Nitrate reductase activity of two leafy vegetables as affected by nickel and different nitrogen forms

Abstract

The author studied the effect of different nickel concentrations (0, 0.4, 40 and 80 lM Ni) on the nitrate reductase (NR) activity of New Zealand spinach (Tetragonia expansa Murr.) and lettuce (Lactuca sativa L. cv. Justyna) plants supplied with different nitrogen forms (NO 3 --N, NH 4 + -N, NH 4 NO 3 ). A low concentration of Ni (0.4 lM) did not cause statistically significant changes of the nitrate reductase activity in lettuce plants supplied with nitrate nitrogen (NO 3 --N) or mixed (NH 4 NO 3 ) nitrogen form, but in New Zealand spinach leaves the enzyme activity decreased and increased, respectively. The introduction of 0.4 lM Ni in the medium containing ammonium ions as a sole source of nitrogen resulted in significantly increased NR activity in lettuce roots, and did not cause statistically significant changes of the enzyme activity in New Zealand spinach plants. At a high nickel level (Ni 40 or 80 lM), a significant decrease in the NR activity was observed in New Zealand spinach plants treated with nitrate or mixed nitrogen form, but it was much more marked in leaves than in roots. An exception was lack of significant changes of the enzyme activity in spinach leaves when plants were treated with 40 lM Ni and supplied with mixed nitrogen form, which resulted in the stronger reduction of the enzyme activity in roots than in leaves. The statistically significant drop in the NR activity was recorded in the aboveground parts of nickel-stressed lettuce plants supplied with NO 3 --N or NH 4 NO 3 . At the same time, there were no statistically significant changes recorded in lettuce roots, except for the drop of the enzyme activity in the roots of NO 3 --fed plants grown in the nutrient solution containing 80 lM Ni. An addition of high nickel doses to the nutrient solution contained ammonium nitrogen (NH 4 + -N) did not affect the NR activity in New Zealand spinach plants and caused a high increase of this enzyme in lettuce organs, especially in roots. It should be stressed that, independently of nickel dose in New Zealand spinach plants supplied with ammonium form, NR activity in roots was dramatically higher than that in leaves. Moreover, in New Zealand spinach plants treated with NH 4 + -N the enzyme activity in roots was even higher than in those supplied with NO 3 --N.

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

“…and lettuce (Lactuca sativa L. cv. Justyna) plants grown with different N forms and regimes (Matraszek 2008). As an example, nickel at 0.4 mM although did not cause any noteworthy change in the NR activity in lettuce plants supplied with nitrate alone or mixture of nitrate and NH 4 NO 3 , NR activity in New Zealand spinach leaves was decreased (in the presence of nitrate) and increased following combined application of nitrate and NH 4 NO 3 .…”

Reduction of Nitrate Content in Response to Salicylic Acid in Spinach and Parsley Fertilized with Two Different N-Sources

“…The activity of NRase is considered a marker of nitrogen assimilation potential (Singh et al, 2002). Literature showed contradictory results regarding NRase activity, whereas, the lowest NRase activity was attributed with nitrogen form of NH 4 + -N than NH 4 NO 3 form as reported in New Zealand spinach and lettuce by Matraszek (2008). However, there are evidences that ammonium ions can dramatically stimulate the NRase activity in the absence of nitrate in Clematis vitalba, but this stimulating effect does not occur in barley and tobacco plants grown under similar conditions (Bungard et al, 1999;Munzarova et al, 2006;Bloom et al, 1992).…”

“…Nitrate accumulation in plants depends on three factors, arranged in the following descending order, application of mineral fertilizer; treatment with physiologically active substances and sorbents; natural and anthropogenic changes in the soil environment (Nazaryuk et al, 2002). It is well known that, type, amount, and form of nitrogen fertilizer influenced nitrate content in leafy vegetables (Hanafy et al, 2000;Chen et al, 2004;Stagnari et al, 2007;Matraszek, 2008).…”

Physiological Response and Comparative Proteomic Analysis of Tobacco Seedling Roots to NH4+

“…This is because NH4 + as the sole nitrogen source may result in plant toxicity (Kotsiras et al, 2005). Combined application of NO3 -and NH4 + can alleviate or eliminate symptoms of NH4 + poisoning in many plants (Tabatabaei et al, 2008), especially under abiotic stress such as salinity, low temperature or heavy metal (Matraszek, 2008;Tang et al, 2011). (Garnica et al, 2009) considered that this synergistic effects is closely related to changes in the endogenous content of polyamines and ethylene, while other studies proposed that this might be dependent on root cytokinin or on nitrogen uptake and assimilation (Debouba et al, 2007).…”