Photoacclimation in the marine alga Nannochloropsis sp. (Eustigmatophyte): a kinetic study |
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Authors: | Fisher, Tamar Minnaard, Johanna Dubinsky, Zvy |
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Affiliation: | 1department of Life Sciences, Bar-Ilan University Ramat Gan, 52900, Israel 2Water Quality Management and Aquatic Ecology, Agricultural University Wageningen Ritzemabosweg 32A, The Netherlands |
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Abstract: | Exponentially growing cultures of Nannochloropsis sp. were transferredfrom high light (650 µ.mol quanta m2 s1)to low light (30 (µrnol quanta m2 s1). Thekinetics of changes in the various parameters of the photoacclimationprocess were followed until steady state was reached. In thisorganism, the observed 4.25 increase in cellular chlorophylla in the low-light-acclimated cells was linearly correlatedwith an increase in the number of photosynthetic units (PSU),while the PSU size remained constant. The new steady state wasreached after a transition period of 87 h and following an initialovershoot in the chlorophyll a concentration. During the processof photoacclimation, harvested and utilized light was increaseddue to a combination of increased cellular chlorophyll and anincrease of the quantum yield. These improvements in efficiencywere coupled with the reduction of respiration. The overalleffect of photoacclimation, therefore, amounted to reducingthe impact of low light on the growth rate of the algae. Ourstudy demonstrates the importance of the photoacclimation processin the context of the planktonic way of life. An index of the'effectiveness of photoacclimation' is proposed. |
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