Plant Life: Structure, Function and Reproduction

Overview

Plant Life is a fundamental topic in the Science portion of OTET Paper II, covering the biology of plants from their basic structure to complex reproductive processes. This topic forms the foundation for understanding ecosystems, food chains and environmental science—all interconnected areas in the syllabus.

For OTET, you must understand the structural organisation of plants (root, stem, leaf, flower), the physiological processes that keep plants alive (photosynthesis, respiration, transpiration) and the mechanisms of plant reproduction (vegetative, asexual and sexual). Questions typically test factual recall of plant parts and their functions, along with application-based questions on processes like photosynthesis.

Mastery of this topic also helps in teaching upper primary students through hands-on activities like observing plant parts, germination experiments and flower dissection—practical knowledge that OTET values.

Key Concepts

• **Cell as the basic unit**: Plant cells have a cell wall (made of cellulose), large central vacuole, plastids (chloroplasts for photosynthesis) and lack centrioles—distinguishing them from animal cells.

• **Root system functions**: Roots anchor the plant, absorb water and minerals through root hairs, and in some plants store food (carrot, radish). Tap roots have one main root; fibrous roots have many similar-sized roots.

• **Stem as the transport highway**: Stems support leaves and flowers, conduct water upward through xylem and food downward through phloem. Modified stems include tubers (potato), rhizomes (ginger) and bulbs (onion).

• **Leaf as the food factory**: Leaves are the primary site of photosynthesis. Stomata on the leaf surface control gas exchange (CO₂ in, O₂ out) and water loss through transpiration.

• **Photosynthesis equation**: Carbon dioxide + Water → (sunlight, chlorophyll) → Glucose + Oxygen. This is the basis of all food chains.

• **Transpiration pull**: Water evaporates from stomata, creating a suction force that pulls water up from roots through xylem—essential for mineral transport.

• **Flower as the reproductive organ**: A complete flower has four whorls—calyx (sepals), corolla (petals), androecium (stamens/male) and gynoecium (pistil/female).

• **Pollination and fertilisation are distinct**: Pollination is pollen transfer to stigma; fertilisation is fusion of male and female gametes inside the ovule, occurring after pollen tube growth.

Formulas / Key Facts

| Fact/Process | Key Detail | |--------------|------------| | Photosynthesis equation | 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ (in presence of sunlight and chlorophyll) | | Site of photosynthesis | Chloroplasts in mesophyll cells of leaves | | Xylem function | Transports water and minerals upward (unidirectional) | | Phloem function | Transports food (sucrose) bidirectionally | | Stomata location | Usually more on lower surface of leaves | | Guard cells | Control opening and closing of stomata | | Parts of pistil | Stigma (receives pollen), Style (tube), Ovary (contains ovules) | | Parts of stamen | Anther (produces pollen) + Filament | | Self-pollination | Pollen from same flower or same plant | | Cross-pollination | Pollen from different plant of same species | | Agents of pollination | Wind, water, insects, birds, animals | | Seed parts | Seed coat (testa), Cotyledon(s), Embryo (radicle + plumule) | | Monocot vs Dicot | Monocot: 1 cotyledon, parallel veins; Dicot: 2 cotyledons, reticulate veins |