Response of pepper leaves epidermal cell under ozone stress to ascorbic acid treatment

The present investigation studied the effectiveness of ozone (O3) concentrations on epidermal cells of pepper (Capsicum frutescens L.) leaves and its response to ascorbic acid (AS). The plants were grown at two sites in Riyadh, King Saud University (KSU) Campus, and the second industrial city (SIC) under an average of 42.33 and 138.66 ppb of O3. Two groups grown at KSU site as a control; one of them was treated with tap water (TW) and the other was treated with TW+AS, while the remaining two groups were transferred to SIC site, treated as described previously. Treatment with 300 mg/L AS was performed once every 15 days until the end of the experiment. The plants grown under separately high concentrations of O3 and AS increased the stomatal numbers, dimensions and cell dimensions in both upper and lower epidermises of leaves in comparison to control plant leaves. Treatment with O3+AS significantly increased the length of the upper and lower epidermal cells, while it decreased the cell widths in comparison to plants grown under only O3. The AS might have a mitigating effect on the impacts of O3 on leaf epidermal cells of the pepper plant particularly, with respect to cell width.