64. Flowers represent a complex array of functionally specialized structures that differ substantially from the vegetative plant body in form and cell types.
    Following are statements made regarding floral meristems.
    A. Floral meristems can usually be distinguished from vegetative meristems by their larger size.
    B. The increase in the size of the meristem is largely a result of increased rate of cell division in central cells.
    C. The increase in the size of the meristem is due to larger size of the cells, which in turn results from rapid cell expansion only.
    D. A network of genes control floral morphogenesis in plants.
    Which combination of the above statements is true?
    (1) A, B and D (2) A, Band C
    (3) B, C and D (4) A, C and D

The correct combination of statements is:

(1) A, B and D

Explanation:

• (A) Floral meristems can usually be distinguished from vegetative meristems by their larger size — Correct. Floral meristems generally have a larger size due to the accumulation of dividing cells.​

• (B) The increase in the size of the meristem is largely a result of increased rate of cell division in central cells — Correct. Central zone stem cells in floral meristems divide and generate peripheral cells that contribute to organ primordia, causing meristem growth.​

• (C) The increase in size of the meristem is due to larger size of cells, which in turn results from rapid cell expansion only — Incorrect. While cell expansion occurs, meristem enlargement mainly depends on cell division rather than cell enlargement.​

• (D) A network of genes control floral morphogenesis in plants — Correct. Floral organ patterning and development are regulated by a complex gene regulatory network involving homeotic genes, meristem identity genes, and signaling pathways.​

Introduction

Floral meristems differ from vegetative meristems in size and developmental potential. Their growth results mostly from active cell division in central stem cells, which generate new cells for floral organ formation. Simultaneously, a complex gene regulatory network directs the spatial and temporal progression of floral morphogenesis.

Floral Meristem Growth Dynamics

• The floral meristem enlarges primarily due to increased cell division, particularly in its central zone, contributing new cells to the periphery where floral organ primordia develop.​

• Cell expansion plays a supporting role but is not the main driver of meristem size changes during floral development.​

Genetic Regulation of Floral Morphogenesis

• A sophisticated network of genes including homeotic genes (ABC genes), meristem identity genes (e.g., LEAFY, APETALA1) and regulatory pathways coordinate floral organ specification and meristem function.​

• Gene interactions ensure proper organ patterning, differentiation, and maintenance of floral meristem determinacy.

Summary Table: Floral Meristem Characteristics and Controls

Conclusion

Floral meristem growth mainly results from the proliferation of central zone cells rather than cell enlargement. Furthermore, its development is orchestrated by complex gene networks ensuring proper floral morphogenesis, confirming statements A, B, and D are correct.