Root morphological responses of three hot pepper cultivars to Cd exposure and their correlations with Cd accumulation

Abstract

Cultivars of hot pepper (Capsicum annuum L.) differ widely in their fruit cadmium (Cd) concentrations. Previously, we suggested that low-Cd cultivars are better able to prevent the translocation of Cd from roots to aboveground parts, but the corresponding mechanisms are still unknown. In this study, we aimed to improve understanding of the root morphological characteristics of the mechanisms involved in two low-Cd and a high-Cd cultivar. Seedlings were grown in nutrient solutions containing 0 (control), 2, and 10 μM Cd for 20 days, and Cd contents for the three cultivars were compared with changes in root morphology. The total root length (RL), root surface area (SA), number of root tips (RT), and specific root length (SRL) of all cultivars were decreased significantly by the 10 μM Cd treatment with the exception of the SA in JFZ, which showed no obvious change. For each cultivar, the 10 μM Cd treatment decreased significantly RL and SA specifically in roots with diameters (RD) of RD ≤ 0.2 mm or 0.2 mm < RD ≤ 0.4 mm, and increased significantly RL and SA specifically in roots with diameters of 0.6 mm < RD ≤ 0.8 mm. Hot pepper cultivars differ greatly in Cd accumulation and root morphology. In the 10 μM Cd treatment, root volume (RV), SA, and RT of all cultivars were negatively correlated with Cd concentration and amount in roots. However, RL, SA, RV, and RT of all cultivars were positively correlated with Cd concentration and amount in shoots, and translocation rate of Cd. The two low-Cd cultivars of hot pepper had less root tips, shorter root length, and smaller root surface area than the high-Cd cultivar in 10 μM Cd treatment, which may play a vital role in reducing root-to-shoot Cd translocation.

RNA-sequencing analysis reveals transcriptional changes in the roots of low-cadmium-accumulating winter wheat under cadmium stress

“…Previous studies have identified low-Cd-accumulating genotypes of rice (Liu et al 2005), pepper (Huang et al 2015a), sweet potato (Huang et al 2015b), and Chinese cabbage (Liu et al 2010), which can grow in heavily contaminated sites and yield agricultural products with low Cd levels. Thus, the use of such genotypes is an effective and feasible measure to decrease dietary Cd exposure (Liu et al 2005).…”

Root tolerance and biochemical response of Chinese lettuce (Lactuca sativa L.) genotypes to cadmium stress

“…Liu, Probst & Liao (2005) attributed the lower Cd 2+ contents in the roots of S. alfedii to the smaller size of root system (smaller root length, surface area and volume). Huang et al (2015) also indicated that pepper cultivar with shorter roots, fewer root tips and smaller surface area had lower capacity for Cd 2+ uptake. Moreover, the tolerance of plants to Cd 2+ stress has also been assessed based on the content of H 2 O 2 produced when the plants were exposed to the stress.…”

Phytoremediation Opportunities with Alimurgic Species in Metal-Contaminated Environments

“…Matching the mobilizing effect of roots in rhizospheric soil [43,44], higher leaching with vegetation cover in uncontaminated pots is expected, compared with uncultivated controls. Root morphology (surface area, diameter, tip density) generally plays an important role in nutrient and metal accumulation, especially for the less mobile Cd [45], and better tolerance to contamination should be expected when root distribution is moved downwards, as found in Sonchus and Tragopogon.…”