EFFECTS OF GIBBERELLINS AND FORCHLORFENURON ON RAPID CHLOROPHYLL FLUORESCENCE KINETICS CHARACTERISTICS IN BLUEBERRY LEAVES

Research on photosynthesis is critically important, as it is the primary means by which plants obtain energy and carbon sources, and it also forms the foundation of plant growth and development. However, studies on photosynthesis in blueberries adjusted with plant regulators require further exploration. This study examines the impact of Gibberellins (GA3) and forchlorfenuron (CPPU) on 8-yearold 'Northland' and 'Bonnie' blueberry varieties. The regulators were applied foliarly at concentrations 50+5, 50+10, 50+20, 100+5, 100+10, 100+20, 150+5, 150+10, 150+20 mg/L during flowering and fruit expansion, using water as a control. Results showed that 100+5 mg/L GA3+CPPU applied during fruit expansion significantly increased chlorophyll content in both varieties. 'Northland' and 'Bonnie' exhibited increases in chlorophyll a by 15.1% and 26.3%, chlorophyll b by 41.7% and 21.0%, and total chlorophyll by 16.0% and 43.4% over the control. This concentration also enhanced photochemical efficiency, decreasing relative variable fluorescence at the J (2 ms) and I (30 ms) steps and raising the quantum yield for electron transport by around 22%. The treatment amplified the number of active photosynthetic reaction centers, promoting photosynthetic efficiency. This study offers valuable insights into optimizing blueberry cultivation through targeted use of plant growth regulators.