NEGATIVE EFFECTS ON PHOTOSYNTHESIS AND CHLOROPLAST PIGMENTS EXPOSED TO HEAVY METALS: A META-ANALYSIS

Abstract

Heavy metals have become some of the main abiotic agents that influence the stress of organisms due to their numerous agricultural and industrial uses that result in bioaccumulation and toxicity at different levels, depending on the type and concentration in the environment. Aluminum and lead are present as a result of anthropogenic activities and cause soil contamination and, consequently, pollution effects on producers such as plants. In this review, we used meta-analysis techniques to assess the effect of aluminum and lead on plant physiology. We calculated the overall effect size for the response variables photosynthesis, maximum quantum efficiency of photosystem II and plastid pigments (chlorophyll a, chlorophyll b and carotenoids). Moreover, we tested the effect of each metal and the phylogenetic relationship for the probability of Fabaceae species to respond to the pollution caused by these heavy metals. Overall, exposure to the heavy metals at high magnitudes affects photosynthesis and chlorophyll b (by reducing its amount). When considering the effect of each metal separately, aluminum reduced the content of the chlorophyll a and chlorophyll b. However, lead reduced photosynthesis, maximum quantum efficiency of photosystem II and chlorophyll b. When considering the Fabaceae species, there was no reduction of the parameters analyzed under stress by heavy metals. Therefore, our results confirm that these heavy metals (aluminum and lead) are toxic to plant physiology, mainly affecting the efficiency of the photosynthetic system and the plastid content.