Leaf water relations, net gas exchange and leaf and root constituent responses to 9 days of drought stress (DS) or soil flooding were studied in 6‐month‐old seedlings of Carrizo citrange [Citrus sinensis (L.) Osb. ×Poncirus trifoliata L.; Carr] and Cleopatra mandarin (Citrus resnhi Hort. ex Tanaka; Cleo) growing in containers of native sand in the greenhouse. At the end of the drought period, both species had similar minimum stem water potentials but Cleo had higher leaf relative water content (RWC) and higher leaf osmotic potential at full turgor () than Carr. Flooding had no effect on RWC but osmotic adjustment (OA) and were higher in Cleo than in Carr. Net CO2 assimilation rate (ACO2) in leaves was decreased more by drought than by flooding in both species but especially in Carr. Leaf water‐use efficiency (ACO2/transpiration) was lower in Carr and was decreased more by DS and flooding stress than in Cleo. Higher values of intercellular CO2 concentration (Ci) in stressed plants than in control plants indicated that non‐stomatal factors including chlorophyll degradation and chlorophyll fluorescence [maximum quantum efficiency of PSII (Fv/Fm, where Fm is the maximum fluorescence and F0, minimum fluorescence in dark‐adapted leaves)] were more important limitations on ACO2 than stomatal conductance. In both genotypes, leaf proline was increased by drought but not by flooding, whereas both stresses increased proline in roots. Soluble sugars in leaves were increased by DS, and flooding decreased leaf sugars in Cleo. In general, DS tended to increase the concentrations of Ca, K, Mg, Na and Cl in both leaves and roots, whereas flooding tended to decrease these ions with the exception of leaf Ca in Cleo. Based on water relations and net gas exchange, Cleo was more tolerant to short‐term DS and flooding stress than Carr.

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The aim of this research was to determine the effects on growth variables and leaf mineral concentration of tomato plants watered with nutrient solutions containing amino acids. Two separate experiments were then carried out to achieve this goal. In the first experiment, plants were watered with seven different nutrient solutions consisting of half-strength Hoagland solution supplemented with single (Alanine, Serine, Phenylalanine, Tyrosine) or combined (Ala + Ser; Phe + Tyr) amino acids, each at 0.2 mM of concentration. The control nutrient solution did not have any amino acids added. Relative to the control, growth variables were not affected by the presence of amino acids. In general, the mixture of Ala + Ser increased the leaf Ca 2+ concentration, and the aliphatic amino acid treatments favoured an increase in leaf K + , Fe, Cu, and Mn concentrations. In addition, amino acids with hydroxyl groups in their structure, Ser and Tyr, increased Mg 2+ concentration. In the second experiment, the nutrient solutions were supplemented with 0.05 mM of the same amino acids (T1). Control plants were irrigated with amino acid-free nutrient solution (T0). The concentration of Ca 2+ , K + , Mg 2+ , Fe, Cu, and Mn in the leaf also increased due the amino acids treatment. Chlorophyll contents in the leaves and amino acids compositions in the xylem sap and leaf water relation were also determined. In conclusion, the data reported in the two experiments point out that the application of amino acids to the nutrient solution has a beneficial effect on the leaf mineral status and on the chlorophyll concentration of the leaves.Additional key words: amino acid fertilization; biofertilizer; hydroponic culture; Solanum lycopersicum L. ResumenEfectos de la aplicación de amino ácidos en la solución nutritiva sobre la composición mineral y el crecimiento de plántulas de tomate En este trabajo se estudiaron los efectos sobre el crecimiento y la concentración mineral de hojas de plantas de tomate cultivadas con soluciones nutritivas con distinta composición en aminoácidos. Para ello se plantearon dos experimentos. En el primero las plantas se regaron con siete soluciones nutritivas 1/2 Hoagland que diferían en la composición de los aminoácidos, todos ellos a una concentración total de 0,2 mM (Ala, Ser, Fen y Tir aplicados de forma individual, dos con la combinación Ala+Ser y Fen+Tir, un control sin aminoácidos). Las variables de crecimiento no mostraron diferencias entre los tratamientos; sin embargo, se observaron cambios en las concentraciones de nutrientes aunque los efectos dependieron de los aminoácidos utilizados. La mezcla de Ala + Ser aumentó la concentración de Ca 2+ , mientras que los tratamientos de aminoácidos alifáticos favorecieron un aumento de K + , Fe, Cu y Mn, y aquellos con grupos hidroxilo (Ser y Tyr) aumentaron el Mg 2+ . En el segundo experimento las plantas se regaron con disolución 1/2 Hoagland (T0) o con disolución 1/2 Hoagland más una mezcla de los 4 aminoácidos (0,05 mM) ensayados (T1). En este experiment...

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