Q.54 The type of embryogeny in which the apical cell of a 2-celled proembryo divides transversely
and both the daughter cells contribute to the development of embryo is known as ________.
- Asterad type
- Crucifer type
- Chenopodiad type
- Caryophyllad type
The type of embryogeny is Caryophyllad type.
Detailed Explanation
In angiosperm embryogenesis, the zygote first divides asymmetrically into apical cell (forms embryo proper) and basal cell (forms suspensor). The question specifies the apical cell of 2-celled proembryo divides transversely, with both daughter cells contributing to embryo development (not suspensor).
Caryophyllad type (Caryophyllaceae family):
-
Apical cell divides transversely into two cells
-
Both terminal and median cells contribute to embryo proper
-
Basal cell forms suspensor
-
Forms T-shaped 4-celled stage
Option Analysis
Asterad type: Radial divisions in apical cell; both cells contribute, but first division longitudinal (not transverse).
Crucifer type (Brassicaceae/onion type): Apical cell divides longitudinally first; classic dicot pattern. Terminal cell forms embryo; median cell absorbed into suspensor.
Chenopodiad type: Basal cell contributes to embryo (both cells from zygote division form embryo parts); apical cell division pattern differs.
Caryophyllad type: Correct—Apical cell transverse division; both daughters contribute to embryo proper.
Introduction
The type of embryogeny where the apical cell of a 2-celled proembryo divides transversely and both daughter cells contribute to embryo development is Caryophyllad type, characteristic of Caryophyllaceae (pink family). This forms the distinctive T-shaped stage unlike longitudinal divisions in Crucifer type.Embryogeny Types Comparison
Type Apical Cell 1st Division Both Daughters to Embryo? Families Stage Shape Caryophyllad Transverse Yes Caryophyllaceae T-shaped Asterad Longitudinal Yes Asteraceae Radial Crucifer Longitudinal No (median → suspensor) Brassicaceae Quadrant Chenopodiad Variable Basal cell contributes Chenopodiaceae Filamentous Development Sequence (Caryophyllad)
-
Zygote → apical + basal cells
-
Apical cell transverse division → terminal + median cells
-
Both terminal & median elongate → form embryo axis
-
Basal cell → suspensor
-
Terminal + median → cotyledons + plumule
Exam Key Points
Remember: Caryophyllad = Caryophyllaceae = Transverse = T-shaped = Both cells contribute. Crucifer type (Arabidopsis) is most commonly tested alternative.
-
