Cadmium against Higher Plant Photosynthesis -a Variety of Effects and Where Do They Possibly Come From?

Abstract

Cadmium, Higher Plants, PhotosynthesisThe complexity of in vivo toxic effects of Cd on higher plants makes almost impossible an accurate distinction between direct and indirect mechanisms of its action on the photosyn thetic apparatus. We, therefore, postulate that multiple Cd effects on plant physiological and metabolic processes may finally be focused on photosynthesis. This would also explain the phenomenon that only a small fraction of Cd entering chloroplasts may cause such disastrous changes in their structure and function. In return, the inhibition of photosynthesis affects numerous metabolic pathways dependent on the primary carbon metabolism.

Toxic Effects of Heavy Metals on Germination and Physiological Processes of Plants

“…In some cases, heavy metal toxicity is, however, reflected by an increase in the activity of these enzymes, for instance, malic enzyme, glucose-6-phosphate dehydrogenase, and peroxidase in leaves. Cadmium has been the most intensively studied inhibitor of dark reactions of photosynthesis (Krupa 1999). It was shown in isolated protoplasts treated with Cd 2+ that the main target of this metal action was the reactions of the Calvin cycle and that activation of RuBisCo was not affected (Weigel 1985).…”

Delayed fluorescence imaging of photosynthesis inhibitor and heavy metal induced stress in potato

“…As a transition metal, it can also participate in Fenton chemistry, producing ROS, which can damage biological macromolecules [27]. Cadmium interferes with the oxygen-evolving complex in PSII, the plastoquinone pool, and ribulose-1,5-bisphosphate carboxylase oxygenase (RubisCo) synthesis [28,29]. It is not a redox active-transition metal, but can indirectly expedite ROS production by substituting an essential micronutrient (e.g., disturbing Fe homeostasis; [30]) or binding non-specifically to thiol groups, thereby disturbing various metabolic processes [31].…”

Effects of cadmium on antioxidant enzyme and photosynthetic activities in leaves of two maize cultivars

“…Recent studies have also indicated that Cd exerts multiple effects on both donor and acceptor sites of PSII. On the donor site, the presence of Cd inhibits the oxygen evolving cycle and, consequently, oxygen evolution; on the acceptor site, it inhibits electron transfer from Q A À to Q B À (Krupa and Moniak, 1998;Krupa, 1999;Sigfridsson et al, 2004).…”