Characteristics of Plants
🌱 Chapter Overview: Living World (Plants)
For AP TET, understanding plants is fundamental. This section covers how we group plants based on their size (Herbs, Shrubs, Trees) and where they live (Habitat). It also details the basic functions of plant parts, which are frequent topics in standard Multiple Choice Questions (MCQs).
1. Classification based on Size & Stem (Growth Habit)
Plants are classified into three major categories based on their height, nature of stem, and lifespan.
A. The Three Main Types
- Herbs: Very small plants with soft, green, delicate stems. They usually have a short lifespan (often 1 season).
- Shrubs: Medium-sized plants with hard/woody stems, but not very thick. Branches arise near the base of the stem, giving a bushy appearance.
- Trees: Tall, large plants with a hard, thick, woody brown stem (called a trunk). Branches appear higher up on the trunk.
💡 Extra Types (Crucial for TET):
Some plants have very weak stems and cannot stand upright:
Some plants have very weak stems and cannot stand upright:
- Creepers: Spread on the ground (e.g., Watermelon, Pumpkin).
- Climbers: Need support (like a stick or wall) to grow up (e.g., Money plant, Grapevine, Bitter gourd).
COMPARISON TABLE: HERB vs. SHRUB vs. TREE
| Feature | Herb | Shrub | Tree |
|---|---|---|---|
| Size | Small (< 1m) | Medium (1m – 3m) | Tall (> 3m) |
| Stem Nature | Green, tender, soft | Hard, woody, thin stem | Hard, thick, woody trunk |
| Branching | Usually none or little | Near the base (bushy) | High above the ground |
| Lifespan | Short (few months) | Many years | Very long (many years) |
| Examples | Tomato, Wheat, Paddy, Grass, Coriander | Rose, Hibiscus, Lemon, Jasmine | Mango, Neem, Banyan, Peepal |
🌍 Real-Life Application: Farmers choose herbs (like wheat or rice) for quick seasonal crops to harvest food rapidly. Gardeners use shrubs (like hedges) for creating boundaries because they are bushy and last long.
2. Classification based on Habitat (Where they live)
Habitat is the natural home of a plant. Plants adapt their features depending on where they grow.
A. Major Habitat Types
- Terrestrial Plants (Mesophytes): Plants that grow on normal land with moderate water. Most common plants around us (Mango, Neem).
- Aquatic Plants (Hydrophytes): Plants that grow in water.
- Floating: Light, spongy stems filled with air (e.g., Water Hyacinth/Eichhornia).
- Submerged: Totally underwater (e.g., Hydrilla).
- Fixed floating: Roots fixed in soil, leaves float (e.g., Lotus).
- Desert Plants (Xerophytes): Plants that grow in dry areas with very little water.
- They have modifications to save water (leaves reduced to spines, fleshy stems to store water).
HABITAT & ADAPTATION TABLE
| Habitat Type | Key Adaptations (Exam Focus) | Common Examples |
|---|---|---|
| Terrestrial (Mesophytes) | Well-developed root systems; normal broad leaves with stomata. | Mango, Apple, Tomato |
| Aquatic (Hydrophytes) | Aerenchyma: Air spaces in stems/leaves to help them float. Poorly developed roots (water is easily available). | Lotus, Water Lily, Hydrilla, Vallisneria |
| Desert (Xerophytes) | Leaves turn into spines/thorns to reduce water loss. Stem becomes green and fleshy to do photosynthesis and store water. deeply penetrating roots. | Cactus (Opuntia), Aloe Vera |
🧠 Memory Shortcut for Adaptations:
- Hydro (Water) = Needs to float = Air bags (spongy stems).
- Xero (Zero Water) = Needs to save = Spines (no leaves to lose water).
3. Plant Parts & Functions
A plant body has two main systems: the Root System (below ground) and the Shoot System (above ground).
A. Root System
Main functions: Anchors plant to soil, absorbs water/minerals.
- Tap Root System: One main thick root with smaller side roots. Seen in Dicot plants (e.g., Bean, Mango, Carrot).
- Fibrous Root System: Cluster of thin, equal-sized roots from the base of the stem. Seen in Monocot plants (e.g., Grass, Rice, Maize).
B. Shoot System (Stem, Leaves, Flowers, Fruits)
| Part | Primary Function (The “Job”) | TET Exam Special Note (Modifications) |
|---|---|---|
| Stem | Supports branches; conducts water from roots to leaves; conducts food from leaves to other parts. | Edible Stems: Potato, Ginger, Turmeric, Sugarcane. (They store food underground but are stems, not roots!) |
| Leaf | “Food Factory”: Performs Photosynthesis using sunlight, water, CO2. Transpiration (releasing excess water) happens through stomata. | Leaves can be modified into spines in Cactus. |
| Flower | Reproductive part: Attracts insects for pollination; turns into fruit. | Cauliflower is actually a flower cluster we eat. |
| Fruit/Seed | Protects seeds; seeds germinate into new plants. | Tomato, Brinjal, Cucumber are technically fruits (botanically), even if we call them vegetables. |
⚠️ Confusing Exam Point:
Is it a Root or a Stem?
Is it a Root or a Stem?
- If it has “eyes” (buds) and nodes, it’s a STEM (e.g., Potato, Ginger).
- If it’s just a tapered end with no buds, it’s a ROOT (e.g., Carrot, Radish, Beetroot, Sweet Potato).
📝 AP TET Exam Tips & Sample Questions
AP TET Memory Formula Sheet (Biology Basics)
- Photosynthesis Needs: Sunlight + Chlorophyll + CO2 + Water → Food (Glucose) + Oxygen.
- Transpiration: Plants “sweating” water vapor through stomata.
- Potato = Stem | Sweet Potato = Root (Classic trap question).
- Venation Hint: Tap root usually has Reticulate venation (net-like leaves). Fibrous root usually has Parallel venation (straight lines, like grass/banana).
Sample AP TET Questions
- Which of the following is NOT a root modification for food storage?
A) Carrot B) Radish C) Potato D) Beetroot
Answer: C (Potato is a modified stem) - Plants that have spongy, air-filled stems are likely found in:
A) Deserts B) Water C) Mountains D) Plains
Answer: B (Aquatic adaptation for floating) - The small pores on leaves used for exchange of gases are called:
A) Roots B) Stomata C) Veins D) Petals
Answer: B
🚀 Speed Tip: In matching questions for TET, if you see “Fibrous Root”, immediately look for monocot examples like “Grass” or “Maize”. This often eliminates 2 wrong options instantly.