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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The use of almond by products as substrate in greenhouses for growing vegetables has a great economic interest. The objective of this work was to assess the use of two almond by-products (almond shell-AS and almond hull-AH), which had been previously conditioned without composting, as substrates for pepper (cv. Caprino F1) production and to study their effects on the yield, fruit size, and fruit mineral content. Physical, physico-chemical, and chemical characteristics of the almond by-products were determined both initially and during the pepper growing season. Initially, all values of the parameters studied -except sulfur and iron-differed significantly between the two substrates. During cultivation, the 18 substrate parameters and variables tested -except bulk density-exhibited significant variations with time for AS; the same occurred for AH, exceptions being pH, total nitrogen N t , N-NH 4 , bulk density, and manganese. The changes in both substrates for the K, N, and S concentrations were significant. The nutrient levels in AH were higher than for AS. The almond shell and almond hull substrates produced slight decreases in total fruit yield with respect to the control (0.79 and 3.22 for AS and AH, respectively), with a lesser decrease for AS, due to reductions in the number of fruits per plant rather than to reductions in individual fruit weight. The plants grown on the AS and AH substrates showed a decrease in total fruit yield, due to reductions in the number of fruits per plant rather than reductions in individual fruit weight.

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Garcia, A. L., Torres, S. C. Z., Heredia, M., and Lopes, S.A. 2012. Citras responses to Xylella fastidiosa infection. Plant Dis. 96:1245-1249.The xylem-limited bacterium Xylella fastido.ia causes the widely disseminated citrus variegated chlorosis disease (CVC). In Brazil, CVC has been known for more than 20 years and affects only sweet orange. Lime and mandarin have remained free of symptoms despite the high inoculum pressure. Knowing the mechanisms underlying this apparent resistance is important to devise new disease control strategies. The reaction of commercial sweet orange ('Caipira', 'Natal'. 'Pera', and 'Valencia'), lime (Mexican and Persian), mandarin ('Cleopatra', 'Cravo', 'Ponkan', and 'Sunki'), and the acid citrus species Rangpur to X. fastidiosa was compared in artificially inoculated seedlings, which were assessed for symptom expression, pathogen isolation, and the amount of apparently occluded xylem vessels in cross-sectioned leaf petioles. Only the sweet orange expressed typical CVC symptoms, varying from 53.8% in Valencia to 63.0% in Caipira. Average percentages of positive isolations {pi) and occluded vessels (ov) were higher in sweet orange (j)i = 59.2 to 75.0; ov = 10.7 to 25.8) than mandarin (j)i = 2.3 to 16.3; ov = 1.4 to 4.0), lime (j)i = 0 to 5.4; ov = 0 to 2.1). or Rangpur {pi = 1,9; ov = 1.1). There were no obvious differences in xylem anatomy among all citrus varieties, suggesting that the mechanisms of resistance to CVC are not related to any physical variation in xylem structure.

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The objective of the present study was to evaluate the marketable fruit yield of sweet pepper plants (Capsicum annuum cv. Orlando) in function of the management of nutrient solution with training system. Plants were grown on coconut coir dust under greenhouse conditions in the southeast of Spain. A randomized block design in split-split plot with four blocks was used to test the effect of the nutrient solution strength (full or half-strength Hoagland nutrient solution), training system (two and three stems per plant) and water salinity (saline and non-saline) on total and marketable yield, fruit quality, and fruit mineral concentration. Salt treatment decreased fruit yield by decreasing the fruit fresh weight but not the number of fruits per plant. Under saline and non-saline conditions, the higher yield of fruits was obtained in plants watered with half-strength Hoagland solution, and grown with three stems per plant. Blossom end rot incidence increased under saline conditions or using full-strength Hoagland solution, but decreased with the combination of half-strength Hoagland solution and three-stem training system. Salt treatment also decreased fruit quality in all the treatments due to a decrease in PO2-, SO4(2-), Fe2+;3+, Cu1+;2+ and Mn2+ concentrations, and fruit shape index. Likewise, plants exposed to salinity and watered with half-strength Hoagland solution and trained with three stems showed a reduction in juice glucose and fructose concentration. Based on these results, an increase of the marketable fruit yield could be obtained under non or moderate saline conditions with the implementation of suitable culture practices.