Abstract
A physiological disorder was observed on pepper (Capsicum annuum L.) seedlings soon after they were transplanted from soil to solution culture. The nutrient solution contained 8 mM NO3-N, 0.7 mM NH4- N, 2 mM Ca, 1 mM Mg, 6.5×10-5M Fe, 5×10-5M B, 9×10-6M Mn, 7×10-6M Zn, 2×10-7M Cu, 8×10-8M Mo.
1. The disorder is characterized by small brownish spots on leaves. In severe cases, leaf abscission and death of the plant may occur. Foliar symptoms on excised shoots were attributed to NaFeEDTA at concentrations above 1.6×10-5M in the nutrient solution.
2. Severe symptoms developed if pepper seedlings were stressed for water while growing on soil and then transferred to nutrient culture solution. The severity of the symptoms reduced if the seedlings were initially transferred from soil to water culture for 2 weeks before being re-transferred to a nutrient solution containing as much as 20.8×10-4M NaFeEDTA. No visible symptoms appeared if the roots of the soil-grown pepper plants were immersed in water for 2 to 4 days before being transferred to a solution containing 1.3×10-4M NaFeEDTA.
3. Among several iron-chelates tested, FeEDDHA was the only one which did not cause the disorder to pepper plants even though the concentration was raised to 5.2×10-4M. No NaFeEDTA was detected in leaves after the plants were cultured on NaFeDTA solution. However, a large amount of unaltered FeEDDHA was detected in leaves of plants grown on this iron-chelate.
