Combined effects of ozone and drought stress on the emission of biogenic volatile organic compounds from <i>Quercus robur</i> L.

Abstract

Abstract. Drought events are expected to become more frequent with climate change. To predict the effect of plant emissions on air quality and potential feedback effects on climate, the study of biogenic volatile organic compound emissions under stress is of great importance. Trees can often be subject to a combination of abiotic stresses, for example due to drought or ozone. Even though there is a large body of knowledge on individual stress factors, the effects of combined stressors are not much explored. This study aimed to investigate changes of biogenic volatile organic compound emissions and physiological parameters in Quercus robur L. during moderate to severe drought in combination with ozone stress. Results show that isoprene emissions decreased while monoterpene and sesquiterpene emissions increased during the progression of drought. We exposed plants with daily ozone concentrations of 100 ppb for 1 h for 7 d, which resulted in faster stomatal closure (e.g., a mean value of −31.3 % at an average stem water potential of −1 MPa), partially mitigating drought stress effects. Evidence of this was found in enhanced green leaf volatiles in trees without ozone fumigation, indicating cellular damage. In addition we observed an enhancement in (C8H8O3)H+ emissions likely corresponding to methyl-salicylate in trees with ozone treatment. Individual plant stress factors are not necessarily additive, and atmospheric models should implement stress feedback loops to study regional-scale effects.

Combined Acute Ozone and Water Stress Alters the Quantitative Relationships between O3 Uptake, Photosynthetic Characteristics and Volatile Emissions in Brassica nigra

“…Our study demonstrated a classic reduction of photosynthetic rate ( A ) by water stress due to diminished g s and CO 2 availability ( Figure 3 and Figure 4 ) as observed in numerous studies [ 26 , 36 , 86 ], and this reduction was only moderately enhanced by O 3 exposure ( Figure 3 A). This further emphasizes that reduced g s prior to O 3 exposure protects photosynthetic machinery and results in a lower effective O 3 dose as observed also in other studies [ 23 ].…”

“…O 3 also activates the production of reactive oxygen species (ROS) [ 18 , 19 ], which in turn activate various defense reactions related to non-volatile and/or volatile metabolites depending on the plant species and genotype [ 20 , 21 , 22 , 23 , 24 ]. Characteristically, O 3 exposure leads to emissions of methanol and lipoxygenase (LOX) pathway volatiles due to damaged cell walls and cell and organelle membranes [ 23 , 25 ] and might also result in emissions of the stress hormone methyl salicylate [ 20 , 23 , 26 ].…”

“…However, constitutive VOC emission levels strongly vary among species [ 37 , 38 , 39 ], and the substrate limitations might not necessarily limit the emissions in relatively low volatile emitters. Furthermore, drought stress differs from other abiotic stresses, such as heat, in that it seldom results in induction of stress volatiles [ 40 , 41 ] or only leads to a minor elicitation of stress volatiles [ 26 ]. Although drought itself does not necessarily lead to elicitation of stress volatiles, it could prime the plants to subsequent stresses, implying modified responses of photosynthetic and volatile emission characteristics upon exposure to a different stress such as ozone stress [ 26 , 40 , 42 , 43 ].…”

“…Furthermore, drought stress differs from other abiotic stresses, such as heat, in that it seldom results in induction of stress volatiles [ 40 , 41 ] or only leads to a minor elicitation of stress volatiles [ 26 ]. Although drought itself does not necessarily lead to elicitation of stress volatiles, it could prime the plants to subsequent stresses, implying modified responses of photosynthetic and volatile emission characteristics upon exposure to a different stress such as ozone stress [ 26 , 40 , 42 , 43 ]. Yet, only a few studies have investigated the impact of combined drought and ozone stresses and simultaneously monitored both photosynthetic and VOC emission characteristics [ 26 ].…”

“…Although drought itself does not necessarily lead to elicitation of stress volatiles, it could prime the plants to subsequent stresses, implying modified responses of photosynthetic and volatile emission characteristics upon exposure to a different stress such as ozone stress [ 26 , 40 , 42 , 43 ]. Yet, only a few studies have investigated the impact of combined drought and ozone stresses and simultaneously monitored both photosynthetic and VOC emission characteristics [ 26 ]. Although both drought and O 3 reduce g s , O 3 can cause stomatal sluggishness, i.e., reduce the responsiveness of stomata to environmental clues such as light and humidity, disturbing the effective control of transpiration [ 44 ] and making the plants more vulnerable to the following stresses [ 45 ].…”