Exogenous Isoprene Confers Physiological Benefits in a Negligible Isoprene Emitter (<i>Acer monspessulanum</i> L.) under Water Deficit

• Main Authors: Elena Ormeño, Justine Viros, Jean-Philippe Mévy, Alain Tonetto, Amélie Saunier, Anne Bousquet-Mélou, Catherine Fernandez
• Format: Article
• Language: English
• Published: MDPI AG 2020-01-01
• Series: Plants
• Subjects: isoprene protection; water deficit; oxidative pressure; negligible terpene emitters; abiotic stress; reactive oxygen species; allelochemicals
• Online Access: https://www.mdpi.com/2223-7747/9/2/159

Isoprene, the main volatile released by plants, is known to protect the photosynthetic apparatus in isoprene emitters submitted to oxidative pressures caused by environmental constraints. Whether ambient isoprene contributes to protect negligible plant emitters under abiotic stress conditions is less clear, and no study has tested if ambient isoprene is beneficial during drought periods in plant species that naturally release negligible isoprene emissions. This study examines the effect of exogenous isoprene (20 ppbv) on net photosynthesis, stomatal conductance and production of H₂O₂ (a reactive oxygen species: ROS) in leaves of <i>Acer monspessulanum</i> (a negligible isoprene emitter) submitted to three watering treatments (optimal, moderate water stress and severe water stress). Results showed that <i>A. monspessulanum</i> exhibited a net photosynthesis increase (+30%) and a relative leaf H₂O₂ decrease when saplings were exposed to an enriched isoprene atmosphere compared to isoprene-free conditions under moderate water deficit. Such physiological improvement under isoprene exposure was not observed under optimal watering or severe water stress. These findings suggest that when negligible isoprene emitters are surrounded by a very high concentration of isoprene in the ambient air, some plant protection mechanism occurs under moderate water deficit probably related to protection against ROS damage eventually impeding photosynthesis drop.