Vulnerability to air embolism of three European oak species (Quercus petraea (Matt) Liebl, Q pubescens Willd, Q robur L)

Abstract

Summary — The vulnerability to water-stress induced cavitation and the petiole leaf specific conductivity (LSC) have been studied on excised branches of Quercus petraea, Q pubescens, Q robur and Q rubra. Seasonal evolution of xylem embolism in the petioles and twigs of mature Q petraea has been followed together with increasing soil water deficit. Field experiments showed that Q petraea suffered from embolism damage in both petioles and twigs after heavy drought. Large differences in terms of vulnerability to cavitation and LSC have been found between species. Q pubescens presented the highest LSC and the lowest vulnerability together with Q petraea. Q robur was found to be more vulnerable than Q petraea although with comparable LSC. Q rubra was the most vulnerable species and exhibited the lowest LSC. It was concluded that these species could be classified according to how their hydraulic mechanism is conceived to resist cavitation events : Q pubescens was the most resistant followed in order by Q petraea, Q robur, and Q rubra. Results are discussed in terms of plant segmentation and drought resistance.

Hydraulic architecture of trees: main concepts and results

“…When petioles reached 90% loss of hydraulic conductivity, the leaf water potential Ψ was approximately -1.9 MPa; at the same Ψ, the stems had lost only about 15% of their maximum hydraulic conductivity. This is in contrast to several Quercus, Fraxinus or Populus species where there is no difference in the VC of stems and petioles [18,20,22]. This study on walnut is the first case showing that drought-induced leaf shedding is preceded by cavitation in petioles before cavitation in stems, due to vulnerability segmentation.…”

Response of Scots pine (Pinus sylvestris L.) and pubescent oak (Quercus pubescens Willd.) to soil and atmospheric water deficits under Mediterranean mountain climate

“…8a), we observed that the maximum predicted PLC in the field approached 30%. Contrastingly, according to the vulnerability curve by [9], pressure causing a 50% loss of xylem conductivity in Q. pubescens was ca. −3.4 MPa (Fig.…”

“…8a). At the same water potentials, Q. pubescens still maintained G s, md at 40% of its maximum value with a corresponding PLC of less than 10%, according to [9] (Fig. 8b).…”

Beech (Fagus sylvatica L.) branches show acclimation of xylem anatomy and hydraulic properties to increased light after thinning

“…Larger diameter vessels had lower xylem vulnerability to cavitation. However, it has been demonstrated that xylem vulnerability is not directly correlated with conduit diameter but dependent on pit pore diameter [3,4,13,17]. Wider vessels had a higher probability to have big pit pores and so be more vulnerable to cavitation.…”

“…We enclosed them in a black airtight plastic bag to reduce water loss through transpiration and brought them rapidly to the laboratory for hydraulic analysis. In the laboratory, the samples were dehydrated by pressurisation [3][4][5] for 30 to 45 min until sap exudation ceased, then enclosed for at least one hour in a black airtight plastic bag to stop transpiration and remove water potential gradients between leaves and xylem tissues. Ψ xylem was assumed to be the negative of the air pressurisation value.…”