The influence of exogenous phytohormones and zinc sulfate on the morphophysiological characteristics of Salvinia natans (Salviniaceae)

Hydrophytic ferns of the family Salviniaceae, such as those of the genus Salvinia, hold promise for application in water purification and bioassessment. The Salvinia species are known for their rapid growth, adaptability, resistance to adverse environmental conditions, and also their ability to adsorb pollutants. The manipulation of plant growth and development through the application of exogenous phytohormones is an effective technique. In laboratory settings, we investigated the impact of exogenous phytohormones and zinc sulfate on the morphophysiological characteristics of young sporophytes of Salvinia natans. During the phase of intensive growth, the addition of exogenous abscisic acid (ABA) at a concentration of 10−5 M to the growth medium inhibited the accumulation of biomass in S. natans sporophytes. However, gibberellic acid (GA3) and cytokinins (kinetin or zeatin) at a concentration of 10−6 M, along with indole-3-acetic acid (IAA) at a concentration of 10−5 M, induced a slight increase in biomass. In sporophytes of S. natans grown in a medium containing varying concentration of zinc sulfate (228, 114, 57, 28.5, and 14.25 mg of zinc per liter of water), sings of chlorosis in floating fronds were observed as early as the second day of cultivation, followed by symptoms of necrosis. There was a decrease in the content of photosynthetic pigments. Sporophyte biomass decreased, as zinc concentration increased, ranging from 9.6% to 51%. Simultaneous application of phytohormones with the highest concentration of zinc sulfate partially mitigated the adverse effects of the metal, reducing biomass degradation and sustaining sporophyte viability. Qualitative alterations in the fern phenotype were observed, highlighting the phytotoxicity of excessive zinc concentrations. This underscores the potential use of S. natans as a bioindicator for water pollution.