GROWTH, LEAF ANATOMY AND MERCURY UPTAKE IN AZOLLA PINNATA AND AZOLLA FILICULOIDES

Abstract

Azolla pinnata and Azolla filiculoides can be used as heavy metal phytoremediators, but A. pinnata is not a hyperaccumulator. Plant response to heavy metals is not only seen from the ability to accumulate heavy metals, but also from the aspects of growth and changes in plant tissue structure. This study aimed to evaluate the development, leaf anatomy, and ability to absorb mercury in Azolla with non-hyperaccumulator and hyperaccumulator characters. The study was conducted by growing A. pinnata and A. filiculoides in containers containing 5 L of hydroponic solution that was either mercury-free or polluted with mercury at a concentration of 0.5 ppm. The results showed that A. filiculoides showed better tolerance and physiological adaptation to mercury contamination compared to A. pinnata, which experienced a decrease in biomass due to low detoxification ability. The detoxification ability of A. filiculoides is also supported by the anatomical adaptation in the form of leaf mesophyll thickening. Although A. pinnata absorbed more mercury, its inability to overcome toxic effects reflected different adaptation strategies. The ability of A. filiculoides to store mercury without disturbing its physiology shows its potential as a promising phytoremediation agent.