The Morpho-Physiological and Nutritional Attributes of Common Bean (Phaseolus vulgaris L.) as Influenced by Mg Availability

Magnesium (Mg) is a macronutrient that is necessary for both plant growth and health. It is involved in different metabolic processes, including photosynthesis, chlorophyll biosynthesis, and many enzymes in plant cells. The plant’s need for magnesium differs from one species to another. Advances in the understanding of common bean requirements for Mg and its relationships with the key metabolic reactions are an essential tool to improve Mg management in Tunisian agrosystems and identify useful markers for assisted breeding efforts. For this purpose, a greenhouse experiment was conducted on two common bean ( Phaseolus vulgaris L.) cultivars (coco nain, CN, and coco blanc, CB) subjected to different Mg concentrations (0, 1, 2, 4, 6, and 8 mM). Plant growth, gas exchange, photosynthetic pigments, and Mg uptake and compartmentation are evaluated. The obtained results demonstrated that the optimal Mg concentration for maximum common bean growth and associated physiological functioning is 6 mM Mg. Below this concentration, plants suffer from Mg deficiency, while above this dose, plants are subjected to Mg toxicity. Photosynthetic pigments as well as photosynthesis are significantly hampered by Mg deficiency as well as toxicity while remaining strictly dependent on plant Mg content. The genotype CN showed better tolerance as compared to CB. It has a greater ability to remobilize Mg in deficient conditions, and its allocation to shoots allows it to maintain important metabolic functions. The calculated stress index (SI) clearly discriminated the studied genotypes and confirmed the tolerance of CN as compared to CB.