Morphology of Flowering Plants: Important Points, Summary, Revision, and Highlights

• Root
• Stem
• Leaf
• Inflorescence
• Flower
• Fruit
• Seed

Morphology of Flowering Plants

The Root

![Types of Root]()

Tap Root: Primary root, formed by elongation of the radicle, bears secondary and tertiary roots and is present in dicot plants such as gram and mustard.

Fibrous Root: Found in monocotyledons, such as rice and wheat, a large number of roots originate at the base of the stem.

Adventitious Root: Primary root that is not formed from the radicle, such as grass, banyan tree, maize, etc.

Modification of the Root

• For Storage:
  • Taproots: Carrot, Turnip
  • Adventitious Roots: Sweet Potato

For Support:

• Prop Roots of Banyan Tree, arising from branches
• Stilt Roots of Maize and Sugarcane, coming out of lower stem nodes

Pneumatophores of Rhizophora are specialized roots present in mangroves that grow upwards above the ground. This helps them to respire in swampy areas where oxygen levels are low.

Root nodules of leguminous plants are used for nitrogen fixation.

The Stem

The plumule develops into a stem.

The part of the stem which bears leaves is called a node and the part between two nodes is known as the internode.

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Modification of the Stem

1. Underground Stems: They assist plants in enduring unfavorable conditions for growth.

2. Rhizome: Runs parallel to the ground and has nodes, internodes, and buds (e.g. ginger and banana).

3. Tubers - The end part becomes enlarged, as in the case of a potato.

4. Corms - They are underground plant stems that grow vertically, such as Colocasia and other plants.

4. Bulb - Stem is reduced and surrounded by scaly leaves, e.g. garlic, onions.

2. Stem Tendrils: These are coiled structures that support and help the delicate stems of plants to climb, such as grapes, cucumbers, and pumpkins.

3. Thorn: Axillary buds are modified into sharp thorns which protect plants from being eaten by animals, such as Bougainvillea and citrus.

4. Subaerial Weak Stem

1. Offsets: Decrease in internode of lateral branches leads to the formation of rosette of leaves, e.g. Eichhornia and Pistia.

2. Suckers - Lateral branches that arise from the underground portion of the stem, such as those found in Chrysanthemum, Banana, and Pineapple plants.

3. Runners: Stems that run horizontally above the ground and produce roots at nodes, e.g. grasses, strawberries.

4. Stolon - Lateral branches arise normally, but then bend down and touch the soil, where a new daughter plant arises, e.g. Mint.

5. Aerial Modification: The stem undergoes a drastic transformation for various adaptations, such as Phylloclade in xerophytic plants. The stem becomes thick and green, containing photosynthetic pigments to produce food, while the leaves are reduced to thorns to minimize water loss through transpiration, as seen in plants like Euphorbia and Opuntia.

The Leaf

Leaves originate from the apical meristem of a shoot.

Normally a leaf consists of three parts: leaf base, lamina, and petiole.

The leaf base attaches to the stem and may have two small, leaf-like structures known as stipules.

Types of Venation:

• Parallel Venation
• Reticulate Venation
• Pinnate Venation
• Palmate Venation

![Types of venation]()

1. Reticulate Veins - Present in dicotyledons, there is a network of veins which are irregularly distributed.

2. Parallel Veins - In monocotyledons, veins are arranged in a parallel pattern.

Types of Leaves:

1. Simple: The lamina is intact and the incision does not extend to the midrib.

2. Compound: Incision that touches the midrib, dividing a leaf into multiple leaflets.

• Pinnately Compound - the leaflets are present on a common axis, the rachis, along the midrib of the leaf, e.g. Neem.

Palmately Compound: Leaflets are attached at the petiole tip, e.g. silk cotton.

Phyllotaxy: The pattern in which leaves are arranged around the stem.

1. Alternate Type: Single leaf present at each node, e.g. Hibiscus and Brassica.

2. Same type - Each node bears a pair of leaves of the same type, e.g. Quercus rubra, Acer saccharum

3. Whorled Type: More than two leaves arise at the node to form a whorl, e.g. Alstonia.

Modification of Leave Policies

Tendrils - Leaves modified to form a long, thread-like structure, providing support to climbers such as peas.

Spine - In xerophytic plants, such as cacti and aloe, spines are used to reduce water loss.

For Storage:

• Garlic
• Onion

Phyllodes - The petiole of certain plants gets modified to form a leaf-like structure, such as in the case of Acacia, which functions like a leaf.

The pitcher of a pitcher plant is a modified leaf that traps insects inside.

Inflorescence

![Inflorescence]()

The arrangement of the flowers around the floral axis

The two main types of inflorescence are:

1. Racemose

2. Cymose

3. Racemose: The main axis of the inflorescence grows indefinitely, and flowers are present laterally in acropetal succession, with the older flowers at the bottom and the younger ones at the top. Types of racemose inflorescence: Raceme, Spike, Umbel, Capitulum, Corymb, Catkin, Spadix, etc.

