Study of Spatio-temporal Variation of Root Water Uptake of Corn and Canola under Drought Stress

The purpose of this study was to investigate the spatio-temporal variation of plant water uptake under optimal moisture conditions and drought stress. Corn and rapeseed plants with two different root development patterns were planted in pots with 48 by 62 cm dimensions in four replications. The internal space of each pot was divided into 18 almost hydraulically isolated regions and then filled with sandy loam soil. The hydraulic isolation was performed by a layer of 2.5 cm of coarse sand. Matric suction of soil was buffered, and the water use was simultaneously measured using handmade tensiometers at suction 40cm. In the end, two pots from each culture were phased with drought stress by increasing the suction of the soil to 100cm. The results showed that both plants extract water from the first (0-10 cm) and the second layer (12.5-22.5 cm) rather than deeper soil under optimal moisture conditions, and tend to uptake more water from deeper and afar regions under drought stress. The water uptake pattern was attributed to the radial and axial hydraulic resistances of roots and soil hydraulic resistance. The hydraulic resistance of soil and root (radial component) becomes more than axial root resistance which results in the less decline of hydraulic potential xylems from proximal to distal regions. Then, the high potential gradient is transversally established across distal roots and promotes water uptake.