Effect of temperature increase on stress indicators in apple leaves

Nedostatak oborina i dugotrajne visoke temperature negativno utječu na procese asimilacije kroz smanjenje sinteze kloroplastnih pigmenata u listu jabuke. Jedna od obrambenih strategija u uvjetima toplinskog stresa je sinteza i akumulacija prolina te intenziviranje procesa antioksidativnog odgovora kroz povećanu sintezu fenola i flavonoida, što doprinosi ukupnom anitoksidativnom statusu biljaka. Cilj istraživanja bio je utvrditi sadržaj kloroplastnih pigmenata, prolina, fenola i flavonoida te antioksidativnu aktivnost u listovima 33 sorte jabuke uzgajane na dva klimatski različita lokaliteta u Hrvatskoj, Osijek i Donja Zelina. Listovi su uzorkovani krajem mjeseca lipnja 2021. i 2022. godine, nakon dugotrajnog razdoblja visokih temperatura. Utvrđen je značajan utjecaj sorte i lokaliteta na sve navedene parametre. Daljnja istraživanja trebalo bi usmjeriti prema povezivanju pokazatelja oksidacijskog stresa u listu s parametrima kvalitete ploda kako bi proizvođači mogli odabrati najstabilniju sortu za svoje uzgojne uvjete.The lack of precipitation and long-term high temperatures negatively affect the assimilation processes by reducing the synthesis of chloroplast pigments in the apple leaf. One of the defense strategies in conditions of heat stress is the synthesis and accumulation of proline and the intensification of the antioxidant response process through increased synthesis of phenols and flavonoids, which contributes to the overall antioxidant status of plants. The aim of the research was to determine the content of chloroplast pigments, proline, phenols and flavonoids and the antioxidant activity in the leaves of 33 apple varieties grown in two climatically different localities in Croatia, Osijek and Donja Zelina. The leaves were sampled at the end of June 2021 and 2022, after a long period of high temperatures. A significant influence of variety and locality on all mentioned parameters was determined. Further research should be directed towards linking indicators of oxidative stress in the leaf with parameters of fruit quality so that producers can choose the most stable variety for their growing conditions