Salinity effects on the stomatal behaviour of grapevine

Area of Science:

• Plant Physiology
• Photosynthesis Research
• Plant Stress Responses

Background:

• Salt stress significantly affects plant physiological processes, including photosynthesis.
• Understanding stomatal behavior under stress is crucial for crop resilience.
• Previous studies indicated non-stomatal inhibition in ABA- and water-stressed grapevine leaves.

Purpose of the Study:

• To investigate the time-course of photosynthesis inhibition in salt-stressed grapevine leaves.
• To differentiate between stomatal and non-stomatal inhibition mechanisms.
• To elucidate the role of stomatal behavior in salt-induced photosynthetic changes.

Main Methods:

• Autoradiograms of ¹⁴CO₂ fixation were used to assess CO₂ uptake.
• Assimilation rate (A) versus intercellular CO₂ partial pressure (C₁) relationships were analyzed.
• Leaf chloride concentrations were monitored in relation to photosynthetic inhibition.

Main Results:

• At chloride levels up to 165 mM, photosynthesis inhibition was linked to uniform stomatal closure.
• At higher chloride levels, non-stomatal inhibition occurred, associated with non-uniform ¹⁴CO₂ uptake.
• The observed non-uniform stomatal behavior explains photorespiration stimulation during salt stress.

Conclusions:

• Grapevine leaves exhibit dual stomatal responses to salt stress, impacting photosynthesis.
• Non-stomatal inhibition at high salt levels is an artifact of non-uniform stomatal behavior.
• This study clarifies mechanisms of photosynthetic impairment and photorespiration in salt-stressed grapevines.