Can cell walls bending round xylem vessels control water flow?

Area of Science:

• Plant Biology
• Plant Physiology
• Xylem Anatomy

Background:

• Water cavitation in plants can cause audible clicks.
• The mechanical behavior of xylem vessels during cavitation is not fully understood.

Purpose of the Study:

• To investigate the structural changes in xylem vessel walls during water cavitation in Nymphoides peltata.

Main Methods:

• Intact vascular bundles from Nymphoides peltata petioles were frozen and freeze-fractured.
• Electron microscopy was used to examine cell wall structure.
• Comparisons were made between wilted and turgid leaves, and with fixed samples.

Main Results:

• Cell walls surrounding xylem vessels in wilted leaves showed an inward deformation.
• Cell walls in turgid leaves or fixed samples appeared straight or slightly bulged outwards.
• Sucrose solution treatment also resulted in slight outward bulging of vessel walls.

Conclusions:

• Xylem vessel wall movement occurs during water cavitation.
• This movement may contribute to the audible clicks associated with cavitation.
• Variable resistance to water flow in plants could be influenced by vessel wall mechanics.