Morphology of Flowering Plants

1. Morphology – Root Architecture, Root Zones & Specialized Modifications

A. Root Concept & Primary Root Types

• Underground, non-green, negatively phototropic, positively geotropic, and positively hydrotropic axis of plant. Lacks nodes and internodes.
• 1. Tap Root System: Directly develops and elongates from the radicle of embryo. Prominent main primary root with lateral branches. Common in Dicots & Gymnosperms (e.g., Mustard).
• 2. Fibrous Root System: Primary root is short-lived/ephemeral and replaced by a large cluster/tuft of thin fiber-like roots originating from base of stem. Common in Monocots (e.g., Wheat, Grasses).
• 3. Adventitious Root System: Roots arising from any part of the plant body other than the radicle (e.g., Banyan tree prop roots, Monstera).

B. Anatomical Zones of Root Tip

1. Root Cap (Calyptera): Thimble-like parenchymatous structure covering root apex (RAM). Secretes mucilage via Golgi bodies for soil lubrication. Absent in aquatic hydrophytes (replaced by root pockets).
2. Region of Meristematic Activity: Few millimeters above root cap. Small, thin-walled, compactly arranged cells with dense cytoplasm undergoing rapid division.
3. Region of Elongation: Proximal to meristematic zone. Cells undergo rapid elongation and enlargement; responsible for length growth.
4. Region of Maturation: Proximal to elongation zone. Cells differentiate into mature permanent tissues. Epidermal cells in this zone form thin, fine Unicellular Exogenous Root Hairs for water and mineral absorption.

C. Specialized Root Modifications

2. Stem Anatomy, Underground/Sub-Aerial/Aerial Modifications & Leaf Basics

A. Stem Characteristics & Modifications

• Ascending axis developing from plumule of embryo. Bears nodes (where leaves arise) and internodes. Positively phototropic, negatively geotropic.
• 1. Underground Stem Modifications (Storage & Perennation):• Rhizome: Dorsiventral horizontal stem (Ginger, Turmeric, Banana).

  • Tuber: Swollen tip with ‘eyes’/buds (Potato).

  • Corm: Unbranched vertical thick stem (Colocasia, Amorphophallus / Zaminkand).

  • Bulb: Highly reduced disc-like stem surrounded by fleshy scale leaves (Onion, Garlic).

• 2. Sub-Aerial Stem Modifications (Vegetative Propagation):• Runner: Creeps horizontally on soil; breaks to form new plants (Grasses, Strawberry).

  • Stolon: Arching lateral branch touching soil (Mint, Jasmine).

  • Offset: Lateral branch with short internodes bearing rosette of leaves and tuft of roots at each node (Eichhornia / Water Hyacinth, Pistia).

  • Sucker: Lateral branch arising underground, growing obliquely upward (Pineapple, Chrysanthemum, Banana).

• 3. Aerial Stem Modifications:• Phylloclade: Flattened or cylindrical green photosynthetic modified stem with unlimited growth (Opuntia – flattened; Euphorbia – cylindrical).

  • Cladode: Phylloclade with only one single internode length (Asparagus, Ruscus).

  • Stem Tendrils: Slender spirally coiled climbing structures modified from axillary buds (Gourds – Cucumber, Pumpkin, Watermelon, Grapevine).

  • Stem Thorns: Woody, straight, pointed protective structures modified from axillary buds (Citrus, Bougainvillea).

B. Leaf Structure & Venation

• Lateral, flattened photosynthetic organ developing exogenously at node from shoot apical meristem in an acropetal order (older leaves at base, younger at apex).

• Main Leaf Parts: Leaf Base (Hypopodium – sheath in monocots, swollen Pulvinus in Legumes), Petiole (Mesopodium – holds blade to light), Lamina / Leaf Blade (Epipodium – green expanded area).
• Types of Venation:• Reticulate Venation: Veinlets form a complex network. Characteristic of Dicots.

  • Parallel Venation: Veins run parallel to each other within lamina. Characteristic of Monocots.

