  We have studied the volatile-to-refractory abundance ratios to investigate
their possible relation with the low-mass planetary formation. We present a
fully differential chemical abundance analysis using high-quality HARPS and
UVES spectra of 61 late F- and early G-type main-sequence stars, 29 are planet
hosts and 32 are stars without detected planets. As the previous sample of
solar analogs, these stars slightly hotter than the Sun also provide very
accurate Galactic chemical abundance trends in the metallicity range $-0.3<{\rm
[Fe/H]}<0.4$. Stars with and without planets show similar mean abundance
ratios. Moreover, when removing the Galactic chemical evolution effects, these
mean abundance ratios, $\Delta {\rm [X/Fe]_{SUN-STARS}}$, versus condensation
temperature tend to exhibit less steep trends with nearly null or slightly
negative slopes. We have also analyzed a sub-sample of 26 metal-rich stars, 13
with and 13 without known planets and find the similar, although not equal,
abundance pattern with negative slopes for both samples of stars with and
without planets. Using stars at S/N $\ge 550$ provides equally steep abundance
trends with negative slopes for both stars with and without planets. We revisit
the sample of solar analogs to study the abundance patterns of these stars, in
particular, 8 stars hosting super-Earth-like planets. Among these stars having
very low-mass planets, only four of them reveal clear increasing abundance
trends versus condensation temperature. Finally, we have compared these
observed slopes with those predicted using a simple model which enables us to
compute the mass of rocks which have formed terrestrial planets in each
planetary system. We do not find any evidence supporting the conclusion that
the volatile-to-refractory abundance ratio is related to the presence of rocky
planets.
