Rethinking how volatiles are released from plant cells

Area of Science:

• Plant Biology
• Biochemistry
• Physiology

Background:

• Plant volatile organic compounds (VOCs) are essential for various ecological interactions.
• Current understanding presumes VOCs are emitted via passive diffusion across cellular barriers.
• Hydrophobic VOCs face challenges partitioning into aqueous cellular environments.

Purpose of the Study:

• To investigate the mechanisms of plant volatile organic compound (VOC) emission.
• To evaluate the feasibility of passive diffusion as the sole mechanism for VOC transport.
• To propose alternative biological pathways for efficient VOC release.

Main Methods:

• Calculations using Fick's first law to model VOC diffusion rates.
• Analysis of membrane partitioning and aqueous compartment diffusion.
• Hypothesizing biological transport mechanisms for hydrophobic compounds.

Main Results:

• Passive diffusion alone would require toxic concentrations of VOCs within plant membranes to match observed emission rates.
• Calculations indicate that diffusion through lipid bilayers is a slow process for VOCs.
• Proposed biological mechanisms can significantly reduce the resistance to VOC movement.

Conclusions:

• Passive diffusion is insufficient to explain observed plant VOC emission rates.
• Biological transport pathways, similar to those for other hydrophobic molecules, are likely involved in VOC emission.
• These pathways enable VOC release at non-toxic intramembrane concentrations.