Morphophysiological responses and programmed cell death induced by cadmium in Genipa americana L. (Rubiaceae)

Abstract

Cadmium (Cd) originating from atmospheric deposits, from industrial residues and from the application of phosphate fertilizers may accumulate in high concentrations in soil, water and food, thus becoming highly toxic to plants, animals and human beings. Once accumulated in an organism, Cd discharges and sets off a sequence of biochemical reactions and morphophysiological changes which may cause cell death in several tissues and organs. In order to test the hypothesis that Cd interferes in the metabolism of G. americana, a greenhouse experiment was conducted to measure eventual morphophysiological responses and cell death induced by Cd in this species. The plants were exposed to Cd concentrations ranging from 0 to 16 mg l(-1), in a nutritive solution. In TUNEL reaction, it was shown that Cd caused morphological changes in the cell nucleus of root tip and leaf tissues, which are typical for apoptosis. Cadmium induced anatomical changes in roots and leaves, such as the lignification of cell walls in root tissues and leaf main vein. In addition, the leaf mesophyll showed increase of the intercellular spaces. On the other hand, Cd caused reductions in the net photosynthetic rate, stomatal conductance and leaf transpiration, while the maximum potential quantum efficiency of PS2 (Fv/Fm) was unchanged. Cadmium accumulated in the root system in high concentrations, with low translocation for the shoot, and promoted an increase of Ca and Zn levels in the roots and a decrease of K level in the leaves. High concentrations of Cd promoted morphophysiological changes and caused cell death in roots and leaves tissues of G. americana.

Morphological, biochemical, molecular and ultrastructural changes induced by Cd toxicity in seedlings of Theobroma cacao L.

“…Structural changes in the chloroplasts of the progeny more susceptible ('Catongo' Â 'Catongo') to stress by metals was probably due to increased ROS, as evidenced by severe damages in the structures of chloroplasts, particularly in thylakoid membranes and the granum (Paramonova et al, 2003). The same was observed in the structure of leaf chloroplasts of Genipa americana subjected to toxicity by Cd (Souza et al, 2011). Furthermore, a study by Daud et al (2009) involving Gossypium hirsutum cultivars (BR001 and GK30) has found ultra-structural changes resulting from increasing Cd concentrations, as for example the higher number of nucleoli.…”

“…As these treatments were selected because Souza et al (2011) in a study of phytotoxicity by Cd, found that the other doses used in this study do not cause changes to the tissue level. Immediately after collection, the plant material was fixed in 3% glutaraldehyde (Merck, Germany) and sodium cacodylate (Merck, Germany) buffer 0.1 M, pH 6.9, for 4 h. Then the samples were transferred to 50% alcohol (Merck, Germany) and stored at 4°C in refrigerator.…”

Cadmium Bioavailability, Uptake, Toxicity and Detoxification in Soil-Plant System

“…Based on the results of light microscopy work with D. carota, Corguinha et al (2012) proposed that Cd affects plant growth in two separate phases, with the first phase impacting the functional and cytological events (1-4 days of Cd exposure), and the second phase impacting cell to cell separation, cell hypertrophy, and thiol-peptide content (4-14 days of Cd exposure). Cadmium is also known to inhibit photosynthesis by a variety of means including: reducing the transcription of genes which are related photosynthesis such as rbcL, psaB and psbA (Qian et al 2010); inactivating Rubisco and phosphoenol pyruvate carboxylase (Bashir et al 2013); inducing lipid peroxidation (Iannone et al 2010), interfering with protochlorophyllide production (Prasad 2004), reducing the activity of enzymes involved in CO 2 fixation and inhibiting chlorophyll biosynthesis (Stobart et al 1985); enhancing proteolysis (Pena et al 2007); interfering with leaf transpiration through changes in stomatal conductance and stomatal density (Souza et al 2011;Baryla et al 2001) and; disturbing nutrient metabolism and plant antioxidant machinery (Gill and Tuteja 2010). For B. napus, Cd application has also been found to reduce the concentration of leaf pigments, including lutein, neoxanthin, β-carotene and violaxanthin (Baryla et al 2001).…”

Effect of cadmium chloride on soybean in presence ofarbuscular mycorrhiza and vermicompost

“…Increase in transpiration rate with increasing cadmium is happening because the stomata remain open and this leads to a decrease in stomatal resistance (Benavides et al, 2005). Cadmium damages chloroplast thylakoid membranes and by inhibiting activity of Calvin cycle enzymes such as Rubisco, and electron transport chain and damaging stomatal cells results in stomatal opening and consequently increases the transpiration (Souza et al, 2011). Vermicompost in addition to the increasing population and activity of beneficial microorganisms in the soil provides nutrients and water needed for the plant, increases the stomatal resistance, and reduces the amount of transpiration (Ortíz-Castro et al, 2009).…”

“…Cadmium exists in contaminated soils as free ions, which easily dissolve in water. Once it accumulates in an organism, cadmium discharges and sets off a chain of biochemical reactions and morpho-physiological changes which may cause cell death in several tissues and organs (Souza et al, 2011). Retarded growth of plants through the effect on meristematic cell division and plant growth regulation has been reported as a cadmium toxicity symptom (Arancon et al, 2004).…”