Antioxidant Responses and Phytochemical Accumulation in Raphanus Species Sprouts through Elicitors and Predictive Models under High Temperature Stress

Abstract

Crop production is being impacted by higher temperatures, which can decrease food yield and pose a threat to human nutrition. In the current study, edible and wild radish sprouts were exposed to elevated growth temperatures along with the exogenous application of various elicitors to activate defense mechanisms. Developmental traits, oxidative damage, glucosinolate and anthocyanin content, and antioxidant capacity were evaluated alongside the development of a predictive model. A combination of four elicitors (citric acid, methyl jasmonate-MeJa, chitosan, and K₂SO₄) and high temperatures were applied. The accumulation of bioactives was significantly enhanced through the application of two elicitors, K₂SO₄ and methyl jasmonate (MeJa). The combination of high temperature with MeJa prominently activated oxidative mechanisms. Consequently, an artificial neural network was developed to predict the behavior of MeJa and temperature, providing a valuable projection of plant growth responses. This study demonstrates that the use of elicitors and predictive analytics serves as an effective tool to investigate responses and enhance the nutritional value of Raphanus species sprouts under future conditions of increased temperature.

Keywords: abiotic stress; antioxidant mechanisms; artificial neural network; methyl jasmonate.

Figure 1

Oxidative stress (MDA content) in sprouts of ER and WR. C₁: Control at 20 °C; C₂: Control at 30 °C; Citric Acid—20 °C represents the citric acid elicitor treatment combined with temperature at 20 °C; Citric Acid—30 °C represents the citric acid elicitor treatment combined with temperature at 30 °C; MeJa—20 °C represents the MeJa elicitor treatment combined with temperature at 20 °C; MeJa—30 °C represents the MeJa elicitor treatment combined with temperature at 30 °C; Chitosan—20 °C represents the chitosan elicitor treatment combined with temperature at 20 °C; Chitosan—30 °C represents the chitosan elicitor treatment combined with temperature at 30 °C; K₂SO₄—20 °C represents the sulphate potassium elicitor treatment combined with temperature at 20 °C; K₂SO₄—30 °C represents the sulphate potassium elicitor treatment combined with temperature at 30 °C. Different letters mean significant differences at p < 0.05 in treatments for radish sprouts analyzed separately (edible and wild radish) according to Tukey test.

Figure 2

GSLs (aliphatic and indole glucosinolates) in sprouts of ER and WR under the application of different elicitors. C₁: Control at 20 °C; C₂: Control at 30 °C; Citric Acid—20 °C represents the citric acid elicitor treatment combined with temperature at 20 °C; Citric Acid—30 °C represents the citric acid elicitor treatment combined with temperature at 30 °C; MeJa—20 °C represents the MeJa elicitor treatment combined with temperature at 20 °C; MeJa—30 °C represents the MeJa elicitor treatment combined with temperature at 30 °C; Chitosan—20 °C represents the chitosan elicitor treatment combined with temperature at 20 °C; Chitosan—30 °C represents the chitosan elicitor treatment combined with temperature at 30 °C; K₂SO₄—20 °C represents the sulphate potassium elicitor treatment combined with temperature at 20 °C; K₂SO₄—30 °C represents the sulphate potassium elicitor treatment combined with temperature at 30 °C. Different letters mean significant differences at p < 0.05 in treatments for radish sprouts analyzed separately (edible and wild radish) according to Tukey test.

Figure 3

Total phenolic content (TPC) and antioxidant capacity (DPPH and ORAC) assays in ER and WR sprouts. C₁: Control at 20 °C; C₂: Control at 30 °C; Citric Acid—20 °C represents the citric acid elicitor treatment combined with temperature at 20 °C; Citric Acid—30 °C represents the citric acid elicitor treatment combined with temperature at 30 °C; MeJa—20 °C represents the MeJa elicitor treatment combined with temperature at 20 °C; MeJa—30 °C represents the MeJa elicitor treatment combined with temperature at 30 °C; Chitosan—20 °C represents the chitosan elicitor treatment combined with temperature at 20 °C; Chitosan—30 °C represents the chitosan elicitor treatment combined with temperature at 30 °C; K₂SO₄—20 °C represents the sulphate potassium elicitor treatment combined with temperature at 20 °C; K₂SO₄—30 °C represents the sulphate potassium elicitor treatment combined with temperature at 30 °C. Different letters mean significant differences at p < 0.05 in treatments for radish sprouts analyzed separately (edible and wild radish) according to Tukey test.

Figure 4

Correlation matrix between different variables at 30 °C, (A) correspond to ER and (B) correspond to WR. RAD: length of the radicle; HYP: hypocotyl length, FW: weight sprouts; GR: germination rate; MDA: malondialdehyde assay; TGLs: total glucosinolates; TAC: total anthocyanins; GRE: glucoraphenin; 4-HGB: hydroxyglucobrassicin; DER: dehydroerucine; GB: glucobrassicin; MGB: 4-methoxyglucobrassicin; TPC: total phenolic content; DPPH: DPPH assay; ORAC: ORAC assay for ER and WR.

Figure 5

Principal component analysis (PCA) at 30 °C. Letter (A) represent the PCA of edible radish, letter (B) represent the PCA of wild radish, letter (C) represent the percentage of explained of edible radish and letter (D) represent the percentage of explained of wild radish. RAD: Length of the radicle; HYP: Hypocotyl length, FW: weight sprouts; GR: germination rate; MDA: Malondialdehyde Assay; TGLs: Total Glucosinolates; TAC: Total anthocyanins; GRE: Glucoraphenin; 4-HGB: Hydroxyglucobrassicin; DER: Dehydroerucine; GB: Glucobrassicin; MGB: 4-methoxyglucobrassicin; TPC: Total phenolic content; DPPH: DPPH assay; ORAC: ORAC assay for ER and WR.

Figure 6

Structure of the ANNs model for the prediction of antioxidant capacity by the DPPH and ORAC method, content of phenolic compounds (TPC), and oxidative stress biomarker malondialdehyde (MDA).