Mortierella volatiles promote plant growth
Plants reduce the CO2 concentration in closed systems
which has to be considered in experimental designs with volatiles
(Nazninet al. , 2013; Piechulla et al. , 2017). In preliminary
experiments, we co-cultivated Arabidopsis seedlings with 5
different Mortierella strains with comparable growth rates and
metabolite features. Since the three fungi with distinctive garlic-like
smells (M. hyalina , M. alpina , M. turficolalis )
induced a stronger growth promotion compared to two non-smelling strains
(M. vinacea , M. longicollis ; Figure S1), we hypothesized
that the sulfur-containing volatiles from the fungi might be involved in
the growth regulation. The major volatile in the headspace of one of
these fungi, M. hyalina , was TMTM, and its abundance prompted us
to investigate it in this study. The stronger growth of seedlings which
are growing in the presence of the fungus compared to those treated with
TMTM demonstrates that the investigated volatile is not the only factor
involved in the growth promoting effect. However, it is difficult to
design experimental set-ups which allow a quantitative comparison of
fungal and volatile effects on plant growth and performance. We assume
that the stabilizing effect of TMTM on the sulfur homeostasis allows
better plant performance under sulfur stress.