engleski

Chlorophyll a fluorescence as an indicator of heat stress in five apple cultivars

Under natural conditions, in the orchards, apple trees are exposed to many adverse environmental stress factors. One of the major abiotic stress is heat stress which can disrupt the photosynthetic apparatus, causing a decrease of apple quality, productivity and overall yield. OJIP test, which explores changes in photosystem II (PSII), has been used for studying the negative eff ects of high temperatures on photosynthetic apparatus in leaves of 5 diff erent apple cultivars: Jonagold Novajo, Golden Delicous Clone B, Red Chief Camspur, Gala Galaxy and Gold Rush.Th e chlorophyll fl uorescence parameter (Fv/Fm) represents the maximum quantum effi ciency of photosystem II (PSII) photochemistry and has been widely used for early stress detection in plants. Five apple cultivars were evaluated for heat stress tolerance in ecological condition of eastern Croatia at Agricultural institute Osijek, during three growing season. From recorded vallues of parameter Fv/Fm during research, it can be concluded that the most tolerant cultivar was Gold Rush. Cultivars Golden Delicous Clone B and Jonagold Novajo can be considered as tolerant, while cultivars Red Chief Camspur and Gala Galaxy as less tolerant cultivars. Our results confi rm that the OJIP test is a reliable indicator of heat tolerance of selected apple cultivars.

apple, heat stress, photosynthesis, chlorophyll fluorescence, maximum quantum effi ciency of PS II (Fv/Fm)

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