Soybean Seedling Growth and Root System Architecture in Response to Temperature.

Temperature affects growth and development plants all stages. Establishment of a healthy root system and vigorous seedling stand early in the season is the first step towards a successful season. However, crop seedling growth and development including root systems are particularly sensitive to changes in temperature. In spite of a large number of studies conducted over the years, there has been little work to investigate soybean responses particularly on temperature effects on root system architecture and seedling growth. An experiment was conducted to investigate the temperature effects on two soybean cultivars with distinct growth habits, determinate type (PR 5333) and indeterminate type (AG 5332) using sunlit plant growth chambers. Five day/night temperature regimes of 20/12, 25/17, 30/22, 35/27, and 40/32 °C were imposed soon after emergence. Plant height, number of nodes, leaf area, and plant component dry weights were measured at 21 days after planting. Several root morphological traits were also measured using WinRHIZO root image analysis system. Significant temperature and cultivar differences were observed among many growth and developmental parameters measured. Plant height was significantly different among the cultivars and PR 5333 had the tallest plants and with more number of nodes on the main stem. However, leaf area was not significantly different between the cultivars across temperatures. The maximum plant growth for most of the shoot and root parameters was observed at about 31°C. The temperature and soybean above- and below- ground growth and developmental responses identified in this study will be useful in assisting management decisions and improving functionality of many soybean crop models.