Dr. M. Ali Khalvati, Wilma Ritter,
Dr. Yuncai Hu, Prof. Dr. Urs Schmidhalter
Institute of Plant Science, Chair of Plant Nutrition
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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.
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Barley plants in greenhouse
Barley plants in chamber
View of the split-root-hyphae system
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