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

Abstract

-The physiological impact of ectomycorrhizal infection was investigated in the association between Tuber melanosporumVitt. and Quercus ilex L. A number of physiological parameters were investigated on 2-year-old seedlings inoculated for 22 months (I-seedlings) compared to non-inoculated plants (NI-seedlings). I-seedlings had a 100% infection rate in root tips compared to a 25% infection rate in root tips of NI-seedlings. I-seedlings had higher values of net assimilation and stomatal conductance than NIseedlings. Root hydraulic conductance per unit root surface area of I-seedlings was much reduced to 0.44× that of NI-seedlings but had 2.5× more fine root surface area than NI-seedlings. When root conductance was scaled by leaf area, the I-seedlings had 1.27× the root conductance per unit leaf area compared to NI-seedlings. I-seedlings also had significantly higher hydraulic conductances of shoots with leaves, of shoots without leaves and lower leaf blade hydraulic resistances.hydraulic conductance / water relations / ectomycorrhiza / Quercus ilex L. / HPFM Résumé -Influence sur la conductance hydraulique et les relations hydriques des semis de Quercus ilex L. des ectomycorrhizes formées par Tuber melanosporum Vitt. L'impact physiologique dû à l'infection d'ectomycorrhizes a été étudié dans l'association Tuber melanosporum Vitt. et Quercus ilex L. Un certain nombre de paramètres physiologiques ont été mesurés sur des semis de 2 ans inoculés pendant 22 mois (semis-i) en comparaison avec des cultures saines (semis-ni). Les semis-i présentent 100 % de taux d'infection des racines, tandis que les semis-ni atteignent un taux de 25 %. Les semis-i ont des niveaux d'assimilation nette plus élevés par rapport aux semis-ni. La conductance hydraulique des racines par unité de surface des racines pour les semis-i est réduite de plus de 0,44 fois par rapport aux semis-ni, mais comporte une surface de racines 2,5 fois inférieure à celle des semis-ni. En rapportant la conductance des racines à la surface des feuilles, la conductance des racines par unité de surface des feuilles des semis-i est 1,27 fois plus élevée que celle des semis-ni. Les semis-i présentent également une conductance hydraulique des rameaux avec feuilles et sans feuilles bien plus élevée, ainsi qu'une moindre résistance hydraulique des feuilles.conductance hydraulique / relations hydriques / ectomycorrhize / Quercus ilex L. / HPFM Abbreviations PAR: photosyntetically active radiation Ψ L : leaf water potential g L : leaf conductance to water vapor Pn: net photosynthesis A L : total leaf surface area A R : total root surface area Ann. For. Sci. 57 (2000) [305][306][307][308][309][310][311][312] 305

Morphological and functional variability in the root system ofQuercus ilexL. subject to confinement: consequences for afforestation

“…The relation between water flow and pressure applied was linear, irrespective of tube type, as also reported by other authors both for the holm oak and other species [17][18][19]26]. For ST, K RL values were extremely low; on the contrary, K RL values for LT were high, in agreement with those reported in other studies for this species [16,17,19].…”

“…For ST, K RL values were extremely low; on the contrary, K RL values for LT were high, in agreement with those reported in other studies for this species [16,17,19]. Such differences between tube types suggest a greater efficiency in water uptake from roots to leaves in LT and MT than in ST.…”

Mycorrhization of Fagaceae Forests Within Mediterranean Ecosystems

“…Accordingly, studies performed in Q. alba inoculated with P. tinctorius revealed higher water potentials and larger root systems than non-inoculated plants (Dixon et al 1980). Also, Q. ilex seedlings inoculated with T. melanosporum exhibited half of root hydraulic conductance than non-mycorrhized roots but presented 2.5-fold more fine root surface area (Nardini et al 2000). The best ECM inoculum for improving drought tolerance is difficult to establish, but their choice should be based on fungal water uptake ability and exploration type.…”

Hydraulic conductance of root and shoot measured with the transient and dynamic modes of the high-pressure flowmeter

“…The high pressure flowmeter (HPFM) is recognized as a rapid, easy and reliable method to measure the hydraulic conductance (k) and is now widely used [2,12,24]. The mean root hydraulic conductance (k r ) obtained with the HPFM on the 5 month-old oak seedling of batch 1 was comparable to these obtained by root system pressurisation on the same plants: 0.29 ± 0.11 and 0.36 ± 0.17 mmol s -1 MPa -1 respectively (data not shown), validating our measurements with the HPFM.…”