The mechanism of the ozone-induced changes in thermoluminescence glow curves of barley leaves

Abstract

The changes in thermoluminescence (TL) signals induced by short-term ozone exposure of leaves are characterized by a down-shift of the peak-temperature of the TL B-band and an increase of a TL band at 55 °C. We investigated the relationship of these changes to photosystem 2 (PS2) photochemistry. The changes were not only detectable in the presence of ozone, but also after irradiation of dark-adapted leaves and after aging of irradiated detached leaf segments. The opposite effect on TL, an up-shift of the peak-temperature of the B-band and the decrease of the intensity of the band at 55 °C were found after infiltration of leaves with nigericin, antimycin A, and diphenyleneiodonium chloride (DPI). Propyl gallate down-shifted the peak-temperature of the B-band. 2,5-dimethyl-1,4-benzoquinone up-shifted the peaktemperature of the B-band and decreased the intensity of the 55 °C band. The intensity of the 55 °C band did not change significantly in the presence of oxygen in comparison to that in nitrogen atmosphere. It decreased with time of dark adaptation (50 % intensity was observed after 3 h of dark adaptation at room temperature), however, it was reactivated to its initial value (at 5 min of dark adaptation) after 1 single-turnover flash. The 55 °C band was not significantly changed in the presence of DCMU. Thus the ozone-induced band at 55 °C is assigned to charge recombination in PS2. Changes in the electron transport chain at the acceptor side of PS2, probably related to the cyclic electron transport around photosystem 1 and/or chlororespiration, could play an important role in the increase of the 55 °C band and the down-shift of the B-band. The changes at the acceptor side indicated by TL can be an expression of a physiological regulatory mechanism functional under stress conditions.

Contrasting effects of water salinity and ozone concentration on two cultivars of durum wheat ( Triticum durum Desf.) in Mediterranean conditions

“…Oxidative injury is also a common consequence of the O 3 uptake by plants (Kangasjarvi et al, 2005), which reduces plants photosynthetic capacity (Morgan et al, 2003;Dermody et al, 2006;Zheng et al, 2000;Skotnica et al, 2005) and whole-plant growth (Akhtar et al, 2010), decreasing of the stomatal conductance (Wittig et al, 2007), alterations in the antioxidant systems (Lee et al, 2003;Herbinger et al, 2005), and accelerated leaf senescence (Massman et al, 2000;Wieser et al, 2000), although the extent of these effects varies among species and cultivars (US EPA, 1986;Gerosa et al, 2009a;Gonzalez-Fernandez et al, 2010). Ozone is thought to affect plants by generating reactive oxygen species (ROS), such as hydrogen peroxide (H 2 O 2 ), superoxide radicals (O 2.…”

Effects of Ozone and Soil Salinity, Singly and in Combination, on Growth, Yield and Leaf Gas Exchange Rates of Two Bangladeshi Wheat Cultivars

“…Ozone has detrimental effects on the growth and productivity of crops (Tiwari et al, 2010). After entering the leaves through stomata, O 3 induces the formation of highly reactive oxygen species (ROS) and free radicals (Foyer and Noctor, 2005), which interact with cellular components to reduce the net photosynthetic rate (Dermody et al, 2006;Skotnica et al, 2005;Morgan et al, 2003) and stomatal conductance (Gerosa et al, 2014;Calatayud et al, 2003). Relatively high concentrations of O 3 cause visible foliar injury, accelerate leaf senescence (Massman et al, 2000), and affect biochemical and physiological processes (Rai et al, 2011;Betzelberger et al, 2010;.…”