Question

Trace the development of embryo after syngamy in a dicot plant

Answer 1

Hint: The two sorts of fusions, syngamy and triple fusion happens in an embryo sac the phenomenon is termed double fertilisation, an occasion unique to flowering plants. The early stages of embryogeny are similar in both monocotyledons and dicotyledons.

Complete step by step answer:
Development of embryo after syngamy in dicot plants:
- After entering one among the synergids, the pollen tube releases the two male gametes into the cytoplasm of the synergid.
- One of the male gametes moves towards the ovum or egg cell and fuses with its nucleus which results in completing the syngamy. This leads in the formation of a diploid cell, the zygote.
- The other male gamete moves towards the where two polar nuclei located within the central cell and fuses with them to produce a triploid primary endosperm nucleus or PEN which results in the fusion of three haploid nuclei it is termed triple fusion.
- The central cell after triple fusion results in formation in the primary endosperm cell (PEC) and develops into the endosperm while the zygote develops into an embryo.
- Embryo formed at the micropylar end of the embryo sac where the zygote is located. Most zygotes divide only after a certain amount of endosperm is formed.
- The zygote gives rise to the proembryo and results in the globular shaped, heart- shaped and mature embryo.
- A typical dicotyledonous embryo, consists of an embryonal axis with two cotyledons.
- The portion of embryonal axis above the extent of cotyledons is the epicotyl, which terminates with the plumule or stem tip.
- The cylindrical portion below the extent of cotyledons is hypocotyl that goes at its lower end in the radicle or root tip. The root tip having a root cap.

Additional Information:
Development of embryo after syngamy in a monocot plant
- Embryos of monocotyledons possess only one cotyledon.
- In the Gramineae family the cotyledon is known as scutellum that is situated towards one side (lateral) of the embryonal axis.
- At its lower end, the embryonal axis has the radical and root cap enclosed in an undifferentiated sheath called coleorhiza.
- The portion of the embryonic axis above the level of attachment of the scutellum is the epicotyl.
- Epicotyl features a shoot apex and a few leaf primordia enclosed within a hollow foliar structure, the coleoptile.


Note:
- The cotyledons of the embryo are simple structures, which are generally thick and swollen due to storage of food reserves as in legumes.
- Mature seeds may be non- albuminous or albuminous.
- Non- albuminous seeds don't have residual endosperm as it is completely consumed during embryo development example: pea, groundnut, sunflower.
- Albuminous seeds retain a part of endosperm as it is not completely used up during embryo development example: wheat, maize, barely.