Beyond leaf projections: the multifunctionality of leaf teeth in Violaceae

Area of Science:

• Plant anatomy and morphology
• Plant physiology
• Biomineralization

Background:

• Leaf tooth morphology, including glands, is a key taxonomic trait in plants.
• The adaptive significance of leaf teeth and the function of associated glands are poorly understood.
• Glands on leaf margins are often overlooked in taxonomic and functional studies.

Purpose of the Study:

• To investigate the morphoanatomy and micromorphology of leaf teeth in two Violaceae species.
• To determine the nature and function of glands associated with leaf teeth.
• To elucidate the adaptive roles of leaf teeth in Pombalia atropurpurea and Anchietea pyrifolia.

Main Methods:

• Light and scanning electron microscopy (SEM) were used to examine leaf teeth.
• SEM with Energy Dispersive Spectroscopy (SEM-EDS) was employed for elemental analysis.
• Guttation experiments were conducted on Pombalia atropurpurea.

Main Results:

• Both species possess vascularized leaf teeth with apical colleters and hydathodes featuring modified stomata.
• Colleters secrete mucilage and proteins during early leaf development, aiding in desiccation protection.
• Hydathodes are active in expanded leaves, facilitating guttation and crystal extravasation.

Conclusions:

• Leaf teeth in Violaceae exhibit multifaceted functions, including protection against desiccation, guttation, and calcium excretion.
• Colleters and modified stomata play crucial roles in these processes.
• The extravasation of crystals through these glands represents a novel function.