GETTING TO KNOW PLANTS:
Plants can be classified on the basis of their height, stem and branches. On these parameters, plants can be of three types, viz. herbs, shrubs and trees.
Creepers- Plants with weak stem that cannot stand upright and spread on the ground are called creepers. Examples: Pumpkin, Watermelon, sweet potato, etc.
Climber- Plants with weak stem that needs support is called climber. Examples: Grapevine, money-plant, cucumber, bean, etc.
Structure of a typical plant: A typical plant contains two main parts, viz. roots and stem. The stem bears leaves, flowers and fruits.
Root- The underground part of a plant is called root. It is usually pale in colour.
The root system consists of two types of roots:
Functions of roots-
Stem- Stem usually grows above the ground. The stem makes the main structural framework of the plant. The stem bears leaves, branches, buds, flowers and fruits. The point from where branches or leaves grow is called node. The portion of a stem between two consecutive nodes is called the internode.
Functions of the stem:
Leaf: The leaf is a thin, flat and green structure which arises from the node of the stem. The green colour of leaves is due to the presence of chlorophyll. Chlorophyll is a green-coloured pigment. The flat green portion of the leaf is called leaf-blade or lamina. The leaf is attached to the stem by a short stalk; called petiole.
Venation: Arrangement of veins in a leaf is called venation. When the veins make a network like structure, it is called reticulate venation, e.g. leaves of banyan, mango, jackfruit, etc. When the veins run parallel to each other, it is called parallel venation, e.g. leaves of paddy, wheat, grass, etc.
Stomata- There are many small openings on the lower surface of a leaf. These are called stomata. Stomata allow gases to enter or exit the leaf. Unwanted water is also removed through stomata; in the form of water vapour.
Transpiration- Loss of water vapour from plants through stomata and lenticels is called transpiration. A major portion of transpiration occurs through stomata.
Functions of Leaves:
Photosynthesis- This is the main function of a leaf. Plants prepare food from carbon dioxide and water; in the presence of chlorophyll and sunlight. This process is called Photosynthesis.
Breathing: Stomata in leaves also facilitate breathing by leaves.
Flower- Flower is the most beautiful and colourful part of a flowering plant. It is the reproductive part of a plant.
Structure of a flower-
Sepal- The outer green leafy structure in a flower is called sepal. Petals make the first whorl of a flower. This whorl is called calyx. It protects the flower at the bud stage.
Petals- The coloured leaf-like structures; next to the sepals; are called petals. The bright colours of the petals, attracts insects. This helps the plants in reproduction. The whorl formed by the petals is called corolla.
Stamens- Around the centre of the flower there are many little stalks with swollen tops. These are called Stamen. It is the male part of the flower. Each stamen consists of a green stalk called filament. A capsule-like structure; called anther is at the top of the stamen. The anther produces pollen grains. Pollen grains are powder like particles and take part in reproduction.
Pistil- It is the female part of the flower. It is a flask- shaped structure in the middle of the flower. It is divided into three parts.