on the inner wall of the ovary or on the peripheral part. E.g., Argemone.

(4) Free central: When there are no septa and ovules are borne on the central axis, the placentation is free central. E.g., Dianthus and Primrose.

(5) Basal: Placenta develop at the base of ovary. E.g., Sunflower and Marigold.

THE FRUIT

A true fruit or eucarpic fruit is a ripened ovary which develops under the influence of ripening ovules and is meant for protecting them. It consists of a pericarp formed from the ovary and seeds formed from ovules. A fruit in which other floral parts like thalamus, base of sepals, petals, etc., fuse with pericarp is called false fruit, accessory fruit or pseudocarp. Examples: Apple, Mulberry, Strawberry, etc. A fruit formed without fertilisation, Le. a seedless fruit Is called parthenocarpic or parthenocarp fruit. Example: Banana.

Fruit (ripened ovary) is made up of seeds and a wall called pericarp. Pericarp is a thick and fleshy part, made up of Epicarp (outer), Mesocarp (middle) and Endocarp (inner).

Important

Ovaries are the source of true fruits. False fruits can emerge from any portion of the plant other than the ovary. Apple is a false fruit since it does not grow from the ovary. In parthenocarpic plants, fruit develops without fertilisation.

Types of Fruit

Fruits are categorised into three classes according to the number of ovaries and flowers involved in the fruit formation process:

(1) Simple Fruits: A simple fruit generally develops from the simple or compound ovary of flower. It can be dry (dry pericarp) or succulent (pericarp fleshy). Examples: Tomato, Grapes, Pear, Plum. etc.

(2) Aggregate Fruits: An aggregate fruit or etaerio is a group of simple fruitlets that are made up of several developed free ovaries that form in a single flower. Fruitlets are the individual ovaries. Aggregate fruits include fruits like blackberry. raspberry and strawberry.

(3) Composite Fruits: A composite or multiple fruits is a group of fruitlets which develops from the different flowers of an inflorescence. Examples: Peepal, Pineapple, Jackfruit, etc.

Important

Drupe: Fruit of mango and coconut is termed as drupe. Such fruits develop from monocarpellary superior ovaries and consist of a single seed.

The pericarp is differentiated in mango as:

(1) an outer thin epicarp.

(2) a middle fleshy edible mesocarp (in case of coconut mesocarp Is fibrous).

(3) an inner stony hard endocaгр.

THE SEED

The seeds are composed of a seed coat and an embryo. The embryo of a seed has a radicle, an embryonal axis, and has one cotyledon (as in wheat or corn) or two cotyledons (as in gram or pea).

Monocotyledonous Seed

Monocot seeds, sometimes known as monocotyledons, include corn, wheat, and rice. Scutellum is the only large cotyledon found in monocotyledonous seed embryos. The scutellum is a shield-shaped structure that occurs laterally to one side of the embryo axis.

Monocotyledons have a branch tip, plumule that is enclosed in a sheath called coleoptile, and a root point, radicle, that is enclosed in coleorhiza, just like dicotyledons. The endosperm of monocotyledonous seeds is protected by a proteinous covering known as the aleurone layer.

The bulk of monocotyledonous seeds is albuminous, meaning they have thick, swollen endosperms that provide nutrition. Hence, monocotyledonous seeds are also called albuminous seeds. Endosperm is the feeding tissue in seeds that are not completely consumed throughout embryo development. Some monocotyledons, such as orchids, are exceptions as endosperm is absent in them. Ginger, banana. coconut, and garlic are examples of monocot seeds.

Dicotyledonous Seed

Dicotyledonous seeds include peas, almonds, and cashews. Dicots are another name for dicotyledons. The word dicotyledons refer to the fact that the seed has two cotyledons. The embryo of a dicotyledonous seed comprises an embryo axis and two cotyledons.

The swollen look of cotyledons is due to the fact that they serve as a reserve food resource for the developing embryo. There are two ends to the embryo axis. The plumule is the portion at the upper end that develops the shoot tip, while the radicle is the region at the lower end that makes the root tip.

The seed coat is a protective shell that surrounds the entire surface. The seed coat is composed of two layers-testa on the outside and tegmen on the inside. Furthermore, a structure known as the hilum connects the seed to the fruit Gram seed is dicotyledonous. The stored food is also present in the cotyledons. An endosperm is absent Gram seed is, therefore, dicotyledonous seed.

Monocotyledonous Seed	Dicotyledonous Seed
The seed contains a single cotyledon.	The seed possesses two cotyledons.
The food is commonly stored inside endosperm (except-Orchids).	The food may be stored inside endosperm or cotyledon.
An aleurone layer of special protein rich cell is found on the outside of endosperm.	This layer is commonly absent in dicots.
The embryo tip may bear special sheaths, coleoptile over plumule and coleorhiza over radicle.	Coleoptile and coleorhiza are absent.
Embryo occupies one side of the seed.	Embryo occupies the whole interior or only the central part of the seed.
Plumule lies at one end near the cotyledon.	Plumule lies in between the two cotyledon.

