TOLERANCE OF ANOXIA AND THE METABOLISM OF ETHANOL IN TREE ROOTS

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SUMMARY

Ethanol can always be detected in the trunks and roots of forest trees and in the roots of pot-grown tree-seedlings under both flooded and unflooded conditions. The constant presence of this anaerobic product indicates that tree-roots and trunks exist continually in a state of total or partial anoxia. In forest trees the ethanol content at the base of the tree trunk was correlated significantly with that found in the roots and fluctuated throughout the year, reaching a maximum in winter and early spring. The highest values were noted in trees exposed to the greatest amount of flooding. Pot-grown trees of Pinus contorta and Picea sitchensis showed an immediate reaction to anoxia with a simultaneous increase in root ethanol content when placed in unaerated water culture. In the flood-intolerant P. sitchensis anoxia induced a twelve-fold increase in ethanol and this attained 5 μmoles g−1 fresh weight, while over the same period the ethanol in the roots of the flood-tolerant Pinus contorta increased only three-fold to 0.7 μmoles g−1 fresh weight. These species provide another example of flooding tolerance being found in association with the ability to limit ethanol production.

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