Morphology of Flowering Plants

Morphology is the study of external forms of organisms. In Angiosperms, it is characterised by presence of roots, stems, leaves, flowers and fruits.

The root is the descending axis of the plant, usually positively geotropic and hydrotropic.

Types of Roots

• Tap Root System: Originates from radicle. Primary root persists. E.g., Dicot plants (Mustard).
• Fibrous Root System: Primary root is short-lived; replaced by many roots from base of stem. E.g., Monocots (Wheat).
• Adventitious Roots: Roots arise from parts other than radicle (e.g., stem, leaves). E.g., Grass, Monstera, Banyan tree.

Regions of Root

1. Root Cap (Protection)
2. Region of Meristematic Activity (Cell division)
3. Region of Elongation (Length growth)
4. Region of Maturation (Root hairs absorbing water/minerals)

Roots modified for functions other than absorption:

• Food Storage:
  Tap roots: Carrot, Turnip.
  Adventitious roots: Sweet potato.
• Prop Roots: Hanging structures supporting the tree. E.g., Banyan tree.
• Stilt Roots: Supporting roots coming out of lower nodes of stem. E.g., Maize, Sugarcane.
• Pneumatophores: Respiratory roots growing vertically upwards along with mangrove vegetation. Has pores called Lenticels. E.g., Rhizophora.

• Underground (Perennation & Storage):
  Potato (Tuber), Ginger/Turmeric (Rhizome), Zaminkand/Colocasia (Corm).
• Stem Tendrils (Support): Are slender and spirally coiled. E.g., Gourds (Cucumber, Pumpkin, Watermelon) and Grapevines.
• Thorns (Protection): Woody, straight, pointed. E.g., Citrus, Bougainvillea.
• Phylloclade (Photosynthesis): Flattened (Opuntia) or Fleshy Cylindrical (Euphorbia). Contain chlorophyll.
• Sub-aerial Modifications (Vegetative Propagation):
  • Runner: Grass, Strawberry.
  • Stolon: Mint, Jasmine.
  • Offset: Pistia, Eichhornia (Aquatic plants).
  • Sucker: Banana, Pineapple, Chrysanthemum.

Venation

• Reticulate: Network of veinlets. Characteristic of Dicots.
• Parallel: Veins run parallel. Characteristic of Monocots.

Phyllotaxy (Pattern of leaf arrangement)

• Alternate: Single leaf at each node. E.g., China rose, Mustard, Sunflower.
• Opposite: Pair of leaves at each node. E.g., Calotropis, Guava.
• Whorled: More than two leaves at a node. E.g., Alstonia.

Arrangement of flowers on floral axis.

Symmetry

• Actinomorphic (Radial): Mustard, Datura, Chilli.
• Zygomorphic (Bilateral): Pea, Gulmohar, Bean, Cassia.
• Asymmetric: Canna.

Position of Ovary

• Hypogynous (Superior Ovary): Mustard, China rose, Brinjal.
• Perigynous (Half Inferior): Plum, Rose, Peach.
• Epigynous (Inferior Ovary): Guava, Cucumber, Ray florets of Sunflower.

Aestivation (Sepal/Petal Arrangement)

• Valvate: Just touch, no overlapping (Calotropis).
• Twisted: One margin overlaps next (China rose, Lady’s finger, Cotton).
• Imbricate: Overlap irregularly (Cassia, Gulmohar).
• Vexillary (Papilionaceous): Standard + 2 Wings + 2 Keel (Pea, Bean).

• Marginal: Ridge along ventral suture (Pea).
• Axile: Multilocular ovary (China rose, Tomato, Lemon).
• Parietal: Inner wall of ovary, false septum called replum (Mustard, Argemone).
• Free Central: Septa absent (Dianthus, Primrose).
• Basal: Base of ovary (Sunflower, Marigold).

Originates from radicle, seen in Dicot plants like Mustard.

Primary root is short-lived, replaced by roots from base of stem. Seen in Monocots like Wheat.

Roots arise from parts other than radicle. Examples: Grass, Monstera, Banyan tree.

Hanging structures in Banyan tree that provide support are called Prop Roots.

