Studies of Elodea nuttallii grown under photorespiratory conditions. I. Photosynthetic characteristics

Studies of Elodea nuttallii grown under photorespiratory conditions. I. Photosynthetic... 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−). http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Plant Cell & Environment Wiley

Studies of Elodea nuttallii grown under photorespiratory conditions. I. Photosynthetic characteristics

Loading next page...
 
/lp/wiley/studies-of-elodea-nuttallii-grown-under-photorespiratory-conditions-i-KgmQF2ocOZ
Publisher
Wiley
Copyright
Copyright © 1991 Wiley Subscription Services, Inc., A Wiley Company
ISSN
0140-7791
eISSN
1365-3040
D.O.I.
10.1111/j.1365-3040.1991.tb01331.x
Publisher site
See Article on Publisher Site

Abstract

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−).

Journal

Plant Cell & EnvironmentWiley

Published: Mar 1, 1991

References

You’re reading a free preview. Subscribe to read the entire article.


DeepDyve is your
personal research library

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

Explore the DeepDyve Library

Search

Query the DeepDyve database, plus search all of PubMed and Google Scholar seamlessly

Organize

Save any article or search result from DeepDyve, PubMed, and Google Scholar... all in one place.

Access

Get unlimited, online access to over 18 million full-text articles from more than 15,000 scientific journals.

Your journals are on DeepDyve

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.

See the journals in your area

DeepDyve

Freelancer

DeepDyve

Pro

Price

FREE

$49/month
$360/year

Save searches from
Google Scholar,
PubMed

Create folders to
organize your research

Export folders, citations

Read DeepDyve articles

Abstract access only

Unlimited access to over
18 million full-text articles

Print

20 pages / month

PDF Discount

20% off