EFFECT OF MAGNESIUM LEVELS IN CULTURE SOL UTION ON GROWTH AND CUT FLOWER QUALITY OF CHRYSANTHEMUM

The relationship between magnesium (Mg) uptake and growth of chrysanth emum plants grown hydroponically in various Mg levels of the culture s olution was investigated. Experiment 1. The growth rate on fresh weigh t basis of chrysanthemum cv. Seiun plants grown at 0, 10, 20, and 40 p pm Mg in the culture solutions for 18 days was evaluated. 1. Mg uptake by chrysanthemum plants increased with increasing Mg concentration in the culture solution. 2. The plant growth rate was unaffected by the Mg concentration at 10, 20, and 40 ppm Mg. Experiment 2. The optimum M g application level for cut flower production of chrysanthemum cv. Shu hounochikara was determined. There were five plots: one was adjusted w eekly to 20 ppm Mg in the culture solution; the other 4 plots, the con centration was fix ed at the beginning of the experiment at 25, 50, 10 0, and 200 mg Mg per two-stem plant. 1. In the 25 and 50 mg Mg plots, Mg was completely absorbed by the roots by the 5th and 7th week after planting, respectively. The upper leaves in the 25 and 50 mg plots app eared undernourished. 2. Mg in the 100 mg plot was wholly absorbed by the 11th week after planting and 2 weeks before flowering. However, th e plants flowered normally and produced high qual ity cut flowers. 3. Plants applied 200 mg Mg produced the cut flowers of high quality. Pla nts grown at a constant 20 ppm Mg level grew and flowered normally, bu t had excessively large leaves and stalks. Based on our results, we re commend that the optimum Mg level in a hydroponic system for producing high quality cut flower is 100 mg per plant or 50 mg per flowering sh oot.