THE EFFECT OF GIBBERELLIC ACID (GA₃) ON GROWTH, PHOTOSYNTHETIC PIGMENTS, AND METAL BIOSORPTION IN THE WATER FERN Salvinia natans (L.) All. UNDER ZINC STRESS

Aim. This study investigates the impact of exogenous gibberellic acid (GA₃) on growth, photosynthetic pigment content, and zinc biosorption by sporophytes of the water fern Salvinia natans at both the initial and final stages of ontogeny. Methods. The ability of S. natans sporophytes to remove zinc from the aquatic environment was assessed by analyzing water samples post-cultivation using a portable Macherey-Nagel PF-12 Plus photometer. Photosynthetic pigments were extracted with 100% acetone and quantified using a Jenway UV-6850 spectrophotometer (UK) at wavelengths of 662, 664, and 440.5 nm, with acetone serving as the control. Results. At both the intensive growth stage and the phase of sorus formation and spore maturation, exogenous GA₃ enhanced fresh and dry biomass accumulation in S. natans sporophytes, increased chlorophyll content, and alleviated the adverse effects of zinc sulfate. These morphological and physiological improvements were more pronounced in mature sporophytes. The study also confirmed the ability of S. natans sporophytes to biosorb zinc ions from the aquatic environment, with zinc uptake in young sporophytes increasing by 10% upon GA₃ application. Conclusions. During its intensive growth phase, S. natans effectively removes zinc compounds from water, demonstrating its potential for phytoremediation. Exogenous GA₃ (10⁻⁶ M) mitigates the toxic effects of zinc (10 mg L⁻¹), enhancing growth and photosynthetic pigment content. Observable phenotypic changes in response to zinc toxicity further suggest that S. natans could serve as a bioindicator of water pollution.