Effects of ozone on isoprene emission from two major <i>Quercus</i> species native to East Asia

Abstract

Quercus species occur widely in East Asia and are major tree species in Japan. The ground-grown seedlings of Quercus serrata and Quercus mongolica var. crispula were exposed to enriched ozone ambient + 40 ppbv over one growing season by using open-top-chambers OTC , and isoprene emissions from the two tree-species were measured across a growing season by using the leaf cuvette method. The isoprene emission rates of the two species were significantly affected by ozone, and the rate of Q. mongolica was reduced to a greater extent by ozone in October than that of Q. serrata. The stomatal conductance of Q. mongolica was higher than that of Q. serrata and not affected by O 3 even in September, suggesting that Q. mongolica absorbed a larger amount of ozone than Q. serrata did. Since the leaf content of the isoprene precursor dimethylallyl diphosphate DMAPP was not significantly different between the enriched ozone and filtered air treatments in July and September, isoprene synthase activity in Q. mongolica leaves might have been reduced to a greater extent by the high concentration of ozone due to higher ozone uptake via stomata. Ozone fumigation was also applied to potted Q. serrata seedlings grown in climate chambers to investigate the ozone effect under different growing conditions. The net photosynthetic rate and isoprene emission rate of the potted seedlings were much lower than those of the ground-grown seedlings in the OTC, regardless of the ozone treatments. Between treatments, the isoprene emission rate and DMAPP content were significantly decreased by enriched ozone, suggesting that reduced production of DMAPP is a cause of the decreased isoprene emission. Our two fumigation experiments revealed that the isoprene emission rates of the two Quercus species was decreased by high ozone concentration, but the possible mechanism may not be identical, depending on the experimental conditions.

Environmental hormesis, a fundamental non-monotonic biological phenomenon with implications in ecotoxicology and environmental safety

“…Furthermore, stress induced by environmental factors may generate biphasic emissions of biogenic volatile organic compounds (VOCs), such as isoprene, suggesting the occurrence of hormesis (Calfapietra et al, 2009;Yuan et al, 2016;Jiang et al, 2017;Tani et al, 2017). VOCs enable a plant-to-plant communication and act as a signal for insect herbivores (Blande et al, 2014).…”

Observation of vertical profiles of NO, O<SUB>3</SUB>, and VOCs to estimate their sources and sinks by inverse modeling in a Japanese larch forest

“…Trace gases such as ozone O 3 and nitrogen oxides NO x in the biosphere influence forest growth and carbon storage Ollinger et al, 2002 . O 3 results in a reduction of carbon fixation and biomass production Reich, 1987;Izuta et al, 1999;Watanabe et al, 2015Watanabe et al, , 2019Tani et al, 2017 , and atmospheric nitrogen deposition can result in increased growth of terrestrial ecosystems Vitousek and Howarth, 1991 . Biogenic volatile organic compounds BVOCs generate secondary organic aerosols that can affect the climate by affecting cloud formation Kanakidou et al, 2005 . Forest ecosystems are also an important sink and source of trace gases and particle matters in the atmosphere Slemr and Seiler, 1984;Yamaguchi et al, 2019 ; thus, observations of trace gas fluxes, such as O 3 Mikkenlsen et al, 2004;Gerosa et al, 2005;Matsuda et al, 2005 , NO x Rummel et al, 2002;Horii et al, 2004;Farmer et al, 2006, and BVOCs Guenther and Hills, 1998: Tani et al, 2002: Mochizuki et al, 2015 in forest ecosystems have been conducted.…”

Seasonal Changes in Interclone Variation Following Ozone Exposure on Three Major Gene Pools: An Analysis of Cryptomeria Japonica Clones

“…In recent years, there has been an increase in the concentration of ozone in Japan due to a decrease in NO titration and an increase in transboundary air pollution [1][2][3]. With long-term ozone exposure effects on plants, changes in the carbon allocation, photosynthetic rate [4], stomatal conductance [5], yield of crops [6], and biogenic volatile organic compound (BVOC) emission characteristics [7] have been reported. The effects of ozone exposure on BVOC emissions have been previously evaluated, and the results of such experiments have not shown a consistent trend with large interspecies variations.…”