Morphophysiological responses, bioaccumulation and tolerance of Alternanthera tenella Colla (Amaranthaceae) to excess copper under in vitro conditions

Abstract

Copper (Cu) is an essential metal and both its deficiency and excess has negative effects on the growth and physiology of plants. Some plant species can tolerate high Cu concentrations due to their anatomical and physiological strategies. These plants can avoid absorption or accumulate this element in their biomass. Thus, the aim was to analyze the anatomical and physiological changes of Alternanthera tenella in response to excess Cu under in vitro conditions. A. tenella plants, previously established in vitro, were transferred to culture media containing 0, 25, 50, 100 or 200 µM Cu. At 30 days of culture, the stem and leaf anatomy, contents of photosynthetic pigments mineral nutrients, chlorophyll fluorescence, and, growth were analyzed. The excess Cu induced lower biomass accumulation. Plants also presented a decline in cell sizes of stem and leaf tissues under high Cu concentrations. Greater formation of druse crystals and lower number of active reaction centers (RC/CSM) were observed with 200 μM Cu. The Cu treatments modulated the contents of mineral nutrients and photosynthetic pigments of the plants. Plants cultured in media with Cu absence or excess (200 μM Cu) presented partial inhibition of electron transport and photochemical activity of photosystem II. Even though A. tenella plants showed clear signs of stress under Cu excess, they also have a strong capacity for Cu bioaccumulation and tolerance. A. tenella plants can be used for phytoremediation or bioindication due to their tolerance and high Cu bioaccumulation capacity. Copper can modulate the morphophysiology of A. tenella under in vitro conditions. A. tenella can be used for phytoremediation or bioindication due to its tolerance and high copper bioaccumulation capacity.