Chapter VII (S) (VI)

Getting to know plants

We can see a lot of variety in plants around us i.e. small, big patches of green on the soil etc.

By knowing about different parts of the plants, we can easily differentiate among them.

Types of Plants- herbs, Shrubs and Trees

Unwanted plants grow with the crops in the crop fields are known as weeds.

Plants with green and tender stems are called herbs. They are usually short

and may not have many branches.

Some plants have the stem branching out near the base. The stem is hard but not very thick. Such plants are called shrubs.

Some plants are very tall and have hard and thick brown stem. The stems have branches in the upper part, much above the ground. Such plants are called trees.

Plants with weak stems that cannot stand upright and spread on the ground are called creepers, while those that take support on neighbouring structures and climb up are called climbers. These are different from the herbs, shrubs and trees.

Important Parts of Plants

STEM  

Stem conducts water so that the minerals dissolved in water can move up in the Stem along with the water.

The water and minerals reach the leaves and other parts attached to the stem, through narrow tubes inside the Stem.

LEAF  

The part of a leaf by which it is attached to the stem is called petiole.

The broad,green part of the leaf is called lamina.

The lines on the leaves are called veins.

The thick vein in the middle of the leaf is called Midrib.

The design made by veins in a leaf is called the leaf venation.

If this design is net-like on both sides of midrib, the venation is reticulate.

In the leaves of grass you might have seen that the veins are parallel to one another. This is parallel venation.

Water comes out of leaves in the form of vapour by a process called transpiration. Plants release a lot of water into the air through this process.

Leaves prepare their food in the presence of sunlight and a green coloured substance present in them. For this, they use water and carbon dioxide from air. This process is called photosynthesis. Oxygen is given out in this process. The food prepared by leaves ultimately gets stored in different parts of plant as starch.

Plants get their food from their own leaves which prepare it with the help of photosynthesis.

We see that the stem supplies leaf with water. The leaf uses the water to make food. The leaves also lose water through transpiration. How do the stem and leaves get the water? That is where

the roots come in!

ROOTS

we could not easily pull out the plants from the soil, right? We dug them out. The roots help in holding the plant firmly in the soil. They are said to anchor the plant to the soil.

For roots of the kind shown in Fig. (a), the main root is called tap root and the smaller roots are called lateral roots.

Plants with roots as shown in Fig.  (b) do not have any main root. All roots seem similar and these are called fibrous roots.

Roots and Leaf venation are very interestingly connected to each other. If you want to know what kind of roots a plant has, he need not pull it out. He just has to look at its leaves. Leaves with reticulate venation have tap roots and Leaves with parallel venation have fibrous roots.

Roots absorb water and minerals from the soil and the stem conducts these to leaves andother parts of the plant. The leaves prepare food. This food travels through the stem and is stored in different parts of a plant. We eat some of these as roots— like carrot, radish, sweet potato, turnip

and tapioca. We also eat many other parts of a plant where the food is stored.

Stem is a two way street . The water and minerals goes up to the different parts of the plant and the food prepared by leaves goes down to the roots for its nourishment.

Flower

Observe Fig. below carefully. Look at the prominent parts of the open flower. These are the petals of the flower. Different flowers have petals of different colours.

Where do you think the petals are in a closed bud? Which is the most prominent part in a bud? Did you see that this part is made of small leaf-like structures? They are called sepals.

To see the inner parts of the flower clearly, you have to cut it open, if its petals are joined. For example, in datura and other bell shape flowers, the petals have to be cut lengthwise and spread

out so that the inner parts can be seen clearly (Fig. below).

Remove the sepals and petals to see the rest of the parts. Study the Fig. below carefully, compare your flower with the illustration and identify the stamens and pistil in your flower.

The innermost part of a flower is called the pistil. If you cannot see it completely, remove the remaining stamens. Identify the parts of the pistil with the help of Fig. below.

Observe the inner parts of the ovary using a lens (Fig. below). Do you see some small bead like structures inside the ovary? They are called ovules.