Effect of Metal Toxicity on Plant Growth and Metabolism: I. Zinc

Abstract

Zinc toxicity and problems with regard to tolerance and ecological significance are briefly discussed. Differential tolerance of plant genotypes exposed to zinc toxicity is a more promising approach to enrich our understanding of zinc tolerance in plants. Knowledge concerning the physiology and biochemistry with regard to phytotoxicity, uptake and transport of zinc and tolerance and its characterization are also discussed. The cytotoxic effects of zinc on plants are elucidated. The major change was seen in the nucleus of the root tip cells due to zinc toxicity. The chromatin material was highly condensed and some of the cortical cells showed disruption and dilation of nuclear membrane in presence of 7.5 mM zinc. The cytoplasm became structureless, disintegration of cell organelles and the development of vacuoles were also observed. The number of nucleoli also increased in response to zinc resulting in the synthesis of new protein involved in heavy metal tolerance. This review may help in interdisciplinary studies to assess the ecological significance of metal stress. phytotoxicity / tolerance / transport / uptake / accumulation / zinc Résumé-Effet de la toxicité des métaux sur la croissance et le métabolisme des plantes : I. Zinc. La toxicité du zinc et les problèmes de tolérance ou de conséquence écologique liés sont brièvement discutés. L'approche en terme de tolérance différentielle des génotypes de plantes exposées à la toxicité du zinc est prometteuse pour l'enrichissement de notre compréhension de la tolérance des plantes au zinc. Les connaissances de la physiologie et la biochimie face à la phytotoxicité, à l'absorption et au transport du zinc, ainsi que la tolérance et sa caractérisation sont aussi discutées dans ce papier. Les effets cytotoxiques du zinc sur les plantes sont maintenant élucidés. La modification majeure concerne le noyau des cellules de l'extrémité des racines. La chromatine est fortement condensée et certaines des cellules corticales montrent la rupture et la dilatation de leur membrane nucléaire en présence de 7.5 mM de zinc. De plus, le cytoplasme perd sa structure, la désintégration d'organites et le développement de vacuoles sont aussi observés. Enfin, le nombre de nucléoles augmente en réponse au zinc. Ils résultent de la synthèse d'une nouvelle protéine impliquée dans la tolérance aux métaux lourds. Cette synthèse bibliographique pourra aider les études interdisciplinaires à évaluer les conséquences écologiques des stress dus aux métaux. phytotoxicité / tolérance / transport / absorption / accumulation / zinc

The influence of duckweed species diversity on ecophysiological tolerance to copper exposure

“…In addition, chlorophyll content of the duckweed was affected by copper. The declines in chla and chlb can be regarded as general responses associated with metal toxicity (Rout and Das 2003;Radic et al, 2010a). The loss of photosynthetic pigment content has been reported to cause a marked effect on the entire metabolism of duckweed (Radic et al, 2010a).…”

Photosynthetic performance of Salvinia natans exposed to chromium and zinc rich wastewater

“…Chromium in particular, being highly soluble and bioavailable, exerts toxic effects on biological systems arising from the possibility of free-diffusion across the cell membrane and its strong oxidative potential (Shanker et al, 2005) whereas Zn-induced damage to living systems mainly includes impairment in functioning of several essential enzymes involved in metabolism (Rout and Das, 2003).…”

Growth and Nutrition of Cacao Seedlings Influenced by Zinc Aplication in Soil

“…Amaral Sobrinho et al (2009) suggested that these soil variables have a strong influence on the adsorption and the consequent availability of heavy metals in soil. According to Maschner (1995), the root system is affected by Zn toxicity conditions, mainly in susceptible varieties; in addition Rout and Das (2003) reported that Zn toxicity was associated with changes in the root physiology, thereby inhibiting the elongation root.…”