Module: | Pre-fertilization: Micro/Megasporogenesis
Q21: Consider the following statements regarding the stages of dicot embryogeny:
1. The zygote divides mitotically to give rise to a multi-celled structure known as the proembryo.
2. The proembryo subsequently passes through distinct morphological stages: the globular, heart-shaped, and mature embryo stages.
3. Embryogeny universally occurs at the chalazal end of the embryo sac where the zygote is originally situated.
Which of the above statements is/are correct?
2. The proembryo subsequently passes through distinct morphological stages: the globular, heart-shaped, and mature embryo stages.
3. Embryogeny universally occurs at the chalazal end of the embryo sac where the zygote is originally situated.
Which of the above statements is/are correct?
✅ Correct Answer: A
The correct option is A. Statements 1 and 2 are correct, but Statement 3 is strictly incorrect.
Embryogeny refers to the early stages of embryo development from the zygote.
Structurally, the diploid zygote undergoes a transverse mitotic division to form the initial proembryo.
As cellular proliferation continues, the mass of cells assumes specific geometries, progressing predictably from a globular shape to a heart shape (as the two cotyledons begin to differentiate), and finally to a fully formed mature dicot embryo.
Statement 3 is a spatial error: the egg cell, and subsequently the zygote, is always located at the micropylar end of the embryo sac, adjacent to the synergids, not the chalazal end.
Thus, embryogeny strictly initiates at the micropylar pole.
Embryogeny refers to the early stages of embryo development from the zygote.
Structurally, the diploid zygote undergoes a transverse mitotic division to form the initial proembryo.
As cellular proliferation continues, the mass of cells assumes specific geometries, progressing predictably from a globular shape to a heart shape (as the two cotyledons begin to differentiate), and finally to a fully formed mature dicot embryo.
Statement 3 is a spatial error: the egg cell, and subsequently the zygote, is always located at the micropylar end of the embryo sac, adjacent to the synergids, not the chalazal end.
Thus, embryogeny strictly initiates at the micropylar pole.