TAILIEUCHUNG - Báo cáo khoa học: "Within crown variation in hydraulic architecture in beech (Fagus sylvatica L): evidence for a stomatal control of xylem embolism"

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp quốc tế đề tài: Within crown variation in hydraulic architecture in beech (Fagus sylvatica L): evidence for a stomatal control of xylem embolism. | Ann. For. Sci. 59 2002 19-27 INRA EDP Sciences 2002 DOI forest 2001002 19 Original article Within crown variation in hydraulic architecture in beech Fagus sylvatica L evidence for a stomatal control of xylem embolism Damien Lemoinea Hervé Cochardb and André Graniera a INRA Unite d Ecophysiologie Forestière 54280 Champenoux France b INRA-PIAF Domaine de Crouel 63039 Clermont-Ferrand France Received 13 March 2001 accepted 6 July 2001 Abstract - The stomatal control of embolism in Fagus sylvatica L. was analysed in response to crown position and experimental changes of trunk hydraulic resistance. On one mature beech tree deep cuts were made in the trunk to increase the resistance to water transfert. We followed the changes in leaf and xylem water potential and stomatal conductance after the cuts at three levels within the canopy. We characterised vulnerability to cavitation for branches taken from two levels of irradiance sun-exposed branches and shaded ones . Some differences appeared between shade and sun-exposed branches. When the leaf water potential dropped stomatal conductances decreased earlier and faster in the shade branches. These results are well correlated with vulnerability to cavitation shade branches being more vulnerable than sun-acclimated branches. Xylem water potential levels producing fifty percent loss of hydraulic conductivity were lower in sun-exposed branches than in shade grown ones MPa vs. MPa on average . Xylem water potentials that induced stomatal closure were above the threshold-value inducing cavitation both for shade and sun-exposed branches. We confirmed that vulnerability to cavitation in Fagus sylvatica can acclimate to contrasting ambient light conditions and we conclued that stomatal response to water stress occured early and sufficiently fast to protect xylem from dysfunction. beech Fagus sylvatica L. xylem embolism stomatal regulation irradiance acclimation Résumé - Variations de l architecture hydraulique du .

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