Answer the following questions:
What is germination ?
What are the special features of the seeds which get dispersed by winds?
3.
How are animals helpful in the dispersal of seeds?
4.
Name the different stags of agriculture.
5.
What does a farmer do to protect his crop ?
6.
Draw a seed to show both its external and internal parts.
Answers
Answer:
seed has the following parts:
Seed coat: It is the outer covering the of seed. It protects the internal parts.
Seed leaves or cotyledons: Cotyledons are present inside the seed. Cotyledons absorb the food from the parent plant and store it for the embryo. They also protect the embryo. Some seeds have two seed leaves like gram, pea, bean, etc. Such seeds are called dicot or dicotyledonous. Some seeds have only one seed leaf. They are called monocot or monocotyledonous.
Embryo or baby plant: It is present inside the seeds which develop into a new plant. The embryo gives rise to a baby shoot (plumule) and root (radical).
SeedStructure of a seed (Source: Shutterstock)
Activity I
Take four shallow dishes. Place cotton in each dish. Take a few gram seeds and put some of them on each dish. Now, follow the steps gives below for each dish.
Dish 1: Keep this dish in a place where it gets an adequate amount of air and warmth. The cotton should be moist.
Dish 2: Place the second dish in the refrigerator and keep the cotton moist.
Dish 3: Place it where it can get an adequate amount of air and warmth. Do not wet the cotton.
Dish4: Place it where it can get adequate sunlight. Keep the seed and the cotton covered with water.
Seed
Result: We will see in this activity the seed germinate only in jar B because jar B had water, air, and warmth required for the seed to germinate. Jar A did not have warmth or sunlight. Jar C there was no air for seed. In jar A, the seed did not get water. This shows that if any condition is missing, the seed will not grow into new plants. So air, water, and sunlight are the conditions necessary for germination.
Germination of a Seed
Germination means the development of a seed into a new plant. All seeds do not germinate. Only those which get suitable conditions grow into new plants. The conditions necessary for a seed to germinate are:
Air to breathe.
Water to make the seed coat soft. This enables the baby plant to break the seed coat open and come out.
Warmth to make its cells active.
Seed
(Source: Shutterstock)
Germination occurs in following stages:
The seeds absorb water through the seed hole. The cells of the embryo start dividing and increasing in size.
The seed coat breaks open and the root (radical) sprout and grows downwards.
Then the shoot (plumule) start growing upwards, which later produces stem and leaves.
When the seedling grows green leaves, it starts making its own food.
By this time, cotyledons dry up and fall. The seedling then develops into a new plant.
SeedGermination of seed (Source: Shutterstock)
Dispersal of Seed
Plants are fixed to the ground. They cannot move from place to place. If all the seeds of a plant fall and germinate near it, they will not get favourable conditions for growth. Therefore, it is necessary for them to get scattered and grow away from the parent plant. The scattering of seed for growing away from their parent plant is called dispersal of a seed.
There are some natural agents that help in scattering the seeds away from the parent plant. These are wind, water, animals and by the explosion of fruits. Some seeds and fruits develop a special structure that helps the