Remember the bird that dropped the seed on the ground?
Most of the plants grow from seeds. Plants bear flowers which develop into fruits. Inside fruits are found seeds. Some fruits have a single seed while others have few or many seeds.
Every seed has an outer covering called seed coat. Each seed contains a small unborn plant called an embryo inside the seed coat. The embryo has two parts –the baby shoot and the baby root. The baby shoot grows above the ground to form the stem, leaves and flowers while the baby root grows under the ground to form the roots.
The leaf the embryo is called the cotyledon. It contains food for the tiny plant to grow. Take a kidney bean (rajma) which has been soaked overnight. Peel off its outer coating and separate the two halves. These are the cotyledons. Look for a tiny curled dot over one of them. What do you think it is?
The growing of a new plant from a seed is called germination. Germination of seeds takes place under certain conditions. Let us read this story to find out haw a big tree grows from a tiny seed.
One day bird dropped a seed on the ground. It remained there till a cow walked over it and unknowingly pushed it deep inside the soil.
It rain that night and the seed got soaked in water.
The seed felt cozy in the warmth and moisture of the soil.
Next day, a tiny shoot came out of the seed. After a week, it speeds out through the soil.
It caught the sunlight and grew further as the days passed.
One morning, some tiny leaves sprouted out of the shoot and started to make food, using sunlight. This made the little plant grow.
Now, years later, the tiny plant has grown into a big tree, all laden with fruits!
Different seeds
The world’s smallest seed is of orchid and the world’s largest seed is found in the double coconut. The peas that we eat are actually seed. Soya beans are the most widely used seeds in the world.
Dispersal of seeds
This is one of the ways seeds produce new plats at the places. This process of spreading seeds is called dispersal.
It is important for seeds to move to far –off places. If all seeds from the parent plant fell to the ground around it, many of them would die due to lack of enough space, light and air.
Seeds get dispersed in different ways. Some of the common agents of seed dispersal are:-
Wind- seeds dispersed by the wind are small and light. Some seeds are hairy or have `wings’ to help them float in air. Cotton and dandelion seeds are dispersed by wind.
Explosion –pea pods burst or explode are when they become dry, scattering the seeds over a large area. The fruits of the rubber tree also burst open and scatter the seeds into the air.
Water- seeds dispersed by water are generally spongy and hence float easily like those of lotus and water lily. Some fruits like the coconut have air trapped between the fibers. Water carries them to far ff places.
Birds and animals-many seeds like those of goose grass have hooks or spines on them. They get attached to the bodies of birds and animals passing by and are carried away to different places.
Dispersal of seeds also occurs when animals and human beings eat fruits like plums and peaches and throw away the hard seeds. Animals that eat seedy fruits like grapes and tomatoes pass out the seeds from their bodies as waste. These seeds, then germinate into new plants under favorable conditions.
Reproduction without seeds
Not all new plants are born from seeds. Sometimes they grow from other parts of the parent plant. This is called vegetative propagation.
Plants with stems grow horizontally along the ground produce buds. New plants grow from these buds. This is called 1budding’. Strawberries grow from seeds as well as from buds on the stems.
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