02382nas a2200229   4500008004100000245010700041210006900148260001200217300001600229490000700245520162100252653002601873653001101899653002401910653001601934653001201950653002101962653001901983653001602002100001802018856011602036       2004                        eng d00aRegulation of root anaerobiosis and carbon translocation by light and root aeration in Isoetes alpinus0 aRegulation of root anaerobiosis and carbon translocation by ligh  c2004///  a1102 - 11110 v273 aThe activity of alcohol dehydrogenase (ADH) was measured in corms and roots of the submerged freshwater macrophyte Isoetes alpinus Kirk. growing in situ, and related to its capacity for internal oxygen transport and to carbohydrate translocation. ADH activity was present in roots but not corms at uniform activity (0.15-0.35 × 10-6 mol g-1 fresh weight s-1) over the entire plant depth range (3-7 m depth), and was intermediate to that developed in excised roots after 1-week exposure to either dissolved oxygen at air-saturation or to anoxia. Responses of photosynthesis and root oxygen release to light intensity confirmed that shoot-to-root oxygen transport saturated at similar light intensities to photosynthetic oxygen evolution, but was positive in the dark and at irradiances below the compensation point for photosynthesis, due to contributions to transport by oxygen diffusion from the external medium. Transport of 14C-labelled photo-assimilates to roots nevertheless ceased when intact plants were exposed to a combination of leaf darkness and root external anoxia, even when high 14C concentrations were present in shoots, but remained high when the roots were provided with external oxygen. The lack of any control over permeability of the root surface to gases in this species suggested that ADH activity and reduced translocation is most likely caused by development of hypoxic tissues in the apical tissue. These results suggest that reductions in ambient light intensity may have indirect effects on I. alpinus viability by increasing the degree of root hypoxia and impairing carbon partitioning.10aAlcohol dehydrogenase10aAnoxia10aAquatic macrophytes10aAssimilates10aLacunae10aOxygen transport10aPhotosynthesis10aRespiration1 aSorrell, B.K.  uhttp://www.scopus.com/inward/record.url?eid=2-s2.0-4544301436&partnerID=40&md5=3f174fe3d7839650597cfe52d3369b91