FLORAL DIAGRAM AND FLORAL FORMULA

Morphological features are used to describe a particular flowering plant species. It needs to be in simple scientific language, brief, and in a proper sequence. The plant is described by its habitat, vegetative characteristics like roots, stems and leaves, and its floral characteristics like-inflorescence and flower parts. After describing the morphology of the plant we proceed to its floral diagram and floral formula.

Floral Diagram

A floral diagram is a diagrammatic representation of flower structure and shows various parts of the flower, their number, their arrangement, and their fusion.

Floral Formula

It is the symbolic representation of floral symmetry, presence or absence, number, cohesion and adhesion of various parts.

A floral formula is a notation that uses numbers, letters, and symbols to give information about the morphology of a flower and its organs. It is used for systematic study and quick comprehension of all the diagnostic features of a flowering plant or a family.

The floral formula gives some extra information like placentation, the position of the mother axis, aestivation, etc., of a flowering plant.

Habit and Habitat of Flowering Plants Habit

It can be a herb, shrub, tree, climber, or creeper.

Habitat It can be hydrophyte, xerophyte, or mesophyte.

(1) Hydrophyte plants are those plants that are adapted to live in an aquatic environment.

(2) Xerophytes are those plants that are adapted to live in dry habitats like deserts.

(3) Mesophytes are those plants that are terrestrial but are neither adapted to particularly dry nor particularly wet environments.

Floral Characters of Flowering Plants

(1) Inflorescence: It can be racemose or cymose.

(2) Flower parts: Can be Bracteate or Ebracteate: Sessile or Pedicellate; Unisexual or Bisexual and Actinomorphic or Zygomorphic.

(3) Calyx: Gamosepalous (sepals united) or Polysepalous (sepals free).

(4) Corolla: Gamopetalous (petals united) or Polypetalous (petals free).

(5) Gynoecium: Apocarpous (free carpels) or Syncarpous (fused carpels).

(i) Нуроgynous (Superior Ovary)

(ii) Perigynous (Half inferior Ovary).

(iii) Epigynous (Inferior Ovary).

(6) Androecium:

(i)Staminode (Sterile Stamen)

(ii) Epipetalous (Stamens attached to Petals),

(iii) Epiphyllous (Stamens attached to Perianth).

(iv) Polyandrous (Free stamens).

(v) Monadelphous (Stamens united into one bunch).

(vi) Diadelphous (Stamens united into two bundles),

(vii) Polyadelphous (Stamens united into many bundles).

Caution

While writing the symbols, students must pay attention to the subscript and superscript characters.

Important

Students must understand that fusion is indicated by enclosing the figure within brackets and adhesion by a line drawn above the symbols of the floral parts.

A dot on the top of the floral diagram represents the position of the mother axis with respect to the flower.

FAMILY SOLANACEAE

Potatoes are a common food used in a lot of dishes. It is used with green vegetables frequently. Potatoes are the main ingredient in a sandwich, and one can say that potato is the king of all vegetables because we use them frequently and it contains high amounts of carbohydrates and gives us a lot of energy. Similarly, other plants like tomato, brinjal, and chilli are also used extensively. All these plants belong to the family Solanaceae. This is an important family. and it has certain characteristics that are unique to them, studying can help us understand the family Solanaceae better.

Important

The members of this family are widely distributed in tropics, subtropics and temperate zones. This Is a large family which Is commonly called the 'Potato family!

Vegetative Characters

(1) Habit: It includes herbs, shrubs, and rarely small trees

(2) Root: taproot

(3) Stem: Herbaceous rarely woody, aerial, erect. cylindrical, branched, solid or hollow, Hairy or glabrous (smooth), Stem is underground in potatoes.

(4) Leaves: Leaves are alternate, simple, rarely pinnately compound, exstipulate (without stipulate), hairy, and show reticulate venation.

Floral Characters

(1) Inflorescence: Solitary, axillary, or cymose (the main axis terminates in a flower, so there is limited growth, shows basipetal succession).

(2) Flower: Bisexual and actinomorphic (flower can be divided into two equal or more radial halves).

(3) Calyx: Sepals are five in number, gamosepalous, valvate aestivation, and persistent.

(4) Corolla: Petals are five in number, gamopetalous, and show valvate aestivation.

(5) Androecium: Stamens are five in number, epipetalous, anthers dithecous (contains two lobes).

(6) Gynoecium: Bicarpellary (two carpels). syncarpous, ovary superior with oblique septa, bilocular, placenta is swollen with many ovules, axile placentation.

(7) Fruit: Many-seeded berries or capsules.

(8) Seed: Many, endospermic (mostly monocots, endosperm present).