Plant surface reactions: an opportunistic ozone defence mechanism impacting atmospheric chemistry

Abstract

Abstract. Elevated tropospheric ozone concentrations are considered a toxic threat to plants, responsible for global crop losses with associated economic costs of several billion dollars per year. Plant injuries have been linked to the uptake of ozone through stomatal pores and oxidative damage of the internal leaf tissue. But a striking question remains: can surface reactions limit the stomatal uptake of ozone and therefore reduce its detrimental effects to plants?In this laboratory study we could show that semi-volatile organic compounds exuded by the glandular trichomes of different Nicotiana tabacum varieties are an efficient ozone sink at the plant surface. In our experiments, different diterpenoid compounds were responsible for a strongly varietydependent ozone uptake of plants under dark conditions, when stomatal pores are almost closed. Surface reactions of ozone were accompanied by a prompt release of oxygenated volatile organic compounds, which could be linked to the corresponding precursor compounds: ozonolysis of cis-abienol (C 20 H 34 O) -a diterpenoid with two exocyclic double bonds -caused emissions of formaldehyde (HCHO) and methyl vinyl ketone (C 4 H 6 O). The ring-structured cembratrien-diols (C 20 H 34 O 2 ) with three endocyclic double bonds need at least two ozonolysis steps to form volatile carbonyls such as 4-oxopentanal (C 5 H 8 O 2 ), which we could observe in the gas phase, too.Fluid dynamic calculations were used to model ozone distribution in the diffusion-limited leaf boundary layer under daylight conditions. In the case of an ozone-reactive leaf surface, ozone gradients in the vicinity of stomatal pores are changed in such a way that the ozone flux through the open stomata is strongly reduced.Our results show that unsaturated semi-volatile compounds at the plant surface should be considered as a source of oxygenated volatile organic compounds, impacting gas phase chemistry, as well as efficient ozone sink improving the ozone tolerance of plants.

Twin-cuvette measurement technique for investigation of dry deposition of O<sub>3</sub> and PAN to plant leaves under controlled humidity conditions

“…As observed in Fig. 14, the value of RH crit , the humidity level where the formation of the leaf surface water film starts, was found at 60 %. However, Jud et al (2016) observed a contribution of semi-volatile organic compounds, in this case diterpenes of Nicotiana tabacum, to non-stomatal sinks of O 3 . These observations demonstrated that special structures or organs can exist on the plant surface as in the case of glandular trichomes of Nicotiana tabacum, which may release stored volatile organic compounds impacting gas phase chemistry.…”

Glandular trichomes as a barrier against atmospheric oxidative stress: Relationships with ozone uptake, leaf damage, and emission of LOX products across a diverse set of species

“…Glandular trichomes, which store and secrete various secondary metabolites such as flavonoids, monoterpenes, or sesquiterpene lactones, are widely distributed on leaf surfaces and may contribute significantly to defence against diverse biotic and environmental challenges (Agati, Azzarello, Pollastri, & Tattini, ; Amme et al, ; Ehleringer, Björkman, & Mooney, ; Fahn & Shimony, ; Heinrich, Pfeifhofer, Stabentheiner, & Sawidis, ; Huci, Beversdorf, & McKersie, ; Jud et al, ; Kostina, Wulff, & Julkunen‐Tiitto, ; Lihavainen et al, ; Paoletti, Seufert, Della, & Thomsen, ; Peiffer, Tooker, Luthe, & Felton, ; Rieseberg, Soltis, & Arnold, ; Thitz et al, ; Wagner, ). Two major types of glandular trichomes, peltate and capitate, have been discerned.…”

Tropospheric sources and sinks of gas-phase acids in the Colorado Front Range

“…We hypothesize that reactions between O 3 and organic surfaces (i.e., soil, organic films) could be one non-photochemical surface-level source of alkanoic acids near the site, though unlikely to account for the entire source. Reactions of O 3 on organic surfaces such as organic films (Donaldson et al, 2005), plant surfaces (Cape et al, 2009;Jud et al, 2016), and human skin (Liu et al, 2016(Liu et al, , 2017 have been reported previously. Soil organic matter and organic films are often rich in alkenes (Vancampenhout et al, 2009;Donaldson et al, 2005;Simpson et al, 2006), which undergo ozonolysis reactions in the presence of O 3 (Criegee, 1975;Wolff et al, 1997).…”