Diurnal temperature alternations on plant growth and mineral absorption in eggplant, sweet pepper, and tomato

A plot experiment was carried out to determine the plant growth and mineral composition of three Solanaceous fruit vegetables for the responses to diurnal temperature alternations. Eggplant, sweet pepper, and tomato were grown in four phytotrons with diurnal temperature fluctuations between day and night temperatures (DIF) set constantly 12 hours day and night of 15/25A degrees C, 17.5/22.5A degrees C, 20/20A degrees C, 25/15A degrees C, and in a plastic-house as a control with average air temperature of 31.3A degrees C at day-time and 19.1A degrees C at night-time. After six weeks of cultivation, the growth of three tested crops as reflected in leaf dry weight, plant height, stem dry weight and root dry weight were significantly reduced by a negative DIF of 15/25A degrees C compared to other DIF treatments and the control. In contrast to the growth parameters, a positive effect was observed on the average mineral absorption in all three crops. A negative DIF of 15/25A degrees C increased Ca, K, and Mg content in the fruit, root, and stem of eggplant and tomato. The results suggest that all DIFs may be beneficial to greenhouse or field grown Solanaceous vegetable producers, by controlling the vegetative growth which will facilitate the crop management, with no limitations on uptake rates of mineral nutrients which are required to determine yield and fruit quality.