Báo cáo khoa học: Photochemical efficiency of photosystem II in rapidly dehydrating leaves of 11 temperate and tropical tree species differing in their tolerance to drought

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Báo cáo khoa học: "Photochemical efficiency of photosystem II in rapidly dehydrating leaves of 11 temperate and tropical tree species differing in their tolerance to drought" Original articlePhotochemical efficiency of photosystem II in rapidlydehydrating leaves of 11 temperate and tropical tree species differing in their tolerance to drought OE E D Dreyer Epron Yog Matig INRA-Nancy, Laboratoire de Bioclimatologie et d’Écophysiologie Forestières, 1 Station de Sylviculture et Production, Champenoux, F-54280 Seichamps, France; 2 IRA-Garoua, Centre de Recherches Agronomiques, Garoua, Cameroon 10 July 1992; accepted 7 September 1992) (Received of PS II photochemical efficiency to rapid and severe leaf dehydrationSummary — Responses tested on 11 different tree species differing in their ability to withstand periods of drought.wereSeedlings of Quercus robur, Q petraea, Q pubescens, Q rubra, Q cerris and Q ilex, and Dalbergiasissoo, Eucalyptus camaldulensis, Acacia holosericea, Azadirachta indica and Populus candicanswere grown in a greenhouse at Nancy. Fifty to 60 leaf disks were punched from a few well-wateredand dark-adapted seedlings and left to dehydrate in complete darkness for up to 6 h. Chlorophyll flu-orescence induction kinetics were recorded with a PAM fluorometer (modulated red light below1 μmol.m s actinic light 220 μmol.m saturating white flashes, 4 000 μmol.m All spe- -2 -1 , , -1 .s -2 ). -1 .s -2cies displayed a remarkable stability for initial and maximal fluorescence F and F for PS II photo- , m 0chemical efficiency of dark-adapted disks, and after 10 min at 220 μmol m s up to relative water -2 -1 ,losses largely above the turgor loss point. Decreases in the latter were the first observed signs ofdysfunction at leaf relative water losses of 0.23-0.40 depending on the species. They were gener- =ally 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 ofthese parameters and known tolerance to drought could be detected among tested species. It isconcluded that sensitivity of the photosynthetic apparatus to leaf dehydration in the absence of irra-diance plays a very minor role in the adaptation of species to drought. Photosynthesis decline in re-sponse to water stress under natural conditions is probably the consequence of stomatal closureand possibly of high levels of irradiance and temperature.photosynthesis / chlorophyll fluorescence / PS II photochemical efficiency / water stress / de-hydration / oak species / tropical tree speciesAbbreviations: D: relative leaf water loss; D 0 at full turgor; D relative leaf water loss at turgor : tl =loss; π osmotic potential at full turgor; ψ ψ leaf water potential, actual value and at turgor w wtl and : : 0loss; PS II: photosystem II; F maximal fluorescence; F initial fluorescence; F F F v mv ;: 0m -F /F : m : 0 =PS II photochemica ...