The most common anion antagonism is between Cl- and NO3-. High Cl supply in the nutrient medium lowers the nitrate uptake and vice versa (Mengel and Kirkby, 1987). The anionic interactions between NO3 and Cl have been interpreted as non-specific replacement effects and not as carrier competition processes (Mengel and Kirkby, 1987).
The antagonism between NO3 and Cl uptake was demonstrated in avocado (Wiesman, 1995; Bar et al, 1997), barley (Smith, 1973; Glass and Siddiqi, 1985), broccoli (Liu and Shelp, 1996), citrus (Chapman and Liebig, 1940; Banuls et al, 1990, 1997; Bar et al, 1997; Cerezo et al, 1997), corn (Imas, 1991), kiwifruit (Smith et al, 1987), melon and lettuce (Feigin, 1985; Wei et al, 1989), groundnut (Wang et al, 1989; Leidi et al, 1992), potato (James et al, 1970), strawberry (Wang et al, 1989), tobacco (Fuqua et al, 1976), tomato (Kafkafi et al, 1982; Zabala, 1984; Feigin et al, 1987) and wheat (Wang et al, 1989; Silberbush and Lips, 1991).
Increasing concentrations of NO3 linearly decreased Cl concentrations in plants (Kafkafi et al, 2001). An increase of 1 mmol NO3 g-1 dry matter prevented the accumulation of 2,38 mmol Cl g-1 dry matter in the tomato plant (Kafkafi et al, 1982). The inhibition of NO3 uptake by Cl depends on the plant species and the concentrations of both NO3 and Cl in the uptake medium (Cerezo et al, 1997). In root cells, the high-affinity, saturable system for NO3 uptake that operates at small NO3 concentrations (Siddiqi et al, 1990) is inhibited by high external Cl, whereas the low-affinity linear system that operates at high NO3 concentrations seems to be inhibited by high internal Cl (Cerezo et al, 1997). The competition of Cl versus NO3 was found to be stronger in salt-sensitive plants, such as groundnut, than in salt-tolerant plants, such as cotton (Leidi et al, 1992).
The Cl content of citrus leaves was 27-39 g kg-1 dry matter in NO3-deficient plants and only 5,3 g kg-1 dry matter in plants with an ample NO3 supply (Adler and Wilcox, 1995). In kiwi fruit, the severity of leaf necrosis following KCl application was attributed not to Cl toxicity but rather to N deficiency, enhanced by competition between Cl and NO3 (Buwalda and Smith, 1991).
Adler, P.R. and G.E. Wilcox. 1995. Ammonium increases the net rate of sodium influx and partitioning to the leaf of musk melon. J. Plant Nutr. 18: 1951-1962.
Banuls, J.E., F. Legaz and E. Primo-Millo. 1990. Effect of salinity on uptake and distribution of chloride and sodium in some citrus scion-rootstock combinations. J. Hortic. Sci. 65: 715-724.
Bar, Y., A. Apelbaum, U. Kafkafi and R. Goren. 1997. Relationship between chloride and nitrate and its effect on growth and mineral composition of avocado and citrus plants. J. Plant Nutr. 20: 715-731.
Buwalda, J.G. and G.S. Smith. 1991. Influence of anions on the potassium status and productivity of kiwifruit (Actinidia deliciosa) vines. Plant Soil 133: 209-218.
Cerezo, M., P. Garcia-Agustin, M.D. Serna and E. Primo-Millo. 1997. Kinetics of nitrate uptake by citrus seedlings and inhibitory effects of salinity. Plant Sci. 126: 105-112.
Chapman, H.D. and G.F. Liebig. 1940. Nitrogen concentration and ion balance in relation to citrus nutrition. Hilgardia 13: 141-173.
Feigin, A. 1985. Fertilization management of crops irrigated with saline water. Plant Soil 89: 285-299.
Fuqua, B.D., J.L. Sims, J.E. Leggett, J.F. Benner and W.O. Atkinson. 1976. Nitrate and chloride fertilization effects on yield and chemical composition of Burley tobacco leaves and smoke. Can. J. Plant Sci. 56: 893-899.
Glass, A.D.M. and M.Y. Siddiqi. 1985. Nitrate inhibition of chloride influx in barley: implications for a proposed chloride homeostat. J. Exp. Bot. 36: 556-566.
Imas, P. 1991. Yield-transpiration relationship under different nutrition conditions. M.Sc. thesis, pp. 84-86. The Faculty of Agriculture, Hebrew University of Jerusalem.
James, D.W., W.H. Weaver and R.L. Reeder. 1970. Chloride uptake by potatoes and the effects of potassium chloride, nitrogen and phosphorus fertilization. Soil Sci. 109: 48-53.
Kafkafi, U., G. Xu, P. Imas, H. Magen and J. Tarchitzky. 2001. Potassium and chloride in crops and soils: The role of potassium chloride fertilizer in crop nutrition. IPI Research Topics No. 22. 220 p.
Kafkafi, U., N. Valoras and J. Letay. 1982. Chloride interaction with NO3 and phosphate nutrition in tomato. J. Plant Nutr. 5: 1369-1385.
Leidi, E.O., M. Silberbush, M.I.M. Soares and S.H. Lips. 1992. Salinity and nitrogen nutrition studies on peanut and cotton plants. J. Plant Nutr. 15: 591-604.
Liu, L. and B.J. Shelp. 1996. Impact of chloride on nitrate absorption and accumulation by broccoli (Brassica oleracea var. italica). Can. J. Plant Sci. 76: 367-377.
Mengel K. and E.A. Kirkby. 1987. Principles of plant nutrition. 4th ed. IPI, Bern. 687 pp.
Siddiqi, M.Y., A.D.M. Glass, T.J. Ruth and T.W. Rufty Jr. 1990. Studies of the uptake of nitrate in barley. I. Kinetics of 13NO3- influx. Plant Physiol. 93: 1426-1432.
Silberbush, M. and S.H. Lips. 1991. Potassium, nitrogen, ammonium/nitrate ratio and sodium chloride effects on wheat growth. I. Shoot and root growth and mineral composition. J. Plant Nutr. 14: 751-764.
Smith, F.A. 1973. The internal control of nitrate uptake unto excised barley roots with differing salt contents. New Phytol. 72: 769-782.
Smith, G.S., C.J. Clark and P.T. Holland. 1987. Chlorine requirement of kiwifruit (Actinidia deliciosa L.). New Phytol. 106: 71-80.
Wang, D.Q, B.C. Guo and X.Y. Dong. 1989. Toxicity effects of chloride on crops. Chinese J. Soil Sci. 30: 258-261.
Wei, S.Q., Z.F. Zhou and C. Liu. 1989. Effects of chloride on yield and quality of lettuce and its critical value of tolerance. Chinese J. Soil Sci. 30: 262-264.
Wiesman, Z. 1995. Rootstock and nitrate involvement in Ettinger avocado response to chloride stress. Sci. Hortic. 62: 33-43.
Zabala, M.D.G. 1984. Evaluation of chloride as a tool for studying nitrate assimilation in plants. Diss. Abstr. Int. 44: 2619.