A growth scale for the phasic development of common buckwheat

Growth scales give a standardized definition of crop development and increase the understanding among researchers and growers. In this research we defined a growth scale for the phasic development of common buckwheat that was mainly based on a sequence of easily recognizable changes occurring on the first and the terminal clusters of inflorescences formed on the main stem. Observations were carried out on plants grown in two years throughout spring. In an attempt to uniform the duration of phasic development across sowing dates, the length of phases and sub-phases was calculated in days and in thermal time using nine combinations of cardinal temperatures. A sequence of stages and various patterns of coordinated development were maintained throughout all sowings and years. Specifically, (1) the first inflorescence became visible after three true leaves had fully expanded on the main stem; (2) flowering reached the terminal inflorescence cluster before full-sized green fruits became visible in the first inflorescence, and (3) fruit ripening in the whole plant ended within two weeks of the end of ripening in the oldest inflorescence. Plant size was increased with the delay of sowing, and the length of the growth cycle was by approximately 400°Cd longer when plants experienced a day length longer than 15 h. This changed the correspondence between flowering and ripening stages, so that full flowering was associated with the development of green fruits in the first inflorescence when the cycle was short, but with their development in the terminal cluster when it was long. Trends in grain yield did not correspond to those in plant size and phase length. We are confident that this growth scale will be a valuable tool for following the progress of buckwheat development and to predict growth patterns and harvest time in response to temperature and photoperiod.