The influence of rootstock on the mineral composition of scion leaves of fruit trees is generally accepted. The present work was carried out to corroborate if this influence is also evident for the mineral nutrient concentrations in flowers. The study was made in an experimental orchard of sweet cherry (Prunus avium, L. cv. 'Van') grafted on three rootstocks: Adara, SL 64 and Cok. Flowers and leaves were sampled at full bloom and 60 days after fuil bloom (DAFB) respectively. They were analyzed for nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sodium (Na), iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu). Floral analysis showed that most nutrients were affected by the rootstock. P and Ca, contents behaved similarly for cherry flower and leaf 60 DAFB. The range of variation of K, Mg, and Cu in flowers, among rootstocks, was shorter than that of leaves. In contrast, the range of variation of Na, Zn, and especially Fe, in flowers was longer than that of leaves.

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Floral analysis could be considered as an alternative versus foliar analysis to diagnose the nutritional status of fruit trees. Taken into account the importance of the dry matter percentage of any plant tissue, preliminary results about fresh and dry weights of flowers from different fruit species are presented in this study. For this purpose, whole flowers (without stalk) at full bloom were sampled from different fruit species grown at the Aula Dei Campus. The fruit tree groups considered for these studies were: almond, apple, apricot, nectarine, peach, pear, plum, sour cherry and sweet cherry. For the last group, three varieties: (Sunburst, Tardif de Vignole and Van) were studied. Significant differences, among groups, for fresh weights, dry weights and dry matter percentages were found.

Paclobutrazol (Pbz) is a triazol that effectively inhibits vegetative growth in peach. Changes in mineral element concentration have been generally found. However, uneven distribution of the elements in the soil may partially account for these differences. To ascertain these effects, an experiment was designed under controlled conditions, in which sugar beet, used as a model plant, was grown hidroponically, treated with Pbz and the results compared to those from unbearing peach trees grown in the open. The beets were treated with 1 M Pbz at the first trifoliate stage, and the peach trees with 2 g Pbz/tree shortly AFB. A reduction of 85 % in leaf area and of 70 % in dry weight were recorded in Pbz-treated beet plants, while in Pbz-treated peach these were of 40 % in leaf area and 29 % in dry weight. Nutrient concentration on dry weight basis varied little (about 8 % in beet and 11 % in peach). However, but global assimilation of nutrients on a leaf basis, when compared with controls, decreased up to the same extend as dry weight in beet (70 %) while in peach it was of 25 %. From these results it can be inferred that the mineral fertilization in Pbztreated peach trees can be reduced to the same extend as the expected reduction in vegetative growth, consequently reducing production costs and environmental contamination.

In previous studies was pointed out that it may be possible to detect subclinical manganese deficiencies in the field before visual symptoms have developed. In this work, by in situ fluorescence measurements, we demonstrate that it is possible to predict, at the beginning of the season, which trees will develop manganese deficiency several months later. Fo/Fm ratio of young manganese deficient leaves without visible symptoms was higher than the measured in the equivalent control leaves. More than 80% of concordance, between the initial measurements and the symptoms lately developed was reached. This facts made us to believe that it could be possible to predict manganese deficiency just when the first leaves appeared and therefore apply effective correcting measures to prevent manganese deficiency in peach trees. Economical repercussion of manganese deficiency, in terms of yield and fruit characteristics, are also discussed.