Effect of micronutrients, phosphorous and chelator to iron ratio on growth, chlorosis and nutrition of apple seedlings

Abstract Apple (Malus domestica) seedlings were exposed to a 2x2x2 factorial arrangement of treatments; phosphate level, micronutrient (Mn, Cu, Zn, Mo and B) level and chelator to Fe ratio level, in solution cultures to assess the effects on growth, development of Fe chlorosis and overall nutrition. Phosphorous was applied at 20 (low) or 400 (high) uM levels, micronutrients at low or high levels and either a 1 to 1 or 10 to 1 ratio of chelator to Fe concentration. After a growth period of 34 days, those seedlings grown under conditions of high chelator to Fe ratio, independent of P or micronutrient level were normal. Under conditions of low chelator to Fe ratio, independent of P level, the high micronutrient level caused chlorosis. Leaf Fe was inversely proportional to the severity of chlorosis. Chlorosis was absent when apple seedling leaf Fe was above 30 ug/g (dry wt. basis). The transport of root Fe to the tops was apparently facilitated when the chelator to Fe ratio was high. Under low chelator to Fe ...