Chapter Notes and Summary
• Classification of plants : There are different kinds of plants at various places. Plants are classified mainly into three groups on basis of their height, stem type and branching pattern.
• Climbers and creepers : Plants having weak stems that take support on neighbouring structures and climb up are known as Climbers, e.g., Money plant, gourd plant, etc. Creepers are plants with weak stems that cannot stand upright, so they spread on ground, e.g., Grape-vine.
• Herbs : These are small plants with soft stem, e.g., Wheat, Paddy.
• Trees : These are large and tall plants with hard and woody stem, e.g., Mango, Neem.
• Shrubs : These are medium sized plants with thin branches, e.g., Rose, Lemon.
• Roots : These are underground parts of a plant. They are two types—Tap root and Fibrous root.
(i) Tap root : In tap root, there is a main root from which many branching roots grow sideways, e.g., Radish, Carrot, etc.
(ii) Fibrous root : It is a cluster of thin fibre-like roots at base of stem, e.g., Maize, Wheat, etc.
• Functions of roots :
(a) Roots hold plant firmly in soil.
(b) They absorb water and minerals from soil.
(c) They prevent soil erosion.
• Modified roots : In some plants, roots get modified and perform additional functions like storage of food, e.g., Turnip, Radish etc. and provide additional support to plant, e.g., in Banyan tree, rope like roots arise from main branches and reach ground to give support. These roots are called Prop roots.
• Stem : It is link between roots, leaves and flowers. stem of a tree is called trunk. point on stem from where a leaf or another branch grows is called node and portion of stem between two nodes is called internode.
Functions of stem :
(a) It carries water and minerals from roots to different parts of plant.
(b) It carries food made by leaves to other parts of plant.
(c) It supports branches, flowers and fruits.
• Modified stem : Some modified stems can store food like potato, ginger, etc. Some can make food such as cactus, prickly pear.
• Leaf : leaves of different plants differ in shape and size. green colour of leaves is due to presence of chlorophyll.
• Parts of a leaf : flat green part of a leaf is called lamina. lamina is attached to stem by a short stalk called petiole. petiole continues in leaf as mid rib that branches out to form a network of lines called veins.
The pattern of veins in leaf is known as leaf venation. It can be reticulate (if network of veins form a crisscross on either side of mid rib) or parallel (if veins are parallel to each other and to mid rib on either side of it).
• Functions of leaves :
(a) Leaves prepare food by process of photosynthesis from carbon dioxide, water, chlorophyll and sunlight.
(b) They release water vapour by process of transpiration.
• Flowers : These are of different sizes, shapes, colours and fragrances. They are actually modified shoots.
• Parts of a flower :
(i) Sepals : outermost green-leafy structures in a flower are called sepals. They protect flower at bud stage.
(ii) Petals : leaf like coloured structures next to sepals are known as petals. bright colour and fragrance of petals attract insects that help plants in reproduction.
(iii) Stamens : These are little stalks with swollen tops around centre of flower. These are male parts of flower. Each stamen consists of a thin green stalk called filament with a bag-like top, called anther which carries pollen grains.
(iv) Pistil or Carpel : A flask-shaped structure in centre of flower is known as pistil or Carpel. It is female part of flower. lower broader portion of pistil is called ovary and narrow upper portion of pistil is called style. sticky end at top of style is called stigma. ovary contains ovules.
• Functions of flower :
(a) Flower contains male and female reproductive organs that are needed for reproduction.
(b) Different coloured flowers makes plant beautiful.