EFFECTS OF MAGNETIC FIELD AND FERTILIZATIONS ON ORGANIC ACIDS IN LOQUAT FRUIT

Effects of magnetic field and fertilizations on organic acid content and related enzyme activities in fruit of the high-acid loquat (Eriobotrya japonica (Thunb.) Lindl. ‘Jiefangzhong’ fruit were studied. Magnetic field and fertilizations significantly decreased malate content, hence reducing the total organic acid content and titratable acidity. Malate reduction in fruit treated with magnetic field was probably a result of increased malate degradation by NADP-dependent malic enzyme (NADP-ME), whose activity was enhanced by magnetic field. In fertilization treated fruit, acid decrease was caused by combined factors including decreased malate synthesis as a result of decreased activities of phosphoenolpyruvate carboxylase (PEPC) and NAD-dependent malate dehydrogenase (NAD-MDH), and increased malate degradation by NADP-ME. Therefore, the mechanisms of malate reduction by magnetic field and fertilization were different.