Since the analytical framework and quantitative tools associated with classical statistics are not efficient to identify and interpret plant strategies for adaptation to a given soil environment, the objective of this study was to utilize concepts of topology in order to analyze the structural changes in soybean root systems in response to soil phosphorus availability. Soybean plants were grown in black plexiglas boxes under controlled environment (temperature and photoperiod). The boxes were packed with substrate mixed with nutrient solution to achieve uniform P concentration for two treatments: +P (15.5 mg L-1 P) and -P (8.5 mg L-1 P). In a completely randomized experimental design, three replicates were sampled at 5, 10, 15, 20, 25, and 30 days after germination. For each treatment, plant age, and replicate, the following attributes were obtained: main root length (order 0), and average number and length of order-1, order-2, and order-3 lateral roots according to their position of origin along the main root. Topological indexes were defined and calculated for both treatments, using the mean values of three replicates. Indexes used in this study were efficient in detecting the structural changes performed by the soybean root systems growing under lower soil P concentration.
Glycine max; root topology; phosphorus; soil nutrients; adaptive strategies