Silicon mitigates cadmium toxicity and modulates positive anatomical changes in tree plants of African mahogany

Abstract

This study aimed to evaluate the effect of silicon mitigation (Si) on Khaya ivorensis exposed to cadmium (Cd) and anatomical changes promoted by Cd in roots and leaves tissues. O delineamento experimental foi inteiramente casualizado em esquema fatorial 4x4 com cinco repetições. Cd and Si treatments were 0, 25, 50, 75 mg L−1 and 0, 100, 150, and 300 mg L−1 respectively. At 25 mg L−1 mg, Cd has shown increases of 30%, 25%, and 33% in Epidermis thickness from adaxial (ETAd), spongy parenchyma thickness (SPT), and root cortex thickness (RCT). Also, 75 mg L−1 Cd decreased epidermis thickness from abaxial (ETAb) and root cortex thickness (RCT) by 70% and 81 %. However, Si attenuated anatomical changes caused by Cd. It occurs especially in combination with treatments at 150 mg L−1 Si and 50 mg L−1 Cd. Under these conditions, ETAb increased by 33%. Both palisade parenchyma thickness (PPT) and spongy parenchyma thickness (SPT) were 48% and 55% thicker than tissues under 50 mg L−1 Cd. The K. ivorensis is tolerant to Cd up to 25 mg L−1 mg because it did not show considerable growth reduction. Si has shown modulation in tissue thickness. It has a positive impact on the vegetative growth of K. ivorensis. Therefore, this study indicates that K. ivorensis tolerates Cd toxicity up to 25 mg L−1 Cd and shows that Si induces anatomical modulations in leaves and roots.