The 2009 ASHS Annual Conference

To investigate the effect of poor supply of magnesium (Mg) on marigold (Tagetes erecta L. ‘First Lady’) growth, appearance and nutrient [Mg, calcium (Ca), iron (Fe) and manganese (Mn)] content of the shoots, a solution culture study with various Mg concentrations was conducted.  Concentrations of Mg up to 8mg/L resulted in stunted plants with a significant amount of chlorotic and necrotic symptoms on the leaves.  A concentration 10 mg Mg/liter resulted in plants free of symptoms.  Ten mg Mg/liter was thus considered incipient deficiency concentration of Mg in marigold.  This concentration of Mg in solution yielded 1.5 % Mg in the plant shoot dry weight.  In this experiment low Mg concentration in the medium, resulted in decreased Mg content and in increased Mn and Ca contents, but had no effect on Fe content in the shoot tissue.  This study indicates that Mg deficiency significantly reduces growth of marigold and affects their appearance.  It also increases Mn uptake by plants making them susceptible to Mn toxicity.