Fructans, ascorbate peroxidase, and hydrogen peroxide in ryegrass exposed to ozone under contrasting meteorological conditions

Abstract

Ozone (O3) is the most abundant tropospheric oxidant as well as an important component of photochemical pollution. Once inside the plant, ozone can produce reactive oxygen species that change the antioxidative pool and the carbohydrate metabolism. The current study aimed to analyze whether the contents and the composition of the fructan, the ascorbate peroxidase activity, and the H2O2 accumulation were changed in Lolium multiflorum ssp. italicum cv. Lema plants as response to short-term exposure to ozone and/or to different meteorological conditions, in two contrasting seasons (winter and summer). Results showed that higher solar radiation tends to decrease fructose content and, along with temperature, increases the ascorbate peroxidase (APX) activity. Such activity and levels of fructans practically did not vary during the time the experiment was being done, but APX daylight variation was modified by the ozone. Thus, the higher levels of this pollutant decreased the APX activity and increased fructose content, as well as changed the size of the fructan chains. Hydrogen peroxide (H2O2) accumulation was higher in plants that were fumigated with ozone when compared to the control, and it decreased throughout the day. As a conclusion, fructan contents increased when the APX activity decreased. It suggested that fructans could also help the defense system when there is a reduction on the APX activity in the plant.

Impacts of abiotic stresses on the physiology and metabolism of cool‐season grasses: A review

“…As reported throughout this review, carbohydrate accumulation is consistently implicated in increased tolerance to abiotic stresses (Rosa et al, 2009). A similar effect following ozone exposure might explain how in Italian ryegrass higher ozone concentrations substantially increased leaf fructose content and altered fructan polymerization (Moretto, Sandrin, Itaya, Domingos, & Figueiredo-Ribeiro, 2009;Pasqualetti et al 2015). Indeed, substantial increases in leaf sucrose and starch content were reported in wheat (Meyer et al, 1997) following exposure to high ozone levels.…”

“…However, Plazek et al (2001) reported that exposure of meadow fescue plants to high ozone concentrations did not alter membrane permeability. In contrast, Pasqualetti et al (2015) using Italian ryegrass (Lolium multiflorum) reported a marked increase in hydrogen peroxide levels after exposure to increased ozone concentrations.…”

“…In addition to ascorbic acid, glutathione, glutathione reductase, superoxide dismutase, and ascorbate peroxidase also participate in the defense mechanisms against oxidation from exposure to high ozone levels (Bassin, Volk, & Fuhrer, 2007;Sharma & Davis, 1997). Pasqualetti et al (2015) reported that in Italian ryegrass ascorbate peroxidase activity was significantly decreased after exposure to ozone stress, indicating that the antioxidative mechanism of the plants was overwhelmed.…”

Responses of Growth, Oxidative Injury and Chloroplast Ultrastructure in Leaves of Lolium perenne and Festuca arundinacea to Elevated O3 Concentrations

“…As one of the most toxic air pollutants, elevated O 3 concentrations could exert serious consequences on plant growth, physiological metabolisms and morphological characteristics [8][9][10][11][12]. The adverse effects of elevated O 3 concentrations on plants including herb species have been well known [13,14]. Elevated O 3 concentration led to leaf injury, decreased photosynthetic rate, and inhibited growth and accelerated senescence of many plant species [15][16][17][18].…”

“…Actually, plants including herb species have developed antioxidative systems to protect plant cells by regulating the production rate or content of intra-cellular ROS such as hydrogen peroxide (H 2 O 2 ) and superoxide anion (O 2 • − ). Changes in the activities of defense enzymes in leaves such as superoxide dismutase (SOD, catalase (CAT), peroxidase (POD) and ascorbate peroxidase (APX) could play an important role in preventing and alleviating the adverse impacts of elevated O 3 by scavenging ROS in many plants [9,14,17,20].…”