Plant Biotechnology

Electronic Journal of Biotechnology ISSN: 0717-3458 Vol. 11 No. 2, Issue of April 15, 2008
© 2008 by Pontificia Universidad Católica de Valparaíso -- Chile Received May 24, 2007 / Accepted November 30, 2007
DOI: 10.2225/vol11-issue2-fulltext-9
RESEARCH ARTICLE

Changes in morpho-physiological attributes of Eucalyptus globulus plants in response to different drought hardening treatments

Rafael E. Coopman*
Departamento de Silvicultura
Facultad de Ciencias Forestales y
Departamento de Botánica
Facultad de Ciencias Naturales y Oceanográficas
Universidad de Concepción
Victoria 631, Barrio Universitario
Casilla 160-C
Concepción, Chile
Tel: 56 041 2204115
Fax: 56 041 2254224
E-mail: rcoopman@udec.cl

Jorge C. Jara
Departamento de Recursos Hídricos
Facultad de Ingeniería Civil Agrícola
Universidad de Concepción
Avenida Vicente Méndez 592
Chillán, Chile
Tel: 56 042 208851
Fax: 56 042 275303
E-mail: jcjara@udec.cl

Leon A. Bravo
Departamento de Botánica
Facultad de Ciencias Naturales y Oceanográficas
Universidad de Concepción
Barrio Universitario s/n
Casilla 160-C
Concepción, Chile
Tel: 56 041 2204115
Fax: 56 041 2254224
E-mail: lebravo@udec.cl

Katia L. Sáez
Departamento de Estadística
Facultad de Ciencias Físicas y Matemáticas
Universidad de Concepción
Avenida Esteban Iturra s/n, Barrio Universitario
Casilla 160-C
Concepción, Chile
Tel: 56 041 2204554
Fax: 56 041 2251529
E-mail: ksaez@udec.cl

Gloria R. Mella
Departamento de Silvicultura
Facultad de Ciencias Forestales
Universidad de Concepción
Victoria 631, Barrio Universitario
Casilla 160-C
Concepción, Chile
Tel: 56 41 2204092
Fax: 56 41 2255164

Rene Escobar
Departamento de Silvicultura
Facultad de Ciencias Forestales
Universidad de Concepción
Victoria 631, Barrio Universitario
Casilla 160-C
Concepción, Chile
Tel: 56 41 2204092
Fax: 56 41 2255164

*Corresponding author

Financial support: Received from the company Forestal Arauco S.A. Grant INNOVA BIO-BIO 03-B1-210-L1 and grant MECESUP, UCO 0214.

Keywords: freezing resistance, root growth potential, stem xylem water potential, water stress, water relationships.

Abbreviations:

e: volumetric module of elasticity
Ψπtlp: osmotic potential at the turgor loss point
Ψπsat: saturation osmotic potential
Ψpd: Predawn stem xylem water potential

Ψsxtw :  stem xylem total water potential
ARL: the average length of the longest three new roots
INT: Ice nucleation temperature.
LT(10, 50, 90): freezing damage indexes of leaves
NNR: new roots longer that 1 cm
RWCtlp: relative water content

Abstract   Full Text

Morpho-physiological attributes exhibited in response to drought hardening at the end of the growing season of Eucalyptus globulus Labill under nursery conditions were studied to evaluate the effect of three drought hardening treatments in morpho-physiological traits used as suitable indicators of drought hardiness, such as, plant growth, root growth potential, plant water relationships and survival. Freezing resistance of drought hardened plants was also studied in order to evaluate cross hardening effects in cuttings of Eucalyptus globulus Labill. Drought hardening consisted in induced water stress by watering restriction, until plant stem xylem water potentials (Ψpd) reached to-0.2, -1.3 and -2.4 MPa. Two water stress-rewatering cycles were applied during 54 days of treatment. The hardening treatments caused a significant reduction in plant height, leaf area, specific leaf area, plant, leaf, stem and root biomass. However, stem diameter was not affected. Root growth potential increased with the exposure to moderate water stress (-1.3 MPa). Drought hardening treatments have not effect on water relationship parameters such as saturation osmotic potential (Ψπsat), volumetric module of elasticity (e), relative water content (RWCtlp) and osmotic potential (Ψπtlp) at the turgor loss point. Only 1.7% and 6% of dehydrated dead plants were observed on treatments at -1.3 and -2.4 MPa respectively. Finally, the freezing damage index of leaves (LT50) was not significantly affected by drought hardening treatments. Furthermore, a reduction of 1.1ºC of supercooling capacity was observed at -2.4 MPa. As a conclusion, drought hardening is an important step of plants production programs during the final phase of nursery, because changes in morphological attributes caused by exposure to moderate drought, enable the plants to maintain the balance between transpiration and absorption areas and increase the capacity of plants to generate new roots.

Supported by UNESCO / MIRCEN network