Spatial and temporal distribution of mung bean (Vigna radiata) and soybean (Glycine max) roots

Spatial and temporal distribution of roots of mung bean and soybean originated from different geographical backgrounds is an important scientific issue. The aim of this study was to research the spatial and temporal distribution of roots system of soybean cultivar ‘Hefeng55’ and mung bean cultivar ‘Jilv7’ which can elucidate differences between soybean roots and mung bean roots in the key spatial and temporal locations. The roots at V6, R2, R4, R5, R6, and R7 stages were collected to acquire data of root length, root surface area, root volume and root dry weight. 49.8%, 11.7%, 13.2%, 14.7% and 10.6% of soybean roots and 57.8%, 10.7%, 11.2%, 11.9% and 8.4% of mung bean roots were in 0-5, 5-10, 10-15, 15-20 and 20-25 cm horizontal soil layers, respectively; 79.2%, 11.5%, 4.3%, 1.8%, 1.1%, 1.0% and 1.1% of soybean roots and 70.0%, 12.3%, 8.0%, 3.0%, 1.6%, 1.7% and 3.4% of mung bean roots were in 0-20, 20-40, 40-60, 60-80, 80-100, 100-120 and 120-140 cm vertical soil layers, respectively. Compared with mung bean, soybean had a much larger root system during development. In horizontal direction, soybean root tended to be more laterally developed, but the distribution of mung bean root was more uniform in vertical direction. With a greater root surface area to weight ratio (AWR), mung bean had a finer root system than soybean. These findings can help to clarify the four-dimensional spatial and temporal distribution characteristics of legumes and may provide reference for production practice of soybean and mung bean in the future.