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SUMMARY

A study is presented of the growth of rooted cuttings of Lodgepole pine and Sitka spruce into waterlogged soil. Lodgepole pine roots penetrated to depths of 20 cm at 10°C in soil devoid of oxygen, whereas Sitka spruce made only shallow growth into the water-table. The growth rate of the pine roots decreased with depth below the water-table and penetration was greater at 10 °C than at 20 °C. Large gas-filled cavities were found in the stele of the pine roots that penetrated the water-table but were absent from the spruce. When pine roots were allowed to grow into a water-table for 2 cm. and were subsequently inundated to a depth of 10 cm, root tip survival was much better than where non-acclimatized roots were flooded.

The results suggest that the deeper penetration of waterlogged soil by Lodgepole pine than Sitka spruce is due to internal oxygen transport in the pine roots; oxygen transport and other possible mechanisms for growth and survival of roots in waterlogged soil are discussed.