CBSE Class 6 Science Ch 7: Getting to Know Plants

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Getting to Know Plants - Science Notes for CBSE Class 6

Chapter 7: Getting to Know Plants

Science Notes for CBSE Class 6

Chapter Summary

  • Introduction to Plants: Plants are living organisms that are found almost everywhere on Earth. They are essential for life as they produce oxygen and food.
  • Classification of Plants: Plants can be broadly classified into three categories based on their stem, height, and branches:
    • Herbs: These are small plants with soft, green, and tender stems. They usually have few branches or no branches. They live for a short period (one or two seasons). Examples: Wheat, paddy, cabbage, coriander.
    • Shrubs: These plants are medium-sized with hard, woody, but not very thick stems. Their stems branch out from near the base. They are bushy and live for several years. Examples: Lemon, rose, jasmine.
    • Trees: These are tall and large plants with thick, hard, woody stems. Their stems branch out much higher up on the stem, away from the ground. They live for many years. Examples: Mango, neem, banyan, peepal.
  • Parts of a Plant: A typical plant consists of several parts, each with a specific function. The main parts are: Root, Stem, Leaf, Flower, and Fruit.
  • Stem: The stem grows above the ground and holds the plant upright. It bears leaves, flowers, and fruits.
    • Functions of Stem:
      1. Support: Provides structural support to the plant, holding leaves and flowers in positions where they can get maximum sunlight.
      2. Transport: Transports water and minerals absorbed by the roots to the leaves and other parts of the plant. It also transports food prepared by the leaves to other parts.
      3. Storage: Some stems store food (e.g., potato, ginger).
    • Experiment: To show transport of water by stem, place a plant with a white flower in coloured water. The stem will absorb the coloured water, and eventually, the white petals will show traces of the colour, indicating water transport.
  • Leaf: Leaves are generally green, flat structures attached to the stem. They are the food factories of the plant.
    • Parts of a Leaf:
      1. Petiole: The stalk that joins the leaf to the stem.
      2. Lamina (Leaf blade): The broad, green, flat part of the leaf.
      3. Veins: Lines on the leaf blade. The thick vein in the middle is called the midrib.
    • Venation: The pattern of veins on the leaf.
      1. Reticulate Venation: Veins form a net-like pattern on both sides of the midrib. Found in broad-leaved plants like peepal, rose.
      2. Parallel Venation: Veins are parallel to each other. Found in grasses and monocots like wheat, maize.
    • Functions of Leaf:
      1. Photosynthesis: Leaves prepare food for the plant using sunlight, water, and carbon dioxide, a process called photosynthesis. They contain a green pigment called chlorophyll, essential for this process.
      2. Transpiration: Leaves release excess water into the air in the form of water vapour through tiny pores called stomata. This process is called transpiration.
  • Root: Roots are generally underground parts of the plant.
    • Functions of Root:
      1. Anchorage: Roots firmly fix the plant to the soil.
      2. Absorption: Roots absorb water and minerals from the soil.
      3. Storage: Some roots store food (e.g., carrot, radish, turnip).
    • Types of Roots:
      1. Taproot: Has a main, thick root from which smaller side roots (lateral roots) branch out. Examples: Mustard, carrot, radish. Plants with reticulate venation usually have taproots.
      2. Fibrous Root: Consists of a cluster of thin, bushy roots arising from the base of the stem. There is no main root. Examples: Wheat, maize, grass. Plants with parallel venation usually have fibrous roots.
  • Flower: The most attractive part of a plant, responsible for reproduction.
    • Parts of a Flower:
      1. Sepals: Green, leaf-like structures at the base of the flower. They protect the flower when it is in the bud stage.
      2. Petals: Often brightly coloured and fragrant parts of a flower. They attract insects for pollination.
      3. Stamens: The male reproductive part of the flower. Each stamen consists of an anther (which produces pollen) and a filament.
      4. Pistil (or Carpel): The female reproductive part of the flower, located in the centre. It consists of three parts:
        • Stigma: The sticky top part that receives pollen.
        • Style: The tube connecting the stigma to the ovary.
        • Ovary: The swollen basal part containing small bead-like structures called ovules, which develop into seeds after fertilization.

Questions and Answers

1. Correct the following statements and rewrite them in your notebook.

  1. (a) Stem absorbs water and minerals from the soil.

    2. Answer: (a) Roots absorb water and minerals from the soil.

  2. (b) Leaves hold the plant upright.

    3. Answer: (b) Stem holds the plant upright.

  3. (c) Roots conduct water to the leaves.

    4. Answer: (c) Stem conducts water to the leaves.

  4. (d) The number of petals and sepals in a flower is always equal.

    5. Answer: (d) The number of petals and sepals in a flower is not always equal.

  5. (e) If the sepals of a flower are joined, its petals are also joined.

    6. Answer: (e) If the sepals of a flower are joined, its petals are usually separate.

  6. (f) If the petals of a flower are joined, then the pistil is joined to the petal.

