Effect of Magnesium on Mineral Nutrition, Chlorophyll, Proline and Carbohydrate Concentrations of Sweet Orange (Citrus sinensis cv. Newhall) Plants

Abstract

Magnesium is an essential nutrient for the growth and development of plants. Its deficiency is becoming a growing concern in many citrus orchards worldwide, adversely affecting numerous functions in plants and limiting their productivity and quality. Three-year-old orange (Citrus sinensis cv. Newhall) plants grafted on Swingle citrumelo (C. paradisi Macf. × Poncirus trifoliata L.) rootstock were irrigated for 63 days with nutrient solutions containing 0, 12, 24, 48, 96, and 192 mg Mg L−1. Thereafter, Mg deficiency-induced changes were investigated in leaf chlorophyll concentration and fluorescence, and in proline and carbohydrate concentration in leaves and roots, as well as in the nutritional status of leaves, stems, and roots. Magnesium concentration in the nutrient solution was positively correlated with the concentration of Mg (leaves, stems, roots), Ca (rootstock’s stem), K (roots), and Fe (leaves, rootstock’s stem), as well as with the total Mg absorption. However, Mg concentration in the nutrient solution was negatively correlated with the concentration of Mn (rootstock’s stem, roots), Ca (leaves, scion’s stems, roots), and Fe (roots), as well as with the total absorption of Mn, Fe, P, K, and Ca. The lower values of the chlorophyll fluorescence parameters were observed by the effect of the highest concentration of Mg. As far as leaf chlorophyll concentration and carbohydrate and proline content of leaves and roots, they were not affected by the Mg treatments. Concluding, this research highlights the significance of Mg management in citrus farming, offering insights into increasing Mg concentrations, understanding root mechanisms in Mg absorption, and suggesting the benefits of fertilization to address Mg deficiency. It emphasizes the importance of careful Mg fertilizer dosages, considering other nutrient interactions, and provides valuable guidance for optimizing Mg nutrition and overall nutrient management in sweet orange trees.