Effects of gamma-aminobutyric acid, melatonin, and potassium phosphite on the growth and photosynthetic efficiency of Citrus aurantium L. seedling

Biostimulants are substances that promote plant growth and activate their metabolic pathways. This study investigated the effects of Gamma-aminobutyric acid (GABA) (۵ and ۱۰ mM), melatonin (۵۰ and ۱۰۰ μM), and potassium phosphite (۲ and ۳ g/l) on the growth and photosynthetic processes of Citrus aurantium L. seedlings. The results showed that the application of ۱۰ mM GABA led to a significant increase in the plant's relative water content and CO۲ assimilation rate. The highest dry weight, stomatal conductance, and the lowest leaf vapor pressure deficit were achieved with the application of ۳ g/l potassium phosphite. Additionally, the maximum photochemical quantum yield of photosystem Ⅱ was found to be significantly higher with ۱۰ mM GABA and ۱۰۰ μM melatonin compared to the control and some other treatments. Furthermore, the application of ۵ mM GABA resulted in a ۳۱% increase in the content of chlorophyll b. Although GABA application led to a decrease in transpiration efficiency, this reduction may be attributed to the plants' higher stomatal conductance. Notably, ۱۰ mM GABA caused the highest increase in stomatal density, while ۵۰ μM melatonin and ۳ g/l of phosphite resulted in the highest stomatal area. The concentrations of malondialdehyde and hydrogen peroxide were reduced in ۱۰ mM GABA, which may have contributed to higher antioxidative potential and improved physiological parameters and plant growth. This research suggests that GABA can enhance the photochemical quantum efficiency of photosystem Ⅱ, improve light absorption efficiency, and modulate stomatal responses leading to enhanced photosynthetic efficiency in C. aurantium.

کلیدواژه ها:

Chlorophyll fluorescence ، GABA ، Gas exchanges ، Growth rate ، KPhi ، Sour orange ، Chlorophyll fluorescence ، GABA ، Gas exchanges ، Growth rate ، KPhi ، Sour orange