Genotypic variation in morphology and freezing resistance of Eucalyptus globulus seedlings subjected to drought hardening in nursery

Eucalyptus globulus Labill is one of the most planted species in Chile, because of its fast growth and superior pulp qualities. Nevertheless, the incidence of drought and frost damage immediately after planting is frequent. The purpose of this work was to study the effect of drought hardening on frost resistance and on variations in morphological traits that may increase drought resistance at nursery phase in four genotypes of E. globulus Labill. Drought hardening treatments consisted in induced water stress by watering restriction, until pre-dawn stem xylem water potentials (\u3a8pd) reached -0.2, -1.8 and -2.6 MPa. Two water stress-rewatering cycles were applied during 54 days of hardening. Plant and root biomasses were affected by the interaction of drought hardening and genotypes. The rest of morphological and alometrical traits were affected independently by drought or genotype. Plant height, leaf area, specific leaf area (SLA), stem, and leaf biomasses decreased with drought hardening, while collar diameter was not affected. Genotypes responded differentially to drought hardening in plant height, leaf area, SLA, and stem, and leaf biomasses. Ice nucleation temperature (INT), and freezing temperatures (FRT), and 50% freezing damage index of leaves (LT50) were affected by the interaction between drought hardening and genotypes. EG-13, EG-23 and EG-22 genotypes became freezing tolerant with drought hardening (-2.6 MPa). Additionally, EG-14 genotype increased its freezing resistance at -1.8 MPa. Therefore, freezing resistance levels and mechanism depend on genotype and drought hardening treatment. The success in tree breeding by genetic selection should be facilitated by improved understanding of the physiology of stress resistance development and survival during water supply limitations. The knowledge of morphological and freezing resistance dependency on the interaction between genotype and drought hardening may be useful nursery management information to improve plantation success

In situ warming in the Antarctic: effects on growth and photosynthesis in Antarctic vascular plants.

The Antarctic Peninsula has experienced a rapid warming in the last decades. Although recent climatic evidence supports a new tendency towards stabilization of temperatures, the impacts on the biosphere, and specifically on Antarctic plant species, remain unclear. We evaluated the in situ warming effects on photosynthesis, including the underlying diffusive, biochemical and anatomical determinants, and the relative growth of two Antarctic vascular species, Colobanthus quitensis and Deschampsia antarctica, using open top chambers (OTCs) and gas exchange measurements in the field. In C. quitensis, the photosynthetic response to warming relied on specific adjustments in the anatomical determinants of the leaf CO2 transfer, which enhanced mesophyll conductance and photosynthetic assimilation, thereby promoting higher leaf carbon gain and plant growth. These changes were accompanied by alterations in the leaf chemical composition. By contrast, D. antarctica showed no response to warming, with a lack of significant differences between plants grown inside OTCs and plants grown in the open field. Overall, the present results are the first reporting a contrasting effect of in situ warming on photosynthesis and its underlying determinants, of the two unique Antarctic vascular plant species, which could have direct consequences on their ecological success under future climate conditions.Los autores agradecen a CONICYT-FONDECYT 11130332, CONICYT-PIA ART11-02, CONICYT, Atracción de Capital Humano Avanzado del Extranjero (MEC-80130020), CONICYT PFB-023 y al Instituto Antártico Chileno (INACH AN-02-12 y FI_02-13). Un agradecimiento especial a la tripulación de la Estación Arctowski y a la Academia Polaca de Ciencias por su apoyo y ayuda durante nuestro trabajo de campo. Los autores agradecen al Dr. Charles L. Guy (Universidad de Florida) su corrección en inglés y su ayuda con la gramática. Los permisos de entrada y recolección de plantas en la ASPA 128 fueron facilitados por el INACH.Publishe

Genotypic variation in morphology and freezing resistance of Eucalyptus globulus seedlings subjected to drought hardening in nursery

Eucalyptus globulus Labill is one of the most planted species in Chile, because of its fast growth and superior pulp qualities. Nevertheless, the incidence of drought and frost damage immediately after planting is frequent. The purpose of this work was to study the effect of drought hardening on frost resistance and on variations in morphological traits that may increase drought resistance at nursery phase in four genotypes of E. globulus Labill. Drought hardening treatments consisted in induced water stress by watering restriction, until pre-dawn stem xylem water potentials (Ψpd) reached -0.2, -1.8 and -2.6 MPa. Two water stress-rewatering cycles were applied during 54 days of hardening. Plant and root biomasses were affected by the interaction of drought hardening and genotypes. The rest of morphological and alometrical traits were affected independently by drought or genotype. Plant height, leaf area, specific leaf area (SLA), stem, and leaf biomasses decreased with drought hardening, while collar diameter was not affected. Genotypes responded differentially to drought hardening in plant height, leaf area, SLA, and stem, and leaf biomasses. Ice nucleation temperature (INT), and freezing temperatures (FRT), and 50% freezing damage index of leaves (LT50) were affected by the interaction between drought hardening and genotypes. EG-13, EG-23 and EG-22 genotypes became freezing tolerant with drought hardening (-2.6 MPa). Additionally, EG-14 genotype increased its freezing resistance at -1.8 MPa. Therefore, freezing resistance levels and mechanism depend on genotype and drought hardening treatment. The success in tree breeding by genetic selection should be facilitated by improved understanding of the physiology of stress resistance development and survival during water supply limitations. The knowledge of morphological and freezing resistance dependency on the interaction between genotype and drought hardening may be useful nursery management information to improve plantation success

Differential accumulation of dehydrin-like proteins by abiotic stresses in Deschampsia antarctica Desv.

Ruiz-Lara, S. Instituto de Biología Vegetal y Biotecnología, Universidad de Talca, Casilla 747, Talca, ChileDehydrins are proteins that accumulate during environmental stresses leading to cell dehydration. Deschampsia antarctica is one of the two vascular plants that have colonized the Maritime Antarctic. This plant is usually exposed to cold, salt and desiccating winds in the field. We proposed that among the factors that allow D. antarctica to survive the harsh environmental conditions is the presence of dehydrins. We studied the accumulation of dehydrins by abscisic acid (ABA), dehydration, NaCl and low osmotic potential. Western blots using an anti-dehydrin antibody revealed a complex pattern of dehydrin-like proteins (DLPs) accumulation in the different treatments. DLPs with apparent molecular weight of 58, 57, 55, 53, 48, 42, 32, 30, 28 and 25 kDa were detected in the different treatments. DLPs accumulation was associated with a decrease in the relative water content (RWC) of the plants. These results suggest that DLPs accumulation could contribute to explain how D. antarctica can survive under adverse Antarctic conditions.http://dx.doi.org/10.1007/s00300-005-0718-

Effect of Fabiana imbricata constituents on Rhopalosiphum padi and Heliothis zea

G. Schmeda-Hirschmann, P. Román , C. Theoduloz. Departamento de Ciencias Biológicas, Universidad de Talca, Casilla 747, Talca, Chile.The main secondary metabolites of Fabiana imbricata showed toxicity towards the greenbug Rhopalosiphum padi when administered in an artificial diet. A dose-dependent toxicity was observed for fabiaimbricatan-15-oic acid and oleanolic acid at doses up to 3.0 mM (p <0.01). Both compounds apparently act as antifeedants at higher doses. Rutin also showed a dose-related toxicity. Scopoletin and p-hydroxyacetophenone were toxic at 6.0 mM. None of the compounds tested were toxic towards the fifth instar Heliothis zea larvae