The Addition of Selenium to the Nutrient Solution Decreases Cadmium Toxicity in Pepper Plants Grown under Hydroponic Conditions

Abstract

Cadmium is absorbed by plants rapidly and without control through the same channels as other essential metals, interfering with their transport and utilization. Many studies have shown that selenium could be utilized as a way to avoid this unwanted transport and other negative effects of Cd. For this reason, the present research study was conducted with four treatments (−Cd/−Se, +Cd/−Se, +Cd/+SeF, and +Cd/+SeR) to determine the type of application of Se that is best (foliarly and/or via the root) as regards the reduction of the toxic effects of Cd on plants. Our results showed that the Cd excess in the nutrient solution resulted in a decrease in the total dry biomass of the plants grown under these conditions, and this decrease was due to the reduction of the growth of the shoot (48% +Cd/−Se, 45% +Cd/+SeF, and 38% +Cd/+SeR, relative to −Cd/−Se). This reduction in growth was due to: (i) the toxicity of Cd itself and (ii) the nutritional disequilibrium suffered by the plants. It seems that under hydroponic conditions, the addition of Se to the nutrient solution, and therefore its absorption through the roots (lower antioxidant activity, superoxide dismutase, H2O2 concentration and higher catalase activity), greatly delayed and reduced the toxic effects of Cd on the pepper plants, as opposed to the foliar application of this element.

Effects of Se Application on Polyamines and Carbon–Nitrogen Metabolism of Pepper Plants Suffering from Cd Toxicity

“…In the first part of the present publication [8], it was shown that the presence of Cd in the nutrient solution (+Cd/−Se, +Cd/+SeF and +Cd/+SeR) decreased the total dry biomass by 48%, 45%, and 38%, respectively, as compared to the control treatment (−Cd/−Se). Therefore, the application of Se through the root palliated the negative effect of Cd in the nutrient solution.…”

“…The objective of the present work is to discover how Cd toxicity affects nitrogen and carbon metabolism of pepper plants, and to identify if, among the mechanisms involved in the tolerance of pepper plants to Cd when Se is applied, they are related with the synthesis and accumulation of polyamines and amino acids. This work is part of another publication by Pérez-Millán et al (2021) [8], which demonstrated that the application of Se reduces the concentration and toxicity of Cd in pepper plants.…”

“…For this study, pepper (Capsicum annuum L.) seeds from the commercial variety 'Cristal' were germinated in sterile vermiculite trays inside a controlled-environment growth chamber. The information related to the germination and crop management have previously been described in Pérez-Millán et al (2021) [8].…”

“…The Se was applied as Na 2 SeO 4 to a final concentration of 10 µM in both the foliar and root treatments. The details of the experimental design can be found in Pérez-Millán et al ( 2021) [8]. The sampling began 15 days from the start of the Cd treatment for the corresponding analytical studies.…”

“…Among these strategies, several studies have reported that Se application can decrease Cd uptake and/or alleviate the toxic effects of Cd on vegetables [4][5][6], such as in the cultivation of pepper [7]. In a previous study with these plants [8], it was observed that Se applied to the root had beneficial effects due to the decrease in the foliar concentration of Cd, and the increase in the concentration of Se in every plant part, thus reducing the toxicity of Cd in the leaves, and maintaining the vegetative growth of the plants.…”