High and low temperatures constitute the most damaging type of abiotic stress and limit the survival, and productivity of plants. The present study aimed to evaluate the role of exogenous applications of acetylsalicylic acid (ASA) in reducing the deleterious effects of cold stress. Phaseolus vulgaris L. seedlings were treated with foliar-sprayed ASA at concentrations of 0–3 mM and then subjected to chilling stress at 4 °C for 2 or 4 days. Growth, photosynthesis, biochemical alterations, oxidative damage and antioxidant enzyme activities as well as the expression of cold-responsive genes (CBF3–COR47), were monitored during the experiment. ASA applications substantially improved several growth and photosynthetic parameters, including shoot biomass, dry weight, and photosynthetic pigments, of P. vulgaris seedlings exposed to different durations of chilling stresses. The ASA foliar spray treatments significantly (p < 0.05) rescued the growth and photosynthetic pigments of P. vulgaris seedlings under different chilling stresses. The total soluble sugars markedly increased during 0–4 days of chilling stress following ASA foliar spraying. The exogenous application of ASA significantly (p < 0.05) increased the accumulation of proline in P. vulgaris seedlings under chilling stress. At the gene expression level, ASA significantly (p < 0.05) upregulated the cold-responsive genes CBF3 and COR47. As a result, we speculate that, the application of exogenous ASA alleviated the adverse effects of chilling stress on all measured parameters, and 1 and 2 mM ASA exhibited the greatest effects.

In this study, a new modified chitosan conjugate (Chito-TZ) was developed via amide coupling between the acid chloride derivative of the methylthio-thidiazole compound and the free primary amino groups of chitosan. The product was characterized using several instrumental investigations, including Fourier-transform infrared spectroscopy (FT-IR), ¹H-Nuclear magnetic resonance, X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and X-ray diffraction (XRD). XRD indicated that the crystalline pattern of chitosan was interrupted after chemical modification with the thiadiazole derivative. Broido’s model was used to determine the thermal activation energy E_a, and the results showed that the E_a for the first decomposition region of Chito-TZ is 24.70 KJ mol⁻¹ lower than that required for chitosan (95.57 KJ mol⁻¹), indicating the accelerating effect of the thiadiazole derivative on the thermal decomposition of Chito-TZ. The modified chitosan showed better antibacterial and antifungal activities than the non-modified chitosan; except for seed germination, chitosan was better. The Chito-TZ showed a low MIC value (25–50 µg mL⁻¹) compared to Chito (50–100 µg mL⁻¹). Moreover, the maximum inhibition percentages for plant-pathogenic fungi, Aspergillus niger, Fusarium oxysporum, and Fusarium solani, were attained at a concentration of 300 µg mL⁻¹ with values of 35.4 ± 0.9–39.4 ± 1.7% for Chito and 45.2 ± 1.6–52.1 ± 1.3% for Chito-TZ. The highest germination percentages (%) of broad bean, shoot and root length and weight, and seed vigor index were obtained after Chito treatment with a concentration of 200 µg mL⁻¹ compared to Chito-TZ.