The effect of high iron doses (Fe2+) on the growth of broccoli plants (Brassica oleracea var. Italica)

A

GR

ON

OM

IA C

OLO

MB

IAN

A

VO

LUM

E X

XX

II

No.

1,

jAN

UA

Ry-

Ap

RIL

201

4

Tarif

a Po

stal

Red

ucid

a No

. 201

4-40

4 4-

72 L

a Re

d Po

stal

de

Colo

mbi

a, v

ence

31

de D

ic. 2

014.

VOLUME XXXII, No. 1 jANUARy-ApRIL 2014 ISSN 0120-9965

VOLUME XXXII, No. 1 jANUARy-ApRIL 2014 ISSN 0120-9965

AgronomiA ColombiAnA

P.O. Box 14490, Bogota-ColombiaPhones: (571) 316 5498 / (571) 316 5000 ext. 19095

Fax: (571) 316 5176 E-mail: [email protected]

http://www.scielo.org.cohttp://www.revistas.unal.edu.co/index.php/agrocol

http://agronomia.unal.edu.co

3 Editorial

PlAnT brEEDing, gEnETiC rESoUrCES AnD molECUlAr biologY / FiTomEJorAmiEnTo, rECUrSoS gEnÉTiCoS Y biologÍA molECUlAr

7 Comparison of DNA extraction methods for detection of citrus huanglongbing in ColombiaComparisión de métodos de extracción ADN para detección de huanglongbing en ColombiaJorge Evelio Ángel, Erick Geovanni Hernández, Néstor Andrés Herrera, Linda Yhiset Gómez, Ángela Patricia Castro, Adriana Milena Sepúlveda, and Everth Emilio Ebratt

ProPAgATion AnD TiSSUE CUlTUrE / ProPAgACión Y CUlTivo DE TEJiDoS

14 Effect of fruit size on the growth and development of Andean blueberry (Vaccinium meridionale Swartz) seedlings from four locations in the Colombian AndesEfecto del tamaño del fruto sobre el crecimiento y desarrollo de plántulas de agraz (Vaccinium meridionale Swartz) en cuatro localidades de los Andes de ColombiaCristian Leonardo García M. and Gustavo Adolfo Ligarreto M.

CroP PhYSiologY / FiSiologÍA DE CUlTivoS

22 The effect of high iron doses (Fe2+) on the growth of broccoli plants (Brassica oleracea var. Italica)Efecto de dosis altas de hierro (Fe2+) sobre el crecimiento de plantas de brócoli (Brassica oleracea var. Italica)Jaime E. Peña-Olmos, Fánor Casierra-Posada, and Misael A. Olmos-Cubides

CroP ProTECTion / ProTECCión DE CUlTivoS

29 Temperature effect on rose downy mildew development under environmental controlled conditionsEfecto de la temperatura en el desarrollo de mildeo velloso bajo condiciones ambientales controladasJuan José Filgueira D. and Angélica Zambrano

36 Evaluation of various conventional methods for sampling weeds in potato and spinach crops Evaluación de diferentes metodologías convencionales de muestreo de malezas en cultivos de papa y espinacaDavid Jamaica and Guido Plaza

PoSThArvEST PhYSiologY AnD TEChnologY / FiSiologÍA Y TECnologÍA PoSCoSEChA

44 Ethylene and 1-MCP affect the postharvest behavior of yellow pitahaya fruits (Selenicereus megalanthus Haw.)Etileno y 1-MCP afectan el comportamiento poscosecha de frutos de pitahaya amarilla (Selenicereus megalanthus Haw.)Yuli Alexandra Deaquiz, Javier Álvarez-Herrera, and Gerhard Fischer

52 Sorption isotherms for oat flakes (Avena sativa L.)Isotermas de adsorción para hojuelas de avena (Avena sativa L.)José Edgar Zapata M., Oscar Albeiro Quintero C., and Luis Danilo Porras B.

SoilS, FErTiliZATion AnD mAnAgEmEnT oF WATEr / SUEloS, FErTiliZACión Y mAnEJo DE AgUAS

59 Nutrient uptake of the criolla potato (Solanum phureja var. Galeras) for the determination of critical nutritional levelsAbsorción de nutrientes en papa criolla (Solanum phureja var. Galeras) para determinar niveles críticos nutricionalesJaime Torres B. and Carlos A. Suarez M.

70 Effect of edaphic and foliar applications of different doses of zinc on the yield of the Criolla Colombia cultivar

Efecto de la aplicación edáfica y foliar de zinc sobre el rendimiento del cultivar Criolla Colombia

Andrés López, Manuel Iván Gómez, and Luis Ernesto Rodríguez

78 Technical evaluation of the fertilization of flue cured tobacco farming in Campoalegre and Garzon, Huila

Evaluación técnica de la fertilización en el cultivo de tabaco Virginia, en los municipios de Campoalegre y Garzón, Huila

Verónica Hoyos and Guido Plaza

86 Near-infrared (NIR) diffuse reflectance spectroscopy for the prediction of carbon and nitrogen in an Oxisol

Espectroscopia de reflectancia difusa por infrarrojo cercano (NIR) para la predicción de carbono y nitrógeno de un Oxisol

Jesús H. Camacho-Tamayo, Yolanda Rubiano S., and Maria del Pilar Hurtado S.

