Cadmium stress alters the redox reaction and hormone balance in oilseed rape (Brassica napus L.) leaves

Abstract

In order to understand the physiological response of oilseed rape (Brassica napus L.) leaves to cadmium (Cd) stress and exploit the physiological mechanisms involved in Cd tolerance, macro-mineral and chlorophyll concentrations, reactive oxygen species (ROS) accumulation, activities of enzymatic antioxidants, nonenzymatic compounds metabolism, endogenous hormonal changes, and balance in leaves of oilseed rape exposed to 0, 100, or 200 μM CdSO4 were investigated. The results showed that under Cd exposure, Cd concentrations in the leaves continually increased while macro-minerals and chlorophyll concentrations decreased significantly. Meanwhile, with increased Cd stress, superoxide anion (O2(• -)) production rate and hydrogen peroxide (H2O2) concentrations in the leaves increased significantly, which caused malondialdehyde (MDA) accumulation and oxidative stress. For scavenging excess accumulated ROS and alleviating oxidative injury in the leaves, the activity of enzymatic antioxidants, such as superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), was increased significantly at certain stress levels. However, with increased Cd stress, the antioxidant enzyme activities all showed a trend towards reduction. The nonenzymatic antioxidative compounds, such as proline and total soluble sugars, accumulated continuously with increased Cd stress to play a long-term role in scavenging ROS. In addition, ABA levels also increased continuously with Cd stress while ZR decreased and the ABA/ZR ratio increased, which might also be providing a protective role against Cd toxicity.

Evolution of Abscisic Acid Signaling for Stress Responses to Toxic Metals and Metalloids

“…First of all, the biosynthesis and signaling pathways of ABA are affected by heavy metal stresses. Elevated endogenous ABA content was detected in rice, potato ( Solanum tuberosum ), oilseed rape ( Brassica napus ), Malus hupehensis , Sedum alfredii , and other plants exposed to Cd, partially due to the upregulation of genes for ABA biosynthesis ( Hsu and Kao, 2003 ; Stroiński et al, 2013 ; Yan et al, 2016 ; Shi et al, 2019 ; Zhang W. et al, 2019 ; Lu et al, 2020b ). In rice, the expression levels of OsNCED3 , OsNCED4 , and OsNCED5 were upregulated by Cd ( Tan et al, 2017 ).…”

Effect of Molybdenum on Plant Physiology and Cadmium Uptake and Translocation in Rape (Brassica napus L.) under Different Levels of Cadmium Stress

“…Under Cd stress, the structure of root tip cell walls of rape is susceptible to Cd-induced damage, which in turn shortens the roots [19] and inhibits the plant growth of rape. Specifically, leaf chlorophyll content is reduced and leaf photosynthetic capacity is decreased [20], while the antioxidant system is destroyed and hormone levels are imbalanced [21,22], leading to severe decline in the biomass and yield of rape [23]. The effect of Cd on rape plants has also been evaluated under the application of beneficial elements, such as Se and Zn [24,25].…”

Evaluation of three wheat (Triticum aestivum L.) cultivars as sensitive Cd biomarkers during the seedling stage

“…The growth repressions of shoots and roots in plants have been considered as direct symptoms of Cd toxicity (Liu et al, 2016;Zhan et al, 2017). Also, the oxidative stress (Haluskova et al, 2010;Yan et al, 2016) and adjustments in photosynthesis and energy metabolism (Elloumi et al, 2014;Ozfidan-Konakci et al, 2018) are apparent deficiencies caused by Cd stress in plant. However, to the best of our knowledge, the ideal sensitive biomarkers of Cd contamination have not been sufficiently explored.…”