Abstract: Various responses to iron deficiency stress were studied in three iron-efficient horticultural crops，Malus xiaojinensis（woody plant），SO4（vine plant，Vitis），Hezuo 906（herb plant，Solanum lycopercicum）. The results showed that iron deficiency could induce both higher ferric-chelate reductase（FCR）activity and lower rhizosphere pH in all the three species. However，by shoot tip removal and Fe deficiency treatment，Hezuo 906 showed a higher FCR activity and a lower rhizosphere pH，while both M. xiaojinensis and SO4 remained at the normal iron level，which suggested that the iron deficiency responses in M. xiaojinensis and SO4 relied on the shoot signal，while the sole root local signal could trigger the responses in Hezuo 906. In split-root experiments of the root system with Fe supply developed some Fe efficiency responses in M. xiaojinensis and Hezuo 906，but not in SO4，showing that the shoot signal in M. xiaojinensis and Hezuo 906 could initiate the response to iron stress，while both the shoot signal and the root local signal were required in SO4. Furthermore，the results exhibited that the root hair formation was induced in M. xiaojinensis and Hezuo 906. The different species of horticultural crops may have various regulating mechanisms to iron stress.

Key words: Malus xiaojinensis, Vitis, Solanum lycopercicum, iron deficiency responses, shoot signal, local signal, regulating mechanism