To identify the different parts of an embryo of a dicot seed - Lab Work

To identify the different parts of an embryo of a dicot seed - Science Practicals

Aim
To identify the different parts of an embryo of a dicot seed (Pea, gram or red kidney bean).

Theory
A seed is a small embryonic plant enclosed inside a seed coat. During sexual reproduction male gamete fuses with female gamete and zygote is formed. After some rest period zygote divides, re-divides and finally develops into an embryo. In the earlier stages of development of embryo there is no difference between monocots and dicots, but their development differs in later stages. The process of development of mature embryo from zygote is called embryogeny.

Materials Required
Permanent slides of dicot embryo showing different stages and a compound microscope.

Procedure
Step 1: Observe each permanent slide in sequence from early stages to maturity first under low-power magnification and then under high-power magnification of a compound microscope.
Step 2: Draw diagrams and identify the different parts.
Step 3: Label the different regions of the embryo.
Observations
1. Zygote divides transversely forming a basal cell towards the micropyle and a terminal cell towards the chalaza.
2. The basal cell divides by transverse divisions and finally forms 6-10 celled suspensors.
3. The uppermost cell of suspensor swells up to form a vesicular cell while the lowest cell of the suspensor is called hypophysis. Hypophysis forms part of the radical and root cap.
4. The terminal embryonal cell divides by transverse and vertical divisions and forms 16-celled globular embryo.
5. The globular embryo later becomes heart-shaped due to its differentiation into cotyledons.
6. The embryo and cotyledons become larger and curved.

Results and Discussions
The prepared permanent slides show successive stages of the development of dicot embryo. The young dicot embryo is globular but changes to heart-shaped structure at maturity due to differentiation into cotyledons.
Precautions
1. Focus the slides properly.
2. Study the slides first under low-power magnification and then under high-power magnification of the compound microscope.
3. Draw diagrams as seen under the microscope.
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