Iron content in vegetative and reproductive organs of nectarine trees in calcareous soils during the development of chlorosis

We investigated for 2 years (1995-1996) the time course development of chlo rosis and the variation of iron (Fe) content in vegetative and reproductive organs in two nectarine orchards planted with cv Spring Red and cv Stark R edgold on calcareous soils of the Po valley (Italy) with the final aim to e valuate possible tools for the early prognosis of Fe chlorosis and a more e fficient fertilization management. Due to the withdrawal of Fe supply, flor al Fe concentration significantly decreased in 1996 as compared with 1995 i n cv Spring Red, but not in Stark Redgold. Correlation coefficients between Fe and chlorophyll (Chl) from the same leaves were always higher when Fe w as considered as amount present per leaf or per unit of leaf area than as l eaf dry weight. The fact that chlorotic and green leaves had similar Fe con centration could be explained by an overestimate of Fe in the chlorotic lea f as a consequence of a reduction of its size. However, the decrease of Chi concentration between 60 and 120 days after full bloom (DAFB) occurred whi le leaf Fe content generally increased, indicating that even during chloros is development leaves were supplied with some iron. We therefore suggest th at the development of chlorosis was associated with an inactivation of Fe i n the leaf apoplast. In 1995, regardless the cultivar, floral Fe concentrat ion and leaf Chl were never correlated. In 1996 floral Fe concentration was linearly related to leaf Chl recorded 60 and 120 DAFB in cv Spring Red onl y. Floral Fe concentration at full bloom 1996, regardless the variety, was linearly related to leaf Chl determined in spring of the previous year, sug gesting that flower Fe concentration might be used for assessing the storag e of iron during the previous season. (C) 2000 Elsevier Science B.V. All ri ghts reserved.