A soil box, which is 20 cm in length, 24 cm in height
and 8 cm in width and made of transparent acrylic
plates, was prepared for root growth experiments
using soil. The soil box was placed in the growth
chamber, where the temperature was maintained at
23 °C and the light was on for 12 h and off for 12 h.
The potting soil was prepared by mixing sand and
field soil. The results of particle size analysis of the
soil are shown in Fig. 7. From this figure, the soil
could be classified as well graded sand (SW) based on
the unified soil classification system.