Abstract
Arbuscular mycorrhizal fungi alleviate drought stress in their host plants via the
direct uptake and transfer of water and nutrients through the fungal hyphae to the
host plants. To quantify the contribution of the hyphae to plant water uptake, a new
split-root hyphae system was designed and employed on barley grown in loamy soil inoculated
with Glomus intraradices under well-watered and drought conditions in a growth chamber with a 14-h light period
and a constant temperature (15 °C; day/night). Drought conditions were initiated 21
days after sowing, with a total of eight 7-day drying cycles applied. Leaf water relations,
net photosynthesis rates, and stomatal conductance were measured at the end of each
drying cycle. Plants were harvested 90 days after sowing. Compared to the control
treatment, the leaf elongation rate and the dry weight of the shoots and roots were
reduced in all plants under drought conditions. However, drought resistance was comparatively
increased in the mycorrhizal host plants, which suffered smaller decreases in leaf
elongation, net photosynthetic rate, stomatal conductance, and turgor pressure compared
to the non-mycorrhizal plants. Quantification of the contribution of the arbuscular
mycorrhizal hyphae to root water uptake showed that, compared to the non-mycorrhizal
treatment, 4 % of water in the hyphal compartment was transferred to the root compartment
through the arbuscular mycorrhizal hyphae under drought conditions. This indicates
that there is indeed transport of water by the arbuscular mycorrhizal hyphae under
drought conditions. Although only a small amount of water transport from the hyphal
compartment was detected, the much higher hyphal density found in the root compartment
than in the hyphal compartment suggests that a larger amount of water uptake by the
arbuscular mycorrhizal hyphae may occur in the root compartment.
Key words
Barley - water uptake - drought - stress -
Glomus intraradices
- photosynthesis - water relations.
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Guest Editor: R. Matyssek
