Effects of Mg deficiency and subsequent recovery on Sulla carnosa leaves

Both effects of Mg2+ deficiency and recovery were studied in Sulla carnosa, a Fabaceae plant with fodder potential. After 5 weeks of culture, the optimum of growth was found at 1.50 mM Mg2+ (control treatment), while at 0 mM Mg2+ S. carnosa growth was severely reduced. This reduction was more pronounced in roots than in shoots indicating an insufficient supply of roots with sugars. Hence, Mg2+ deficiency was found to promote a marked increase of soluble sugars and starch in S. carnosa leaves resulting in an alteration of chloroplast ultrastructure. In control plants, chloroplast ultrastructure showed the development of a typical thylakoid system with small starch grains. Grown for one week at 1.50 mM Mg2+, Mg-recovered plants showed that the negative effects of magnesium deficiency could be reversed. Thus, as compared to deficient ones, these plants displayed an important improvement of all studied parameters.