Influence of the ectomycorrhizas formed by Tuber melanosporum Vitt. on hydraulic conductance and water relations of Quercus ilex L. seedlings

The physiological impact of ectomycorrhizal infection was investigated in t he association between Tuber melanosporum Vitt. and Quercus ilex L. A numbe r of physiological parameters were investigated on 2-year-old seedlings ino culated for 22 months (I-seedlings) compared to non-inoculated plants (NI-s eedlings). I-seedlings had a 100% infection rate in root tips compared to a 25% infection rate in root tips of NT-seedlings. I-seedlings had higher va lues of net assimilation and stomatal conductance than NI-seedlings. Root h ydraulic conductance per unit root surface area of I seedlings was much red uced to 0.44x that of NI-seedlings but had 2.5x more fine root surface area than NI-seedlings. When root conductance was scaled by leaf area, the I-se edlings had 1.27x the root conductance per unit leaf area compared to NI-se edlings. I-seedlings also had significantly higher hydraulic conductances o f shoots with leaves, of shoots without leaves and lower leaf blade hydraul ic resistances.