Root Temperature and Percentage NO3−/NH4+ Effect on Tomato Development II. Nutrients Composition of Tomato Plants1

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Abstract
The possibility of supplying nutrients daily to tomato plants (Lycopersicum esculentum Mill.) grown in various seasons raised the question of the best percentage NO3‐/ NH4+ to be supplied to these plants. The effect of four (8, 16, 24, and 34 C) temperatures and four percentage NO3‐/NH4+ (100/0, 75/25, 50/50, and 0/100) on the nutrient composition of tomato plants were studied. To obtain constant pH, percentage NO3‐/NH4+ and temperature continuous flow technique was used. The solution was flushed through the pots at a rate of 1 liter/hour.Increasing root temperature increased total‐N, P, Mg, and K in the shoot irrespective of percentage NO3‐/ NH4+ in the solution. Calcium concentration increased in the shoot with increasing temperature only when the plants were fed with NO3‐ as the only source of N. The presence of NH4+> in the nutrient solution caused a decrease in Ca concentration in tomato plants grown in temperatures 16 C and above. Increase in the root temperature increased total‐N and Ca, slightly increased P, and decreased Mg and K. Increasing root temperature increased N‐N03‐ concentration in the shoot, while decreasing it in thc roots. Low root temperature caused accumulation of N‐NO3‐ and K in the roots. It is suggested that the hindering of translocation of these ions at low temperature is one of the factors that slows down growth of tomato plants fed with nutrient solution containing a high ratio of NO3‐.