Effects of heavy metals and high temperature on Atlantic Forest species: analysis of their tolerance capacity

Changes in temperature and the deposition of potential pollutants in the soil, such as heavy metals, may damage plant communities, altering their physiological processes. High temperature may also cause a series of morpho-anatomical, physiological and biochemical changes in plants. However, tolerant plant species tend to restrict these harmful effects. The present study investigates the impact of atmospheric warming on the accumulation capacity of heavy metals (Zn, Ni, Cu) in the roots and leaves of a pioneer species (Croton floribundus) and a non-pioneer species (Esenbeckia leiocarpa) native to the Atlantic Forest of southeastern Brazil. The experimental design involved exposing the plants to two soil treatments: without excess metals (-M) and with excess metals (+M), along with varying thermoperiods of 26 ºC day/19 ºC night and 32 ºC day/20 ºC in growth chambers. Over a 28-day period, we assessed weekly metal content, translocation, growth parameters, a non-enzymatic antioxidant (glutathione) and indicators of cell damage or oxidative stress (chlorophylls a and b, total chlorophyll (a+b), carotenoids, malondialdehyde and conjugated diene hydroperoxide contents). Both species exhibited increased metal accumulation under excess metals, employing distinct translocation strategies. C. floribundus showed high translocation rates of Ni to leaves and E. leiocarpa immobilized Ni in the roots. Atmospheric warming reduced Cu and Ni translocation from roots to leaves in both species. C. floribundus displayed lower physiological damage compared to E. leiocarpa, demonstrating robust growth. We concluded that the pioneer species possessed greater tolerance to oxidative stress induced by temperature and metal-related environmental factors than the non-pioneer species, confirming our hypothesis. In addition, our finding provides valuable insights for conservation and management of ecosystems affected by climatic and pollutant changes.