The article discusses the metabolic implications of stress-induced proline accumulation in plants. Proline accumulation is a common response to various biotic and abiotic stresses, but its benefits to plants under adverse conditions have been debated. While proline is known to mediate osmotic adjustment, stabilize subcellular structures, and scavenge free radicals, the cytoplasmic pool of free proline may not be sufficient to explain all biophysical effects. The authors propose that proline accumulation may also reduce cellular acidification, prime oxidative respiration for energy recovery, and maintain NAD(P)+/NAD(P)H ratios compatible with normal metabolism. A small increase in proline biosynthesis can significantly impact the reduction of the cellular NADP pool, enhancing the oxidative pentose phosphate pathway and supporting increased secondary metabolite production and nucleotide synthesis. The extreme sensitivity of proline synthesis and degradation may benefit by regulating metabolic processes affected by stress. The interconversions of proline and Δ1-pyrroline-5-carboxylate (P5C) in different cell types and the transfer of redox potential between tissues may constitute a form of metabolic signaling, potentially influencing gene expression in response to stress. The article highlights the need for further research to understand the mechanisms by which proline accumulation alleviates the effects of osmotic stress and other environmental challenges.The article discusses the metabolic implications of stress-induced proline accumulation in plants. Proline accumulation is a common response to various biotic and abiotic stresses, but its benefits to plants under adverse conditions have been debated. While proline is known to mediate osmotic adjustment, stabilize subcellular structures, and scavenge free radicals, the cytoplasmic pool of free proline may not be sufficient to explain all biophysical effects. The authors propose that proline accumulation may also reduce cellular acidification, prime oxidative respiration for energy recovery, and maintain NAD(P)+/NAD(P)H ratios compatible with normal metabolism. A small increase in proline biosynthesis can significantly impact the reduction of the cellular NADP pool, enhancing the oxidative pentose phosphate pathway and supporting increased secondary metabolite production and nucleotide synthesis. The extreme sensitivity of proline synthesis and degradation may benefit by regulating metabolic processes affected by stress. The interconversions of proline and Δ1-pyrroline-5-carboxylate (P5C) in different cell types and the transfer of redox potential between tissues may constitute a form of metabolic signaling, potentially influencing gene expression in response to stress. The article highlights the need for further research to understand the mechanisms by which proline accumulation alleviates the effects of osmotic stress and other environmental challenges.