The Effect of Light Stress and Other Culture Conditions on Photoinhibition and Growth of Dunaliella tertiolecta.

This work aimed to examine the effects of high light stress as well as other culture conditions including HCO3 − concentration, temperature, salinity, and pre-acclimation on photoinhibition and growth of halotolerant alga Dunaliella tertiolecta. Significant photoinhibition of D. tertiolecta was observed during a short period of exposure (6 hours) to high intensity of lights (1000, 1500, and 2000 μmol photons m-2 s-1); however, after 2 days of continuous light exposure, the alga adapted to high light stress and reached similar growth rates as low light exposure. The increase in HCO3 − concentration in the culture medium did not reduce photoinhibition, but the growth rate and chlorophyll contents increased with increasing HCO3 − concentrations. Temperature had significant effects on photoinhibition. Combined high temperature and high light intensity led to more serious photoinhibition and reduced cell growth rates, so did combined low salinity and high light intensity. Pre-acclimation by 50, 200, or 500 μmol photons m-2 s-1 each for 1, 3, or 6 hours (a total of nine treatments) did not significantly influence photoinhibition or cell growth of D. tertiolecta, probably because the acclimation periods were not long enough.