95 Determination of an efficient irrigation schedule for the cultivation of rose cv. Freedom under greenhouse conditions in Colombia

Determinación de una programación de riego eficiente para el cultivo de la rosa cv. Freedom bajo condiciones de invernadero en Colombia

Jhon Jairo Arévalo, Javier Enrique Vélez S., and Diego Sebastiano Intrigliolo

103 Tree-ring growth and hydro-climatic variability in temperate dendrochronologies of northern Mexico

Crecimiento de anillos y variabilidad hidro-climática en dendrocronologías templadas del norte de México

José Návar and Liliana Lizárraga-Mendiola

EConomY AnD rUrAl DEvEloPmEnT / EConomÍA Y DESArrollo rUrAl

113 Characterization and typification of citrus production systems in the department of Meta

Caracterización y tipificación de los sistemas de producción citrícola en el departamento del Meta

José Alejandro Cleves-Leguízamo and Alfredo Jarma-Orozco

122 Critical reflections on the New Rurality and the rural territorial development approaches in Latin America

Visión crítica sobre los enfoques de la Nueva Ruralidad y el desarrollo territorial rural en América Latina

César Ramírez-Miranda

130 Reappraising the multiple functions of traditional agriculture within the context of building rural development investigative skills

Revalorización de las múltiples funciones de las agriculturas del campesinado en el contexto de la construcción de competencias investigativas en desarrollo rural

Álvaro Rivas G. and Heimar Quintero V.

138 Proposal for a strategic management plan for experimental agricultural and academic farm “El Cairo” of Arauca

Propuesta de un plan de gestión estratégica para la granja académica experimental universitaria “El Cairo” de Arauca

Elías Nieves, Lilia Teresa Bermudez, and Luis Felipe Rodríguez

APPEnDiX / AnEXoS

146 Requirements for publishing in Agronomía Colombiana153 Subscriptions

CENTRO EDITORIAL

Agronomía Colombiana is a technical-scientific publication classified by Colciencias in category A2 of the Índice Nacional de Pu-blicaciones Seriadas y Científicas y Tecnológicas (Publindex) (Colombia). The journal is indexed in the Scientific Electronic Library Online (SciELO) and Scopus. Internationally, the journal is referenced in Redalyc, Latindex, AGRIS (FAO) and integrated in CABI Full Text and the following databases of CAB-ABSTRACTS: Agricultural Engineering Abstracts, Agroforestry Abstracts, Crop Physiology Abstracts, Field Crop Abstracts, Grasslands and Forage Abstracts, Horticultural Science Abstracts, Irrigation and Drainage Abstracts, Maize Abstracts, Nematological Abstracts, Ornamental Horticulture, Plant Breeding Abstracts, Plant Growth Regulator Abstracts, Postharvest News and Information, Potato Abstracts, Review of Agricultural Entomology, Review of Aromatic and Medicinal Plants, Review of Plant Pathology, Rice Abstracts, Seed Abstracts, Soils and Fertilizers, Sugar Industry Abstracts, Weed Abstracts y World Agricultural Economics and Rural Sociology Abstracts.

The authors of the articles submitted to the journal Agronomía Colombiana must be aware of and avoid scientific misconduct related to: scientific fraud in all or part of the data of the study and data falsification and manipulation; dishonesty due to fictitious authorship or gifting or exchange of co-authorship, duplicate publications, partial or complete, in different journals and self-plagiarism by reusing portions of previous writings; citation omission, citation copying without consultation and excessive self-citation, among others.

Reproduction and quotation of material appearing in the journal is authorized provided the following are explicitly indicated: journal name, author(s) name, year, volume, issue and pages of the source. The ideas and observations recorded by the authors are their own and do not necessarily represent the views and policies of the Universidad Nacional de Colombia. Mention of products or commercial firms in the journal does not constitute a recommendation or endorsement on the part of the Universidad Nacional de Colombia; furthermore, the use of such products should comply with the product label recommendations.

EDITORIAL COMMITTEE

María Isabel Chacón, Faculty of Agricultural Sciences, Universidad Nacional de Colombia, Bogota.

Juan Pablo Fernández Trujillo, Departamento de Ingeniería de Alimentos y del Equipamiento Agrícola, Universidad Politécnica de Cartagena, Murcia, Spain.

Gustavo Ligarreto, Faculty of Agricultural Sciences, Universidad Nacional de Colombia, Bogota.

Luis Alberto López Pérez, Department of Statistics, Faculty of Sciences, Universidad Nacional de Colombia, Bogota.

Hermann Restrepo, Faculty of Agricultural Sciences, Universidad Nacional de Colombia, Bogota.

Leo Rufato, Centro Agroveterinário, Universidade do Estado de Santa Catarina, Lages, SC, Brazil.

Paulo César Tavares de Melo, Escola Superior de Agricultura Luiz de Queiroz, Universidade de São Paulo, Piracicaba, SP, Brazil.

Christian Ulrichs, Division Plant Ecophysiology, Faculty of Agriculture and Horticulture, Humboldt-Universität zu Berlin, Germany.

SCIENTIFIC COMMITTEE

Agim Ballvora, INRES-Plant Breeding and Biotechnology, University of Bonn, Germany.

Yoav Bashan, Environmental Microbiology and Biotechnology, Northwestern Center for Biological Research (CIBNOR), La Paz, Mexico.

Carmen Büttner, Division Phytomedicine, Faculty of Agriculture and Horticulture, Humboldt-Universität zu Berlin, Germany.

