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<p>Plants exposed to salinity and drought often employ distinct adaptive strategies, which can influence their energy metabolism and overall physiological responses. This study investigated the morphological, biochemical, and physiological responses of two-year-old grafted carob (<i>Ceratonia siliqua</i> (L.)) plants to salt and drought stresses, along with an analysis of their cost-benefit ratios. Two sets of plants were grown under field conditions: for salt stress, plants were irrigated with saline water at concentrations of 0, 30, 60, 120, and 240 mM NaCl; for drought stress, irrigation was 100%, 75%, 50%, and 25% of the plants’ water requirements. Results showed that salt stress significantly inhibited growth, particularly reducing collar diameter (gain of severe salt stress 35.81%; control 122.11%). Higher salt concentrations decreased the membrane stability index (61.67%; control, 76.69%) and increased electrolyte leakage (up to 44%), while levels of proline and soluble sugars rose (up to 5.79 µmol. g<sup>− 1</sup> FW and 10.78&#xa0;mg. g<sup>− 1</sup> FW, respectively). Severe drought stress, on the other hand, enhanced the activities of phenol oxidase (up to 50 UE/mg of protein), polyphenol oxidase (up to 131.51 UE/mg of protein), catalase (up to 239.83 µmol/min/mg of protein), and increased hydrogen peroxide levels (up to 1.95 µmol/g FW). Both primary and secondary metabolites, especially under moderate to severe stress conditions, were significantly elevated. Severe drought also resulted in higher osmolyte levels, particularly proteins (up to 12.73 mg.g<sup>− 1</sup> FW) and soluble sugars (up to 8.55 mg.g<sup>− 1</sup> FW), while total nitrogen content decreased (0.0746% DW). Both stressors triggered increased antioxidant defense mechanisms and the accumulation of osmotic regulators, highlighting the carob plant’s adaptive responses to these environmental challenges. While drought stress reduced irrigation costs, the reduction was insufficient to fully offset the negative effects of drought. According to our cost-benefit analysis, the most favorable treatment was the 25% drought stress level (i.e., 75% of the plant’s water requirements).</p>

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Morphological, physiobiochemical and enzymatic responses of grafted Carob trees to salt and drought stresses across the seasons, and determination of the optimal irrigation regime through a cost analysis

  • 期刊论文

  • 发表日期：

    2025年11月19日

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  • Salma Tabi,
  • Mouaad Amine Mazri,
  • Fouad Elame,
  • Mouad Oumahmoud,
  • Fatima Ezzahra Tiouidji,
  • Ahmed Wifaya,
  • Abdelghani Tahiri,
  • Abderrahim Amarraque,
  • Ilias El Ouahidi,
  • Naima Ait Aabd,
  • Abdelaziz Mimouni,
  • Nadya Wahid,
  • Meriyem Koufan

摘要

Plants exposed to salinity and drought often employ distinct adaptive strategies, which can influence their energy metabolism and overall physiological responses. This study investigated the morphological, biochemical, and physiological responses of two-year-old grafted carob (Ceratonia siliqua (L.)) plants to salt and drought stresses, along with an analysis of their cost-benefit ratios. Two sets of plants were grown under field conditions: for salt stress, plants were irrigated with saline water at concentrations of 0, 30, 60, 120, and 240 mM NaCl; for drought stress, irrigation was 100%, 75%, 50%, and 25% of the plants’ water requirements. Results showed that salt stress significantly inhibited growth, particularly reducing collar diameter (gain of severe salt stress 35.81%; control 122.11%). Higher salt concentrations decreased the membrane stability index (61.67%; control, 76.69%) and increased electrolyte leakage (up to 44%), while levels of proline and soluble sugars rose (up to 5.79 µmol. g− 1 FW and 10.78 mg. g− 1 FW, respectively). Severe drought stress, on the other hand, enhanced the activities of phenol oxidase (up to 50 UE/mg of protein), polyphenol oxidase (up to 131.51 UE/mg of protein), catalase (up to 239.83 µmol/min/mg of protein), and increased hydrogen peroxide levels (up to 1.95 µmol/g FW). Both primary and secondary metabolites, especially under moderate to severe stress conditions, were significantly elevated. Severe drought also resulted in higher osmolyte levels, particularly proteins (up to 12.73 mg.g− 1 FW) and soluble sugars (up to 8.55 mg.g− 1 FW), while total nitrogen content decreased (0.0746% DW). Both stressors triggered increased antioxidant defense mechanisms and the accumulation of osmotic regulators, highlighting the carob plant’s adaptive responses to these environmental challenges. While drought stress reduced irrigation costs, the reduction was insufficient to fully offset the negative effects of drought. According to our cost-benefit analysis, the most favorable treatment was the 25% drought stress level (i.e., 75% of the plant’s water requirements).