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Titolo:
A CO2-flux mechanism operating via pH-polarity in Hydrilla verticillata leaves with C-3 and C-4 photosynthesis
Autore:
van Ginkel, LC; Bowes, G; Reiskind, JB; Prins, HBA;
Indirizzi:
Univ Groningen, Dept Plant Biol, NL-9750 AA Haren, Netherlands Univ Groningen Haren Netherlands NL-9750 AA L-9750 AA Haren, Netherlands Univ Florida, Dept Bot, Gainesville, FL 32611 USA Univ Florida Gainesville FL USA 32611 Dept Bot, Gainesville, FL 32611 USA
Titolo Testata:
PHOTOSYNTHESIS RESEARCH
fascicolo: 1, volume: 68, anno: 2001,
pagine: 81 - 88
SICI:
0166-8595(2001)68:1<81:ACMOVP>2.0.ZU;2-D
Fonte:
ISI
Lingua:
ENG
Soggetto:
ELODEA-CANADENSIS; AQUATIC MACROPHYTES; C-4-TYPE PHOTOSYNTHESIS; BICARBONATE UTILIZATION; POTAMOGETON; ASSIMILATION; LOCALIZATION; INDUCTION; PLANTS; CO2;
Keywords:
aquatic plant; CO2 concentrating mechanism; CO2 flux mechanism; C-3 photosynthesis; C-4 photosynthesis; Elodea; Hydrilla; malate; oxaloacetate; pH polarity; redox state;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Agriculture,Biology & Environmental Sciences
Life Sciences
Citazioni:
26
Recensione:
Indirizzi per estratti:
Indirizzo: Prins, HBA Univ Groningen, Dept Plant Biol, POB 14, NL-9750 AA Haren, Netherlands Univ Groningen POB 14 Haren Netherlands NL-9750 AA Netherlands
Citazione:
L.C. van Ginkel et al., "A CO2-flux mechanism operating via pH-polarity in Hydrilla verticillata leaves with C-3 and C-4 photosynthesis", PHOTOSYN R, 68(1), 2001, pp. 81-88

Abstract

The aquatic angiosperm Hydrilla verticillata lacks Kranz anatomy, but has an inducible, C-4-based, CO2 concentrating mechanism (CCM) that concentrates CO2 in the chloroplasts. Both C-3 and C-4 Hydrilla leaves showed light-dependent pH polarity that was suppressed by high dissolved inorganic carbon (DIC). At low DIC (0.25 mol m(-)3), pH values in the unstirred water layer on the abaxial and adaxial sides of the leaf were 4.2 and10.3, respectively. Abaxial apoplastic acidification served as a CO2 flux mechanism (CFM), making HCO3- available for photosynthesis by conversion to CO2. DIC at 10 molm(-3) completely suppressed acidification and alkalization. The data, along with previous results, indicated that inhibition was specific to DIC, andnot a buffer effect. Acidification and alkalization did not necessarily show 1:1 stoichiometry; their kinetics for the apolar induction phase differed, and alkalization was less inhibited by 2.5 mol m(-3) DIC. At low irradiance (50 mu mol photons m(-2) s(-1)), where CCM activity in C-4 leaves is minimized, both leaf types had similar DIC inhibition of pH polarity. However, as irradiance increased, DIC inhibition of C-3 leaves decreased. In C-4 leaves the CFM and CCM seemed to compete for photosynthetic ATP and/or reducing power. The CFM may require less, as at low irradiance it still operatedmaximally, if [DIC] was low. Iodoacetamide (IA), which inhibits CO2 fixation in Hydrilla, also suppressed acidification and alkalization, especially in C-4 leaves. IA does not inhibit the C-4 CCM, which suggests that the CFMand CCM can operate independently. It has been hypothesized that irradiance and DIC regulate pH polarity by altering the chloroplastic [DIC], which effects the chloroplast redox state and subsequently redox regulation of a plasma-membrane H+-ATPase. The results lend partial support to a down-regulatory role for high chloroplastic [DIC], but do not exclude other sites of DIC action. IA inhibition of pH polarity seems inconsistent with the chloroplast NADPH/NADP(+) ratio being the redox transducer. The possibility that malate and oxaloacetate shuttling plays a role in CFM regulation requires further investigation.

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Documento generato il 28/11/20 alle ore 15:29:14