Daniel G. Debouck, Genetic Resources Unit, International Center for Tropical Agriculture (CIAT), Cali, Colombia.

Derly J. Henriques da Silva, Departamento de Fitotecnia, Universidade Federal de Viçosa, Viçosa, MG, Brazil.

Idupulapati Rao, Tropical Soil Biology and Fertility Institute, International Center for Tropical Agriculture (CIAT), Cali, Colombia.

Manuel Talón, Instituto Valenciano de Investigaciones Agrarias (IVIA), Moncada, Valencia, Spain.

Lorenzo Zacarías, Instituto de Agroquímica y Tecnología de Alimentos (IATA-CSIC), Burjassot, Valencia, Spain.

jANUARy-APRIL 2014VOLUME XXXII No. 1 ISSN (print): 0120-9965 / ISSN (online): 2357-3732

PUbliCATion oF A SCiEnTiFiC-TEChniCAl nATUrE bY ThE FACUlTY oF AgriCUlTUrAl SCiEnCES oF ThE UnivErSiDAD nACionAl DE ColombiA, bogoTA

© Universidad Nacional de Colombia Faculty of Agricultural Sciences

Publication registered at the Ministerio de GobiernoResolution No. 00862 of March 24, 1983

Information, correspondence, subscription and exchange:

Revista Agronomía Colombiana Faculty of Agricultural Sciences, Universidad Nacional de Colombia P.O. Box 14490, Bogota-ColombiaPhone: (571) 316 5498 / 316 5000 ext. 19095Fax: 316 5176E-mail: [email protected]

Electronic version available at:http://www.scielo.org.cohttp://www.revistas.unal.edu.co/index.php/agrocolhttp://agronomia.unal.edu.co

ISSN: 0120-9965 (Print)ISSN: 2357-3732 (Online)

Published: Quarterly Number of copies: 1,000

Editorial assistanceArley García

Translator and English proofreaderChristopher King

Electronic Design and DevelopmentIsabel Sandoval

PrinterDigiprint

RECTORIGnACIo MAnTILLA

DEANvíCToR JULIo FLóREZ RonCAnCIo

DIRECTOR-EDITORGERHARD FISCHER

Tarifa Postal Reducida No. 2014-404 4-72 La Red Postal de Colombia, vence 31 de Dic. 2014.

our cover:Huanglongbing (HLB) or citrus greening disease is now regarded as one of the most serious diseases of citrus worldwide. Symptoms of the disease occur in all parts of the affected plants, and can be observed more easily during the cold months of the year and on young plants. Blotchy mottle is the most diagnostic symptom and is best observed on mature leaves in the interior part of the canopy (top left). This symptom favors field detection. The blotchy mottle is asymmetric (top center); is limited by the mid-vein of the leaf, but not by lateral veins. Another symptom of the disease is the presence of corky veins (top right). In HLB-affected trees severe and premature fruit drop can occur. Fruits are observed to be lopsided or asymmetrical with a curved columella (bottom left and center). Sectors of yellow or chlorotic branches on affected trees can be observed (bottom right). Photos and text courtesy of H. Gomez-USDA-APHIS-PPQ.

Received for publication: 14 January, 2014. Accepted for publication: 19 March, 2014.

1 Plant Ecophysiology Research Group, Faculty of Agricultural Sciences, Universidad Pedagogica y Tecnologica de Colombia. Tunja (Colombia). [email protected]

Agronomía Colombiana 32(1), 22-28, 2014

The effect of high iron doses (Fe2+) on the growth of broccoli plants (Brassica oleracea var. Italica)

Efecto de dosis altas de hierro (Fe2+) sobre el crecimiento de plantas de brócoli (Brassica oleracea var. Italica)

Jaime E. Peña-Olmos1, Fánor Casierra-Posada1, and Misael A. Olmos-Cubides1

ABSTRACT RESUMEN

Tests were carried out under greenhouse conditions in Tunja (Colombia) in order to evaluate the effect of Fe2+ toxicity on the growth of broccoli plants. ‘Legacy’ hybrid Brassica oleracea var. Italica plantlets were grown in glass containers with a nutritive solution. Iron sulfate was added to the substrate in order to produce excess iron at concentrations of 100 and 200 mg L-1; a control without iron sulfate applications was used. The fol-lowing evaluations were made: leaf area, total dry weight of the plants, distribution of dry mass (DM) in the different organs, absolute growth rate, relative growth rate, net assimilation rate and the root:shoot ratio. The total DM decreased drastically in the plants subjected to excess Fe2+, the growth indices progres-sively decreased with increases in the Fe2+ concentrations in the substrate and the distribution of DM in the organs varied as a function of the needs of the plants, with 15.85 and 11.10% less DM in the roots of the plants subjected to Fe2+ than in the control plants, at 100 and 250 mg L-1, respectively.

Con el objetivo de evaluar el efecto de la toxicidad por Fe2+ sobre el crecimiento de plantas de brócoli, se llevó a cabo un ensayo bajo condiciones de invernadero en Tunja (Colombia). Se utilizaron plántulas de Brassica oleracea var. Italica híbrido ‘Legacy’, sembradas en contenedores de vidrio con solución nutritiva. Se adicionó sulfato de hierro al sustrato para inducir el exceso del metal, en concentraciones de 100 y 250 mg L-1 y un control sin aplicación de sulfato de hierro. Se evaluó el área foliar, el peso seco total de la planta y la distribución de la materia seca (MS) en los diferentes órganos, se calculó la tasa de crecimiento absoluto, tasa de crecimiento relativo, tasa de asimilación neta y la relación raíz:vástago. El peso seco total disminuyó drásticamente en las plantas sometidas a exceso de Fe2+, los índices de crecimiento disminuyeron progresivamente a medida que aumentó la concentración de Fe2+ en el sustrato y la distribución de la MS en los órganos varió en función de las necesidades de la planta, siendo 15,85 y 11,10% menor la proporción de MS en las raíces de las plantas sometidas a toxicidad por Fe2+ que en las plantas control, para 100 y 250 mg L-1, respectivamente.

