Harmful effects of radicals generated in polluted dew on the needles of Japanese Red Pine (Pinus densiflora)

Abstract

The effects of free radicals, ·OH and ·NO, generated in polluted dew water on needles of Pinus densiflora (Japanese Red pine) were investigated. • ·OH-generating solutions (HOOH with Fe(III) and oxalate ion; ·OH treatment) and ·OH-and ·NO-generating solutions (NO 2 -; ·OH/·NO treatment) were regulated at 25, 50 and 100 µmol and pH 4.4. HOOH only (HOOH treatment) was used as a control solution. Solutions were applied as a mist to the needle surface of P. densiflora seedlings before dawn twice a week for 3 months.• Within a month, net photosynthesis at near saturating irradiance ( Pn ) and stomatal conductance ( gl ) of ·OH-treated needles decreased with increasing solution concentration. The HOOH treatment had no effects on any of the measured parameters. Therefore, ·OH in the artificial dews caused the decreases in Pn and gl . In ·OH/·NO-treated needles, gl increased during the experiment, but Pn was unchanged. In all experiments, the characteristics of PSII were not significantly altered.• Free radicals in polluted dew water have harmful effects on the photosynthesis of P. densiflora and compound effects of ·OH and ·NO are different.

Chemical Characteristics of Fog Water at Mt. Tateyama, Near the Coast of the Japan Sea in Central Japan

“…Perhaps, the background concentrations of peroxides in the troposphere may increase over Japan. Peroxides act as an oxidant for SO 2 and contribute to vegetation damage, as does O 3 (Möller 1989;Ennis et al 1990;Hewitt and Terry 1992;Kume et al 2001). Relatively high concentrations (65 μM) of peroxides were observed in dew water where peroxide concentrations are usually low (<5 μM) at sites of low altitude, at Murododaira in September 2008 ).…”

“…Relatively high concentrations (65 μM) of peroxides were observed in dew water where peroxide concentrations are usually low (<5 μM) at sites of low altitude, at Murododaira in September 2008 ). Kume et al (2001) reported that 100 μM of H 2 O 2 results in serious damage to vegetation. OH radicals formed by Fenton's reaction of H 2 O 2 in the liquid phase may damage vegetation (Kume et al 2001).…”

“…Kume et al (2001) reported that 100 μM of H 2 O 2 results in serious damage to vegetation. OH radicals formed by Fenton's reaction of H 2 O 2 in the liquid phase may damage vegetation (Kume et al 2001). Not only strong acidic fogs but also high concentrations of photochemical oxidants, such as peroxides, may be causing the forest decline at Mt.…”

Seasonal changes in needle water content and needle ABA concentration of Japanese red pine, Pinus densiflora, in declining forests on Mt. Gokurakuji, Hiroshima prefecture, Japan

“…Gokurakuji, ·OH formation rates in dew on needle surfaces were found to be about twice as large as those in the nondeclining stands (Nakatani et al 2001). Exposure experiments using ·OH-generating mists as simulated dew water showed several harmful effects on the needles of P. densiflora seedlings (Kume et al 2001a;Kobayashi et al 2002;Chiwa et al 2005) and the Pn and growth of Prunus mume seedlings (Yoon et al 2006). Kume et al (2001a) also suggested that NO· and/or gaseous HONO formation on the needle surface might have a harmful effect on stomatal guard cells of the pine seedlings.…”

Modelling of stem biomass accumulation in Pinus densiflora seedlings exposed to aqueous-phase OH radicals generating mist

“…Hydrogen peroxide (H 2 O 2 ) is well known as a reactive 12 oxygen species that forms in plant cells and it affects biochemical processes such as 13 photosynthetic pathways under environmental stresses, such as high light intensity 14 and the presence of air pollutants (Asada, 1999;Halliwell and Gutteridge, 1999; 15 Kondo, 2002). Although gaseous H 2 O 2 had little effect on plant functions (Polle 16 and Junkermann, 1994), Kume et al (2001) and Kobayashi et al (2002) showed 17 that a mist containing iron-oxalate-H 2 O 2 , which simulates polluted morning dew 18 in the declining pine forests, changes some physiological traits, such as needle CO 2 19 assimilation rate of the Japanese red pine. Kume et al (2005) suggested that these cohort 2000 with a fixed ratio.…”