Abstract. The photosynthetic characteristics of Elodea nuttallii grown in wastewater in continuous flow reactors in a greenhouse were investigated. The diurnal changes in dissolved inorganic carbon (DIC), dissolved oxygen (DO) and pH were monitored. Photosynthesis removed both CO2(aq) and HCO3− from the reactors. A stoichiometry of 1.19:1 was observed between HCO3− removal during photosynthesis and OH− production during photosynthesis, consistent with theories regarding direct bicarbonate utilization. In laboratory experiments, the light compensation points (гPPFD) were similar (31–35μmol m−2 s−1) to reported values for other macrophytes; however, the light saturation level was high (1100μmol m−2 s−1) and similar to values reported for aerial portions Of heterophyllous macrophytes. The kinetics of photosynthetic oxygen evolution (Km (CO2) = 96mmol m−3; Vmax= 133mmol g−1 Chl h−1) and the CO2 compensation point (г= 44cm3 m−3) suggested an adaptive, low photorespiratory state in response to low carbon concentrations. Photosynthetic Vmax values were slightly, but significantly higher (P 0.001) at pH 8.0 compared to pH 4.5. While CO2 utilization at pH 8 could account for most of the observed phototsynthetic rates, an HCO3− component was present, suggesting two separate transport systems for HCO3− and CO2(aq) in E. nuttallii. The activity of RUBISCO (160.3 mmol g−1 Chl h−1 was one of the highest reported values for aquatic macrophytes. Compared to RUBISCO, we observed lower activities of the β‐carboxylating enzymes phopho enolpyruvate carboyxlase (PEPcase), 24.1 mmol g−1 Chl h−1; phosphor enol pyruvate carboxykinase (PEPCKase), 14 mmol g−1 Chl h−1. This suggests that the potential light‐independent fixation of carbon in E. nuttallii was much less than RUBISCO‐dependent fixation. The RUBISCO/PEPcase ratio was 6.6, indicating that E. nuttallii was similar to Myriophyllum sp. in possessing a physiological adaptation to low CO2 levels which is hypothesized to include carbonic anhydrase (CA) and an active transport system for HCO3−. CA levels were surprisingly low in E. nuttallii (14.2 EUmg Chl−).
Plant Cell & Environment – Wiley
Published: Mar 1, 1991
It’s your single place to instantly
discover and read the research
that matters to you.
Enjoy affordable access to
over 18 million articles from more than
15,000 peer-reviewed journals.
All for just $49/month
Query the DeepDyve database, plus search all of PubMed and Google Scholar seamlessly
Save any article or search result from DeepDyve, PubMed, and Google Scholar... all in one place.
Get unlimited, online access to over 18 million full-text articles from more than 15,000 scientific journals.
Read from thousands of the leading scholarly journals from SpringerNature, Elsevier, Wiley-Blackwell, Oxford University Press and more.
All the latest content is available, no embargo periods.
“Hi guys, I cannot tell you how much I love this resource. Incredible. I really believe you've hit the nail on the head with this site in regards to solving the research-purchase issue.”Daniel C.
“Whoa! It’s like Spotify but for academic articles.”@Phil_Robichaud
“I must say, @deepdyve is a fabulous solution to the independent researcher's problem of #access to #information.”@deepthiw
“My last article couldn't be possible without the platform @deepdyve that makes journal papers cheaper.”@JoseServera