The rangeland grass, Bouteloua gracilis was inoculated with its mycorrhizal symbiont, Glomus
fasciculatus, to determine the influence of vesicular-arbuscular mycorrhizae on water status,
stomatal behaviour and photosynthesis as well as gross plant morphology, biomass and
phosphorus content. Mycorrhizal infection increased transpiration rates by over 100 % with 50
to 70 % lower leaf resistances to water vapour diffusion. Leaf xylem pressure was not different
between mycorrhizal and non-mycorrhizal plants indicating that whole-plant resistance to water
transport was reduced by more than 50 %. Photosynthetic rates under saturating light conditions
increased 68 % with infection as a consequence of a 33 % reduction in stomatal resistance and
a 67 % reduction in mesophyll resistance to CO2 uptake. Mycorrhizal infection did not affect
biomass or gross plant morphology after 30 weeks of growth, but increased chlorophyll and
phosphate concentrations by 28 % and 70 % respectively. These physiological changes indicate
that mycorrhizae may substantially alter survival ability of Bouteloua gracilis.
The rangeland grass, Bouteloua gracilis was inoculated with its mycorrhizal symbiont, Glomusfasciculatus, to determine the influence of vesicular-arbuscular mycorrhizae on water status,stomatal behaviour and photosynthesis as well as gross plant morphology, biomass andphosphorus content. Mycorrhizal infection increased transpiration rates by over 100 % with 50to 70 % lower leaf resistances to water vapour diffusion. Leaf xylem pressure was not differentbetween mycorrhizal and non-mycorrhizal plants indicating that whole-plant resistance to watertransport was reduced by more than 50 %. Photosynthetic rates under saturating light conditionsincreased 68 % with infection as a consequence of a 33 % reduction in stomatal resistance anda 67 % reduction in mesophyll resistance to CO2 uptake. Mycorrhizal infection did not affectbiomass or gross plant morphology after 30 weeks of growth, but increased chlorophyll andphosphate concentrations by 28 % and 70 % respectively. These physiological changes indicatethat mycorrhizae may substantially alter survival ability of Bouteloua gracilis.
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