Key words: plant nutrition, dry mass partitioning, iron sulfate, toxicity to plants.

Palabras clave: nutrición de los cultivos, distribución de la materia seca, sulfato de hierro, toxicidad de las plantas.

CROP PhySiOlOgy

introduction

Toxicity due to excess iron is a frequent problem in acid soils (Nenova, 2006) and can be caused by microbial action in flooded soils, which results in the reduction of insoluble Fe3+ in favor of soluble Fe2+, which can be taken up by the roots of plants in excessive quantities (Becker and Asch, 2005). In addition, when the content of this metal is high in the soil, the symtomatology seen in affected plants cor-responds to deficiencies of other elements considered as antagonistic to iron, such as in the case of Mn (Hanke, 2008), P and ZN, in addition to H2S toxicity conditions (Kirk, 2004).

Currently, the relationship between iron toxicity severity, expressed symptoms and crop yield has not been clearly es-tablished (Asch et al., 2005). However, the principal symp-tom associated with Fe2+ is called browning or yellowing of the leaves, fundamentally characterized in Oryza sativa plants, which causes a reduction in growth, principally in height and tillering, and an increase in sterility of the panicle (Audebert, 2006a). In addition, the physiological behavior of the plants under Fe2+ toxicity conditions has been documented for various vegetative species under laboratory and natural conditions, fundamentally based on parameters such as the accumulation of dry and fresh mass, root and shoot lengths, number of leaves, and leaf

23Peña-Olmos, Casierra-Posada, and Olmos-Cubides: The effect of high iron doses (Fe2+) on the growth of broccoli plants (Brassica oleracea var. Italica)

area (Nenova, 2006). Similarly, excess iron toxicity in the soil has been related to the behavior of photosynthetic ap-paratus in broccoli plants, principally based on measure-ments of the fluorescence of chlorophyll a (Peña-Olmos and Casierra-Posada, 2013).

Taking into account the fact that, in Colombia, the major-ity of soils have acidity problems (Casierra-Posada et al., 2008) and that excess iron toxicity is a frequent limitation associated with low pH values in the soil (Nenova, 2006). The present study aimed to evaluate the growth of Brassica oleracea var. Italica plants subjected to excess Fe2+ stress.

Materials and methods

The evaluation was developed in a glass greenhouse of the Facultad de Ciencias Agropecuarias of the Universidad Pedagogica y Tecnologica de Colombia - UPTC (Tunja, Colombia), with an average temperature inside the green-house of 15.8°C, 72.0% relative humidity and an average photosynthetically active radiation (PAR) of 1,380 µmol m-2 s-1. One-month-old ‘Legacy’ hybrid broccoli plantlets (Brassica oleracea var. Italica) were used as the initial plant material, sown in glass containers with a nutritive solution of the following composition in mg L-1: 40.3 nitric nitrogen; 4.0 ammonical nitrogen; 20.4 phosphorus; 50.6 potassium; 28.8 calcium; 11.4 magnesium; 1.0 sulfur; 1.12 iron; 0.012 manganese; 0.012 copper; 0.0264 zinc; 0.106 boron; 0.0012 molybdenum and 0.00036 cobalt.

Approximately 20 d after transplant, iron sulfate was added to the plants at concentrations of 100 and 200 mg L-1 in order to induce excess iron; a control without an iron sul-fate application was also used. The pH of the solutions was 5.5, 5.3 and 6.2, respectively. The iron additions were done progressively in order to avoid damaging the plants. 44 d after transplant, the leaf area was determined using an LI-3000-A® integrated meter (LI-COR, Lincoln, NE), the DW of the roots, the stems, the leaves and total DW were also determined through oven drying at 105ºC until constant weight. In addition, the distribution of the dry material in the different organs was determined as a percentage of the DW assigned to each organ in respect to the total DW of the plant. Based on the DW, the root:shoot ratio was calculated as a coefficient between the root DW and the aerial parts DW. At the begining of the experiment, the initial leaf area and DW were recorded for 20 plants in order to have the initial values needed for the calculation of the growth indices (absolute growth rate (AGR), relative growth rate (RGR) and net assimilation rate [NAR]).

The greenhouse was prepared using tubes and hoses for the connection of an aeration system for the glass containers in order to oxygenate the nutritive solution of the plants. The experimental units were arranged with a completely random design with three treatments and 15 repetitions per treatment. An analysis of variance (ANAVA) was car-ried out and the treatments were compared using a Tukey mean comparison test (P≤0.05). The statistical analysis was done with version 19.0.0 of IBM-SPSS statistics (IBM Corporation, New York, NY).

Results and discussion

The total DW of the plants was markedly lower in the plants subjected to iron toxicity; the concentrations of 100 and 250 mg L-1 of the metal induced a reduction in the total DM of the plants of 73.63 and 84.81%, respectively, in regard to the control plants (P≤0.05) (Fig. 1).

