This study was carried out to evaluate the effect of exogenous proline on the growth, biochemical responses, and plant recovery of drought-stressed oilseed rape plants after renewed irrigation. The experiment was conducted under controlled laboratory conditions. After 21 days of cultivation, 3–4 leaf stage seedlings were sprayed with proline (1 mM), then subjected to prolonged drought stress for 8 days to achieve a severe water deficit, next, irrigation was resumed and recovery was assessed after 4 days. The results show that exogenous application of proline reduced the drought-induced growth inhibition of seedlings while maintaining relative water content (RWC) and growth parameters closer to those of irrigated plants. Proline had a positive effect on chlorophyll accumulation and membrane permeability while decreasing ethylene, H₂O₂, and MDA levels. Moreover, after 4 days of recovery, the H₂O₂ content of the proline-treated plants was significantly lower (2-fold) and the MDA content was close to that of continuously irrigated plants. Thus, all these biochemical reactions influenced plant survival: after drought + proline treatment, the number of surviving plants was two times higher than that of drought-treated plants. The findings show that exogenous proline has antioxidant, osmotic, and growth-promoting properties that improve the drought tolerance of winter oilseed rape plants and is, therefore, beneficial for drought adaptation in oilseed rape.

Improving wheat drought stress tolerance is a critical and challenging task, and more research is necessary since many parts of the world depend on this crop for food and feed. Our current work is focused on the influence of probiotic microorganisms in combination with calcium salts on the physiological and biochemical metabolic pathways that wheat uses when exposed to drought stress and on the analysis of gene expression levels that contribute to wheat drought tolerance. The research was conducted in the laboratory under controlled conditions, simulating a prolonged drought. Seedlings were treated with different microorganisms (Bacillus subtilis, Lactobacillus paracasei, and some yeast) in 10⁵ CFU/mL concentrations for seed priming and later in the same concentration for seedling spraying. A total of 70 g/m² CaCO₃ or 100 g/m² CaCl₂ was added to the soil before sowing the seeds. Almost all tested treatments improved plant growth and positively affected prolonged drought resistance in winter wheat. Bacillus subtilis, in combination with calcium salts, had the greatest effect on maintaining the relative leaf water content (RWC). The proline, malondialdehyde (MDA), and H₂O₂ tests proved the significant positive impact of the treatments on the plant’s response at the biochemical level, with growth parameters close to those of irrigated plants, for example, the ones treated with B. subtilis alone or with Ca salts had the lowest H₂O₂ content, 0.86–0.96 μmol g⁻¹ FW, compared to 3.85 μmol g⁻¹ FW for the Control, along with lower levels of drought-induced gene expression. All the presented results show statistically significant differences (p < 0.05). This study showed that tested microorganisms in combination with calcium salts can activate plants’ defense reactions in response to drought. The practical significance of this study is that these ecological measures can be useful under field conditions.

The study aimed to examine the changes in winter oilseed rape (Brassica napus L.) under simulated prolonged drought and to assess the effects of a microbial biostimulant ProbioHumus and calcium, individually and in combination, in order to improve the plant’s drought resistance and to identify the biochemical processes occurring in the plant tissues. The oilseed rape cv. ‘Visby’ was grown under controlled laboratory conditions. CaCO₃ (hereafter, Ca) (3.71 g) was added to the soil of one pot at 70 g m⁻². Seedlings at the 3–4 leaf stage were sprayed with ProbioHumus 2 mL 100 mL⁻¹ and exposed to drought for 8 days to achieve a high water deficit. Irrigation was then resumed, and recovery was assessed after 4 days. The data showed that the microbial biostimulant alleviated the physiological and biochemical response of oilseed rape to drought stress. ProbioHumus + Ca reduced plant wilting by increasing leaf relative water content (RWC) by 87% and induced drought tolerance by increasing endogenous proline content 4-fold, increasing photosynthetic pigment content in leaves by 10–28%, reducing H₂O₂ by 53% and malondialdehyde (MDA) by 45%, and stimulating stomata opening (by 2-fold on the upper and 1.4-fold in the lower leaf surface), vs. drought control. The most effective measure to increase plant survival and/or resume growth after drought was the application of a microbial biostimulant with additional calcium to the soil. The practical implications of this research point to the potential benefits of applying these ecological measures under field conditions.

