How pollen and ovule development underlay dioecy in Chloroluma gonocarpa (Sapotaceae)

Area of Science:

• Plant reproductive biology
• Angiosperm sexual systems
• Floral development

Background:

• Chloroluma gonocarpa (Sapotaceae) displays cryptic dioecy, a sexual system with morphologically perfect but functionally unisexual flowers.
• Pistillate flowers have developed stigmas and ovules, while staminate flowers possess functional anthers and reduced stigmas/ovules.

Purpose of the Study:

• To conduct an anatomical analysis of floral development in C. gonocarpa.
• To determine the precise stage of sexual organ abortion in staminate flowers.
• To elucidate the developmental pathway leading to cryptic dioecy in this species.

Main Methods:

• Conventional anatomical techniques were employed for light microscopy.
• Flowers at various developmental stages were collected, fixed, and processed.
• Sporogenesis and gametogenesis were described for both flower types.

Main Results:

• Pollen development was observed exclusively in staminate flowers.
• Ovule development initiated in both flower types but ceased in staminate flowers post-meiosis.
• Normal ovule and pistil development proceeded in pistillate flowers.

Conclusions:

• Post-meiosis abortion of ovules in staminate flowers is the mechanism underlying cryptic dioecy in C. gonocarpa.
• The findings suggest that dioecy in this species may have evolved from a gynodioecious ancestor.