Aquatic adventitious roots of the wetland plant Meionectes brownii can photosynthesize: implications for root function during flooding.
• Many wetland plants produce aquatic adventitious roots from submerged stems. Aquatic roots can form chloroplasts, potentially producing endogenous carbon and oxygen. Here, aquatic root photosynthesis was evaluated in the wetland plant Meionectes brownii, which grows extensive stem-borne aquatic roots during submergence. • Underwater photosynthetic light and CO(2) response curves were determined for aquatic-adapted leaves, stems and aquatic roots of M. brownii. Oxygen microelectrode and (14)CO(2)-uptake experiments determined shoot inputs of O(2) and photosynthate into aquatic roots. • Aquatic adventitious roots contain a complete photosynthetic pathway. Underwater photosynthetic rates are similar to those of stems, with a maximum net photosynthetic rate (P(max)) of 0.38 μmol O(2) m(-2) s(-1); however, this is c. 30-fold lower than that of aquatic-adapted leaves. Under saturating light with 300 mmol m(-3) dissolved CO(2), aquatic roots fix carbon at 0.016 μmol CO(2) g(-1) DM s(-1). Illuminated aquatic roots do not rely on exogenous inputs of O(2). • The photosynthetic ability of aquatic roots presumably offers an advantage to submerged M. brownii as aquatic roots, unlike sediment roots, need little O(2) and carbohydrate inputs from the shoot when illuminated.
School of Plant Biology, Faculty of Natural and Agricultural Sciences, The University of Western Australia, Crawley, WA 6009, Australia. sarah.rich@grs.uwa.edu.au
Sarah Meghan
SM
Rich
Martha
M
Ludwig
Ole
O
Pedersen
Timothy David
TD
Colmer
D059001:Aquatic Organisms / Q000254:growth & development / Q000502:physiology* / Q000528:radiation effects; D018533:Biomass; D002734:Chlorophyll / Q000378:metabolism; D055868:Floods; D008027:Light; D009928:Organ Specificity / Q000528:radiation effects; D010100:Oxygen / Q000378:metabolism; D010313:Partial Pressure; D010788:Photosynthesis / Q000502:physiology* / Q000528:radiation effects; D018517:Plant Roots / Q000254:growth & development / Q000502:physiology* / Q000528:radiation effects; D031995:Saxifragaceae / Q000254:growth & development / Q000502:physiology* / Q000528:radiation effects; D053833:Wetlands
D002734:Chlorophyll; D010100:Oxygen