Effect of cadmium on growth and oxidative metabolism of faba bean plants

Abstract

The effect of CdCl 2 (0-50 µM) on the growth, physiological parameters and leaf antioxidative enzymes of faba bean plants was studied in order to investigate the possible involvement of this metal in the generation of oxidative stress. In the roots and leaves of faba bean plants Cd produced a significant inhibition of growth, as well as a reduction in the transpiration rate, photosynthetic efficiency ( 14 CO 2 -fixation), ribulose-1,5-bisphosphate-carboxylase/oxygenase (Rubisco) activity and leaf pigment content, and an alteration in the nutrient status in booth roots and leaves. An increased level of free proline was also detected. The results suggest that the treatment of faba bean plants with CdCl 2 induced a concentration-dependent oxidative stress situation in the leaves, characterized by an accumulation of H 2 O 2 , as a result of the inhibition of the antioxidant enzymes glutathione reductase (GR) and catalase (CAT). These results point to the possible induction of leaf senescence by cadmium.

Role of salicylic acid in regulation of cadmium toxicity in wheat ( Triticum aestivum L.)

“…Pretreatment of plants with SA induced a considerable increase in 14 CO 2 assimilation, photosynthetic activity and chlorophyll content, as also reported by Khan et al (2003), Moussa and Khodary (2003) and Krantev et al (2006). The activities of both carboxylating enzymes (RuBPC and PEPC) exhibited a strong reduction at all the Cd concentrations applied (Moussa, 2004;Krantev et al, 2006). Pretreatment of wheat plants with SA before exposure to Cd alleviated the inhibitory effect of Cd on these enzyme activities (Moussa and Khodary, 2003;Krantev et al, 2006).…”

“…This differential accumulation of Cd can be considered as potentiating the physiological effect of SA. Cd is known to inhibit plant growth (Moussa, 2004), while the growth-inducing properties of SA were reported in Cd-treated barley (Metwally et al, 2003) and rice (Choudhury and Panda, 2004). Cadmium toxicity leads to water balance disturbances, manifested by a decrease in RWC, as observed by Costa and Morel (1994).…”

“…The growth inhibition produced by Cd could be due mainly to the effect of this heavy metal on growth and on the photosynthesis rate (Metwally et al, 2003). Cd stress decreased the rate of CO 2 assimilation and photosynthetic efficiency, and led to the degradation of chlorophyll and the inhibition of biosynthesis, which could result in disturbances in the electron transport rates of PSI and PSII, leading to the generation of oxygen free radicals (Moussa, 2004). Treatment with SA increased the pigment contents (Moussa and Khodary, 2003;Krantev et al, 2008).…”

“…Cd 2+ , as a divalent cation, may displace the Mg 2+ ions which act as activators for Rubisco, resulting in a loss of activity (Wildner and Henkel, 1979). The highest Cd concentration decreased the Rubisco regeneration capacity of the Calvin cycle and photosynthesis (Moussa, 2004). These severe alterations in chlorophyll level, the high extent of lipid peroxidation, the decrease in RuBPC and PEPC activity and CO 2 -fixation rates are some of the factors responsible for damage to the photosynthetic process (Krantev et al, 2006;Moussa, 2004).…”

“…In fact, at least 70% of the Cd intake by humans originates from plant foods (Wagner, 1993), leading to a potential threat to human health (Shah and Dubey, 1998). Cadmium has been shown to cause many morphological, physiological, biochemical and structural changes in plants, such 322 as water imbalance, inhibition of seed germination and photosynthesis, reduction of growth, especially of root growth, disturbances in mineral nutrition and sugar metabolism, and therefore strongly influences biomass production (Sanità di Toppi and Gabbrielli, 1999;Moussa, 2004), finally leading to the death of the plant (Kahle, 1993). Cadmium produces alterations in the functionality of membranes by inducing changes in lipid composition (Ouariti et al, 1997), affecting the enzymatic activities associated with membranes, such as that of H + -ATPase (Fodor et al, 1995), and decreasing the photosynthetic rate due to the reduced chlorophyll content and the enzymatic activity involved in CO 2 fixation (Greger and Ögren, 1991).…”