• Simple vs. Compound Leaves:• Simple: Lamina intact or incisions do not touch the midrib. Axillary bud present in axil of leaf.

  • Compound: Incisions reach midrib, breaking lamina into multiple leaflets. Axillary bud is present in axil of compound leaf, but NEVER in axil of leaflets!

  ↳ Pinnately Compound: Leaflets on common axis / rachis (e.g., Neem).

  ↳ Palmately Compound: Leaflets attached at common point at tip of petiole (e.g., Silk Cotton).

3. Phyllotaxy, Leaf Modifications & Inflorescence Types

A. Phyllotaxy (Leaf Arrangement Pattern)

B. Specialized Leaf Modifications

• Food Storage: Fleshy leaves storing water and food (Onion, Garlic).
• Leaf Tendrils: Modified for climbing support (Pea plant).
• Leaf Spines: Defensive pointed structures reducing transpiration (Opuntia, Cacti).
• Phyllode: Green, expanded, photosynthetic petiole replacing short-lived compound lamina (Australian Acacia).
• Insectivorous Insect Traps: Leaves modified to trap and digest insects for nitrogen (Pitcher plant, Bladderwort, Venus flytrap).

C. Inflorescence Types (Racemose vs. Cymose)

Arrangement of flowers on the floral axis (Peduncle):

4. Flower Symmetry, Thalamus Position & Estivation Modes

A. Floral Symmetry & Thalamus Insertion

• 1. Symmetry Types:• Actinomorphic ($\oplus$ / Radial): Flower can be divided into two equal radial halves in any radial plane passing through center (Mustard, Datura, Chilli).

  • Zygomorphic ($\% / \dagger$ / Bilateral): Divided into two equal halves in only one vertical plane (Pea, Gulmohar, Bean, Cassia).

  • Asymmetric: Cannot be divided into two equal halves in any plane (Canna).

• 2. Position of Floral Parts on Thalamus:• Hypogynous (Superior Ovary – $\underline{G}$): Gynoecium occupies highest position, other parts situated below it (Mustard, China Rose, Brinjal).

  • Perigynous (Half-Inferior Ovary – $G-$): Gynoecium situated in center and other parts located on rim of thalamus at same level (Plum, Rose, Peach).

  • Epigynous (Inferior Ovary – $\overline{G}$): Thalamus encloses ovary completely and fuses with it; other parts arise above ovary (Guava, Cucumber, Ray florets of Sunflower).

B. Estivation Modes (Calyx / Corolla Arrangement)

C. Androecium Cohesion & Adhesion Terminology

• Adhesion (Attachment to other whorls):• Epipetalous: Stamens attached to petals (Solanaceae e.g., Brinjal – $\overbrace{C A}$).

  • Epiphyllous / Epitepalous: Stamens attached to perianth/tepals (Liliaceae e.g., Lily, Onion – $\overbrace{P A}$).

• Cohesion (Stamen fusion among themselves):• Monadelphous: Stamens fused into 1 bundle by filaments (China Rose).

  • Diadelphous: Fused into 2 bundles (Pea – $A_{(9)+1}$).

  • Polyadelphous: Fused into many bundles (Citrus).

  • Syngenesious: Anthers fused, filaments free (Sunflower).

  • Synandrous: Both anthers and filaments fused completely (Cucurbits).

5. Gynoecium, Placentation Patterns & Fruit Structure

A. Placentation Types (Ovule Arrangement in Ovary)

B. Fruit Anatomy & Drupe Special Case

• Ripened mature ovary developed after fertilization. Wall of fruit is Pericarp (differentiated into outer Epicarp, middle Mesocarp, and inner Endocarp).
• Drupe Fruit (Mango & Coconut): Simple fleshy 1-seeded fruit developing from monocarpellary superior ovaries:• Mango: Thin epicarp, fleshy edible mesocarp, hard stony endocarp.

  • Coconut: Thin epicarp, fibrous mesocarp (coir source), hard endocarp, edible liquid/solid endosperm.

