ИСТИНА

We carried out a combined analysis of stellar activity and the Li content for two sets of F, G, K stars. We confirm the Li depletion accordingly to the mixing theory which is sensitive to the depth of the convection zone. We found that the Li-activity correlation exists only in re-stricted intervals of T_eff and it is tighter for the stars with 5700>T_eff>5200 K. That means that both the Li abundance and the chromospheric activity index change similarly when we pass from the solar-type stars to the later-type ones. A general behaviour of stellar activity should vary abruptly when the depth of the convection zone exceeds 0.35 stellar radius. We propose to take into account this additional factor of activity formation for two groups of stars (the hotter and cooler than the Sun) separately in contrast to the common usage of the Rossby number.