The effect of calcium spray on leaf and bract distortion,bound:Unbound calcium ratio,and calcium distribution in two poinsettia cultivars

To deteimine if direct Ca sprays could affect the distribution and binding of Ca in the leaves and the severity of leaf/bract distortion in two varieties of poinsettia (Euphorbia pulcherimma Willd.), we applied either 100 mg.l^‐1 or 400 mg.l^‐1 of Ca either one time or weekly to leaves of distortion‐ susceptible ('V‐14 Glory') and nonsusceptible ('Annette Hegg Dark Red,’ AHDR) cultivars. Only weekly spraying with 400 mg.l^‐1 Ca reduced distortion in V‐14 plants, compared to controls or AHDR plants. Both bound and unbound Ca concentrations were higher in AHDR leaves than in V‐14 leaves, but these differences were not correlated with distortion severity. EDX analysis demonstrated that distorted regions of V‐14 leaves and bracts had lower Ca concentrations than did undistorted regions or AHDR leaves; weekly spraying with 400 mg.r¹ Ca produced relatively uniform leaf Ca distribution in V‐14 leaves. Localized Ca deficiencies appear to produce the bract/leaf distortion in ‘V‐14 Glory plants, and these deficiencies can be partially overcome by weekly Ca spray applications.