The capacity and critical stage of Cd absorption and accumulation of different pepper cultivars

Objectives  Understanding the Cadmium (Cd) accumulation dynamics of different pepper cultivars could help to find a way for escaping Cd contamination and achieving safe pepper production.

Methods  A field experiment was carried out using 8 pepper cultivars, including four chili pepper and four vegetable pepper cultivars. The total Cd content in the test soil was 0.194 mg/kg. Plant samples were collected during transplanting (0 day), seedling stage (32 days), fruiting stage (65 days) and maturity stage (111 days). The biomass and Cd content in root, stem, leaf and fruit of pepper were assessed.

Results  Cd content in chili pepper leaves was lower than that in vegetable pepper leaves at all the 4 sampling stages. Cd content in vegetable pepper fruit was higher at fruiting stage, while that in chili pepper fruit was higher at maturity stage. YJ425 and SJ5 cultivars had the lowest fruit Cd content among the chili and vegetable pepper cultivars, respectively. The rapidest Cd accumulation occurred during seedling stage. From 0 to 32 days after transplanting, the Cd content in roots, stems and leaves of chili pepper increased by 14.9, 51.2 and 51.9 times, and that in roots, stems and leaves of vegetable pepper increased by 8.9, 25.6 and 39.9 times. The Cd accumulation became slow during fruiting and maturity stages. From 32 to 65 days after transplantation, the Cd content in roots, stems and leaves of chili pepper increased by 0.35, 0.55 and –0.13 times, respectively, while that in roots, stems and leaves of vegetable pepper increased by 0.20, 0.01 and –0.29 times, respectively. From 65 to 111 days after transplantation, Cd content in roots, stems and leaves of chili pepper increased by –0.29, 0.44 and –0.40 times, respectively, while that in roots, stems and leaves of vegetable pepper increased by –0.34, –0.14 and –0.32 times, respectively. The Cd transfer efficiency between organs were different among pepper varieties. The chili pepper had lower root-stem Cd transfer efficiency, while vegetable pepper had lower stem-leaf, leaf and stem to fruit Cd transfer efficiency during the whole growing stages. The fruit Cd content significantly correlated with stem Cd content during the seedling stage (P < 0.01) and the Cd transfer efficiency from stem and leaf to fruit (P < 0.05).

Conclusions  The Cd accumulation was rapidest during seedling stage, and slowed down in fruiting and maturity stages of pepper. Fruit Cd content significantly correlated with stem Cd accumulation during seedling period, and the transfer efficiency from leaf and stem to fruit. The vegetable pepper absorbed more Cd than chili pepper, but accumulated lesser Cd in fruit and had lower transfer efficiency of Cd from stem and leaf to fruit than chili pepper.