Abstract

Excess ammonium and nitrate are associated with physiological disorders in plants; however, these disturbances can be minimized with the use of silicon, especially in plants supplied with ammonium. The objective of this study was to evaluate the effect of silicon on the presence of excess ammonium and nitrate in two cucumber varieties (Cucumis sativus) on physiology and growth of the plants. The experiment was carried out in hydroponic cultivated cucumber plants, at the São Paulo State University, Brazil. A completely randomized design was used with four replications, in a 2 × 3 × 2 factorial corresponding to two sources of nitrogen (ammonium and nitrate) at a concentration of 10 mmol L^-1, three silicon concentrations (0, 1 and 10 mmol L^-1) and two varieties of cucumber (Tsubasa and Hokushin). At 28 days after treatment application, evaluations were performed for silicon and nitrogen accumulation in the shoots, green color index, number of stomata, nitrate reductase activity, height, leaf number and dry matter mass. Silicon promoted an increase in the growth variables and improved the physiological parameters of the plants only when supplying the ammonium N source. The use of Si, independent of the cucumber variety, mitigated the toxicity of ammonium, resulting in greater total nitrogen accumulation and dry matter of plants; however, it did not benefit the plants under excess nitrate nitrogen.

Key words: Cucumis sativus, nitrogen, nutritional disorder, beneficial element, stress.

Abbreviation

MSD, minimum significant difference; EDDHMA, ethylenediamine-N, N-bis 2, hydroxy-methyl phenylacetic acid; GCI, green color index; DM, dry matter mass; NS, number of stomata.