Responses to water stress in an ABA‐unresponsive hybrid poplar (Populus koreana×trichocarpa cv. Peace) II. Hydraulic properties and xylem embolism

Abstract

SUMMARYWe compared the xylem hydraulic properties of potted cuttings of two poplar clones {Populus koreana x trichocarpa cv. Peace and P. x etiratnericana cv. Robusta) known to differ in their sensitivity to ABA and in their ability to close their stomata during a period of drought. 'Robusta' can control stomatal aperture, whereas 'Peace' can only close the stomata of immature leaves. 'Peace' did not exhibit any specific hydraulic property that could compensate for its lack of response to a water deficit. The two clones did not differ in their petiole or internode xylem vulnerability to embolism, both being highly vulnerable (onset of embolism observed at -1-2 MPa minimum leaf w^ater potential, ^^.nJ. Both clones became embolised rapidly when pots were dehydrated, but the onset of embolism was slightly delayed in 'Robusta'. 'Peace' was nevertheless capable of maintaining low xylem embolism near its apex and we associated this feature with the active stomatal control occurring in immature leaves. We conclude that efficient stomatal regulation is essential for maintaining the integrity of xylem sap fiow under drought conditions and that 'Peace' shows an exception to the general rule of stomatal control of embolism.

Different responses of two contrasting Populus davidiana populations to exogenous abscisic acid application

“…Similarly, exogenous ABA application alone has been shown to enhance drought tolerance in previous studies (Gibson et al, 1991;Wan and Zwiazek, 2001). Studies with an ABA-unresponsive hybrid poplar also confirmed a role for ABA in development of drought tolerance (Cochard et al, 1996). Accordingly, ABA may function as a trigger to initiate the process for drought adaptation and enhance drought tolerance in most groups of higher plants.…”

Morphological and physiological responses of two contrasting Poplar species to drought stress and exogenous abscisic acid application

“…Similarly, previous studies also showed that exogenous ABA application alone [14,18,31,32] or endogenous ABA content increased rapidly under water stress [20,33] could enhance drought tolerance in woody plants. ABA is a hormonal stress signal that moves in the xylem from the root to the different parts of the shoot where it regulates transpirational water loss and leaf growth [34][35][36].…”

Hydraulic architecture of trees: main concepts and results

“…In the second, trees favour a large stomatal conductance g s ; in the last they seem to close their stomata before a significant degree of embolism can occur. (from Cochard, unpublished collected results): PT = Populus trichocarpa, [21]; JR = Juglans regia, (Cochard and Améglio, unpublished); VM = Vaccinum corymbosum, [6]; FS = Fagus sylvatica, [24]; PP = Prunus persica, [4]; PH = Pinus halepensis, (Froux and Huc, unpublished); QR = Quercus robur; QP = Quercus petraea, [20]; PA = Picea abies, [69] climatic conditions. A significant progress on that field will be realized by improving our knowledge about the anatomical connections between the root system and the shoot.…”

“…Cochard et al [21], studied the water relations of a Populus hybrid (trichocarpa × koreana) known to lack efficient stomatal closure in the presence of soil water stress. It was actually found that only stomata in mature leaves were unresponsive to water stress.…”