Theory & Procedure, Embryo of Dicot Seeds Class 10 Notes | EduRev

Science Class 10

Class 10 : Theory & Procedure, Embryo of Dicot Seeds Class 10 Notes | EduRev

The document Theory & Procedure, Embryo of Dicot Seeds Class 10 Notes | EduRev is a part of the Class 10 Course Science Class 10.
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Objective

Our objective is to identify the different parts of an embryo of dicot seeds- pea, gram and bean.

Theory

A seed is a small embryonic plant enclosed inside a seed coat. It is the ripened and fertilised ovule of gymnospermic and angiospermic plants. A seed has a three parts:

  1. An embryo
  2. A supply of nutrients for the embryo
  3. A seed coat

The embryo is an undeveloped plant inside a seed from which a new plant develops. All seeds do not have the same size, shape and colour. We will be looking at the embryo of a pea, gram and bean seed to identify their different parts.

Plant Embryo

Plant embryos in seeds have structures called cotyledons. A cotyledon is the central portion of a seed embryo to which the epicotyls- the immature shoot, and the radicle- the immature roots, are attached.

Plants are classified according to the number of cotyledons present in the embryo. If the embryo has one cotyledon (monocotyledon) it is a monocot plant, and if there are two cotyledons (dicotyledon), it is a dicot plant.

Seed Subdivision

Based on the type and location of storage materials, seeds can be subdivided into endosperms and non endosperms.

Endospermic Seeds

Endospermic seeds are those that have an endosperm in the mature seed. It is fleshy, oily, surrounds the embryo, and functions as the sole food storage organ. Inside the seed coat, a thin and papery cotyledon is present. Monocot plants have endospermic seeds.

Non-endospermic Seeds

Non-endospermic seeds do not have an endosperm in the mature seed. The cotyledons are thick and fleshy, and function as the sole food storage organs. Dicot plants have non-endospermic seeds.

Theory & Procedure, Embryo of Dicot Seeds Class 10 Notes | EduRev

Seed Germination

Germination is the process in which the seed breaks apart, and the embryo inside begins to grow with the help of water and nutrients from the soil. Seeds normally begin to germinate when they get an appropriate range of soil, temperature and when water and oxygen are available. During germination the seeds absorb water either through the micropyle (pore like opening), if it is present, or through the testa (outer seed coat) when it is permeable. The entry of water activates the embryo cells.

Germination in a Dicot Seed (Pea, Gram and Bean)

The pea, gram and bean seeds have two seed coats that envelope and protect the embryo. The outer seed coat called the testa is thick and strong. The inner coat is called tegmen, which is thin and membranous.

The outer seed coat has a notch on one side and a scar along the notch, called the hilum. It is the hilum that attaches the seed to the inner margin or the seed stalk. There is a small pore called micropyle located at one end of the hilum. The seed imbibes water through the microphyle.

Once soaked for the required time, the part of the plant that first emerges from the seed is the embryonic root known as the radicle. The radicle allows the seedling to anchor itself to the ground and start absorbing water.

After the root starts absorbing water, an embryonic shoot emerges from the seed. This shoot comprises of three main parts- the cotyledons (seed leaves), the hypocotyl (section of shoot below the cotyledons), and the epicotyl (section of shoot above the cotyledons).

Theory & Procedure, Embryo of Dicot Seeds Class 10 Notes | EduRev

Learning Outcomes

  • Students understand the meaning of cotyledons, endosperm, embryo, etc.
  • Students understand the different parts of the embryo of the dicot seed.
  • Students understand the difference between endospermic and non-endospermic seeds.
  • Students understand the experiment better through the animated demonstration.

Materials Required

Theory & Procedure, Embryo of Dicot Seeds Class 10 Notes | EduRev

Pea Seed

Real Lab Procedure

  • Take some pea seeds and put them in a beaker containing distilled water.
  • Soak the pea seeds overnight.
  • Take one seed from the beaker using a forceps and place it in a watch glass.
  • Remove the seed coat of the pea seed, using the forceps and the needle.
  • Pick the seed using the forceps and place it on the stage plate of the dissection microscope.
  • Separate the two cotyledons of the pea seed using the forceps and the needle.
  • Observe the seed through the dissection microscope.

Observations

  • Pea seeds are round in shape.
  • One end of the embryonic axis called the plumule, lies enclosed between the two cotyledons. It develops into the shoot.
  • We can see a epicotyl and a hypocotyl on each seed, which is located above the root and below the stalk of the cotyledon.
  • The other end of the embryonic axis called the radicle, protrudes outside the cotyledons. This develops in to the root.
  • The pea seed contains two thick fleshy cotyledons which are foods storage organs.
  • Since two cotyledons are seen in pea seeds, they are dicot seeds.

Gram Seed

Real Lab Procedure

  • Take some gram seeds and put them in a beaker containing distilled water.
  • Soak the gram seeds overnight.
  • Take one seed from the beaker using a forceps and place it in a watch glass.
  • Remove the seed coat of the gram seed, using the forceps and the needle.
  • Pick the seed using the forceps and place it on the stage plate of the dissection microscope.
  • Separate the two cotyledons of the gram seed using the forceps and the needle.
  • Observe the seed through the dissection microscope.

Observations

  • Gram seeds are round in shape.
  • We can easily identify a scar called hilum.
  • A micropyle can be observed on the gram seed through which the seed imbibes water.
  • The gram seed contains two thick fleshy cotyledons that are foods storage organs.
  • We can observe a plumule on the gram seed which giving rise to the first true leaves.
  • The radicle is the embryonic root inside the seed which grows downward in the soil.
  • Above the radicle we can see an embryonic stem or hypocotyl.
  • Since two cotyledons are seen in gram seeds, they are dicot seeds.

Red Kidney Bean

Real Lab Procedure

  • Take some seeds of red kidney bean and put them in a beaker containing distilled water.
  • Soak the bean seeds overnight.
  • Take one seed from the beaker using a forceps and place it in a watch glass.
  • Remove the seed coat of the bean seed, using the forceps and the needle.
  • Pick the seed using the forceps and place it on the stage plate of the dissection microscope.
  • Separate the two cotyledons of the bean seed using the forceps and the needle.
  • Observe the seed through the dissection microscope.

Observations

  • The beans are kidney shaped.
  • There is a scar along the notch called the hilum.
  • A small pore called micropyle is located at one end of the hilum.
  • One end of the embryonic axis called the plumule lies enclosed between the two cotyledons. It develops into the shoot.
  • We can observe a hypocotyl which is an embryonic stem.
  • The other end of the embryonic axis called the radicle protrudes outside the cotyledons. This develops in to the root.
  • The kidney bean seed contains two thick fleshy cotyledons that are foods storage organs.
  • Since two cotyledons are seen in bean seeds, they are dicot seeds.

Simulator Procedure (as performed through the Online Labs)

  • To change the type of the seed use the drop down list, ‘Select the seed type:’
  • To change the sample seed use the drop down list, ‘Select the sample seed:’
  • Drag the forceps towards the seed and remove the seed cover.
  • Drag and drop the seed onto the stage of the microscope using the forceps.
  • Drag the needle and forceps toward the seed to separate the two cotyledons.
  • Click on the eye piece of the compound microscope to enlarge the view of  seeds.
  • Drag and place the correct choice to the corresponding part of seed embryo. (If the choice is wrong, the selection goes back.)
  • Click on the information icon to see the inference.
  • You can redo the experiment anytime by clicking on the ‘Reset’ button.

Precautions

  • Seed should be soaked overnight in distilled water.
  • Be careful when removing the seed coat from the seed, to avoid damage to it.
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