Temperature Control of Node Appearance and Initiation Rate in Soybean.

Accurate prediction of leaf area dynamics is crucial for robust simulation of crop growth and yield. No study has looked at the effect of temperature on soybean node appearance and initiation rates and how these two processes are coordinated. The objective of this work was to determine the influence of temperature on both rates of node appearance and initiation in soybean. Plants from two maturity groups (MG II and III) were grown in pots in the greenhouse under constant photoperiod (15 h). Plants were exposed to four contrasting temperature regimes: 15ºC, 20ºC, 25ºC, and a fourth treatment in which temperature was gradually increased during the experiment from 15 ºC to 25ºC. Plants were staged and dissected every 2 and 4 days, respectively, between sowing and physiological maturity (R7) to determine the number of appeared and initiated nodes. Both node appearance and initiation rates were higher with increasing temperature, with an estimated phyllochron of 63 ºCd (T_b= 9 ºC) for both MGs. There was a strong coordination between rates of leaf appearance and initiation, irrespective of MG or temperature regime, with two nodes initiated per appeared node. This study demonstrates the influence of temperature on both node appearance and initiation rates and the coordination between the two processes. These findings can be used to further improve existing soybean simulation models on their ability to predict phenology, leaf area, and final yield.

Keywords: node appearance, node initiation, temperature, coordination model