4. Cymose: A type of inflorescence in which the main axis terminates in a flower and has limited growth, with flowers borne in a basipetal order (i.e. older flowers at the top and new flowers at the bottom). Types of Cymose Inflorescence: Monochasial Cyme, Dichasial Cyme, etc.

Special Types of Inflorescence

1. Verticillaster: Flowers that are sessile and arranged in a dichasial cyme, such as Ocimum and Salvia.

2. Cyathium: A cup-shaped structure formed by an involucre of bracts, with a single female flower surrounded by numerous male flowers, e.g. Euphorbia.

3. Hypenthodium: Both male and female flowers are present in a cavity with an apical opening called an Ostiole, e.g. Fig.

The Flower

A flower has four whorls: Calyx, Corolla, Androecium, and Gynoecium. These are attached to the swollen terminal of the pedicel called the Thalamus.

Flower Symmetry:

1. Actinomorphic: Flowers that are radially symmetrical, such as chilli, datura, and mustard.

2. Zygomorphic - When a flower can be divided into two equal parts in only one vertical plane, such as Cassia, pea, etc.

Flowers can have either 3, 4, or 5 floral appendages, depending on whether they are trimerous, tetramerous, or pentamerous, respectively.

Bracteate flowers have bracts present at the base of the pedicel, while Ebracteate flowers have no bracts.

Types of Flowers Based on the Position of the Ovary:

1. Hypogynous- The gynoecium is located at the highest point, above all other parts. The ovary is referred to as superior, such as in the case of brinjal, china rose, and mustard.

2. Perigynous - Gynoecium is present at the same level as the rest of the parts of a flower, with the ovary being known as half inferior, e.g. peach, plum, rose.

3. Epigynous- The ovary is completely enclosed by the thalamus and other parts are located above it. The ovary is known as inferior, for example, the ray florets of a sunflower, guava, and cucumber.

Parts of a Flower

Calyx: The outermost whorl of a flower is composed of leaf-like structures known as sepals.

Gamosepalous: Sepals United

Polysepalous: Sepals that are free from one another

Corolla: Made up of bright-colored petals, present after sepals.

Gamopetalous: Petals United

Polypetalous: Petals that are free from one another

Aestivation: A form of dormancy in which an animal enters a state of decreased activity during periods of extreme environmental conditions, such as heat or drought.

It is the mode of arrangement of sepals and petals. The main types of aestivations are:

• Valvate
• Imperfectly valvate
• Twisted valvate
• Connivent
• Quincuncial

Valvate: Sepals or petals that just touch each other and do not overlap in a whorl, e.g. Calotropis.

Twisted - Sepal or petal overlaps the next sepal or petal in a whorl, as seen in plants such as cotton, china rose, and lady’s finger.

Imbricate: The margins of the sepals and petals of a flower, such as a Gulmohar or Cassia, overlap each other in a random pattern, rather than in one direction.

Vexillary - The largest petal overlaps two petals (wings) that are located laterally on both sides, and also overlaps the two anterior petals (keel) in the same way. This type of flower is also referred to as “papilionaceous”, and can be seen in plants such as beans and peas.

Androecium: It is the male reproductive part of a flower and consists of stamens. Each stamen is composed of a filament and anthers.

Staminode: Sterile Stamen

Epipetalous: Stamens attached to petals.

Polyandrous: Stamens that are free

Monadelphous: Stamens that are united and present as one bundle.

Diadelphous: Stamens united in two bundles

Polyadelphous: Stamens that are united and present in more than two bundles.

Gynoecium: It is a female reproductive part that consists of carpels. Each carpel is composed of three parts: stigma, style, and ovary.

Apocarpous: More than one carpels present, which are free from each other, such as in a rose or lotus flower.

Syncarpous: Fruits composed of multiple carpels fused together, such as tomatoes and mustard.

Placentation: The process by which a placenta is formed and functions in the development of an embryo.

The specific arrangement of ovules in the ovary is called placentation. Types of placentation include:

• Axile Placentation
• Parietal Placentation
• Basal Placentation
• Free Central Placentation

1. Marginal: e.g. Pea

2. Axile: e.g. Lemon, China Rose

3. Parietal

• e.g. Argemone, mustard

4. Free Central

• Primrose
• Dianthus

5. Basal Plants

• e.g. Marigold, Sunflower

The Fruit

It is a mature and ripe ovary after fertilization.

Parthenocarpic Fruit: The fruit formed without fertilization, resulting in seedless fruits such as pineapple.

A fruit is composed of a seed and a pericarp. The pericarp is a fleshy layer made up of three parts; the epicarp, the mesocarp, and the endocarp.

The Seed

The ovule develops into a seed after fertilisation.

A seed consists of a seed coat and an embryo. The embryo is composed of a radicle, an embryonal axis, and one or two cotyledons in monocotyledons (such as maize and wheat) and dicotyledons (such as pea and gram) respectively.

| Dicotyledonous Seed | Monocotyledonous Seed |

| The seed coat is made up of two layers; outer testa and inner tegmen |