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Ozone-induced cytochemical and ultrastructural changes in leaf mesophyll cell walls

1997; NRC Research Press; Volume: 27; Issue: 4 Linguagem: Inglês

10.1139/cjfr-27-4-453

1208-6037

M.S. Günthardt-Georg, Carolyn J. McQuattie, Christoph Scheidegger, C. Rhiner, Rainer Matyssek,

Turfgrass Adaptation and Management

Cuttings of birch (Betula pendula Roth), poplar (Populus ×euramericana (Dode) Guinier cv. Dorskamp), and alder (Alnus glutinosa (L.) Gaertn.) were exposed in the open field to ambient ozone (O3), in both full sunlight and shade conditions, and in field fumigation chambers to filtered air (FA) or FA plus added O3 (75 nL·L n1 ) from 07:00 to 19:00, 19:00 to 07:00, or for 24 h. Appearance of O3-induced leaf symptoms was related to changes at the cellular level, especially in the cell wall. Changes were analyzed by light, fluorescence, transmission electron, and low-temperature scanning electron microscopy. Visible leaf symptoms appeared after 23n39 days of fumigation in chambers at all three elevated O3 regimes. Shaded birch showed increased sensitivity to ambient O3 compared with birch grown in sunlight. In the presence of visible O3 injury, mesophyll cell walls of birch and poplar leaves were thickened, and droplet-like exudates (projections) formed on cell walls adjacent to intercellular air spaces and increased as symptoms worsened. The main exudate constituents were esterified pectins (calcium pectate), a small amount of protein (more than in the cell wall proper), and callose (in poplar leaves only). These exudates indicate that O3 has caused a slow intercellular oxidative process to occur at the cell walls. Resume : Des boutures de bouleaux (Betula pendula Roth), de peupliers (Populus ×euramericana (Dode) Guinier cv. Dorskamp) et diaulnes (Alnus glutinosa (L.) Gaertn.) ont OtO exposOes, diune part, ‡ des concentrations diozone (O3) contenues dans liair ambiant en plein champ (en plein soleil ou ‡ liombre) et diautre part, dans des chambres de fumigation, ‡ de liair filtrO ou ‡ de liair filtrO enrichi diO3 (75 nL·L n1 ), de 07:00 h ‡ 19:00 h, ou de 19:00 h ‡ 07:00 h, ou pendant 24 h. Les symptUmes (dus ‡ liO3) visibles sur les feuilles correspondaient ‡ des modifications au niveau cellulaire, particulirement des parois de la cellule. Les changements constatOs ont OtO analysO ‡ liaide de microscopes optiques, ‡ fluorescence, Olectronique ‡ transmission et Olectronique ‡ balayage ‡ basse tempOrature. Les symptUmes visibles sur les feuilles des arbres sont apparus aprs 23n39 jours, aussi bien lors des fumigations nocturnes, diurnes ou en continu. ? liombre, la sensibilitO ‡ liO 3 ambiante des feuilles de bouleau Otait accrue. Lorsquiil y avait des symptUmes visibles sur les feuilles de bouleau et de peuplier, les parois des cellules du mOsophylle orientOe vers liespace aOrien intercellulaire siOpaississaient et formaient des callositOs, dont le nombre augmentait en fonction de la gravitO des symptUmes. Ces callositOs sont composOes de pectines estOrifiOes (sous forme de pectate de Ca), diune petite quantitO de protOines (mais en plus grande quantitO que dans la paroi cellulaire elle-mŒme), ainsi que de callose (seulement pour les feuilles de peupliers). Ces callositOs indiquent quiun lent processus dioxydation intercellulaire est en cours.