Getting To Know Plants: CBSE Class 6 Science Chapter Notes & Solutions

Classification of Plants based on Growth and Stems

To study plants easily, we classify them into five distinct categories based on their height, nature of stem, and where their branches appear:

1. Herbs: These are small plants with green, tender, and delicate stems. They usually have very few branches and live for a short time (e.g., coriander, mint, tomato, mustard).
2. Shrubs: These are medium-sized plants with hard, woody stems that branch out near the base. The stem is hard but not very thick (e.g., rose, lemon, hibiscus, jasmine).
3. Trees: These are very tall plants with thick, hard, woody, and brown stems called trunks. The branches emerge high up from the ground (e.g., mango, banyan, neem, coconut).
4. Creepers: Plants with weak stems that cannot stand upright and instead spread horizontally along the ground (e.g., watermelon, pumpkin).
5. Climbers: Plants with weak stems that take the support of neighboring structures like walls, sticks, or other trees to climb upward (e.g., money plant, grapevine, pea plant).

Key Parts of a Plant and Their Functions

Stem

The main axis that bears leaves, flowers, and fruits. It conducts water and minerals from roots to other parts, and transports prepared food from leaves to the rest of the plant.

Lamina and Petiole

The broad, green, flat part of a leaf is called the lamina. The thin stalk that attaches the leaf lamina to the stem is called the petiole.

Leaf Venation

The design or pattern formed by veins in a leaf. It is 'reticulate' if it forms a net-like design (e.g., peepal, rose) and 'parallel' if the veins run parallel to each other (e.g., grass, wheat).

Transpiration

The biological process by which water vapor escapes from the tiny pores (stomata) on the surface of leaves into the atmosphere.

Photosynthesis

The process by which green leaves prepare food using carbon dioxide, water, and sunlight in the presence of a green pigment called chlorophyll.

Step-by-Step Science Experiment: Testing a Leaf for Starch

1. Step 1: Pluck the Leaf — Take a green leaf from a healthy plant that has been exposed to sunlight for a few hours.
2. Step 2: Boil in Water — Place the leaf in a beaker filled with water and boil it for a few minutes. This breaks down the cell walls and makes the leaf soft.
3. Step 3: Remove Chlorophyll (Boil in Alcohol) — Place the boiled leaf in a test tube containing spirit/alcohol. Place this test tube in a beaker of hot water (water bath) and heat until the green pigment (chlorophyll) completely dissolves into the alcohol, leaving the leaf pale/white.
4. Step 4: Rinse the Leaf — Carefully remove the pale leaf from the alcohol and wash it thoroughly in clean, warm water to remove any residual spirit.
5. Step 5: Apply Iodine Solution — Place the washed leaf flat on a white tile and add a few drops of iodine solution to it. Observe the color change.
6. Result and Conclusion — The leaf turns blue-black in color. This confirms the presence of starch, proving that green leaves make food through photosynthesis.

The Root-Leaf Secret Connection (Must-Know for Exams!)

Did you know you can tell what kind of roots a plant has just by looking at its leaves? You don't even need to dig up the plant! Use this simple rule to score full marks in your CBSE practical exams:

• Rule 1: If the leaf has reticulate venation (net-like design), the plant will always have a taproot system (e.g., mustard, carrot, rose).
• Rule 2: If the leaf has parallel venation (straight parallel lines), the plant will always have a fibrous root system (e.g., grass, wheat, maize, banana).

Common Mistake: Students often draw net-like venation on a grass leaf when drawing fibrous roots. Remember to always match parallel venation with fibrous roots!

Practice Questions with Solutions

• Q: What is the main difference between taproot and fibrous root systems? A: Step 1: Identify the main taproot structure. A taproot system has one thick main root called the taproot, with smaller roots branching off called lateral roots. Step 2: Identify the fibrous root structure. Fibrous roots do not have a main root. Instead, many similar-looking roots grow together in a bunch or cluster directly from the base of the stem. Step 3: Compare examples. Taproots are found in pea, mustard, and carrot plants. Fibrous roots are found in grass, wheat, and onion plants. Final answer: Taproots have a single deep main root with smaller branches, whereas fibrous roots consist of a clustered group of thin, similar-sized roots with no primary main root.
• Q: List the four main parts of a flower and state their basic functions. A: Step 1: List the outermost green part. Sepals are small green leaf-like structures that protect the flower when it is in the bud stage. Step 2: List the colorful part. Petals are bright, colorful, and often scented parts that attract insects and birds for pollination. Step 3: List the male reproductive part. Stamens consist of anther (which produces pollen grains) and filament (the stalk supporting the anther). Step 4: List the female reproductive part. Pistil (or carpel) is the innermost part consisting of stigma (receptive surface for pollen), style (tube), and ovary (contains ovules which turn into seeds). Final answer: The four main parts of a flower are Sepals (protection), Petals (attraction), Stamens (male reproduction), and Pistil (female reproduction).
• Q: How do stems act like a two-way traffic street? A: Step 1: Analyze upward movement. The stem carries water and dissolved mineral salts from the roots up to the leaves and other growing parts of the plant. Step 2: Analyze downward/outward movement. The leaves prepare food through photosynthesis, and the stem transports this prepared food downward and outward to all parts of the plant, including roots for storage. Step 3: Conclude the flow. Because transport occurs in both opposite directions (upward and downward), it is described as a two-way street. Final answer: The stem acts like a two-way traffic street because it transports water upwards from roots to leaves and moves prepared food downwards from leaves to the rest of the plant.
• Q: Explain transpiration in plants and why it is important. A: Step 1: Define transpiration. It is the process by which water is lost from leaves in the form of water vapor through microscopic pores called stomata. Step 2: Explain why it occurs. Plants absorb a large amount of water from the soil, but use only a small portion for growth. The excess water is evaporated. Step 3: Highlight its importance. Transpiration creates a suction pull (transpiration pull) that helps pull water and minerals up from the roots to tall branches. It also helps in cooling down the plant in hot weather. Final answer: Transpiration is the loss of excess water as vapor from leaves. It is vital because it creates a suction pull to transport water upwards and keeps the plant cool.

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