FigURE 1. Total dry weight of the broccoli plants subjected to iron toxici-ty. Means with different letters indicate significant differences according to the Tukey test (P≤0.05) (n = 15). Error bars indicate standard error.

Mehraban et al. (2008) found that elevated concentrations of Fe2+ in the substrate strongly decreased radicle devel-opment, supported on the DW, especially when the Fe2+ doses surpassed 50 mg L-1 because high concentrations of the metal increased the peroxidation of lipids, particularly in the radicle zone, which was accompanied by stunted growth of the same. This radicle behavior affected the complete development of the plants because reductions in radicle volume and losses of radicle hairs can induce a drastic decrease in the relative content of water in plants (Dorlodot et al., 2005).

In rice, the DW of roots, veins and foliar lamina did not demonstrate significant differences when the plants were subjected to high iron concentrations in the substrate

a

bb

Control 100 2500

2

6

4

Iron (mg L-1)

Tota

l dry

wei

ght p

er p

lant

(g)

24 Agron. Colomb. 32(1) 2014

(Majerus et al., 2007). However, the progressive decrease in the DM in the roots, stems, and leaves in the present study is evidence of impeded growth, produced by a high flow of Fe2+ ions towards the interior of the plant. Becker and Asch (2005) indicated that a strategy used by rice plants to offset excess Fe2+ is the accumulation of the metal in the stems and leaves; highly elevated concentrations of this metal cause early defoliation in these plants in an attempt to attenuate the toxic effects in the plant with a consequent decrease, and in some cases complete cessation of growth in differ-ent organs of the plant, as occurred in the present study.

Decreases in the total DW of pea plants were reported by Nenova (2006) at 41 d after sowing and with a Fe2+

concentration of 40 mg L-1 in the substrate. This was due to the fact that the iron toxicity induced the formation of reactive oxygen species, which could be the cause of the growth inhibition. However, Batty and Younger (2003) confirmed that growth inhibition may occur before Fe2+ concentrations in the plant tissues are toxic, which suggests that a strong flow of Fe2+ towards the plant tissues creates a barrier that impedes the entrance of other nutrients that are essential for the growth and development of the plants. For example, in the cultivation of rice, high applications of Fe2+ in the substrate increase the concentrations of the metal in the roots, veins and foliar lamina, which reduce the concentrations of K, Ca, Mg, Mn and P in the shoots of the plants, which affects the growth and development of the crop (Majerus et al., 2007).

By definition, leaves are reserve organs and Fe2+ is an immo-bile element, and so is constantly accumulated within the vacuoles of foliar tissue cells and cannot be redistributed during senescence (Audebert, 2006b). The strong decrease in the leaf area of the plants subjected to excess iron in the preset study suggests that the constant flow of the metal through the conductor tissues of the plants was sufficiently strong to cause premature loss of the leaves in the evalu-ated plants. This may have been due to the low levels of soluble protein, total soluble sugars, chlorophyll a, b and total chlorophyll, as induced by the Fe2+ (Mehraban et al., 2008), which decreased foliar growth and expansion and the useful leaf life, and, consequently, caused a reduction in crop yield (Audebert, 2006b). Similarly, excess iron toxicity induced an increase in the lipids peroxidation of leaves in Eugenia uniflora (De Oliveira-Jucoski et al., 2013), which affected the structure and process of cellular division, drastically decreasing foliar expansion.

FigURE 3. Dry matter partitioning in broccoli plants subjected to iron toxicity. Means with different letters indicate significant differences ac-cording to Tukey test (P≤0.05) (n = 15). Error bars indicate standard error.

The assignment of DM to the different organs presented significant differences between the evaluated treatments (P≤0.05) (Fig. 3). The distribution of photoassimilates towards the leaves increased with the 100 mg L-1 Fe2+ ap-plication in the substrate, while the 250 mg L-1 addition produced a higher flow of photosynthates towards the stem and lower development in the leaves and roots, respectively.

The reduction of the DM percentage destined for the roots in the plants subjected to iron toxicity in the pres-ent study corresponds with the high accumulation of Fe2+ in the plants, which reduced plant growth (Mehraban et al., 2008); however, the chlorophyll contents also de-creased as a consequence of oxidative stress (Gajewska and Skłodowska, 2007), in this case, due to the increase of

LeavesStemRoots

b a c

bb

a

ab b

Control 100 2500

60

40

20

100

80

Iron (mg L-1)

Dry

mat

ter p

artit

ioni

ng (%

)

FigURE 2. Leaf area of the broccoli plants subjected to iron toxicity. Means with different letters indicate significant differences according to the Tukey test (P≤0.05) (n = 15). Error bars indicate standard error.

The control plants presented the highest foliar area value, followed by the plants subjected to the 100 and 250 mg L-1 Fe2+ concentrations in the nutritive solution, in which the values were reduced by 60.87 and 87.98%, respectively (P≤0.05) (Fig. 2).

a

c

b

Control 100 2500

200

100

400

300

Iron (mg L-1)

Leaf

are

a (c

m2 )

25Peña-Olmos, Casierra-Posada, and Olmos-Cubides: The effect of high iron doses (Fe2+) on the growth of broccoli plants (Brassica oleracea var. Italica)

the Fe2+ concentration in the plant tissues (Mehraban et al., 2008), which would limit the photosynthetic activity of the same and also cause a smaller proportion of photo-assimilates produced in the leaves and translocated towards the roots for growth and development. Peña-Olmos and Casierra-Posada (2013), who worked with the same plants as the present study, found that the electron transport rate (ETR) in the leaves decreased drastically with an increase in the iron concentration of the substrate, which directly affected the photosynthetic activity of the plants.

