Plant Process and Function

en Effects of gamma-aminobutyric acid, melatonin, and potassium phosphite on the growth and photosynthetic efficiency of Citrus aurantium L. seedling Effects of gamma-aminobutyric acid, melatonin, and potassium phosphite on the growth and photosynthetic efficiency of Citrus aurantium L. seedling باغبانی Horticulture پژوهشي Research <div dir="ltr" style="text-align: justify;">Biostimulants are substances that promote plant growth and activate their metabolic pathways. This study investigated the effects of Gamma-aminobutyric acid (GABA) (5 and 10 mM), melatonin (50 and 100 μM), and potassium phosphite (2 and 3 g/l) on the growth and photosynthetic processes of Citrus aurantium L. seedlings. The results showed that the application of 10 mM GABA led to a significant increase in the plant's relative water content and CO2 assimilation rate. The highest dry weight, stomatal conductance, and the lowest leaf vapor pressure deficit were achieved with the application of 3 g/l potassium phosphite. Additionally, the maximum photochemical quantum yield of photosystem Ⅱ was found to be significantly higher with 10 mM GABA and 100 μM melatonin compared to the control and some other treatments. Furthermore, the application of 5 mM GABA resulted in a 31% 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, 10 mM GABA caused the highest increase in stomatal density, while 50 μM melatonin and 3 g/l of phosphite resulted in the highest stomatal area. The concentrations of malondialdehyde and hydrogen peroxide were reduced in 10 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.</div> <div style="text-align: justify;">Biostimulants are substances that promote plant growth and activate their metabolic pathways. This study investigated the effects of Gamma-aminobutyric acid (GABA) (5 and 10 mM), melatonin (50 and 100 μM), and potassium phosphite (2 and 3 g/l) on the growth and photosynthetic processes of Citrus aurantium L. seedlings. The results showed that the application of 10 mM GABA led to a significant increase in the plant's relative water content and CO2 assimilation rate. The highest dry weight, stomatal conductance, and the lowest leaf vapor pressure deficit were achieved with the application of 3 g/l potassium phosphite. Additionally, the maximum photochemical quantum yield of photosystem Ⅱ was found to be significantly higher with 10 mM GABA and 100 μM melatonin compared to the control and some other treatments. Furthermore, the application of 5 mM GABA resulted in a 31% 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, 10 mM GABA caused the highest increase in stomatal density, while 50 μM melatonin and 3 g/l of phosphite resulted in the highest stomatal area. The concentrations of malondialdehyde and hydrogen peroxide were reduced in 10 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.</div> Chlorophyll fluorescence, GABA, Gas exchanges, Growth rate, KPhi, Sour orange Chlorophyll fluorescence, GABA, Gas exchanges, Growth rate, KPhi, Sour orange 49 60 http://jispp.iut.ac.ir/browse.php?a_code=A-10-1871-1&slc_lang=en&sid=1 Faezeh Fateminia Faezeh Fateminia faezeh.fateminia_s97@gau.ac.ir No Department of Horticultural Sciences, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran Department of Horticultural Sciences, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran Esmaeil Seifi Esmaeil Seifi esmaeilseifi@gau.ac.ir Yes Department of Horticultural Sciences, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran Department of Horticultural Sciences, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran Ali Dehestani Ali Dehestani a.dehestani@sanru.ac.ir No Genetics and Agricultural Biotechnology Institute of Tabarestan, Sari Agricultural Sciences and Natural Resources University, Sari, Iran Genetics and Agricultural Biotechnology Institute of Tabarestan, Sari Agricultural Sciences and Natural Resources University, Sari, Iran Pooyan Mehrabanjoubani Pooyan Mehrabanjoubani P.mehraban@sanru.ac.ir No Department of Basic Sciences, Sari Agricultural Sciences and Natural Resources University, Sari, Iran Department of Basic Sciences, Sari Agricultural Sciences and Natural Resources University, Sari, Iran Ali Asadi Kangarshahi Ali Asadi Kangarshahi kangarshahi@gmail.com No Department of Soil and Water, Mazandaran Agricultural and Natural Resources Research and Education Center, AREEO, Sari, Iran Department of Soil and Water, Mazandaran Agricultural and Natural Resources Research and Education Center, AREEO, Sari, Iran