2. Plants: Structure and Function
Complete solutions to the Exercises. Maharashtra State Board (Balbharati), Grade Seven General Science.
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Exercises
(a) Spiny fruits: Jackfruit, datura, castor
(b) Spiny stem: Rose, cactus (nivdung), acacia (babhul)
(c) Red flowers: Hibiscus, rose, gulmohar
(d) Yellow flowers: Sunflower, marigold, Indian laburnum (bahava)
(e) Leaves which close at night: Tamarind, touch-me-not (lajalu), rain tree
(f) Single-seeded fruits: Mango, ber, coconut
(g) Many-seeded fruits: Papaya, guava, watermelon
Flower observed: Hibiscus (jaswand)
The hibiscus flower is large and red. It is attached to the stem by a stalk called the pedicel. The swollen tip of the pedicel is the receptacle. All the parts of the flower are on it.
The outer green part is the calyx. It has five sepals. It protects the flower in the bud stage.
Next is the corolla. It has five large, coloured petals. They attract insects.
In the centre there is a long tube. Many stamens are attached to it. Each stamen has a filament and an anther. The anther contains pollen grains. The stamens form the male part, the androecium.
The female part is the gynoecium. It has an ovary, a style and stigmas. The ovary contains ovules. The stigma receives pollen grains.
(a) Jowar and moong
Similarities: Both are flowering crop plants. Both have roots, stem, leaves, flowers and seeds. Their seeds are used as food.
| Jowar | Moong |
|---|---|
| Monocot plant | Dicot plant |
| Fibrous roots | Tap root |
| Long, narrow, simple leaf | Compound leaf with three leaflets |
| Parallel venation | Reticulate venation |
(b) Onion and coriander
Similarities: Both are small plants. Both grow from seeds. Both are used in cooking.
| Onion | Coriander |
|---|---|
| Monocot plant | Dicot plant |
| Fibrous roots | Tap root |
| Hollow, tube-like leaves; fleshy leaf bases form the bulb | Small leaves divided into many parts |
| Parallel venation | Reticulate venation |
(c) Leaves of banana and mango
Similarities: Both are simple, green leaves. Both make food. Both have a petiole and a mid-vein.
| Banana leaf | Mango leaf |
|---|---|
| Very large and broad | Medium-sized, long and narrow |
| Parallel venation | Reticulate venation |
| Soft; tears easily | Thick and leathery |
| Monocot plant | Dicot plant |
(d) Coconut tree and jowar stalk plant
Similarities: Both are monocot plants. Both have fibrous roots and parallel venation. Their stem is unbranched.
| Coconut tree | Jowar |
|---|---|
| Tall tree | Crop plant |
| Lives for many years | Lives for a few months |
| Hard, woody trunk | Soft stalk with nodes |
| Large compound leaves at the top | Long, narrow leaves along the stalk |
(A) Monocotyledonous seed (maize grain)
The picture shows a maize grain. It has only one cotyledon. It does not split into two parts. Plants from such seeds have fibrous roots. Examples: wheat, rice, jowar.
(B) Dicotyledonous seed (bean / gram)
The picture shows a bean seed. It has two cotyledons. After soaking, it splits into two equal parts. The cotyledons store food for the young plant. Examples: pea, groundnut, moong.
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- Root: It fixes the plant in the soil. It absorbs water and minerals. Some roots store food.
- Stem: It supports branches, leaves and flowers. It carries water and food to all parts.
- Leaf: It makes food by photosynthesis. Exchange of gases takes place through leaves.
- Flower: It is the reproductive part. It forms fruits and seeds.
- Fruit: It protects the seeds. It helps in spreading the seeds.
- Seed: It grows into a new plant.
(1) Leaves with smooth surface – Rubber plant, mango, lotus
The rubber plant has large, thick and shiny leaves. They are very smooth. A white milky juice comes out when a leaf is broken.
(2) Leaves with rough surface – Teak, sunflower, pumpkin
Teak is a tall tree. Its leaves are very large. Their surface is rough because of tiny hairs.
(3) Fleshy leaf – Aloe, bryophyllum (panfuti)
Aloe (korphad) has long, thick and fleshy leaves. They store water and a jelly-like juice. So the plant can live in dry places.
(4) Spines on leaf – Pineapple, agave (ghaypat), prickly poppy
The pineapple plant has long, stiff leaves. Their margins have sharp spines. The spines protect the plant from animals.
The plant parts hidden in the grid are marked in colour. Words run down, across and diagonally upwards.
- Root cap – 1st column, downwards
- Root hair – last row, left to right
- Radicle – 7th column, downwards
- Flower – last column, downwards
- Stem – 6th column, top four letters
- Bud – 1st row, 2nd to 4th letters
- Petals – 7th row, left to right
- Calyx, node, vein, leaf – diagonals, reading upwards to the right
- Open the Paint program on the computer.
- Draw the outline of a leaf with the Curve or Pencil tool. Draw its veins.
- Fill the leaf with green colour. Write its name with the Text tool.
- Make a folder in your name. Save each sketch in it with File → Save As.
Draw simple and compound leaves, and leaves with parallel and reticulate venation.