Boosting banana resilience: Calcium supplementation enhances osmolyte and secondary metabolites production and strengthens the antioxidant machinery in drought and cold-exposed banana plants

Banana (Musa spp.) is a vital tropical fruit crop cultivated worldwide and is known for its nutritional value. The cultivation of bananas is often challenged by environmental stresses such as cold and drought, which can adversely affect plant productivity. In response to these challenges, plants deploy adaptive mechanisms to mitigate the impacts of environmental stresses. Calcium (Ca²⁺), recognized as a universal second messenger, is pivotal in cellular responses to hormones, pathogens, and stress factors. This study explores the potential of exogenous calcium supplementation as a cost-effective and promising solution, influencing metabolic activities and signal transductions in plants. To investigate the defensive role of Ca²⁺ supplementation in banana plants subjected to drought (200 mM Mannitol) and cold (14 °C) stress, comprehensive analyses were conducted to elucidate the mechanism underlying Ca²⁺-mediated stress tolerance. The plants were treated with mannitol, cold or Hoagland, and then supplemented with CaCl₂ (15 mM). Exogenous Ca²⁺ treatment significantly increased the proline content and maintained water balance and cellular stability. Additionally, it enhanced the production of protective secondary metabolites and activated key antioxidant enzymes, countering oxidative stress. Molecular analysis revealed an upregulation of calcium-binding proteins involved in stress response, while Ca²⁺ treatment reduced lipid peroxidation, as indicated by lower malondialdehyde (MDA) levels, signifying improved membrane integrity and reduced oxidative damage. These findings underscore the protective impact of exogenously supplied calcium, offering insights for sustainable strategies to enhance banana resilience in the face of environmental challenges and climate change.