Abstract
The environmental factors which control the growth of Microcystis developing massively in eutrophic water-bodies have been investigated such as light and temperature, but effect of potassium on the growth have not been evaluated.
The generation time of Microcystis was 22-32 hrs at 0-2.5 mM KCl whereas they could not grow at 5-40 mM KCl. At 10 mM NaCl, the growth rate was almost the same as that in the control cells although they were unable to grow at 5 mM K2SO4, indicating that the inhibition of growth is responsible for potassium, but not for chloride. The apparent Km(NaHCO3) values in photosynthesis of Microcystis cells were 56 μM without KCl and 279 μM with KCl(40 mM) and no significant difference in Vmax between them was observed. It is concluded from these observations that inhibitory effect of potassium on photosynthesis in Microcystis leads to the suppression of Microcystis growth.
