Title : Impact of Elevated Ozone and Wounding on Foliage Stress Volatile Emissions and Gas Exchange of Tasmanian Blue Gum (Eucalyptus globulus)
Abstract:
Ozone and wounding are two key abiotic stress factors significantly affecting plant eco-physiological activity, but there is a substantial lack of knowledge on their interactive effects on plant constitutive and stress-elicited volatile (VOC) emissions and time-dependent modifications during a combined stress recovery period. We studied the changes in photosynthetic characteristics and modifications of constitutive and stress-induced volatile emissions upon acute ozone (4-6 ppm) and wounding treatments through recovery (0.5-75 h) in Eucalyptus globulus. Application of acute ozone and wounding treatments showed impaired photosynthetic characteristics and increased emissions of constitutive and induced VOC through recovery period. Photosynthetic characteristics were surprisingly resistant to all ozone and wounding treatments with ca. 70 % reduction in net assimilation rate at 0.5 h since the stress across treatments and then substantial recovery to ca. 50 % of initial rate observed at 75 h. Constitutive isoprene emissions were significantly enhanced by ozone and combined ozone and wounding treatments and the enhanced emissions stayed at high level throughout the recovery phase, but wounding alone reduced isoprene emission. Furthermore, all stress treatments enhanced emissions of lipoxygenase pathway volatiles (LOX), mono- and sesquiterpenes. In contrast, LOX emissions, total monoterpene and sesquiterpene emissions decreased through recovery period. However, a secondary rise in total sesquiterpene emissions at 75 h and for monoterpene (Z)-?-ocimene at 10-25 h was observed. Through the treatments and recovery period, stomatal ozone uptake rate and volatile emission rates were poorly correlated, reflecting possible scavenging effect of volatile isoprenoids.
