Pollen, tapetum and orbicule development in Modiolastrum malvifolium (Malvaceae)

Area of Science:

• Plant reproductive biology
• Palynology
• Malvaceae family studies

Background:

• Orbicules are typically associated with secretory tapeta, but their presence on a peritapetal membrane with a plasmodial tapetum was previously noted in Abutilon pictum.
• Further investigation in other Malvaceae species is crucial to confirm these findings.

Purpose of the Study:

• To investigate pollen and microsporangium development in Modiolastrum malvifolium.
• To determine the type of tapetum and the location of orbicule formation in this species.

Main Methods:

• Anthers at various developmental stages were examined using transmission electron microscopy and light microscopy.
• Acetolysis-resistant membranes and pollen walls were isolated for analysis.

Main Results:

• Microspore tetrads exhibited a tetrahedral arrangement, and pollen grains were released at the bicellular stage.
• The study identified an invasive, non-syncytial tapetum and the formation of a peritapetal membrane containing orbicules.

Conclusions:

• This study reports orbicules on a peritapetal membrane in a species with an invasive, non-syncytial tapetum for the first time.
• The presence of orbicules is not a definitive characteristic for distinguishing between secretory, plasmodial, or intermediate invasive, non-syncytial tapetum types.