Vessels in ferns: structural, ecological, and evolutionary significance

Area of Science:

• Plant Anatomy
• Xylem Physiology
• Evolutionary Biology

Background:

• Fern xylem anatomy has been studied extensively using scanning electron microscopy (SEM).
• Previous research provides a foundation for interpreting SEM-based findings on fern xylem structures.
• Understanding xylem structure is vital for comprehending water transport in plants.

Purpose of the Study:

• To summarize and interpret findings from 20 papers on fern xylem anatomy.
• To highlight distinctive features of fern xylem, including vessel and tracheid presence, perforation plates, and pit membranes.
• To discuss the functional and evolutionary implications of these xylem features in ferns.

Main Methods:

• Analysis of macerated fern xylem, supplemented with sections.
• Utilized scanning electron microscopy (SEM) for detailed structural examination.
• Interpretation of pit membrane features based on established guidelines.

Main Results:

• Fern xylem is characterized by numerous vessels and tracheids, with vessels present in roots and rhizomes.
• Distinctive features include multiple end-wall and lateral-wall perforation plates, and porose pit membranes.
• Pit dimorphism and porosities in pit membranes facilitate interconnections between tracheary elements and between roots and rhizomes.

Conclusions:

• The fasciculate packing of tracheary elements in ferns facilitates the formation of numerous perforation plates.
• Porosities in pit membranes are widespread and likely evolved for efficient water transport and interconnection, especially in adventitious root systems.
• Fern xylem adaptations suggest a long evolutionary history and efficient water column maintenance, overriding the benefits of tracheids in some contexts.