[Spectroscopic properties of Heterosigma akashiwo under iron limitation]

Room-temperature absorption spectra of H. akashiwo cells under iron limitation showed a chlorophyll c absorption peak at 630 nm, 2 nm blue-shifted from its normal position of 632 nm. Moreover, because of the increase in the relative carotenoid abundance compared to Chl a, there was an extra shoulder peak at 480 nm for the iron-limited cells. Their fluorescence spectra (77 K) have one prominent chlorophyll emission peak at 685 nm. By comparison with Fe-replete cells (10 mumol.L-1), the fluorescence yield from 685 nm band increased by about 2 times in Fe deplete cells (5 nmol.L-1), and about 1.4 times in low iron cells (100 nmol.L-1), respectively. 48 h after Fe addition, the height of 685 nm peak was considerably decreased from that observed in low iron (100 nmol.L-1) and iron deficient (ID) cells before Fe addition, which indicated that there was a significantly higher energy dissipation, and thus, a less effective photosynthesis under the lack of Fe.