tailieunhanh - Báo cáo khoa học: "Vulnerability to freeze stress of seedlings of Quercus ilex "

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp quốc tế đề tài: "Vulnerability to freeze stress of seedlings of Quercus ilex. | 553 Ann. Sci. For. 55 1998 553-565 Inra Elsevier Paris Original article Vulnerability to freeze stress of seedlings of Quercus ilex L. an ecological interpretation Andrea Nardini Lia Ghirardelli Sebastiano Salleo Dipartimento di Biologia Università di Trieste Via L. Giorgieri 10 34127 Trieste Italy Received 5 September 1997 22 January 1998 Abstract - The vulnerability to freeze stress of seedlings of Quercus ilex L. was studied with the aim of defining the limits of the potential distribution area of this species in its northernmost habitat. In December 1996 seedlings were freeze stressed up to -8 C for 3 d. Frost caused extensive functional damage to seedlings in terms of a leaf water status b root Kr and stem Ks hydraulic conductance c tissue disorder in the root only nine seedlings out of 50 survived . In comparison with unstressed seedlings Kj and Ks of freeze-stressed seedlings were reduced by 90 . Root anatomy of freeze-stressed seedlings revealed that a cortex cells were dehydrated and had become separated from one another b the endodermis was oversuberized thus isolating the stele from the cortex. Our conclusion was that Q. ilex is extremely vulnerable to freeze stress so that the distribution area of the species is restricted to zones with no frost events. Inra Else-vier Paris Quercus ilex L. freeze stress root and stem hydraulic conductance I water relations Resume - La vulnérabilité au stress par congelation des semis de Quercus ilex L. une interpretation écologique. La vulnérabilité au stress par congelation des semis de Quercus ilex L. a été étudiée avec 1 objectif de definir les limites de 1 extension géographique potentielle de cette espéce dans son habitat le plus septentrional. En décembre 1996 des semis ont subi le stress par congelation jusqu a -8 c pour 3 j figure 7 . La gelée a provoqué des dommages remarquables aux plantes pour ce qui concerne a la condition hydrique des feuilles figure 3 b la conduc-tivité hydraulique de la racine Kr et du .