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SUMMARY

Post-dormant seedlings with dormant roots were grown with their roots divided between two containers of loam or peat soil corresponding to wet/wet, dry/dry and wet/dry; the soil matric potentials were: loam, minus 6 kPa (wet) and minus 60 kPa (dry); peat, minus 5 kPa (wet) and minus 30 kPa (dry). In both soils the wet/dry treatment had little effect on leaf water potential, or on total plant growth compared with the wet/wet, but produced very uneven root development. Most growth of primary and woody roots occurred in the wet soil. Water supplied to one-half of the root system did not increase growth of the half in dry soil, compared with the dry/dry treatment. Fewer roots emerged from dormancy in the dry than in the wet soil and at any one time, fewer roots were growing in the dry soil. The extension of main root axes in the dry soil was only slightly slower than in the wet soil. However, in the dry soil some roots were dying while others were extending and at the final harvest no increase was recorded in total root length.

When both halves of the root system were in dry soil, leaf water potential was slightly reduced and shoot and root growth were significantly reduced compared with the wet/wet treatment.

Soil adhered strongly to roots grown in the dry soil and the significance of this in plant water relations is discussed.