Unit 2: Structural Organisation in Plants and Animals

Introduction

The description of life forms on earth began with natural history, focusing on structural features both external and internal. These descriptions laid the groundwork for future scientific inquiries into physiology and evolutionary biology.

Chapter 5: Morphology of Flowering Plants

Overview

• Morphology refers to the form and structure of plants.
• Key components of flowering plants: roots, stems, leaves, flowers, and fruits.
• Adaptations in plant structures help in classification and understanding environmental interactions.

5.1 The Root

• Dicotyledonous Plants: Primary root system seen in mustard; forms tap root system with lateral roots.
• Monocotyledonous Plants: Fibrous root system seen in wheat, where primary root is short-lived.
• Adventitious Roots: Arise from non-radical parts, e.g., grass, banyan.
• Functions: Water/mineral absorption, anchorage, storage, and synthesis of growth regulators.
• Regions: Root cap, region of meristematic activity, elongation, and maturation.

5.2 The Stem

• Ascending part of the axis with branches, leaves, flowers, and fruits.
• Functions include support, conduction, storage, and vegetative propagation.

5.3 The Leaf

• Lateral, flattened structure attached to the stem.
• Parts: Leaf base, petiole, lamina.
• Venation: Reticulate in dicots, parallel in monocots.
• Types of Leaves: Simple vs compound (pinnately and palmately compound).
• Phyllotaxy: Arrangement of leaves (alternate, opposite, whorled).

5.4 The Inflorescence

• Arrangement of flowers on the floral axis.
• Types: Racemose (main axis grows continuously) and Cymose (main axis terminates in a flower).

5.5 The Flower

• Reproductive unit of angiosperms.
• Whorls: Calyx, corolla, androecium, gynoecium.
• Symmetry: Actinomorphic (radial), Zygomorphic (bilateral).
• Flower Types: Hypogynous, perigynous, epigynous.

5.6 The Fruit

• Mature or ripened ovary after fertilization.
• Types: Parthenocarpic (without fertilization).
• Components: Pericarp (epicarp, mesocarp, endocarp in drupes like mango and coconut).

5.7 The Seed

• Develops from ovules post-fertilization.
• Dicotyledonous Seed: Testa and tegmen coat, hilum, micropyle, embryo.
• Monocotyledonous Seed: Endospermic, with aleurone layer and scutellum.

5.8 Semi-Technical Description

• Detailed description of plant parts in sequence using scientific language.
• Floral diagram and formulae to summarize characteristics.

5.9 Solanaceae Family

• Known as the potato family.
• Vegetative Characters: Herbs, shrubs, trees.
• Floral Characters: Actinomorphic, bisexual flowers.
• Economic Importance: Food sources (tomato, potato), spices, medicine.

Summary

• Flowering plants exhibit vast diversity in structure and function.
• Root systems differentiate into tap or fibrous roots.
• Stem and leaf structures are adapted for various functions including photosynthesis and support.
• Flowers, as reproductive structures, vary greatly and form the basis for plant classification.
• Fruits and seeds are integral to the reproductive cycle of flowering plants.
• Importance of scientific representation through diagrams and formulas for plant classification.

Exercises

• Compare leaf types: pinnately vs palmately compound.
• Define key terms: aestivation, placentation, actinomorphic, zygomorphic.
• Explain inflorescence types: racemose vs cymose.
• Describe and diagram plant families such as Solanaceae.