Abiotic stress – a challenge for the master enzyme plasma membrane H+-ATPase

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The plasma membrane (PM) H+-ATPase is crucial for plant vitality, establishing an electrochemical proton gradient essential for cell-wall acidification, cell-extension growth, and energizing transport processes. Abiotic stresses can negatively impact enzyme functions, disrupting physiological processes and plant development. This thesis investigates the effects of abiotic stress on the PM H+-ATPase's two main functions. It examines magnesium (Mg) deficiency in developing maize leaves and salt stress in developing maize kernels. Mg deficiency, common in crops with inadequate fertilization, can lead to reduced yields. The study employs hydroponic experiments with varying Mg concentrations to assess key growth processes, revealing that cell division is not affected by Mg deficiency, as DNA replication and nutrient availability remain intact. However, the PM H+-ATPase's activity is inhibited by Mg deficiency, leading to reduced apoplastic acidification and impaired cell-extension growth, which limits maize growth. In contrast, salt stress negatively impacts kernel development, particularly at 2 days after pollination (DAP), when PM H+-ATPase activity declines, resulting in a lower pH gradient and reduced hexose import. This decrease in hexoses lowers cell energy status, impairing cell division and ultimately reducing kernel number and grain yield. The findings indicate that PM H+-ATPase impairment due to Mg deficiency and salt str