This study was carried out to evaluate the effect of exogenous proline on growth, biochemical responses, and plant recovery of drought-stressed oilseed rape plants after renewed irrigation. The experiment was conducted under controlled laboratory conditions. After 21 days of cultivation, 3-4 leaf stage seedlings were sprayed with proline (1 mM), then subjected to prolonged drought stress for 8 days to achieve a severe water deficit, then irrigation was resumed and recovery was assessed after 4 days. The results show that exogenous application of proline reduced drought-induced growth inhibition of seedlings while maintaining relative water content (RWC) and growth parameters closer to those of irrigated plants. Proline had a positive effect on chlorophyll accumulation and membrane permeability while decreasing ethylene, H2O2, and MDA levels. Moreover, after 4 days of recovery, the H2O2 content of the proline-treated plants was significantly lower (2-fold) and the MDA content was close to that of continuously irrigated plants. Thus, all these biochemical reactions influenced plant survival: after drought + proline treatment, the number of surviving plants was 2 times higher than that of drought-treated plants. The findings show that exogenous proline has antioxidant, osmotic, and growth-promoting properties that improve the drought tolerance of winter oilseed rape plants and is, therefore, beneficial for drought adaptation in oilseed rape.

The main objective of this study was to investigate the changes in winter oilseed rape (Brassica napus L.) under simulated prolonged drought and to assess the effects of a microbial biostimu-lant ProbioHumus and calcium, individually and in combination, in order to improve the plant's drought resistance and to identify the biochemical processes occurring in the plant tis-sues. The oilseed rape cv. 'Visby' was grown under controlled laboratory conditions. CaCO3 (hereafter Ca) (3.71 g) was added to the soil of one pot at 70 g m-2. After 21 days of cultivation, 3-4 leaf stage seedlings were sprayed with ProbioHumus 2 ml 100 ml-1 and exposed to drought for 8 days to achieve a high water deficit. Irrigation was then resumed and recovery was assessed af-ter 4 days. The results showed that the microbial biostimulant alleviated the physiological and biochemical response of oilseed rape to drought stress. ProbioHumus + Ca reduced plant wilting by increasing leaf relative water content (RWC) by 87% and induced drought tolerance by in-creasing endogenous proline content by 4-fold, photosynthetic pigment content in leaves by 10-28%, reducing H2O2 by 53% and malondialdehyde (MDA) by 45%, and by stimulating stomata opening (by 2-fold on the upper and 1.4-fold in the lower leaf surface), vs drought control. The most effective measure to increase plant survival and/or resume growth after drought was the application of a microbial biostimulant with additional calcium to the soil.

Improving wheat drought stress tolerance is a critical and challenging task, and more research is necessary since many parts of the world depend on this crop for food and feed. Our current work is focused on the influence of probiotic microorganisms in combination with calcium salts on the physiological and biochemical metabolic pathways that wheat uses when exposed to drought stress and on the analysis of gene expression levels that contribute to wheat drought tolerance. The research was conducted in the laboratory under controlled conditions, simulating a prolonged drought. Seedlings were treated with different microorganisms (Bacillus subtilis, Lactobacillus paracasei, and some yeast) in 105 CFU/ml concentrations for seed priming and later in the same concentration for seedling spraying. 70 g/m2 CaCO3 or 100 g/m2 CaCl2 was added to the soil before the sowing seeds. Almost all tested treatments improved plant growth and positively affected prolonged drought resistance in winter wheat. Bacillus subtilis, in combination with calcium salts, had the greatest effect on maintaining the relative leaf water content (RWC). Proline, MDA, and H2O2 tests proved a significant positive impact of the treatments on the plant's response at the biochemical level and growth parameters close to those of irrigated plants, along with lower levels of drought-induced gene expression. This study showed that tested microorganisms in combination with calcium salts can activate plants' defense reactions in response to drought. The practical significance of this study is that these ecological measures can be useful under field conditions.