Light acclimation of photosynthesis in three charophyte species
In: Aquatic Botany. Elsevier Science: Tokyo; Oxford; New York; London; Amsterdam. ISSN 0304-3770; e-ISSN 1879-1522, more |  |
| Keywords | Chemical reactions > Photochemical reactions > Photosynthesis
Irradiance
Pigmentation
Charophyceae [WoRMS]
Marine/Coastal | | Author keywords | Charophyceae; Lamprothaninium; irradiance; photosynthesis; pigmentation |
| Authors | | Top | - Küster, A.
- Schaible, R.
- Schubert, H., more
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| Abstract | The main aim of this study was to investigate if the charophyte species Chara baltica, Chara canescens (two populations from the Baltic Sea (BS) and the Gulf of Korinth, Greece (GK)), and Lamprothamnium papulosum exhibit different acclimation capacities to irradiance. Growth, photosynthesis and pigment content were examined in the laboratory under six irradiance conditions (35-500 µmol photons m−2 s−1). Growth experiments showed increasing growth rates from 35 µmol photons m−2 s−1 (~10 mg fresh weight (FW)) up to 70 µmol photons m−2 s−1 (~20 mg FW) in C. baltica, from 35 µmol photons m−2 s−1 (~15 mg FW) up to 380 µmol photons m−2 s−1 (~145 mg FW) in C. canescens (BS), and up to the highest growth irradiance in algae of L. papulosum (35 µmol: ~5 mg FW; 500 µmol: ~20 mg FW). The species were tested for their ability to acclimate to different growth irradiances (Eg) by calculating Pmax (maximum photosynthesis rate at saturating irradiances), alpha(the efficiency of light utilization at limiting irradiance), and Ek (the light saturation point of photosynthesis, Pmax/alpha). All species exhibited increasing Pmax with increasing Eg. Whereas both populations of C. canescens increased alpha with increasing Eg, L. papulosum and C. baltica did not acclimate alpha at all. Ek, the irradiance at which photosynthesis ceased to be light-limited, was constant for all Chara species within the range of irradiances tested. Chl a/Chl b ratios of all species were constant over the whole range of Eg. Chl a/carotenoid ratios were constant in C. baltica, whereas Chl a/carotenoid ratios in L. papulosum and C. canescens (BS) decreased from 250 and 70 µmol photons m−2 s−1 upwards, respectively. Pigmentation analysis showed that Chl a/carotenoid acclimation was mainly caused by species-specific capacity to raise the content of lutein and carotene (C. canescens (BS), C. canescens (GK)) and xanthophyll cycle pigments (XCP; L. papulosum). The non-photochemical quenching (NPQ) capacities of L. papulosum, C. canescens (BS), and C. canescens (GK) were dependent from preacclimation status of algae, whereas NPQ of C. baltica was independent from growth irradiance. Our results indicate that C. baltica and C. canescens (BS) were light saturated within the chosen irradiances, whereas C. canescens (GK) and L. papulosum did not reach their limits of high-light acclimation. The photosynthetic pigments lutein, alpha- and beta-carotene are suggested to act as photo-protective pigments in L. papulosum and C. canescens. |
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