Effects of Chromium VI stress on green alga Ulva lactuca (L.)

In order to contribute to the understanding of its response to metal stress, Ulva lactuca (L.) was treated with different concentration of chromium (VI) (0.2, 0.5, 1, and 5 mM K2CrO4), and alterations in Fv/Fm ratio (maximal photochemical efficiency of PSII) and cell viability were investigated. Significant alterations of the maximal photochemical efficiency of PSII (Fv/Fm) ratio were observed in response to the increase in chromium concentration. The Fv/Fm ratio decreased in Ulva lactuca following 2 h treatment with 1 and 5 mM Cr(VI) solution. The cell viability was decreased in cells exposed to higher Cr(VI) concentrations. Thallus cell morphology was altered in thalli exposed to chromium. A cytotoxic effect of chromium was demonstrated for the first time using acridine orange/ethidium bromide staining in macroalgae. In 1 and 5 mM of Cr(VI) treated samples, the rate of necrotic cells increased about 76.93% and 84.23%, respectively.