You are here:
RESPONSE OF THE PHOTOSYNTHETIC APPARATUS OF PHAEODACTYLYM TRICORNUTUM (BACILLARIOPHYCEAE) TO NITRATE, PHOSPHATE OR IRON STARVATION
Citation:
Geider, R., J. LaRoche, R. Greene, AND M. Oliazola. RESPONSE OF THE PHOTOSYNTHETIC APPARATUS OF PHAEODACTYLYM TRICORNUTUM (BACILLARIOPHYCEAE) TO NITRATE, PHOSPHATE OR IRON STARVATION. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/J-94/506.
Description:
The effects of nitrate, phosphate, and iron starvation and resupply on photosynthetic pigments, selected photosynthetic proteins, and photosystem II (PSII) photochemistry were examined in the diatom Phaeodactylum tricornutum Bohlin (CCMP1327). lthough cell chlorophyll a (chl a) content decreased in nutrient-starved cells, the ratios of light-harvesting accessory pigments (chl c and fucoxanthin) to chl a were unaffected by nutrient starvation. he chl a-specific light absorption coefficient (a*) and the functional absorption cross-section of PSII (o) increased during nutrient starvation, consistent with reduction of intracellular self-shading (i.e. a reduction of the "package effect") as cells became chlorotic. he light-harvesting complex proteins remained a constant preparation of total cell protein during nutrient starvation, indicating that chlorosis mirrored a general reduction in cell protein content. he ratio of xanthophyll cycle pigments diatoxanthin and diadinoxanthin chl a increased during nutrient starvation. hese pigments are thought to play a photo-protective role by increasing dissipation of excitation energy in the pigment bed upstream from the reaction centers. espite the increase in diatoxanthin and diadinoxanthin, the efficiency of PSII photochemistry, as measured by the ratio of variable to maximum fluorescence (Fv/Fm) of dark-adapted cells, declined markedly under nitrate and iron starvation and moderately under phosphate starvation. arallel to changes in Fv/Fm were decreases in abundance of the reaction center protein D1 consistent with damage of PSII reaction centers in nutrient-starved cells. he relative abundance of the carboxylase/oxygenase (RUBISCO), decreased in response to nitrate and iron starvation but not phosphate starvation. ost marked was the decline in the abundance of the mall subunit of RUBISCO in nitrate-starved cells. he changes in pigment content and fluorescence characteristics were typically reversed within 24 h of resupply of the limiting nutrient.