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Unbreathing seal

PLoS ONE 14, e0212462 (2019).

Biologists love parafilm. The waxy, stretchy, self-sealing, hydrophobic, malleable, clean, soft to the touch but resistant material has a special place in our hearts. Who has not nervously rolled a ball of parafilm between their fingers while contemplating life choices after a failed experiment? This product has many uses, from sealing flasks to pipetting microdrops directly onto it. We also grow plants in agar plates wrapped with parafilm, probably even if we received conflicting advice. It is convenient to keep moisture in, but Arabidopsis old-timers warned us that the low gas permeability creates problems such as saturated humidity, CO2 deprivation and ethylene accumulation, leading to stressed plants and obscured phenotypes. A team from Iowa State University, led by Ludovico Cademartiri, has now directly measured the CO2 concentration in sealed plates and assessed some of the biological consequences.

Credit: Heiti paves / alamy stock photo

The authors engineered small, high-resolution sensors of CO2 concentration, and compared Arabidopsis plates sealed with parafilm or porous surgical tape. The impressive differences start after only a few days post-germination, before the first true leaves emerge. While O2 concentration is stable, massive daily fluctuations in CO2 concentration showed that the plants were struggling to maintain growth and accumulate starch. Surgical tape was better as it allowed some gas exchange, with plants looking almost as healthy as aerated controls, but an unintended consequence was that they become susceptible to CO2 changes caused by the breathing of the experimenters. A transcriptome analysis describes the significant effect of using parafilm on stress, photosynthesis and metabolism gene expression. Finally, the researchers provide a set of useful methodological guidelines.

This study reminds us that there is always a need, when new tools are available, to re-assess familiar knowledge and question even the most established protocols.

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Correspondence to Guillaume Tena.

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Tena, G. Unbreathing seal. Nat. Plants 5, 336 (2019).

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