Relationship Between Iron Deficiency Stress and Endogenous Hormones in Iron-Efficient versus Inefficient Apple Genotypes

ABSTRACT

In solution culture at different iron (Fe) concentrations, both contents of endogenous hormones or the IAA oxidase activities in the roots and the diffusive IAA contents in the stem apex were analyzed for Malus xiaojinensis (an Fe-efficient apple genotype) or M. baccata (an Fe-inefficient apple genotype). The results showed that higher amounts of IAA in M. xiaojinensis were transported from the stem apex into roots under Fe deficiency stress, which resulted in a great enhancement of the root IAA content, being 4–5 times higher at Fe deficiency than at a normal Fe level. Root IAA content of M. baccata did not show any obvious change at both deficiency and normal level of Fe. When the appearance of leaf chlorosis was used as the test point by the time, there was no remarked difference in fluctuation of the root GA₃ or ABA contents between M. xiaojinensis and M. baccata, although the developing trends of the root GA₃ or ABA contents were slightly lagging for M. xiaojinensis. The results obtained in this experiment suggested that IAA might be a signal factor of inducing Fe deficiency response in plant of genus Malus.

Keywords:

• Fe Stress
• hormone
• IAA
• leaf chlorosis
• Malus

ACKNOWLEDGMENTS

This research was supported partially by the National Project for Transgenic Plants (JY04-B-02), the Ministry of Education of China and the Natural and Science Founding Committee of Beijing Municipality.

We are grateful to Dr. V. C. Baligar of USDA, Beltsville, Maryland, for his advice in conducting the experiment and correcting English of the manuscript.