Accompanying ions of ammonium sources and nitrate : ammonium ratios in tomato plants

The tomato (Solanum lycopersicum L.) cultivar Micro- Tom (MT) is widely used in physiological studies, but the effects of nitrate (NO 3) and ammonium (NHthorn4) ratios (NO 3 : NHthorn4 ratios) and, in particular, the effects of the accompanying ions in NHthorn4 sources are unknown. To determine whether the accompanying ions in NHthorn4 sources influence NHthorn4 toxicity, the effects of NO 3 : NHthorn4 ratios on the physiology, electrolyte leakage index, nutrition, and dry weight were studied using hydroponics. The NHthorn4 sources were ammonium chloride (NH 4 Cl) or ammonium sulfate [(NH 4) 2 SO 4], and five NO 3 : NHthorn4 ratios were used: 100 : 0, 75 : 25, 50 : 50, 25 : 75, and 0 : 100. The NO 3 source was calcium nitrate [ Ca(NO 3) 2], and the nitrogen (N) concentration was 15 mmol L- 1. The results indicate that NH 4 Cl or (NH 4) 2 SO 4 can be used in studies on NHthorn4 toxicity because the accompanying ions did not influence the tomato plants. In addition, NO 3 : NHthorn4 ratios of 100 : 0 and 75 : 25 resulted in the highest dry weight of tomato plants, whereas ratios of 25 : 75 or 0 : 100 were toxic.