The low ferric chelate reductase activity and high apoplastic pH in leaves cause iron deficiency chlorosis in ‘Huangguan’ pears grafted onto quince A grown in calcareous soil

•Low Fe transfer within the leaf was tightly correlated with Fe deficiency chlorosis.•High apoplastic pH enhanced Fe deposition near the leaf midrib of HG-QA in calcareous soil.•Low FCR activity inhibited Fe reduction in leaves of HG-QA in calcareous soil.•Rootstocks were involved in the regulation of leaf Fe utilization by scions.