Effect of Applied Iron Concentration on Growth and Phylloclade Marginal Chlorosis of Holiday Cactus (Schlumbergera sp.)

Abstract

Two studies were conducted to determine the effect of applied Fe concentration on the occurrence of phylloclade marginal chlorosis in holiday cactus. Schlumbergera sp. `White Christmas', `Twilight Tangerine', `Christmas Charm', and `Lavender Doll' were grown in either solution culture or a peat-based medium and supplied with a nutrient solution containing Fe-EDTA at either 0, 0.18, 0.36, 0.54, or 0.72 mm. Growth decreased while marginal chlorosis increased on all cultivars as Fe-EDTA treatment levels increased. Phylloclade marginal chlorosis developed more severely and consistently in plants grown in peat-based media versus solution culture. Marginal chlorosis and accumulation of Fe in the potting medium occurred very slowly, and first symptoms were not observed until after about 2 months of treatment. Symptomatic phylloclade tissue had a greater Fe concentration than corresponding asymptomatic phylloclade tissue. Cultivars varied in tissue Fe concentration and symptom severity across Fe-EDTA treatments. There were no significant correlations in other tissue micronutrient concentrations with either Fe treatment or symptom development. The pH of either the culture solution or peat-based medium leachate did not change significantly throughout either study, and there were no significant amounts of Fe+2 detected in solution. Chemical name used: ferric ethylenediaminetetraacetic acid, monosodium salt (Fe-EDTA).