The increase in the percentage of DM in the leaves of the plants subjected to 100 mg L-1 Fe2+ could be the result of a compensatory behavior of the plants, due to the drastic decrease of the radicle development and the consequent decrease in the uptake of essential nutrients as a result of the high flow of Fe2+ ions towards the interior of the plants requiring a higher efficiency of the same in the capture of light in order to supplement the nutritional require-ments throughout the structure, offsetting the low radicle development and producing an osmotic readjustment in the plant. Peña-Olmos and Casierra-Posada (2013), found in broccoli that the maximum quantum efficiency of pho-tosystem II (Fv/Fm) decreased notably with an increase in the Fe2+ concentration of the substrate, concluding that the stress levels of the plants were elevated, possibly due to the accumulation of Fe2+ ions in plant tissues. Many studies have reported that abiotic stress induces an increase in ac-cumulated sugars in the aerial parts of plants and exercises a strong influence on the partition of assimilates in different plant species (Majerus et al., 2007).

For example, Majerus et al. (2007) found that the concen-tration of soluble sugars decreased in the roots with the application of Fe2+, reaching 80% less in plants stressed with 500 mg L-1 Fe2+ in comparison with the control plants. However, the same authors indicated that the concentra-tions of soluble sugars increased with Fe2+ applications both in the veins and in the foliar lamina. This increase in the concentration of soluble sugars in leaves, added with the decrease of same in the roots, suggests that sucrose load and its subsequent translocation from the aerial part towards the leaves are inhibited under conditions of excess Fe2+ stress, especially in susceptible crops. An increase in concentrations of sucrose, glucose and fructose, as a result of a modification in the activities of the sucrose phosphate synthase, sucrose synthase and invertase, was found in Lupinus albus leaves subjected to a water deficit (Pinheiro et al., 2001), which, possibly deals with the protection of cellular structures and/or with the osmotic regulation of plants under conditions of severe stress. This did not occur

in the plants under 250 mg L-1 Fe2+, possibly due to fact that the concentration of the metal was so high that it almost completely stopped vegetative growth.

The highest accumulation of DM which was found in the stems of the plants treated with 250 mg L-1 Fe2+ may have possibly been due to the plants having two options in the presence of stress induced by excess iron. The first is to tolerate the elevated concentrations of iron in the foliar tissues and the second is to create a barrier to impede the entrance of excess iron into the vegetative tissues. A tolerance to excess iron in broccoli has yet to have been reported; therefore, it is possible to think that the second option is more likely for the counteraction of iron toxicity. This, due to the fact that plants create a barrier of oxidation at the rhizosphere level in order to decrease the entrance of Fe2+ ions towards the vegetative tissues, was stabilized by the canalization of molecular oxygen through the stem and towards the roots, using gas conducting tissue or aer-enchyma (Becker and Asch, 2005); for which, plants under conditions of excessive Fe2+ in the substrate must invest a higher percentage of photoassimilates in the formation of gas conducting tissue in the stem.

Table 1 presents the absolute growth rate (AGR), the relative growth rate (RGR) and the net assimilation rate (NAR) of the evaluated broccoli plants. The AGR presented signifi-cant differences between the treatments (P≤0.05) with the 100 and 250 mg L-1 Fe2+ applications producing decreases in this variable of 74.77 and 85.98%, respectively. Similarly, the 100 and 250 mg L-1 Fe2+ applications caused a 28.89 and 42.22% decrease in the RGR, respectively (P≤0.05). The Fe2+ toxicity induced a decrease in the NAR value with the addition of 100 mg L-1 of 49.09 and 40.00% with the application of 250 mg L-1.

Nenova (2006) found in pea plants that, 34 d after the induction of toxicity with 40 mg L-1 Fe2+, the AGR value decreased 69.12% in comparison with the plants subjected to 2 mg L-1 Fe2+. This was possibly related to a decreased in the electron transport rate, affecting the Calvin cycle and causing a decrease in the carboxylation:oxigenation ratio of Rubisco, which would favor photorespiration (Kampfen-kel et al., 1995). Peña-Olmos and Casierra-Posada (2013) found that, in broccoli, the electron transport rate (ETR) decreased notably with an increase in Fe2+ concentration in the substrate. Furthermore, these authors determined the photochemical extinction coefficient (qP) and concluded that the value of this variable is inversely proportional to the Fe2+ content in the substrate, which directly affects the photosynthetic capacity of the plant as well as its growth.

26 Agron. Colomb. 32(1) 2014

Nenova (2006) reported that the RGR value was reduced 51.95% in plants subjected to applications of 40 mg L-1 Fe2+ 34 d after the induction of the toxicity, in comparison to plants with optimal Fe2+ applications (2 mg L-1). Similarly, Snowden and Wheeler (1993), who worked with 43 plant species native to British swamps, found that high Fe2+ con-centrations (10-100 mg L-1) significantly reduced the RGR in all the species except two (Eriophorum angustifolium and Juncus effusus); furthermore, the same authors confirmed that the dicotyledonous plants were more susceptible to Fe2+ toxicity, possibly due to the fact that monocotyledons are generally more porous in the shoots, which facilitates the diffusion of oxygen towards the roots of the plants. Among the dicotyledons, six species reduced their RGR 60% when 10 mg L-1 Fe2+ was added, in comparison with the control plants, showing evidence of sensitivity of the dicotyledon-ous class to excess Fe2+ stress. Similarly, Oliveira-Jucoski et al. (2013) found that a high accumulation of iron in the plant tissues of Eugenia uniflora, induced by elevated concentrations of the metal in the substrate, produced a reduction in the RGR.

