Ultrastructure and Lipid Alterations Induced by Cadmium in Tomato (Lycopersicon esculentum) Chloroplast Membranes

Abstract

The effects of cadmium (Cd) uptake on ultrastructure and lipid composition of chloroplasts were investigated in 28-day-old tomato plants (Lycopersicon esculentum var. Ibiza F1) grown for 10 days in the presence of various concentrations of CdCl2. Different growth parameters, lipid and fatty acid composition, lipid peroxidation, and lipoxygenase activity were measured in the leaves in order to assess the involvement of this metal in the generation of oxidative stress. We first observed that the accumulation of Cd increased with external metal concentration, and was considerably higher in roots than in leaves. Cadmium induced a significant inhibition of growth in both plant organs, as well as a reduction in the chlorophyll and carotenoid contents in the leaves. Ultrastructural investigations revealed that cadmium induced disorganization in leaf structure, essentially marked by a lowered mesophyll cell size, reduced intercellular spaces, as well as severe alterations in chloroplast fine structure, which exhibits disturbed shape and dilation of thylakoid membranes. High cadmium concentrations also affect the main lipid classes, leading to strong changes in their composition and fatty acid content. Thus, the exposure of tomato plants to cadmium caused a concentration-related decrease in the fatty acid content and a shift in the composition of fatty acids, resulting in a lower degree of fatty acid unsaturation in chloroplast membranes. The level of lipid peroxides and the activity of lipoxygenase were also significantly enhanced at high Cd concentrations. These biochemical and ultrastructural changes suggest that cadmium, through its effects on membrane structure and composition, induces premature senescence of leaves.

Assessment of cadmium tolerance and phytoextraction ability in young Populus deltoides L. and Populus × euramericana plants through morpho-anatomical and physiological responses to growth in cadmium enriched soil

“…However, the percentage of palisade tissue, palisade thickness and cell area increased in Salix fragilis exposed to Cd. In our study, the decrease of palisade cell area observed in the Populus × euramericana clone is in agreement with the findings of Djebali et al (2005), who reported a reduction of mesophyll cell size, reduced intercellular spaces, and severe alterations of chloroplast fine structure in tomato upon Cd exposure. Furthermore, Cd treatment affected adaxial epidermis cell size only in the Populus × euramericana clone.…”

“…Cd causes structural and functional alterations in photosynthetic apparatus, resulting in reduced or inhibited photosynthesis (Parmar et al 2013). Furthermore, Cd toxicity may provoke an increase in peroxidation of chloroplast membrane lipids by enhancement of lipoxygenase activity, resulting in disorganization of thylakoid membranes and decreased concentration of both chlorophylls and carotenoids (Djebali et al 2005). High Cd concentrations in plant tissues can also affect other physiological processes, such as water regime, mineral nutrient uptake and ion metabolism (Parmar et al 2013).…”

Pb and Cd on growth, leaf ultrastructure and essential oil yield mint (Mentha arvensis L.)

“…It can be also associated with a microtubules disruption which may alter the shape and the synthesis of cell wall caused by the action of Pb (LIU et al, 2009). Chloroplast changes observed in cells of M. arvensis treated with Pb were already described in Potamogeton crispus treated with Pb, resulting in dilation of chloroplasts and disruption of their membranes (HU et al, 2007), possibly by reducing the concentration of membrane lipids caused by contamination with Pb as noted in the chloroplasts of Lycopersicon esculentum leaves (DJEBALI et al, 2005).…”

Calcium application enhances growth and alleviates the damaging effects induced by Cd stress in sesame (Sesamum indicumL.)

“…The reduced production of H 2 O 2 and lipid peroxidation in calcium-treated plants suggest the potential of calcium in reversing ROSinduced oxidative damage. The increased peroxidation of membrane lipids in cadmium-stressed plants is due to the increased lipoxygenase activity, which results in the rapid generation of peroxides and hydroxyl radicals and thus imposes deteriorating effects on cellular organelles (Djebali et al 2005). Recently, it was demonstrated that the application of calcium to cadmium-stressed mustard (Ahmad et al 2015) and faba bean (Siddiqui et al 2012) plants caused significant reductions in lipid peroxidation by downregulating the production rates of ROS.…”