6. Botanical Technical Symbols & Major Families (Part 1)

A. Semi-Technical Floral Symbols Reference

Br = Bracteate | Ebr = Ebracteate | $\oplus$ = Actinomorphic | $\%$ = Zygomorphic | $\succ^{7}$ = Bisexual | $K$ = Calyx | $C$ = Corolla | $P$ = Perianth | $A$ = Androecium | $G$ = Gynoecium | $\underline{G}$ = Superior Ovary | $\overline{G}$ = Inferior Ovary

B. Family Brassicaceae / Cruciferae (Mustard Family)

• Features: Tetramerous cruciform flowers, tetradynamous stamens ($A_{2+4}$), parietal placentation with replum.
• Floral Formula: $$\mathbf{\oplus \ \succ^{7} \ K_{2+2} \ C_4 \ A_{2+4} \ \underline{G}_{(2)}}$$
• Examples: Mustard, Radish, Turnip.

C. Family Fabaceae / Papilionaceae (Legume Family)

• Features: Root nodules with Rhizobium, pinnately compound leaves with pulvinus, vexillary estivation ($C_{1+2+(2)}$), diadelphous androecium ($A_{(9)+1}$), marginal placentation.
• Floral Formula: $$\mathbf{\% \ \succ^{7} \ K_{(5)} \ C_{1+2+(2)} \ A_{(9)+1} \ \underline{G}_1}$$
• Examples: Pea, Gram, Arhar, Moong, Soyabean, Indigofera (dye), Sunhemp (fibre), Sesbania, Lupinus, Glycyrrhiza (mulethi medicine).

D. Family Solanaceae (Potato Family)

• Features: Persistent calyx ($K_{(5)}$), epipetalous stamens ($\overbrace{C_{(5)} A_5}$), bicarpellary syncarpous swollen placenta placed obliquely with axile placentation.
• Floral Formula: $$\mathbf{\oplus \ \succ^{7} \ K_{(5)} \ \overbrace{C_{(5)} \ A_5} \ \underline{G}_{(2)}}$$
• Examples: Potato, Tomato, Brinjal, Chilli, Belladonna, Ashwagandha, Tobacco, Petunia.

E. Family Malvaceae (Mallow Family)

• Features: Epicalyx present ($Epi_{3\text{–}7}$), twisted estivation, monadelphous kidney-shaped monothecous anthers ($\mathbf{A}_{(\infty)}$).
• Floral Formula: $$\mathbf{\oplus \ \succ^{7} \ Epi_{3\text{–}7} \ K_{(5)} \ C_5 \ A_{(\infty)} \ \underline{G}_{(5\text{–}\infty)}}$$
• Examples: Cotton, China Rose (Hibiscus), Lady’s Finger (Okra).

7. Major Families (Part 2 – Asteraceae & Poaceae)

A. Family Asteraceae / Compositae (Sunflower Family)

• Largest dicot family. Head / Capitulum inflorescence with two types of florets:• Ray Florets: Outer, Zygomorphic, Female, Inferior Ovary.

  ↳ Formula: $$\mathbf{\% \ \Psi \ K_{\text{pappus}} \ C_{(5)} \ A_0 \ \overline{G}_{(2)}}$$

  • Disc Florets: Central, Actinomorphic, Bisexual, Syngenesious Stamens.

  ↳ Formula: $$\mathbf{\oplus \ \succ^{7} \ K_{\text{pappus}} \ \overbrace{C_{(5)} \ A_{(5)}} \ \overline{G}_{(2)}}$$

  • Calyx modified into hairy Pappus for wind seed dispersal; basal placentation.

B. Family Poaceae / Graminae (Grass Family)

• Economically most important monocot family. Inflorescence spikelet; floral bracts modified into Glumes, Lemma, and Palea.
• Perianth reduced to 2 scale-like Lodicules. Versatile anthers, feathery stigma, basal placentation. Fruit = Caryopsis.
• Floral Formula: $$\mathbf{\% \ \succ^{7} \ P_{2\text{ (lodicules)}} \ A_3 \ \underline{G}_1}$$
• Examples: Wheat, Rice, Maize, Barley, Sugarcane, Oats, Bamboo.