Ovule Development and Embryo Sac Formation

Female Reproductive AnatomyPage 1

The carpel serves as the basic unit of the female reproductive structure, comprising the ovary, style, and stigma. The pistil represents the entire female organ, which can be simple or compound. Key anatomical features within the ovary include the micropyle, which facilitates pollen tube entry, and the chalaza, where the nucellus, integuments, and funiculus converge.

MegasporogenesisPage 1

Megasporogenesis is the process where a megasporocyte undergoes meiosis to form four haploid megaspore nuclei. Through differentiation of archesporial cells, a megaspore mother cell is formed. Typically, the chalazal megaspore remains functional while the others degenerate, preparing for transition into the female gametophyte.

MegagametogenesisPage 1

Megagametogenesis involves the development of the female gametophyte from the functional megaspore. Through three rounds of mitosis, eight nuclei are formed. These organize into the egg apparatus (egg cell and synergids), polar nuclei in the central cell, and antipodal cells, creating a seven-celled structure known as the embryo sac.

Hormonal and Genetic RegulationPage 1

Ovule development is tightly regulated by hormones and genes. Auxins, cytokinins, brassinosteroids, and gibberellins each play distinct roles in cell division, elongation, patterning, and integument morphogenesis. Additionally, specific genes such as STM and WUS are essential for early initiation and integument formation, with integuments eventually maturing into the protective seed coat.