title: Evolutionary and ecophysiological significance of sugar utilization by the peat moss Sphagnum compactum (Sphagnaceae) and the common charophycean associates Cylindrocystis brebissonii and Mougeotia sp. (Zygnemataceae).
abstract: OBJECTIVE
  The goal of this study was to illuminate the evolutionary history and ecological importance of plant mixotrophy-the uptake and utilization of exogenous organic compounds. •
  
  
  METHODS
  We quantitatively assessed the effect of sugar amendments on laboratory growth of Sphagnum compactum as a representative emergent peat moss and two species of ecologically associated zygnematalean algae, Cylindrocystis brebissonii and Mougeotia sp. •
  
  
  RESULTS
  Together with observations published elsewhere, our results suggest that under carbon or light limitation, the uptake of exogenous sugars by cells of charophycean algae and peat mosses may help these organisms maintain positive carbon balance. Utilization of 1% glucose by aquatic-grown algae helped to relieve dissolved inorganic carbon limitation, enhancing photoautotrophic growth by factors of 9.0 and 1.7, respectively. After an 8-wk growth period, amendments of 1% and 2% glucose enhanced air-grown moss biomass by 28 and 39 times, respectively, that of controls lacking sugar amendments. After 9 wk, 1% fructose enhanced biomass by 21 times, and 2% sucrose enhanced biomass by 31 times. •
  
  
  CONCLUSIONS
  Our results indicate that plant mixotrophy is an early-evolved trait. The results also indicate that quantitative differences in sugar utilization by bryophytes and charophycean algae correlate with relative investments in protective cell-wall polyphenolics measured in previous studies, suggesting that sugar utilization may subsidize the cost of producing phenolic wall compounds in bryophytes.
authors: Department of Botany, University of Wisconsin, Madison, Wisconsin, USA 53706-1381.
authors: Linda E
authors: LE
authors: Graham
authors: Eunsoo
authors: E
authors: Kim
authors: Patricia
authors: P
authors: Arancibia-Avila
authors: James M
authors: JM
authors: Graham
authors: Lee W
authors: LW
authors: Wilcox