Nocturnal Transpiration May Be Associated with Foliar Nutrient Uptake

Area of Science:

• Plant physiology
• Environmental science
• Biogeochemistry

Background:

• Aerosols contribute to plant nutrition through foliar uptake, particularly at night when humidity is high.
• Stomata typically close at night to prevent water loss, limiting nutrient absorption.
• Nocturnal stomatal opening could enhance nutrient uptake by increasing boundary layer humidity.

Purpose of the Study:

• To test the hypothesis that deliquescent leaf surface salts from aerosols can trigger nocturnal stomatal opening and enhance foliar nutrient uptake.
• To investigate the influence of ambient aerosols and foliar phosphorus application on nocturnal transpiration in P-deficient plants.

Main Methods:

• Comparison of plant responses in filtered (aerosol-free) and unfiltered (ambient) air.
• Measurement of nocturnal transpiration, minimum leaf conductance (gmin), turgor loss point, and solute accumulation.
• Analysis of leaf surface characteristics using scanning electron microscopy.

Main Results:

• Plants in ambient air showed sustained nocturnal transpiration, unlike those in filtered air.
• Foliar phosphorus application increased nocturnal transpiration in both ambient and filtered air conditions.
• Evidence of salt crusts on stomata and higher solute accumulation in ambient air plants supported stomatal nutrient uptake.

Conclusions:

• Deliquescent leaf surface salts from aerosols appear to play a role in triggering nocturnal transpiration.
• Foliar nutrient uptake via stomata at night is a plausible mechanism, especially under nutrient-deficient conditions.
• Further research is needed to fully elucidate this nocturnal plant-aerosol interaction.