Root growth, water uptake and canopy development in Eucalyptus viminalis seedlings
1994
Phillips, J.G. | Riha, S.J. (Cornell Univ., Ithaca (USA). Dept. of Soil, Crop and Atmospheric Sciences)
A split-root experiment was conducted using Eucalyptus viminalis seedlings which were exposed to 3 watering regimes under conditions of a drying soil profile. Seedlings were grown in columns in which the soil was divided horizontally with a soft wax plate. Watering treatments were composed of (1) both upper and lower sections of the column well watered (W-W), (2) only the lower section well watered (D-W), and (3) water withheld completely from both upper and lower sections (D-D). Increase in above- and below-ground biomass was determined from initial and final harvests after 25 days of treatment. Whole-column water loss and leaf extension were depressed as SWP in the upper section of D-W and D-D decreased to -0.4 MPa over the first 8-10 days. However, water loss did not decrease significantly in the lower section of treatment D-W relative to the lower section of treatment W-W during this period. This indicated that water extraction by roots remaining in wet soil was not severely inhibited by the decrease in transpiration associated with the soil conditions in the upper profile. Root distribution at the end of the experiment indicated significant growth in the lower section of treatment D-W. There was evidence that hydraulic lifting of water between column sections may have occurred, as periodic increases in soil water potential of the unwatered upper section of D-W were observed.
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