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Background <p><i>Rosmarinus officinalis</i> is a medicinal and aromatic plant valued for its high levels of phenolics, flavonoids, and essential oils. However, drought stress can negatively affect plant growth, nutrient uptake, and the accumulation of bioactive compounds. Since biostimulants are increasingly used to mitigate the adverse effects of water deficiency and improve plant performance, this study aimed to evaluate the effects of different drought levels and selected biostimulants on the growth, mineral nutrition, physiological characteristics, and phytochemical composition of rosemary.</p> Results <p>The experiment was conducted as a pot trial in the open field and analyzed as a two-factor completely randomized design (CRD). The two factors consisted of drought stress and biostimulant treatments. The drought factor included three irrigation levels: full irrigation, one-third restricted irrigation, and two-thirds restricted irrigation. The biostimulant factor comprised five treatments: control (without biostimulant), ascorbic acid, gibberellic acid, Bacillus megaterium, and Frateuria aurantia. Restricted irrigation reduced all growth parameters, iron and manganese minerals, total carotenoids, chlorophyll a, total chlorophylls biochemical contents, and phenolic components such as catechine hydrate, vanillin, naringin, and cinnamic acid. it also increased phosphate and zinc, total antioxidant, malondialdehyde, resveratrol, and chrysin parameters. However, biostimulant applications alleviated many of these negative effects. Gibberellic acid was the most effective treatment, significantly enhancing seedling growth (3.06%), root length (11.28%), seedling dry weight (16.17%), potassium uptake (27.19%), total flavonoid content (37.97%), antioxidant activity (37.83%), and the accumulation of phenolic compounds—including vanillin (150%), rutin (4.81%), rosmarinic acid (5.31%), and chrysin (24.01%) compared with the control. Ascorbic acid was the most effective treatment for increasing root fresh weight (33.60%) and resveratrol content (130.00%). Application of Frateuria aurantia markedly increased root fresh weight (26.33%), total carotenoids (11.24%), quercetin (8.69%), and the uptake of calcium (11.50%), magnesium (8.64%), and manganese (2.70%), while also producing the reduction in malondialdehyde levels (22.09%). In contrast, Bacillus megaterium exhibited relatively limited effects and was primarily distinguished by promoting cinnamic acid content (22.22%) and total antioxidant activity (33.34%) to the greatest extent relative to the control.</p> Conclusions <p>The findings suggest that biostimulants may help alleviate drought stress in rosemary under pot conditions. Among the tested treatments, gibberellic acid and ascorbic acid showed greater potential for improving plant growth, physiological performance, and phytochemical quality. Overall, biostimulant applications may represent a promising approach for pot-grown rosemary, although further field studies are needed to confirm these findings.</p>

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Comparative effects of chemical and PGPR-based biostimulants on growth, mineral uptake, and biochemical responses of Rosmarinus officinalis under drought stress

  • 期刊论文

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  • 发表日期：

    2026年8月4日

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  • Muhammed Said Yolcu

摘要

Background

Rosmarinus officinalis is a medicinal and aromatic plant valued for its high levels of phenolics, flavonoids, and essential oils. However, drought stress can negatively affect plant growth, nutrient uptake, and the accumulation of bioactive compounds. Since biostimulants are increasingly used to mitigate the adverse effects of water deficiency and improve plant performance, this study aimed to evaluate the effects of different drought levels and selected biostimulants on the growth, mineral nutrition, physiological characteristics, and phytochemical composition of rosemary.

Results

The experiment was conducted as a pot trial in the open field and analyzed as a two-factor completely randomized design (CRD). The two factors consisted of drought stress and biostimulant treatments. The drought factor included three irrigation levels: full irrigation, one-third restricted irrigation, and two-thirds restricted irrigation. The biostimulant factor comprised five treatments: control (without biostimulant), ascorbic acid, gibberellic acid, Bacillus megaterium, and Frateuria aurantia. Restricted irrigation reduced all growth parameters, iron and manganese minerals, total carotenoids, chlorophyll a, total chlorophylls biochemical contents, and phenolic components such as catechine hydrate, vanillin, naringin, and cinnamic acid. it also increased phosphate and zinc, total antioxidant, malondialdehyde, resveratrol, and chrysin parameters. However, biostimulant applications alleviated many of these negative effects. Gibberellic acid was the most effective treatment, significantly enhancing seedling growth (3.06%), root length (11.28%), seedling dry weight (16.17%), potassium uptake (27.19%), total flavonoid content (37.97%), antioxidant activity (37.83%), and the accumulation of phenolic compounds—including vanillin (150%), rutin (4.81%), rosmarinic acid (5.31%), and chrysin (24.01%) compared with the control. Ascorbic acid was the most effective treatment for increasing root fresh weight (33.60%) and resveratrol content (130.00%). Application of Frateuria aurantia markedly increased root fresh weight (26.33%), total carotenoids (11.24%), quercetin (8.69%), and the uptake of calcium (11.50%), magnesium (8.64%), and manganese (2.70%), while also producing the reduction in malondialdehyde levels (22.09%). In contrast, Bacillus megaterium exhibited relatively limited effects and was primarily distinguished by promoting cinnamic acid content (22.22%) and total antioxidant activity (33.34%) to the greatest extent relative to the control.

Conclusions

The findings suggest that biostimulants may help alleviate drought stress in rosemary under pot conditions. Among the tested treatments, gibberellic acid and ascorbic acid showed greater potential for improving plant growth, physiological performance, and phytochemical quality. Overall, biostimulant applications may represent a promising approach for pot-grown rosemary, although further field studies are needed to confirm these findings.