Effect of Day and Night Temperatures on the Growth and Development of Common Buckwheat (Fagopyrum esculentum Moench)

We studied the growth and development of common buckwheat grown in the growth chambers (natural sunlight type) with the controlled day-night air temperatures 30-24°C, 25-19°C and 19-15°C in Experiment 1 and 25-15°C, 23-17°C and 20-20°C in Experiment 2. The length and elongation rate of the main stem were greater at relatively high temperatures (25-19°C) than at low temperatures (19-15°C). In the highest temperature condition (30-24°C), although the main stem was the longest in the early stage, the elongation rate was lower and the elongating period was shorter than in lower temperature conditions, giving rise to the shortest final main stem length. They had slender stems, and almost all plants lodged in this condition. The hypocotyle was more slender than the first to third internodes. The higher the temperature, the more slender the hypocotyle and the shape of the plant was unstable to stand upright at high temperatures. The comparison of the plants grown in different day and night temperature conditions with the same daily mean temperature showed that the rate of main stem elongation was lower, the smaller the day-night temperature difference (DIF). The developmental growth such as flowering, the number of leaves, nodes and flower clusters on the main stem was mainly influenced by the daily mean temperature irrespective of DIF.