Seasonal variation in glutathione reductase activity in coastal and montane populations of lodgepole pine (Pinus contorta)
Harris, Wylie N.
Dalton, David A.
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Increased activity of antioxidant defense enzymes, such as glutathione reductase (GR), is one mechanism employed by plants to prevent oxidative damage during low-temperature stress. Lodgepole pine (Pinus contorta Dougl.) was chosen to test the hypotheses that 1) enhanced GR activity would accompany cold acclimation and 2) montane populations (P. contorta var. latifolia) would have a higher level of GR activity than coastal populations (P. contorta var. contorta). Seasonal changes in specific activity of GR in needles of P. contorta were monitored in montane and coastal populations. Greenhouse and growth chamber experiments were performed to investigate the effect of temperature on GR activity and total glutathione content. Glutathione content and specific activity of GR were consistently higher in the montane site than in the coastal site during the winter. GR activity peaked at the onset of freezing low temperatures in the montane population but soon decreased again despite the persistence of freezing temperatures. Seedlings exposed to low temperatures in a growth chamber had higher levels of GR activity than did comparable seedlings maintained under higher temperatures, however, total glutathione was similar for both treatments. These data suggest that GR and glutathione may play a central role in cold acclimation especially during early phases and that these factors account in part for the considerable cold tolerance of lodgepole pine