NITROGEN ASSIMILATION AND ZINC TOXICITY TO ZINC‐TOLERANT AND NON‐TOLERANT CLONES OF DESCHAMPSIA CESPITOSA (L.) BEAUV.

Abstract

SUMMARYThe effect of nitrate and ammonium nutrition on the toxicity of zinc to zinc-tolerant and nontolerant clones of Deschampsia cespitosa (L.) Beauv. was investigated. Zinc and nitrogen source interacted in their effect on root growth and zinc tended to be less toxic if ammonium was the nitrogen source. Root growth of the non-tolerant clone was inhibited by ammonium. Zinc caused chlorosis in nitrate-grown tolerant plants but not in ammonium-grown plants. Zinc caused a decrease in the concentrations of reduced nitrogen compounds in leaves and decreased nitrate translocation to them. The zinc concentration in roots was slightly decreased in ammonium-grown plants. In vivo nitrate reductase activity was stimulated by high zinc concentrations in the tolerant clone. Asparagine and proline accumulated in response to zinc treatment in the non-tolerant clone. Ammonium nutrition also induced asparagine accumulation and such accumulation was much greater in the non-tolerant clone.The small decrease in zinc toxicity when ammonium is the nitrogen source could be only partly accounted for by lower zinc uptake. It is suggested that asparagine which accumulates in ammonium-grown plants, forms an intracellular complex with zinc and thereby decreases its toxicity.

Genetic and agronomic approaches to decreasing acrylamide precursors in crop plants

“…For example, cadmium, a major pollutant worldwide, has been shown to induce asparagine accumulation in both lettuce and lupins Morel, 1994, Costa andSpitz, 1997). Asparagine can bind to or react with cadmium, copper, lead and zinc to generate less toxic compounds (White et al 1981, Bottari and Festa, 1996, Smirnoff and Stewart, 1987 Pathogen attack…”

In vivo speciation of zinc in Noccaea caerulescens in response to nitrogen form and zinc exposure

“…Uptake and assimilation of NO 3 -or NH 4 + influences the production of organic acids and amino acids, hence the form of N has the potential to affect the ligands available for Zn complexation and thus Zn speciation (Foyer et al 2003;Marschner 1995;Stitt et al 2002;Tills and Alloway 1981;Van Beusichem et al 1988). Organic acids (malate and citrate) and amino acids (histidine [His], proline [Pro] and asparagine [Asn]) have been indicated to either complex with Zn in hyperaccumulating plants (Salt et al 1999;Sarret et al 2002;Sarret et al 2009), to co-increase with Zn accumulation (Callahan et al 2007), or to occur at higher concentrations in Zn-tolerant plants (Schat et al 1997;Smirnoff and Stewart 1987). Furthermore, differences in Zn speciation were detected in plant tissues of rocket (Eruca vesicaria L. Cavalieri) grown in soil with or without compost which varied in N and Zn composition and a few other characteristics (Terzano et al 2008).…”

Role of proline under changing environments

“…124 Heavy metal-tolerant populations of Deschampsia and Silene have been shown to contain a higher constitutive content of proline as compared with non-tolerant counterparts. 14,125 In a study performed by Sharma et al 126 exogenous proline protected the activity of glucose-6-phosphate dehydrogenase and nitrate reductase in vitro against inhibition by Cd and Zn. This protection was due to the formation of a proline-metal complex.…”