Qualitative and Quantitative Analysis of Tannin Content in Dominant Mangrove Species of Thailand

Mangrove constitutes a critical component of transitional ecosystems that bridge terrestrial and marine environments, providing substantial ecological contributions to both environments. Mangrove taxa have undergone extensive physiological and anatomical adaptations to optimize survival and reproductive success within the unique environmental conditions of intertidal habitats. Specialized adaptive structures in mangrove species include modified root systems, salt‐secreting glands, and salt tolerance mechanisms. Mangrove substrate toxicity elicits tannin synthesis in mangroves, leading to the accumulation of these contents within plant tissues. Tannin accumulation in plants within specific zones should correlate with developmental patterns specific to that region, since tannins are produced to counteract toxicity linked to mangrove habitats. Tannin quantification using the Prussian blue assay is based on the production of ferric ferrocyanide precipitates via ferrous ion oxidation by tannin compounds. The majority of plant specimens exhibited the highest tannin production in the stem bark, which was consistent with anatomical characteristics, given that this tissue region comprises highly metabolically active cells. Xylocarpus moluccensis exhibited higher tannin concentrations in root bark compared to stem bark, indicating effective adaptation to its landward zone habitat. These tannins may function to mitigate the toxicity of ferric ions present in the muddy substrate. Plants in the seaward zone, including Avicennia alba and Sonneratia caseolaris , were found to synthesize tannins in stems, bark, and leaves. The leaf anatomy of these species features salt‐secreting glands that facilitate salt excretion from leaves, thereby providing adequate space within the leaf tissue for tannin accumulation.