Effect of NaCI and supplemental calcium on growth parameters and nitrate reductase activity in maize

Abstract

In this study, investigated were the effects of NaCl (60 mmol·dm -3 ) and NaCl supplemented with different salts (5 mmol·dm -3 CaCl 2 , CaSO 4 , CaCO 3 , KCl), on growth of two maize varieties (Cyrkon and Limko). After 7 days of cultivation in nutrient solution the growth response to salinity of both maize varieties was similar. NaCl led to a dramatic decrease in growth of plants (approx. 50% reduction in fresh and dry weight of root, and 70% reduction in fresh weight of shoot). Addition of extra Ca 2+ or K + to nutrient solution containing NaCl did not definitely improve the growth parameters of maize. However, among the tested salts, CaCl 2 had a beneficial visual effect on maize seedlings. In other cases the plants showed noticeable symptoms of salt damage. In long term exposure to salinity (two weeks) growth of Cyrkon was more inhibited than Limko. Comparison of growth responses in short-term exposure to salinity (7 days) with long-term (14 days) showed that in Cyrkon variety the negative effects of NaCl were intensified and addition of CaCl 2 to salinized solution had not positive effects on growth. On the contrary, in Limko variety, there was a significant improvement in growth (especially in root dry weight). This fact indicates that during longer exposure to salinity Limko was able to adapt to those conditions. Salinity caused a significant decrease in leaf nitrate reductase activity (60% and 30% reduction respectively in Limko and Cyrkon). Addition of CaCl 2 to salinized nutrient solution resulted in greater enzyme inhibition in Cyrkon (50% decline in relation to plants grown under sole NaCl), and 30% increase in Limko. Inhibition of nitrate reductase activity did not cause a decrease in concentration of soluble protein in maize leaves.

Sodium Chloride (NaCl)-Induced Physiological Alteration and Oxidative Stress Generation in Pisum sativum (L.): A Toxicity Assessment

“…Many factors influence how salt affects NR activity including plant species, nitrogen supply availability, salt content, and time duration of stress exposure to plants. Like present observation, exposure to increasing levels of NaCl significantly decreased the activity of NR in roots and leaf tissues of various agriculturally important vegetable crops including Solanum lycopersicum L. (tomato), Cucumis sativus L. (cucumber), Zea mays L. (maize), Beta vulgaris L. (sugar beet), V. radiata L. (green gram), Cicer arietinum L. (chickpea), etc.…”

Effect of salt and water stresses on growth, nitrogen and phosphorus metabolism in Cucumis sativus L. seedlings

“…Decreased energy availability and nutritional imbalance (dramatic decrease in nitrate content) might have a serious consequence in plant metabolism and growth. Most of literature data show that nitrate reductase activity decreases under salt stress (Khan and Srivastava 1998;Abd-El Baki et al 2000;Saca³a et al 2002;Saca³a et al 2005). Thus, we assume that the decline in NR activity under NaCl stress is predominantly due to a decreased nitrate supply.…”

Mechanisms of sodium uptake by roots of higher plants

“…The resulting depolarisation of the plasma membrane, together with the reduced Ca 2+ concentrations, could lead to a breakdown in the K + /Na + selectivity, enabling Na + influx and inducing the leakage of cytosolic K + from the cell (Cramer et al 1985;Horie et al 2006;Kloareg et al 1987;Rubio et al 2003;Stassart et al 1981;Tuna et al 2007;Zhong and Läuchli 1993a, b). The mitigating effect of supplemental Ca 2+ on inhibitory Na + transport may, therefore, be due to the replacement of displaced Ca 2+ , thus restoring cell wall stability and plasma membrane integrity, facilitating higher K + /Na + selectivity, increasing Na + exclusion, and so improving plant salt tolerance (Bolat et al 2006;Chen et al 2007;Colmer et al 1994;Cramer et al 1987;Davenport et al 1996;Horie et al 2006;Liu and Zhu 1997;Lynch et al 1987;Melgar et al 2006;Sacala et al 2005;Tobe et al 2003;Tuna et al 2007;Zhong and Läuchli 1993b). However, increasing external Ca 2+ does not improve the salt tolerance of all species: changing the Na/Ca ratio did not have an effect on sodium chloride uptake by rice (Oryza sativa L.) (Yeo and Flowers 1985) and supplemental Ca 2+ could not improve growth of salt-stressed Brassica (Schmidt et al 1993).…”