SEM studies on vessels in ferns. 2. Pteridium.

Area of Science:

• Plant anatomy
• Wood science
• Pteridophyte biology

Background:

• Xylem structure is crucial for water transport and plant survival.
• Pteridium aquilinum (bracken fern) exhibits wide ecological tolerances, suggesting specialized vascular structures.
• Previous studies on bracken fern xylem anatomy yielded conflicting results regarding lateral wall perforations.

Purpose of the Study:

• To investigate the detailed structure of xylem vessels in Pteridium aquilinum roots and rhizomes.
• To confirm or refute the presence of lateral wall perforations using advanced microscopy.
• To characterize the morphology of perforation plates and lateral wall pitting.

Main Methods:

• Scanning electron microscopy (SEM) was employed to examine xylem from Pteridium aquilinum roots and rhizomes.
• Detailed morphological analysis of tracheary elements, including end and lateral walls, was performed.
• Comparison of SEM observations with previous light microscopy findings.

Main Results:

• All studied tracheary elements were identified as vessels.
• End wall perforation plates were consistently scalariform, with variations in bar width and pit membrane remnants.
• Lateral wall perforations, previously debated, were confirmed by SEM, alongside novel observations of interconnecting grooves on vessel walls.
• Non-porose lateral wall pitting exhibited either striate thickenings or smooth surfaces.

Conclusions:

• Pteridium aquilinum xylem possesses specialized vessel structures, including confirmed lateral wall perforations and grooves.
• These unique anatomical features may contribute to the genus's broad ecological adaptability.
• SEM provides critical insights into fern xylem morphology, resolving previous ambiguities.