Extreme Acid Stress in a Red Mung Bean (Vigna radiata) Microecosystem: An Ecotoxicological Perspective on Plant Failure and Fungal Emergence at pH 2

Abstract

Environmental pH is a fundamental physico-chemical factor influencing organismal performance, nutrient availability, chemical behaviour and biological interactions. Although extreme pH conditions are expected to impair seed germination and plant development, different biological components may respond differently to the same environmental stress. This study evaluated the responses of red mung bean (Vigna radiata) across a broad aqueous pH gradient, with particular attention to the unexpected emergence of visible fungal growth under extreme acidity. Seeds were exposed for seven days in Petri dish microcosms at pH 2, 3, 4, 5.5, 7, 8.5, 9.5, 10.5 and 12, with three replicates per treatment. Germination, seedling height, leaf development, general biological condition and cumulative biomass were assessed. Responses across the pH gradient were nonmonotonic, with mean germination ranging from 13.33% at pH 12 to 50.00% at pH 5.5. Mean germination at pH 2 was 16.67%, while cumulative plant biomass declined to zero. In contrast, pH 12 produced the lowest mean germination but retained measurable biomass, indicating contrasting biological responses at the two pH extremes. Most notably, conspicuous fungal colonization repeatedly developed in the pH 2 microcosms after approximately six days and became more extensive by Day 7, whereas comparable fungal growth was not recorded under the other pH treatments. The findings do not demonstrate that extreme acidity directly stimulated fungal growth. Instead, they support a testable ecotoxicological hypothesis whereby severe acid stress impaired seed viability and plant establishment, potentially generating deteriorating organic substrates that could subsequently be exploited by acid tolerant or opportunistic fungi. The study illustrates how an extreme environmental stressor may simultaneously suppress one biological component while permitting another to become conspicuous, emphasizing the importance of considering indirect biological responses and potential microecosystem shifts alongside conventional phytotoxicity endpoints.

Keywords: Acid Stress; Ecotoxicology; Fungal Colonization; Microecosystem; pH Stress; Red Mung Bean; Vigna radiata

Citation

Najwa Asrin Yusairi NA, Az Zahra Nur Anbiah SF, Hanim Ahmad Ahyad NA, Saravanan T, Alias AM, Hashim EI, et al. Extreme Acid Stress in a Red Mung Bean (Vigna radiata) Microecosystem: An Ecotoxicological Perspective on Plant Failure and Fungal Emergence at pH 2. WebLog J Environ Sci. wjets.2026.i2101. https://doi.org/10.5281/zenodo.23113616