    7. Answer: (f) If the petals of a flower are joined, then the pistil is usually separate from the petal.

2. Draw (a) a leaf, (b) a taproot, (c) a flower.

Answer: (Drawing-based question. Students should draw the following diagrams):

  • (a) Leaf: A typical leaf showing petiole, lamina, midrib, and veins.
  • (b) Taproot: A main thick root with smaller lateral roots branching from it (e.g., carrot or mustard root).
  • (c) Flower: A complete flower showing sepals, petals, stamens (anther and filament), and pistil (stigma, style, and ovary).

3. Can you find a plant in your school or home that has a long but weak stem? Write its name. Which category would you classify it into?

Answer: Yes, a money plant (Pothos) or a bitter gourd plant has a long but weak stem. These are classified as climbers or creepers. Climbers take support and climb up, while creepers spread on the ground.

4. Why is the root important for a plant? List two functions of roots.

Answer: Roots are very important for a plant because they perform vital functions:

  1. Anchoring the plant: Roots firmly fix the plant to the soil, providing stability and preventing it from being easily pulled out by wind or water.
  2. Absorption of water and minerals: Roots absorb water and essential mineral nutrients from the soil, which are crucial for the plant's growth and survival.
  3. Storage of food: Some roots, like those of carrots, radishes, and turnips, store food prepared by the plant.

Two main functions are anchoring and absorption.

5. What are the important parts of a flower? Describe briefly the function of each part.

Answer: The important parts of a flower and their functions are:

  1. Sepals:
    • Description: These are the green, leaf-like structures at the base of the flower.
    • Function: They protect the inner parts of the flower when it is in the bud stage.
  2. Petals:
    • Description: These are often brightly coloured and fragrant parts of the flower.
    • Function: Their attractive colours and scent attract insects (like bees) and birds for pollination.
  3. Stamen:
    • Description: This is the male reproductive part, consisting of an anther (produces pollen) and a filament (stalk supporting the anther).
    • Function: Produces pollen grains which are essential for reproduction.
  4. Pistil:
    • Description: This is the female reproductive part located in the center of the flower, consisting of the stigma, style, and ovary.
      • Stigma: Top sticky part that receives pollen.
      • Style: Tube connecting stigma to ovary.
      • Ovary: Swollen base containing ovules.
    • Function: Contains ovules that develop into seeds after fertilization. It is involved in producing fruits and seeds.

6. List the different types of venation in leaves and draw a diagram to show each.

Answer: There are two main types of venation in leaves:

  1. Reticulate Venation:
    • Description: In this type, the veins form a net-like pattern on both sides of the midrib.
    • Examples: Leaves of peepal, rose, mango, tulsi.
    • (Students should draw a leaf with a net-like vein pattern.)
  2. Parallel Venation:
    • Description: In this type, the veins are parallel to each other. They may be parallel to the midrib or to each other.
    • Examples: Leaves of grasses, maize, wheat, banana.
    • (Students should draw a leaf with parallel veins, e.g., a grass blade.)

7. What is the difference between a taproot and a fibrous root? Draw a diagram of each.

Answer:

Feature Taproot Fibrous Root
Structure Consists of a single, thick main root from which thinner lateral roots branch out. Consists of a cluster of thin, thread-like roots of similar size that arise from the base of the stem. No prominent main root.
Depth Penetrates deeper into the soil. Spreads out closer to the soil surface.
Associated Venation Typically found in plants with reticulate venation (e.g., rose, mango). Typically found in plants with parallel venation (e.g., grass, maize).
Examples Carrot, Radish, Mustard, Pea, Turnip. Wheat, Maize, Rice, Grass, Onion.

Diagrams:

  • (Students should draw a diagram showing a taproot with a main root and branching lateral roots.)
  • (Students should draw a diagram showing a fibrous root with a bunch of similar-sized roots emerging from the stem base.)

8. Write a short note on the importance of leaves.

Answer: Leaves are incredibly important for a plant's survival and for life on Earth. They are often called the "food factories" of the plant because their primary function is to prepare food through a process called photosynthesis. During photosynthesis, leaves use sunlight, water absorbed by roots, and carbon dioxide from the air to produce glucose (food) and oxygen. The oxygen released is vital for the survival of humans and animals.

Another crucial function of leaves is transpiration. Through tiny pores called stomata, leaves release excess water in the form of water vapour, which helps in the upward movement of water and minerals in the plant and also helps cool the plant. Without leaves, plants would not be able to produce their own food, and the oxygen cycle would be severely disrupted, impacting all living organisms.

9. Fill in the blanks:

  1. (a) Green plants prepare their own food by the process of ________________.

    2. Answer: (a) Green plants prepare their own food by the process of photosynthesis.

  2. (b) The food prepared by the plant is stored in different parts as ________________.

    3. Answer: (b) The food prepared by the plant is stored in different parts as starch.

  3. (c) Water and minerals from the soil are absorbed by the ________________.

    4. Answer: (c) Water and minerals from the soil are absorbed by the roots.

  4. (d) The part of a plant that prepares food is the ________________.

    5. Answer: (d) The part of a plant that prepares food is the leaf.

  5. (e) The process of giving out water vapour by plants is called ________________.

    6. Answer: (e) The process of giving out water vapour by plants is called transpiration.

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