Ethanol synthesis by anoxic root segments from five cedar species relates to their habitat attributes but not their known differences in vulnerability to Phytophthora lateralis root disease

Abstract

Ethanol synthesis by anoxic root segments from Port Orford cedar (Chamaecyparis lawsoniana (A. Murray bis) Parl.); yellow cedar (Chamaecyparis nootkatensis (D. Don) Spach); Atlantic white cedar (Chamaecyparis thyoides (L.) Britton, Sterns & Poggenb.); western redcedar (Thuja plicata Donn ex D. Don), and incense cedar (Calocedrus decurrens (Torr.) Florin ) was compared to determine whether the amounts that they produced during flooding could contribute the known greater vulnerability of Port Orford cedar to infection by Phytophthora lateralis Tucker & Milbrat. Roots were incubated in water at 5, 15, 25, and 35 °C for 14 days with periodic sampling. After 12 h of anoxic stress, Atlantic white cedar and yellow cedar roots produced equal quantities of ethanol that were about two times more than produced by the other three species, which did not differ from one another. The roots remained anoxic for 14 days, with ethanol concentrations increasing 6 to 11 times depending on the species. After 14 days, Atlantic white cedar remained the highest ethanol producer at two to three times more than the other species, whereas incense cedar yields were the lowest. Yellow cedar, western redcedar, and Port Orford cedar had intermediate levels of ethanol. The similarity in responses of Port Orford cedar to the other species is strong evidence that ethanol is not an important contributor to its known greater vulnerability to P. lateralis infection. In general, root incubation temperature affected ethanol synthesis similarly for all species. Increases in temperature from 5 to 15 °C or 15 to 25 °C doubled the ethanol yields at 12 h. Literature ratings of anaerobic tolerance for these cedars were compared with ratings based on their ethanol yields after 12 h or 14 days of anoxia. The latter rating appears to more closely correspond with the cedars associations to wet, mesic environments and their likelihood of experiencing anoxia via flooding.