Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp quốc tế đề tài:"Photochemical efficiency of photosystem II in rapidly dehydrating leaves of 11 temperate and tropical tree species differing in their tolerance to drought. | Ann Sci For 1992 49 615-625 Elsevier INRA 615 Original article Photochemical efficiency of photosystem II in rapidly dehydrating leaves of 11 temperate and tropical tree species differing in their tolerance to drought E Dreyer 1 D Epron 1 OE Yog Matig 2 INRA-Nancy Laboratoire de Bioclimatologie et d Ecophysiologie Forestieres Station de Sylviculture et Production Champenoux F-54280 Seichamps France 2 IRA-Garoua Centre de Recherches Agronomiques Garoua Cameroon Received 10 July 1992 accepted 7 September 1992 Summary Responses of PS II photochemical efficiency to rapid and severe leaf dehydration were tested on 11 different tree species differing in their ability to withstand periods of drought. Seedlings of Quercus robur Q petraea Q pubescens Q rubra Q cerris and o ilex and Dalbergia sissoo Eucalyptus camaldulensis Acacia holosericea Azadirachta indica and Populus candicans were grown in a greenhouse at Nancy. Fifty to 60 leaf disks were punched from a few well-watered and dark-adapted seedlings and left to dehydrate in complete darkness for up to 6 h. Chlorophyll fluorescence induction kinetics were recorded with a PAM fluorometer modulated red light below 1 S 1 actinic light 220 saturating white flashes 4 000 . All species displayed a remarkable stability for initial and maximal fluorescence Fo and Fm for PS II photochemical efficiency of dark-adapted disks and after 10 min at 220 pmol m-2 s-1 up to relative water losses largely above the turgor loss point. Decreases in the latter were the first observed signs of dysfunction at leaf relative water losses of depending on the species. They were generally accompanied by significant decreases in the photochemical efficiency of open reaction centers which revealed increased PS II thermal deexcitation. No correlation between evolution of either of these parameters and known tolerance to drought could be detected among tested species. It is concluded that sensitivity of the .
