Respostas morfoanatômicas e bioquímicas de Lantana fucata Lindl. (verbenaceae) cultivada em solo com excesso de cobre

Abstract

The present work aimed to evaluate the morphoanatomical and biochemical responses of Lantana fucata cultivated in soil with excess of copper, since the species presents tolerance to high doses of the metal and potential for its phytostabilization in the soil. Cultivation was carried out in a greenhouse and the experiment used five treatments, T0= (without addition of copper), T1= 210, T2= 420, T3= 630, T4= 840 mg Cu kg-1 soil. After 100 days of cultivation, leaves and roots of L. fucata were collected and processed using usual methodologies for observations under optical microscopy and for the determination of dry mass. With regard to biochemical analysis, the sheets were prepared with methodologies already validated for the extraction of chlorophylls and characterization and quantification of secondary metabolites, using the techniques of high-performance liquid chromatography and mass spectrometry. Excess copper had no visible effects on shoots, but T2 and T3 leaves exhibited thicker mesophyll. The excess of copper in the treatments caused changes in the root, such as the darkening of the root apex, shortening of the roots, the increase in the formation of lateral roots, as well as damage to the meristematic region and cap. In more distal areas of the root, accumulation of phenolic compounds in cortical cells, development of an exoderm and early differentiation of the xylem vessel elements was observed. However, despite these morphoanatomical changes, excess copper did not negatively affect growth, with an increase in dry mass at T2. Regarding the biochemical variables analyzed in L. fucata, the excess of copper caused a decrease in the concentration of total a, b and chlorophylls, in addition to causing a decrease in the concentrations of two key compounds of secondary metabolism, p-coumaric acid and cinnamic acid in T3 and T4. At the same time, an increase in other metabolites, mainly from the phenolic compounds class, was observed. Despite the damage seen in root morphoanatomy and photosynthetic pigments, L. fucata seems to support high copper concentrations, possibly due to the development of tolerance strategies related to lateral root formation and the increase of phenolic compounds in roots and leaves.