Differential Impacts of pH and Acid Type on Seed Germination and Seedling Growth in

Elevated acidity from natural and anthropogenic sources can be a significant stressor for plants, affecting essential processes such as nutrient uptake and growth. While low pH (< 4) is generally considered stressful for plants, differential impacts of distinct acid types-organic versus inorganic, strong versus weak-on plant growth and development remain unclear. To address this knowledge gap, we evaluated the responses of two Brassicaceae species to organic (acetic) and inorganic (hydrochloric, sulfuric) acids at three pH levels (pH 2.5-5.5) to determine whether acid responses are solely pH-dependent or if acid type specificity plays a role in plant functional responses, thereby providing insights into the mechanisms of acid responses and tolerance. Plant responses varied based on acid types, even at the same pH levels. Hydrochloric acid promoted higher seed germination but hindered seedling growth and morphological development of roots, shoots, and leaves, while acetic and sulfuric acids had the opposite effects. These results highlight the influence of acid types on plant functions, specifically affecting distinct developmental stages. These findings suggest that plant responses to acid stress are not solely pH-dependent but are significantly influenced by the specific chemical properties of the acids involved, providing valuable insights for managing acid-impacted wild plant communities.