Kampfenkel et al. (1995) confirmed that the rate of photosynthesis in conditions of saturated CO2 in leaves of Nicotiana plumbaginofolia decreased 40% after ex-posure to excess Fe2+ as a consequence of an increase in foliar Fe2+ content; which in turn caused a 25% decrease in the starch content of the studied leaves. In the pres-ent study, the NAR decreased in the plants subjected to excess Fe2+ and this variable is directly proportional to the rate of photosynthesis of the plants. The reduction in the synthesis of sucrose and starch in the leaves exposed to Fe2+ toxicity was accompanied by an inhibition of photosynthesis, an increase in reduced A quinones (QA)

and high photochemical extinction coefficient values qN (photochemical losses related to heat, pH gradient and photoinhibition), all under conditions of high radiation and with very few variations with low radiation (Neuhaus et al., 1989; Neuhaus and Stitt, 1991). This increase in the reduced QA was the result of the low pool of the same and as a consequence of increased non-photochemical losses. This induces a low electron transport rate which, together with the ionic stress produced by the excess Fe2+,

causes a decrease in the synthesis of photoassimilates in the leaves of plants. However, in addition to a decrease in the rate of photosynthesis as a consequence of excess Fe2+, a increase in the respiration rate of the stressed leaves is produced, which supposes a higher consumption or rup-ture of hexoses, for which the leaves subjected to high Fe2+ concentrations suffered a strong decrease in the contents of glucose and fructose in comparison with the controls (Kampfenkel et al., 1995). This is supported by studies car-ried out by Peña-Olmos and Casierra-Posada (2013), who found an increase of initial fluorescence (F0) in the same plants as the present study. This increase was possibly due to damage in the reaction centers of photosystem II (PSII) (Vieira et al., 2010) or to a decrease in the transference of excitation energy from the antenna complex towards the reaction centers (Baker and Rosenqvist, 2004), which may have produced a decrease in the photoinhibition of PSII.

TABlE 1. Absolute growth rate (AGR), relative growth rate (RGR) and net assimilation rate (NAR) of broccoli plants subjected to iron toxicity.

iron Absolute growth rate Relative growth rate Net assimilation rate

(mg l-1) (g d-1) (g g d-1) (g cm-2 d-1)Control 0.107±6.9·10-3 a 0.045±7.0·10-4 a 5.5·10-4±2.0·10-5 a

100 0.027±8.0·10-4 b 0.032±2.0·10-4 b 2.8·10-4±8·10-6 c

250 0.015±8.0·10-4 b 0.026±4.0·10-4 c 3.3·10-4±2·10-5 b

Means with different letters in each column indicate significant differences according to the Tukey test (P≤0.05) (n = 15), ± standard error.

a

b b

Control 100 2500

0.2

0.1

0.4

0.3

Iron (mg L-1)

Root

:sho

ot ra

tio

FigURE 4. Root:shoot ratio in broccoli plants subjected to iron toxicity. Means with different letters indicate significant differences according to Tukey test (P≤0.05) (n=15). Error bars indicate standard error.

The root:shoot ratio presented significant differences be-tween the treatments (P≤0.05). The addition of 100 and 250 mg L-1 Fe2+ to the substrate in which the broccoli plants grew induced a reduction of 19.29 and 13.72% in the value of this variable with respect to the control plants (Fig. 4).

Snowden and Wheeler (1993) suggested that plants can be classified as tolerant to excess Fe2+ by taking into account

27Peña-Olmos, Casierra-Posada, and Olmos-Cubides: The effect of high iron doses (Fe2+) on the growth of broccoli plants (Brassica oleracea var. Italica)

the root:shoot ratio. In this way, these authors considered that if Fe2+ applications induced decreases in said ratio with respect to control plants, the plants should be considered sensitive to excess iron due to the fact that the root is more affected than the aerial part of the plant. A higher root:shoot ratio in tolerant plants is possibly due to fact that a high Fe2+ concentration in the substrate causes a higher accumulation of ochre deposits in the roots, which would increase the radicle mass. Similarly, Kampfenkel et al. (1995) suggested that under conditions of excess Fe2+, it is separated and stored in the necrotic points that are developed in the leaves as a consequence of the same stress, as well as in the vacuoles of the mesophyll cells, with which the DW of the leaves would increase in rela-tion to the roots of the plant, producing a decrease in the root:shoot ratio.

Conclusions

The analysis of variance carried out with the data obtained for the different parameters of the plant growth evaluation of the present study allowed for the conclusion that the iron toxicity produced stress in the evaluated plants, which affected the proportion and accumulation of DM in the different plant organs. The reduction in the leaf area expansion and in the evaluated growth indices evidenced a decrease in crop development. And so, it is evident that the exposure of Brassica oleracea var. Italica plants to high Fe2+ levels in the substrate negatively affects the general function of these plants.

