Anatomical and metabolic response of roots of Picea mariana (Mill) BSP, Picea glauca (Moench) Voss, Pinus banksiana Lamb., Pinus contorta Dougl. var. latifolia Engelm., and Larix laricina (DuRoi) K. Koch to anoxia and cold temperature

Rates of carbon dioxide efflux were measured from roots of Picea mariana, Picea glauca, Larix laricina, Pinus contorta and Pinus banksiana exposed to oxia (OX), root anoxia (RA) and total plant anoxia (TPA). Ratios of mean TPA to OX efflux rates at 5{dollar}spcirc{dollar}C suggested that P. mariana had a higher TPA CO{dollar}sb2{dollar} increase than the other species. This elevated ratio was further demonstrated in a follow-up experiment, which also showed that L. laricina had the highest OX rates. These data supported the hypotheses that, at low temperatures, roots of P. mariana are capable of high rates of fermentation and roots of L. laricina are capable of high rates of respiration. Further, L. laricina showed rhizospheric oxidation, which is evidence of internal O{dollar}sb2{dollar} diffusion, while P. mariana did not. This indicated the potential for respiration sustained by internal gas diffusion in L. laricina, but not for P. mariana. Both pine species also showed evidence for respiration supported through internal O{dollar}sb2{dollar} diffusion, although their oxic CO{dollar}sb2{dollar} rates were low in comparison to L. laricina. Picea glauca showed no evidence of O{dollar}sb2{dollar} diffusion from roots. Examination of root anatomy suggested limited internal O{dollar}sb2{dollar} diffusion in these species.; A combination of low temperature and anoxia in solution culture caused a significant decrease in percent translocation of {dollar}sp{lcub}14{rcub}{dollar}C to Pinus contorta roots. Increasing the solution temperature eliminated this reduction in translocation. Anoxia, but not low temperature, decreased translocation in Picea mariana roots. Anoxia did not reduce translocation in Pinus banksiana, Picea glauca, or Larix laricina. Therefore, with the exception of Picea mariana, the apparent internal diffusion of O{dollar}sb2{dollar} within the root does not appear to be necessary for translocation during periods of solution anoxia. Cold soil temperatures in combination with anoxia may be equally important in influencing translocation of carbohydrate to roots of conifers.; Regardless of physiological differences, growth of roots of P. mariana and L. laricina did not occur during periods of high water table in the field. This indicates that internal O{dollar}sb2{dollar} diffusion does not support root growth in these species.