Attenuation of Drought Stress in Brassica Seedlings with Exogenous Application of Ca2+ and H₂O₂

Abstract

Drought is one of the most common abiotic stresses, affecting the growth and productivity of crop plants globally, particularly in arid and semi-arid regions. Different strategies are used to mitigate the impact of drought among crop plants. Exogenous application of different substances are known to decrease the effects of various abiotic stresses, including drought stress. The aim of this study was to evaluate the effect of Ca²⁺ and H₂O₂ in developing drought stress tolerance in Brassica napus "Bulbul-98" seedlings. Brassica napus "Bulbul-98" seedlings were exposed to 5, 10 and 15 mM Ca²⁺ and 2, 5 and 10 μM H₂O₂ concentrations twice at an interval of two days for up to 20 days after germination. Drought stress decreased relative water content (RWC), chlorophyll content and increased proline, H₂O₂, soluble protein and electrolyte leakage in Brassica seedlings. Exogenous Ca²⁺ (5, 10,15 mM) and H₂O₂ (2, 5, 10 μM) supplementations, during drought stress induction, showed a significant increase in RWC by 5.4%, 18.06%, 26.2% and 6.87%, 13.9%, 18.3% respectively. Similarly, with the exogenous application of Ca²⁺ (5, 10, 15 mM) and H₂O₂ (2, 5, 10 μM), chlorophyll content was increased by 15.03%, 22.2%, and 28.4%, and 9.6%, 23.3%, and 27.5% respectively. It was confirmed that the seedlings under drought stress that were supplemented with Ca²⁺ and H₂O₂ recovered from water content reduction and chlorosis, and were able to grow normally.

Keywords: SDS-PAGE; drought stress; electrolyte leakage; proline; relative water content.

Figure 1

H₂O₂ and CaCl₂ pre-treatment effect on the of the rate of water loss (A) over time (h, 1H, 2H, 3H and 4H); Relative water content (B) of Brassica napus “Bulbul-98” seedlings under irrigated (WW) and drought stress (WS) conditions (B). In accordance with Least Significant Difference (LSD) test, the bars with at least one common alphabet are not significantly different at p ≤ 0.05.

Figure 2

H₂O₂ and CaCl₂ supplementation effect on the content of chlorophyll (A) and protein content (B) of the Brassica napus “Bulbul-98” seedlings under irrigated (WW) and drought stress (WS) conditions. In accordance to Least Significant Difference (LSD) test, the bars with at least one common alphabet are not significantly different at p ≤ 0.05.

Figure 3

Effect of H₂O₂ and CaCl₂ supplementation on percent electrolyte leakage (%) from Brassica napus “Bulbul-98” seedlings under irrigated (WW) and drought stress (WS) conditions. In accordance with the Least Significant Difference (LSD) test, the bars with at least one common alphabet are not significantly different at p ≤ 0.05.

Figure 4

H₂O₂ and CaCl₂ supplementation effect on the proline (A) and H₂O₂ content (B) of the Brassica napus “Bulbul-98” seedlings under irrigated (WW) and drought stress (WS) conditions. In accordance to Least Significant Difference (LSD) test, the bars with at least one common alphabet are not significantly different at p ≤ 0.05.

Figure 5

SDS-PAGE electrophoregram of total soluble proteins of “Bulbul-98” seedlings under irrigated (A) and drought stress (B) conditions after H₂O₂ and CaCl₂ pre-treatment. Upper and lower arrowheads in each electrophoregram shows the large and small subunits of Rubisco. NS, non-supplemented.