Using the flower Fe concentration for estimating chlorosis status in fruit tree orchards:: A summary report

The mineral analysis of leaves from deciduous fruit trees is not always useful for assessing the Fe nutritional status, because Fe-chlorotic leaves may have considerable concentrations of total Fe (the "Fe-chlorosis paradox"). Another major problem with this approach is that at the recommended time for leaf sampling it is unlikely that any corrective measure could improve crop yield and/or fruit quality. The analysis of flowers, that can be completed in various species before leaves have emerged, has been proposed as a tool to predict the Fe status of the tree later in the year. In this report we summarize the results obtained so far using this technique, in several experiments made in different Mediterranean countries such as Spain, Greece, Italy and Portugal. In peach orchards showing chlorosis the Fe concentration in whole flowers is usually correlated with the chlorophyll concentration later in the year. Preliminary experiments in other crops, such as orange, indicate that the Fe concentration in flowers is also correlated with the leaf chlorophyll content. Furthermore, a peach cultivar grafted on an Fe-efficient rootstock had a higher flower Fe concentration than when grafted on an Fe-inefficient one. This may indicate that the Fe concentration in flowers could be a good estimate of the mobile or active Fe fraction in the tree. Problems for a general application of this technique for diagnosis and prognosis of the Fe nutritional status of trees are discussed.