PARENT SESSION
Oral Session #102: Soil Ecology: Mycorrhizae .
Presiding: N. Johnson
Friday, August 9. 9:00 AM to 12:00 PM. Apache Meeting Room, TCC.
Effect of mycorrhizal colonisation on water relations and growth of Zea mays in compacted soils.
Sharples, Jade*,1, Farquhar, Graham1, Masle, Josette1, 1 The Australian National University, Canberra, ACT, Australia
ABSTRACT- Under compacted soil conditions, plant root functioning may be restricted by mechanical impedance and/or by poor soil aeration which may in turn limit water and nutrient availability. Mycorrhizal infection has been firmly established to increase nutrient absorption; however their role in water absorption is relatively unclear. We hypothesise that under compacted soil conditions, mycorrhizal roots may overcome the nutrient and water limitation often associated with high soil bulk density. In an attempt to clarify the role of mycorrhizal associations in compacted soil, Zea mays, was grown in soils with bulk densities of 1.1 g cm3 and 1.4 g cm3 both in mycorrhizal association with the arbuscular mycorrhizal fungus Glomus pellucidum and without mycorrhizal association. Two different isolates of G. pellucidum were used. The range of soil densities and water content was such that effects of variations in soil strength could be investigated while keeping sufficient water and oxygen supply to roots. Non- mycorrhizal Z. mays were also grown at the two different bulk soil densities at high and low P concentrations. Mycorrhizal associations enhanced the growth of Z. mays in non-compacted soil (1.1 g cm3) however under compacted conditions (1.4 g cm3) the associations conferred no benefit to the host plant. One fungal isolate largely increased both the photosynthesis and the stomatal conductance of Z. mays while the other isolate showed no effect. The addition of high P concentration to the soil overcame the compaction effect in non-mycorrhizal plants.
KEY WORDS: soil compaction, mycorrhizal association