Gametophore growth and morphological adaptation of Sphagnum cuspidatulum to aluminum phytotoxicity and its accumulation potential in vitro

Gametophore growth and morphological adaptations of Sphagnum cuspidatulum Müll. Hal., to aluminum (Al) toxicity were investigated under in vitro conditions using Al 2 (SO 4 ) 3 at concentrations of 0, 50, 100, and 300 μM. Aluminum accumulation in moss tissue was quantified via inductively coupled plasma-mass spectrometry, while elemental localization and ultrastructural changes were assessed using energy-dispersive X-ray spectroscopy and scanning transmission electron microscopy. At 300 μM Al, moss growth was significantly inhibited, with a relative growth rate of 2.3 mg g −1 day −1 and gametophore length reduced to 4 mm, compared to 24 mm in control and 230 mm in field-collected specimens. Aluminum accumulation increased with dosage, ranging from 114.7 to 489.1 mg kg −1 . Cellular adaptations to Al toxicity included reduced hyaline cell size, enlarged vacuoles, and Al sequestration in cell walls. Highest Al atomic percentage (4.8 %) was observed in cell walls in the 300 μM Al treatment. Aluminum exposure reduced pH and induced secretion of amino acids, phenolic acids, and organic acids including phenylalanine, cinnamic acids, and propionic acid. Elevated antioxidant levels suggest a protective response against oxidative stress induced by Al toxicity. These findings highlight the morphological and physiological resilience of S. cuspidatulum to Al toxicity and support its potential use as a bioindicator for Al contamination in wetland ecosystems. • Elevated aluminum accumulation caused stress in Sphagnum cuspidatulum , inhibiting growth and morphology. • Hyaline cell reduction underlies S. cuspidatulum 's mechanism to tolerate Al. • Low pH can enhance Al toxicity, which is the key factor limiting growth of S. cuspidatulum . • Sphagnum cuspidatulum increased L -phenylalanine and phenolic acid secretion under Al stress. • Sphagnum cuspidatulum is a suitable metal bioindicator in selected wetland forest ecosystems.