Physiological and morphological responses of the root system of Indian mustard (Brassica juncea L. Czern.) and rapeseed (Brassica napus L.) to copper stress

Abstract

Copper (Cu) is an essential microelement for growth and development, but in excess it can cause toxicity in plants. In this comparative study, the uptake and accumulation of Cu as well as the morphological and physiological responses of Indian mustard (Brassica juncea L. Czern.) and rapeseed (Brassica napus L.) roots to Cu treatment were investigated. The possible involvement of redox active molecules (reactive oxygen species and nitric oxide) and modification in cell wall structure associated with Cu-induced morphological responses were also studied. In short- and long-term treatments, B. juncea suffered more pronounced growth inhibition as compared with B. napus. In addition to the shortening of primary and lateral roots, the number and the density of the laterals were also decreased by Cu. Exposure to copper induced nitric oxide generation in the root tips and this event proved to be dependent on the duration of the exposure and on the plant species. In short- and long-term treatments, Indian mustard showed more significant activation of superoxide dismutase (SOD), inhibition of ascorbate peroxidase (APX) and oxidation of ascorbate (AsA) than B. napus. Moreover, H2O2-dependent lignification was also observed in the Cu-exposed plants. In longer term, significant AsA accumulation and callose deposition were observed, reflecting serious oxidative stress in B. juncea. Based on the morphological and physiological results, we conclude that rapeseed tolerates Cu excess better than Indian mustard.

Evaluation of stress effects of copper oxide nanoparticles in Brassica napus L. seedlings

“…Previous studies have shown that elongations of roots in plants are affected by the redox status in their apical region (Córdoba-Pedregosa et al 2005). Changes in the redox status contribute to cell wall secondary thickening resulting in the reduction of cell growth and are negatively correlated with root elongation (Feigl et al 2013). In this study, for the first time, we observed callose deposition as a result of CuO NPs exposure in roots of B. napus seedlings.…”

“…Treatment with PI indicated cytotoxicity, in the root tips of B. napus seedlings treated with CuO NPs. As reported earlier as in the case of excess Cu (Feigl et al 2013), the enhanced ROS generation as a result of the increased Cu levels under CuO NPs treatment caused the cytotoxicity in roots of B. napus seedlings.…”

“…In this study, for the first time, we observed callose deposition as a result of CuO NPs exposure in roots of B. napus seedlings. It has been known from previous studies that Cu is an efficient inducer of callose formation in B. napus roots (Feigl et al 2013). The callose deposition could inhibit cell wall loosening and thereby negatively affect root growth by inhibiting the passage of signal molecules or supply of carbon required for root growth in plants (Jones et al 2006).…”

“…It was reported that loss of cell viability in root tips (in the meristem) could lead to the inhibition of root elongation in Brassica spp. (Feigl et al 2013). Previous studies have shown that elongations of roots in plants are affected by the redox status in their apical region (Córdoba-Pedregosa et al 2005).…”

“…According to a study by Ali et al (2014), the stress responses of two cultivars of B. napus exposed to same concentrations of Cd showed different responses. Feigl et al (2013) reported that when exposed to Cu excess the morphological adaptation strategy, especially, the root system development in B. juncea and B. napus showed differences. In a previous study, we observed toxic responses in B. juncea seedlings exposed to CuO NPs (Nair and Chung 2015).…”