Effect of Pre-harvest Spray Application of Diethyl Aminoethyl Hexanoate on the Energy Metabolism in Longan Fruit Pericarp during Postharvest Storage

The effect of pre-harvest spray application of diethyl aminoethyl hexanoate (DA-6) at a concentration of 10 mg/kg on the energy metabolism in the fruit pericarp of postharvest ‘Fuyan’ longan (Dimocarpus longan Lour. cv. Fuyan) during storage was investigated by measuring the contents of adenosine triphosphate (ATP), adenosine diphosphate (ADP), adenosine monophosphate (AMP), energy charge, the activities of adenosine triphosphatase (ATPase) and nicotinamide adenine dinucleotide kinase (NADK), and the contents of nicotinamide adenine dinucleotide (NAD), reduced nicotinamide adenine dinucleotide (NADH), oxidized nicotinamide adenine dinucleotide phosphate (NADP) and reduced nicotinamide adenine dinucleotide phosphate (NADPH). The results demonstrated that compared with the control group, pre-harvest spray application of DA-6 displayed higher levels of ATP, ADP and energy charge, higher activities of H⁺-ATPase, Ca²⁺-ATPase and Mg²⁺-ATPase in pericarp plasma membrane, vacuolar membrane and mitochondrial membrane, higher activity of NADK, higher contents of NADPH and NADP, and lower amounts of AMP, NADH and NAD. These data indicated that pre-harvest spray application of DA-6 could maintain the energy requirement for normal physiological metabolism of postharvest longan fruit, keep the balance between intracellular and extracellular ion concentrations to maintain the structural integrity and the function of plasma membrane, vacuolar membrane and mitochondrial membrane, and eventually delay pericarp browning of longan fruit.