Improving understanding of the plastochron of determinate and indeterminate soybean cultivars

Abstract

The aim of this study was to identify plastochron phases in soybean cultivars with determinate and indeterminate growth habits. Experiments were conducted from 2010/2011 to 2022/2023 at four locations in Rio Grande do Sul state (RS), Brazil, using 25 soybean cultivars with determinate (6) and indeterminate (19) growth habits. This study divided the plastochron into phases during the soybean node emission stage. In irrigated cultivars with a determinate growth habit, the plastochron has an early and late phase of 59.7 and 65.7 °C day node-1, respectively. In rainfed (non-irrigated) environments, there is no difference between the early and late plastochron phases. The early and late plastochrons of irrigated cultivars with an indeterminate growth habit are 64.1 °C day node-1, while the intermediate phase is 58.5 °C day node-1. In rainfed environments, the average value of the early and intermediate phases is 60.6 °C day node-1, with a late plastochron of 79.4 °C day node-1. Dividing the plastochron into phases during node emission, as proposed in this study, improves understanding of vegetative development in soybean cultivars with determinate and indeterminate growth habits and establishes ecophysiological foundations for chronological function construction.