AcknowledgementsThis study was developed with the support of the Research Directorate (Dirección de Investigaciones - DIN) of the Uni-versidad Pedagógica y Tecnológica de Colombia (UPTC), Tunja, within the Jóvenes Investigadores UPTC program, and with the support of the Plant Ecophysiology Research Group of the Faculty of Agricultural Sciences of the UPTC.

literature cited

Asch, F., M. Becker, and D.S. Kpongor. 2005. A quick and efficient screen for resistance to iron toxicity in lowland rice. J. Plant Nutr. Soil Sci. 168, 764-773.

Audebert, A. 2006a. Diagnosis of risk and approaches to iron toxicity management in lowland rice farming. pp. 6-17. In: Audebert, A., L.T. Narteh, P. Kiepe, D. Millar, and B. Beks (eds.). Iron toxicity in rice-based systems in West Africa. Africa Rice Center (WARDA), Cotonou, Benin.

Audebert, A. 2006b. Iron partitioning as a mechanism for iron toxicity tolerance in lowland rice. pp. 34-46. In: Audebert, A.,

L.T. Narteh, P. Kiepe, D. Millar, and B. Beks (eds.). Iron toxic-ity in rice-based systems in West Africa. Africa Rice Center (WARDA), Cotonou, Benin.

Baker, N.R. and E. Rosenqvist. 2004. Applications of chlorophyll f luorescence can improve crop production strategies: an examination of future possibilities. J. Exp. Bot. 55, 1607-1621.

Batty, L.C. and P.L. Younger. 2003. Effects of external iron concentra-tion upon seedling growth and uptake of Fe+2 and phosphate by the common reed, Phragmites australis (Cav.) Trin ex. Steudel. Ann. Bot. 92, 801-806.

Becker, M. and F. Asch. 2005. Iron toxicity in rice - conditions and management concepts. J. Plant Nutr. Soil Sci. 168, 558-573.

Casierra-Posada, F., J.F. Cárdenas-Hernández, and H.A. Roa. 2008. Efecto del aluminio sobre la germinación de semillas de trigo (Triticum aestivum L.) y de maíz (Zea mayz L.). Rev. Orinoquia 12(1), 45-56.

De Oliveira-Jucoski, G., J. Cambraia, C. Riveiro, J. Alves-De Oliveira, S. Oliveira-De Paula, and M.A. Oliva. 2013. Impact of iron toxicity on oxidative metabolism in young Eugenia uniflora L. plants. Acta Physiol. Plant 35(5), 1645-1657.

Dorlodot, S., S. Lutts, and P. Bertin. 2005. Effects of ferrous iron toxicity on the growth and mineral composition of an inter-specific rice. J. Plant Nutr. 28(1), 1-20.

Gajewska, E. and M. Skłodowska. 2007. Relations between tocoph-erol, chlorophyll and lipid peroxides contents in shoots of Ni-treated wheat. J. Plant Physiol. 164(3), 364-366.

Hanke, F. 2008. La nutrición de la planta y su problemática en la agricultura. Editorial Juan de Castellanos, Tunja, Colombia.

Kampfenkel, K., M. Van Montagu, and D. Inzé. 1995. Effects of iron excess on Nicotiana plumbagnifolia plants, implications to oxidative stress. Plant Physiol. 107, 725-735.

Kirk, G.J.D. 2004. The biogeochemistry of submerged soils. John Wiley & Sons, Chichester, UK.

Majerus, V., P. Bertin, and S. Lutts. 2007. Effects of iron toxicity on osmotic potential, osmolytes and polyamines concentrations in the African rice (Oryza glaberrima Steud.). Plant Sci. 173, 96-105.

Mehraban, P., A.A. Zadeh, and H.R. Sadeghipour. 2008. Iron toxicity in rice (Oryza sativa L.), under different potassium nutrition. Asian J. Plant Sci. 7, 251-259.

Nenova, V. 2006. Effect of iron supply on growth and photosystem II efficiency of pea plants. Gen. Appl. Plant Physiol. (Special Issue) 32, 81-90.

Neuhaus, H.E., A.L. Kruckeberg, R. Feil, and M. Stitt. 1989. Reduced activity mutants of phosphoglucose isomerase in the cytosol and chloroplast of Clarkia xantiana. Planta 178, 110-122.

Neuhaus, H.E. and M. Stitt. 1991. Inhibition of photosynthetic su-crose synthesis by imidodiphosphate, an analog of inorganic pyrophosphate. Plant Sci. 76, 49-55.

Peña-Olmos, J.E. and F. Casierra-Posada. 2013. The photochemical efficiency of photosystem II (PSII) in broccoli plants (Brassica oleracea var Italica) affected by excess of iron. Rev. Orinoquia 17(1), 15-22.

28 Agron. Colomb. 32(1) 2014

Pinheiro, C., M.M. Chaves, and C.P. Ricardo. 2001. Alterations in carbon and nitrogen metabolism induced by water deficit in the stems and leaves of Lupinus albus L. J. Exp. Bot. 52, 1063-1070.

Snowden, R.E.D. and B.D. Wheeler. 1993. Iron toxicity to fen plant species. J. Ecol. 81, 35-46.

Vieira, D.A.P., T.A. Portes, E. Stacciarini-Seraphin, and J.B. Teix-eira. 2010. Fluorescência e teores de clorofilas emabacaxizeiro cv. pérolasubmetido a diferentes concentrações de sulfato de amônio. Rev. Bras. Frutic. 32(2), 360-368.