Pedro José Correia

Effectiveness of different foliar iron applications to control iron chlorosis in orange trees grown on a calcareous soil

The effectiveness on controlling Fe chlorosis in orange trees grown on calcareous soils was tested. The treatments were Fe(II) sulfate (500 mg Fe L−1), sulfuric acid (0.5 mM H2SO4), Fe(III)-chelate (Hampiron 654 GS, 120 mg Fe L−1) and distilled water as a control. A non-ionic wetting agent was used in all treatments. The use of frequent foliar sprays alleviated Fe chlorosis in orange trees. Sprays of Fe(II) sulfate increased the concentrations of chlorophyll, Fe and zinc in leaves and improved fruit size and quality compared to fruits of control trees. Sprays of Fe(III)-chelate also increased leaf chlorophyll and Fe concentrations and improved fruit quality, but did not increase fruit size. Sprays of sulfuric acid alone slightly increased leaf chlorophyll and Fe concentrations, without improving fruit size and quality. These results suggest that foliar sprays with Fe could help to avoid yield and quality losses caused by Fe chlorosis in citrus orchards. Furthermore, these treatments could be done with relatively cheap materials such as solutions containing Fe(II) sulfate.

The use of floral analysis to diagnose the nutritional status of orange trees

A field experiment was conducted in a commercial orange orchard (Citrus sinensis L. cv. ‘Valencia late’), established on a calcareous soil in the south of Portugal, to investigate if flower analysis could be used to diagnose the nutritional status of the trees and predict fruit quality. In April 1996, during full bloom, flowers and leaves were collected from 20 trees. Leaf samples were again collected in June and August from the same trees. In February 1997 the fruits were harvested and their quality evaluated. The concentrations of phosporous (P) and magnesium (Mg) in flowers were correlated with those in leaves, and were also predictive of the chlorophyll content of leaves 60 days later. However, by 120 days after full bloom these effects were masked, possibly by a fertilizer application carried out by the farmer. The iron (Fe) concentration in flowers was correlated with chlorophyll measured either 60 or 120 days after full bloom. These parameters can therefore be used to predict the appearance of iron chlorosis. Fresh weight and diameter of fruit were related to flower P, Mg, and manganese (Mn) concentrations, while the percentage of citric acid in the fruit juice was inversely correlated with Fe flower concentrations.

Seasonal variations of leaf water potential and growth in fertigated carob-trees (Ceratonia siliqua L.)

Variations of predawn and midday leaf water potential and relative growth rates were studied in mature carob trees (Ceratonia siliqua L. cv “Mulata”) submitted to a fertigation experiment. Three levels of irrigation were tested: 0%, 50% and 100%, based on daily standard evaporation values. For each irrigation level two nitrogen amounts were applied −21 and 63 kg N ha-1 year-1 as ammonium nitrate. The experiment was run between July 91 and August 1993. Measurements of leaf water potential and absolute branch length increments were made at monthly intervals, during the entire experimental period or during seasonal growth, respectively. Leaf water potential was related to soil volumetric water content, maximum and minimum air temperature and daily evaporation. Predawn leaf water potentials were always higher than −1.1 MPa. Midday leaf water potential values presented very large seasonal variations and very low values independent of treatments. The low leaf water potentials observed for the fertigated trees during summer, suggest that this parameter may be related not only to the evaporative demand but also to growth investment. The amount of fertigation was positively correlated with vegetative growth increment and fruit production. Practical implications for irrigation schedules of leaf water potential patterns together with drought adaptation mechanisms of carob tree are discussed.

A new medium formulation for in vitro rooting of carob tree based on leaf macronutrients concentrations

AbstractExperiments were performed to optimize the macronutrients concentrations for in vitro rooting of Ceratonia siliqua micropropagated shoots. Several dilutions of Murashige and Skoog (MS) medium were tested: full-strength MS, half-strength MS (

ROOT FERRIC CHELATE REDUCTASE IS REGULATED BY IRON AND COPPER IN STRAWBERRY PLANTS

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Nutritional Evaluation of Nitrogen and Potassium Fertilization of Carob Tree under Dry-Farming Conditions

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Nutritional and physiological responses of the dicotyledonous halophyte Sarcocornia fruticosa to salinity

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