The effects of magnesium deficiency on sugar partitioning do not restrict the root growth in eucalyptus young plants

Abstract

The symptoms of magnesium (Mg) deficiency have been well documented in crop plants. The relationship between sugar partitioning and Mg deficiency consists an important abiotic stress that may restrict root growth and limit the success of planting in the field. Despite of this, the primary physiological effects of low Mg availability remain largely unknown in eucalyptus. This paper aimed to investigate how the Mg deficiency affects biochemical aspects of sugar partitioning associated to dry matter accumulation in roots of young Eucalyptus urophylla plants. Experimental work was carried out at a greenhouse, arranged by completely randomized design, consisted by split plot 5x4, with five Mg concentrations (0, 25, 50, 75 and 100 % Mg levels of nutrient solution) and four times of evaluations – 15, 30, 50 and 120 days after planting (DAP). Soluble (SS) and reducing (RS) sugar contents, invertase and sucrose synthase activity and shoot and root dry matter weight were measured. Increased sugar concentrations, both SS and RS, were found in leaf tissues from 30 DAP. In root tissues, neither RS nor SS content showed differences between Mg deficiency and control. Significant differences were also not found neither in root dry matter accumulation, nor in shoot/root dry matter ratio. Mg deficiency did not affect sucrose cleaving in roots, which was predominantly catalyzed by acidic invertase, followed by susy and neutral invertase. We concluded that Eucalyptus urophylla is tolerant to Mg deficiency, since the sugar accumulation in leaf tissues is not enough to constrain dry matter accumulation in roots.