Biosilicification in monocots: Comparative analysis highlights contrasting patterns of deposition

Area of Science:

• Plant biology
• Biomineralization
• Evolutionary botany

Background:

• Understanding plant biomineral uptake is key to plant growth.
• Silica deposition in plants, forming phytoliths, is a controlled process.
• In monocots, biosilicification is diverse and limited to commelinids and orchids.

Purpose of the Study:

• To investigate diverse silica deposition patterns in monocots using energy-dispersive x-ray spectroscopy (EDX/EDS).
• To evaluate evolutionary origins and losses of phytoliths in monocots.
• To explore the relationship between silica deposition, cell chemistry, and phylogenetic distribution.

Main Methods:

• Utilized energy-dispersive x-ray spectroscopy (EDX/EDS) mapping on leaf transverse sections.
• Analyzed silica deposition patterns across a range of monocot species.
• Performed character optimizations on existing phylogenies to infer evolutionary events.

Main Results:

• Identified at least two independent evolutionary origins of phytoliths in monocots, with subsequent losses.
• Silica deposition occurs in various cell types (bundle sheath, epidermal) and locations (lumen, cell walls).
• Ferulic acid presence is closely associated with silica deposition, except in orchids; high leaf silica doesn't always correlate with deposition.

Conclusions:

• EDX data reveal the structural and biochemical complexity of plant biomineral inclusions.
• The diversity and restricted phylogenetic distribution of monocot phytoliths are partly explained by cell chemistry.
• Further comparative studies are needed to fully understand plant biomineralization.