Supporting roots coming out of the lower nodes of the stem in Maize and Sugarcane.

Respiratory roots in mangroves like Rhizophora. Grow vertically upwards, possess pores (Lenticels).

Potato (Tuber), Ginger/Turmeric (Rhizome), Zaminkand/Colocasia (Corm) are stems modified for storage/perennation.

Present in gourds (Cucumber, Pumpkin, Watermelon) and Grapevines. Developed from axillary buds.

Woody, straight, pointed structures in Citrus and Bougainvillea. Modified axillary buds.

Flattened (Opuntia) or fleshy cylindrical (Euphorbia) green stems containing chlorophyll for photosynthesis.

Lateral branch with short internodes and rosette of leaves found in aquatic plants like Pistia and Eichhornia.

Characteristic of Monocots. Veins run parallel to each other within lamina.

A single leaf arises at each node. Examples: China rose, Mustard, Sunflower.

A pair of leaves arise at each node. Examples: Calotropis and Guava.

More than two leaves arise at a node and form a whorl. Example: Alstonia.

In Australian Acacia, leaves are short-lived. The petiole expands, becomes green and synthesises food.

Main axis continues to grow. Flowers borne laterally in acropetal succession (younger at top).

Main axis terminates in a flower (limited growth). Flowers borne in basipetal order.

Radial symmetry. Flower can be divided into equal halves in any radial plane. E.g., Mustard, Datura, Chilli.

Bilateral symmetry. Divided into equal halves in only one vertical plane. E.g., Pea, Gulmohar, Bean, Cassia.

Cannot be divided into two similar halves by any plane. Example: Canna.

Gynoecium occupies highest position (Superior Ovary). Examples: Mustard, China rose, Brinjal.

Thalamus grows around ovary. Ovary is half inferior. Examples: Plum, Rose, Peach.

Thalamus encloses ovary completely. Ovary is Inferior. E.g., Guava, Cucumber, Ray florets of Sunflower.

Sepals/Petals just touch one another at margin, without overlapping. E.g., Calotropis.

One margin overlaps that of the next one. Examples: China rose, Lady’s finger, Cotton.

Margins overlap but not in any particular direction. Examples: Cassia and Gulmohar.

Standard (largest) overlaps two lateral Wings, which overlap two Keel. E.g., Pea, Bean (Fabaceae). Also called Papilionaceous.

A sterile stamen is called a Staminode.

Carpels are free. Examples: Lotus and Rose.

Carpels are fused. Examples: Mustard and Tomato.

Placenta forms a ridge along the ventral suture of ovary. E.g., Pea.

Placenta is axial and ovules attached in a multilocular ovary. E.g., China rose, Tomato, Lemon.

Ovules develop on inner wall of ovary. False septum (Replum) present. E.g., Mustard, Argemone.

Ovules on central axis, septa absent. E.g., Dianthus, Primrose.

Placenta develops at base of ovary, single ovule attached. E.g., Sunflower, Marigold.

Stony fruit. Mango and Coconut. Develop from monocarpellary superior ovaries, one seeded.

Stony Endocarp (hard), Fleshy Mesocarp (edible).

Coconut is a Drupe with fibrous mesocarp.

Fruit formed without fertilization of ovary. E.g., Banana. They are seedless.

A proteinaceous layer separating embryo from endosperm in Monocot seeds (Maize).

The single large, shield-shaped cotyledon in monocot seeds (grains).

In Lily (Liliaceae), calyx and corolla are not distinct, termed Perianth (Tepals).

Zygomorphic, Vexillary aestivation, Diadelphous androecium (9+1), Marginal placentation.

Actinomorphic, Epipetalous stamens, Bicarpellary obliquely placed syncarpous superior ovary, swollen placenta.

Perianth (tepals), Epiphyllous stamens, Tricarpellary syncarpous superior ovary, axile placentation.

Colchicum autumnale (Liliaceae) yields Colchicine (used to induce polyploidy).

Indigofera is a dye yielding plant belonging to family Fabaceae.

Fumigatory plant belonging to family Solanaceae.

Stamens are attached to the petals. E.g., Brinjal (Solanaceae).