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Drought tolerance of Scots pine in diverse growth conditions on a dune estimated on the basis of carbohydrates and chlorophyll fluorescence in needles Variation in the needle carbohydrate concentrations in Scots pine along the height profile on a forested dune in south-western Estonia were measured in spring. To assess the tolerance of trees, carbohydrate concentrations were compared with shoot morphology and photosystem II quantum efficiency (chlorophyll fluorescence). To test a potential effect of drought events on trees, chlorophyll fluorescence was measured in needles after drying and recovery, and dependcies of the treatment effects on the location on the dune were looked for. Water concentration in detached needles was reduced by a partial drying in laboratory. Needles were recovered by an addition of water. Carbohydrate concentrations were rather constant irrespective of shoot morphology and the tree location on the dune. The reduction in the photosynthetic efficiency, observed after the treatment, depended on the site. The results indicated that trees growing at lowest relative heights on the dune were potentially more vulnerable to drought than other trees on the dune at relative height of 5 to 25 m. Hariliku männi põuataluvus mitmekesistes kasvutingimustes luitel hinnatuna okaste süsivesikute sisalduse ning klorofülli fluorestsentsi järgi Süsivesikute sisaldus erinevused männiokastes olid väikesed, kuigi keskkonnatingimused ja puistu tihedus varieeruvad luitel oluliselt. Püstitati hüpotees, et puistu arengu jooksul süsivesikute moodustumine puudes ja kasutamine kasvuks ning mullaprotsessides tasakaalustuvad. Arvatavasti on luite tipus esinev vee ja mineraalainete raskendatud omastamine tasakaalustatud soodsate valgustingimuste poolt. Süsivesikute sisaldus okastes ja võrsete morfomeetrilised näitajad korreleerusid. Tärklise ja sahharoosi sisaldus oli suurem võrsetes ja okastes, millel oli suurem kuivmass. Fotosüsteem II kasuteguri analüüs klorofülli fluorestsentsi (Genty parameetri) järgi näitas, et vähene sademete hulk maikuus ei põhjusta puudel stressi. Täiendav okaste kuivatamine laboritingimustes suurendas erinevusi Genty parameetri osas. Tulemuste põhjal oletati, et luite kõrgematel kohtadel paiknevad puud taluvad põuda paremini kui puud, mis asuvad luite jalamil. Siiski on klorofülli fluorestsentsi analüüsi ja okaste laboratoorse töötlemise metoodikat vaja edasi arendada, kuna okaste kuivamine sõltus proovi massist. Täpsemate meetodite juures peab säilima praeguse metoodika kasutamise lihtsus ja analüüsikiirus.