Impacts of copper on photosynthetic pigments and anatomy of Alcantarea imperialis (Bromeliaceae) under in vitro conditions

Abstract

Description of the subject. Knowledge of morphophysiological status of plants and their responses to excess metals, such as copper (Cu), allows determining their potential use as bio-indicators. In vitro techniques are promising in studies that involve physiology and anatomy because they can isolate the effects of trace elements on morphophysiological features from other possible stress factors. Objectives. The aim was to verify the morphophysiological changes and adjustments of Alcantarea imperialis induced by excess Cu under in vitro conditions. Method. Alcantarea imperialis plants were transferred to in vitro culture media containing a concentration gradient of Cu (0, 25, 50, 100, or 200 μM). After 90 days, the contents of photosynthetic pigments and Cu were analyzed along with growth and anatomical features. Results. Plants cultured with Cu concentrations higher than 50 µM Cu had clear signs of toxicity, such as chlorosis. Plants exposed to 200 µM Cu showed a severe level of toxicity and were dead after 90 days. A drastic reduction of all photosynthetic pigments, as well as their ratios, was verified with exposure to 100 µM Cu. Plants exposed to that copper level presented the smallest stomata area, the lowest xylem number, as well as the thinnest vessel elements. The Cu content in the plants increased linearly as a function of Cu concentrations in the medium. Alcantarea imperialis plants can bioaccumulate high amounts of Cu. Conclusions. Alcantarea imperialis plants have good potential for bio-indication in urban areas due to their high Cu bioaccumulation capacity and clear morphophysiological changes. However, they have a low tolerance to very high Cu levels.