Effect of CO, NOx and SO2 on ROS production, photosynthesis and ascorbate-glutathione pathway to induce Fragaria×annasa as a hyperaccumulator

Abstract

A study was conducted to determine the effect of carbon monoxide (CO), nitroxide (NOx) and sulfur dioxide (SO2) on ROS production, photosynthesis and ascorbate-glutathione pathway in strawberry plants. The results showed that both singlet oxygen (O2(-1)) and hydrogen peroxide (H2O2) content increased in CO, NOx and SO2 treated strawberry leaves. A drastic reduction of primary metabolism of plants (photosynthesis), with the closure of stomata, resulted in a reduction of protein, carbohydrate and sucrose content due to production of reactive oxygen species (ROS) under prolonged exposure of gas stress. The resulting antioxidant enzymes were increased under a low dose of gas stress, whereas they were decreased due to a high dose of gas stress. Our results indicate that increased ROS may act as a signal to induce defense responses to CO, NOx and SO2 gas stress. The increased level of antioxidant enzymes plays a significant role in plant protection due to which strawberry plants can be used as a hyperaccumulator to maintain environmental pollution, however, the defense capacity cannot sufficiently alleviate oxidative damage under prolonged exposure of CO, NOx and SO2 stress.

Keywords: Ascorbate–glutathione pathways; Fragaria×annasa; Hyperaccumulator; Photosynthesis; ROS production.

Graphical abstract

Fig. 1

Production of reactive oxygen species (ROS) (A) H₂O₂ and (B) O2⁻¹ determination, as affected by low, medium and high dose of CO, NO_x, and SO₂. Vertical bars indicate ±SE by means with n=3. Means denoted by different letters are significantly different at p<0.05 according to the Tukey's studentized range test.

Fig. 2

Changes in photosynthetic parameters (A) photosynthesis rate, (B) F_V/F_m ratio, as affected by low, medium and high dose of CO, NO_x, and SO₂. Vertical bars indicate ±SE by means with n=3. Means denoted by different letters are significantly different at p<0.05 according to the Tukey's studentized range test.

Fig. 3

Changes in the content of photosynthetic pigments (A) total chlorophyll (B) carotenoid, as affected by low, medium and high dose of CO, NO_x, and SO₂. Vertical bars indicate ±SE by means with n=3. Means denoted by different letters are significantly different at p<0.05, according to Tukey's studentized range test.

Fig. 4

Representative images of stomata, as affected by low, medium and high doses of CO, NO_x, and SO₂. Thin layer of leaf outer covering were peeled off carefully and laid on a glass slide, covered with a cover slip, and were observed under a light microscope (Leica CME) at 40× magnification.

Fig. 5

Regulation of RuBisCO larger and smaller subunits to low, medium and high doses of CO, NO_x and SO₂ (A) SDS-PAGE of leaf proteins from control and gas stressed plants, (B) quantification of the large subunit protein band. Vertical bars indicate ±SE by means with n=3. Means denoted by different letters are significantly different at p<0.05 according to Tukey's studentized range test.

Fig. 6

Changes in content of (A) total carbohydrate and (B) sucrose content, as affected by low, medium and high dose of CO, NO_x, and SO₂. Vertical bars indicate ±SE by means with n=3. Means denoted by a different letter are significantly different at p<0.05 according to Tukey's studentized range test.

Fig. 7

Changes in antioxidant enzyme activities (A) SOD (B) CAT (C) GR and (D) APX as affected by low, medium and high dose of CO, NO_x, and SO₂. Vertical bars indicate ±SE by means with n=3. Means are denoted by different letters are significantly different at p<0.05 according to Tukey's studentized range test.