Apoplastic pH during low-oxygen stress in Barley

Area of Science:

• Plant Physiology
• Plant Stress Responses
• Molecular Biology

Background:

• Oxygen deprivation (anoxia) triggers an energy crisis in plants, with varying tolerance levels.
• The apoplast, an extracellular compartment, plays roles in storage, reactions, and membrane transport.
• The apoplast's role during oxygen shortage and systemic signaling in plants remained largely unexplored.

Purpose of the Study:

• To investigate the significance of the apoplast during oxygen stress in Hordeum vulgare (barley).
• To determine if information about apoplastic changes during oxygen stress is transmitted systemically within the plant.

Main Methods:

• Utilized non-invasive ion-selective microprobes inserted through stomata.
• Directly measured apoplastic fluid pH and its changes in barley leaves.
• Applied anoxia and hypoxia treatments to roots and leaves to assess systemic signaling.

Main Results:

• Barley leaves exhibited apoplastic alkalinization and membrane depolarization under oxygen stress.
• Anoxia induced persistent apoplastic alkalinization, while hypoxia caused transient changes.
• Anoxia information was systemically signaled from roots to leaves as an apoplastic pH increase, unlike hypoxia.
• Anoxia significantly reduced the proton motive force by over 70%, impairing H(+)-driven transport.

Conclusions:

• Anoxia-induced apoplastic alkalinization is a general stress response with significant impact on proton motive force.
• Reduced proton motive force under anoxia affects the transport of energy-rich compounds.
• Plant anoxia tolerance is linked to the ability to maintain proton motive force and H(+) turnover for energy harvesting during crisis.