Olavi Kiirats

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A number of useful photosynthetic parameters are commonly derived from saturation pulse-induced fluorescence analysis. We show, that qP, an estimate of the fraction of open centers, is based on a pure ‘puddle’ antenna model, where each Photosystem (PS) II center possesses its own independent antenna system. This parameter is incompatible with more realistic(More)
An important adaptation to CO2-limited photosynthesis in cyanobacteria, algae and some plants was development of CO2-concentrating mechanisms (CCM). Evolution of a CCM occurred many times in flowering plants, beginning at least 15-20 million years ago, in response to atmospheric CO2 reduction, climate change, geological trends, and evolutionary(More)
The effects of salinity (sea water at 0 ‰ versus 30 ‰) on gross rates of O2 evolution (J O2) and net rates of CO2 uptake (P N) were measured in the halotolerant estuarine C4 grasses Spartina patens, S. alterniflora, S. densiflora, and Distichlis spicata in controlled growth environments. Under high irradiance, salinity had no significant effect on the(More)
Kranz anatomy, with its separation of elements of the C4 pathway between two cells, has been an accepted criterion for function of C4 photosynthesis in terrestrial plants. However, Bienertia cycloptera (Chenopodiaceae), which grows in salty depressions of Central Asian semi-deserts, has unusual chlorenchyma, lacks Kranz anatomy, but has photosynthetic(More)
A mutant of the NAD-malic enzyme-type C(4) plant, Amaranthus edulis, which lacks phosphoenolpyruvate carboxylase (PEPC) in the mesophyll cells was studied. Analysis of CO(2) response curves of photosynthesis of the mutant, which has normal Kranz anatomy but lacks a functional C(4) cycle, provided a direct means of determining the liquid phase-diffusive(More)
The exchange of CO2 and O2 was measured in leaves using specially constructed equipment capable of responding to rapid transients. Optical measurements provided information on cytochrome f and P 700 oxidation in the light. The following results were obtained: i) The solubilization of CO2 was used to calculate the pH of the chloroplast stroma in darkened(More)
Wild-type (wt) Arabidopsis plants, the starch-deficient mutant TL46, and the near-starchless mutant TL25 were grown in hydroponics under two levels of nitrate, 0.2 versus 6 mM, and two levels of CO(2), 35 versus 100 Pa. Growth (fresh weight and leaf area basis) was highest in wt plants, lower in TL46, and much lower in TL25 plants under a given treatment.(More)
The rapid transients of CO2 gas exchange have been measured in leaves ofHelianthus annuus L. In parallel experiments the assimilatory force FA, which is the product of the phosphorylation potential and the redox ratio NADPH/NADP, has been calculated from measured ratios of dihydroxyacetone phosphate to phosphoglycerate in the chloroplast stroma and in(More)
Assimilatory power was measured in ten C(3) species by means of a rapid-response gas exchange device as the total amount of CO(2) fixed in N(2)-CO(2) atmosphere after switching the light off. Different steady-state levels of the assimilatory power were obtained by varying light intensity and O(2) and CO(2) concentrations during the preexposition periods in(More)
The terrestrial plant Borszczowia aralocaspica (Chenopodiaceae) has recently been shown to contain the entire C(4) photosynthesis mechanism within individual, structurally and biochemically polarized chlorenchyma cells rather than in a dual cell system, as has been the paradigm for this type of carbon fixation (Nature 414: 543-546, 2001). Analysis of carbon(More)