Acid waters in tank bromeliads: Causes and potential consequences

Area of Science:

• Plant physiology
• Ecology
• Biochemistry

Background:

• Acidity significantly impacts plant performance.
• The causes and prevalence of low pH in bromeliad tank water are largely unknown.
• Bromeliad tanks are crucial microhabitats in neotropical plant communities.

Purpose of the Study:

• Investigate the pH of bromeliad tank water across eight species.
• Determine the causes of tank water acidification in Guzmania monostachia.
• Explore the relationship between low pH, aquaporin expression, and plant physiological responses.

Main Methods:

• Field measurements of tank water pH for eight bromeliad species.
• Controlled experiments with artificial tanks and Guzmania monostachia under varying light.
• Measurement of aquaporin transcripts, leaf hydraulic conductance, and CO2 concentration.
• Assay of proton pump activity using stimulators and inhibitors.

Main Results:

• Mean tank water pH was 4.7 ± 0.06; lower pH observed in Guzmania monostachia under higher light.
• Tank water pH decreased over time in plant tanks but not in artificial tanks.
• Aquaporin transcription increased at lower pH, while leaf hydraulic conductance remained unaffected.
• Tank water acidification was linked to light-responsive proton pumps and inversely related to CO2 concentration.

Conclusions:

• Guzmania monostachia actively acidifies tank water using light-responsive leaf proton pumps.
• Low pH enhances aquaporin transcript levels, suggesting a role in nutrient uptake rather than water transport.
• Understanding tank water acidity is crucial for bromeliad ecology and nutrient cycling.