Ana M. Garau

Elastic and osmotic adjustments in rooted cuttings of several clones of Eucalyptus camaldulensis Dehnh. from southeastern Australia after a drought

Summary Eucalyptus camaldulensis Dehnh., considered as a drought tolerant species, was examined in relation to some mechanisms linked to drought tolerance (cell-wall elastic adjustment and osmotic adjustment) and to the intraspecific variation related to those features. Rooted cuttings of five clones obtained from three different provenances from Australia (Gilgandra: 106, 109; Lake Albacutya: 119, 125; Condamine: 105) were gradually submitted to a water limitation regime. Water stress curtailed relative leaf area growth rate, pre-dawn relative water content (RWC) and noon stomatal conductance (gs) in all clones. Shoot water parameters were estimated at the end of the drought period by pressure-volume (P–V) analysis through a repeat pressurization method. The curves obtained were analyzed by Schulte’s P–V Curve Analysis Program. Drought decreased very significantly the osmotic potential at full turgor (χπFT) and at the turgor loss point (χπTLP), with a significant clone effect: 105 had the lowest values (–2.12±0.04 MPa and –2.39±0.05 MPa). Osmotic adjustment (OA) on average was 0.34±0.02 MPa. Drought increased maximum bulk modulus of elasticity (ɛMAX) by 6.60.7 MPa. There were no clonal differences in either OA or elastic adjustment.Water stress increased significantly turgor potential at full turgor (χFT), and differences between control and stress plants show that the OA recorded did not fully account for the positive changes in turgor of stressed plants. Drought decreased shoot turgid mass/dry mass ratio (TM/DM), again with a significant clone effect: 105 had the lowest value (2.66±0.11). Reduced shoot TM/DM combined with increases in ɛMAXduring stress were indicative of cell wall adjustment, reduced turgor-loss volumes and tightening of the cell walls around the protoplasts, suggesting a cell size reduction. No effects were observed on RWC at the turgor loss point. A regression model that considered ɛMAX and χπFT explained best the response patterns of stressed plants. The mechanisms observed in Eucalyptus camaldulensis that delay growth while maintaining turgor and water uptake allow us to consider it as a dehydration postponement species.

Changes in Eucalyptus camaldulensis essential oil composition as response to drought preconditioning

Abstract Water deficit, a common constraint in forestry, is the main cause of plant stress during plantation. The survival and growth of seedlings is also compromised by herbivory during establishment. The potential of nursery preconditioning to enhance survival chances of future trees by reducing palatability or attracting beneficial insects as a result of changes in chemical defences may be an answer to overcome this situation. Changes in essential oil production and composition were evaluated by GC and GC-MS in Eucalytus camaldulensis seedlings submitted to drought during four weeks at the last stage of nursery period (20 weeks). Significant changes in essential oil relative composition were found. Seedlings (young leaves) submitted to drought developed a terpenoid blend, which has been previously associated to mature leaves and related to their higher resistance towards herbivory. Total amount of non-oxygenated terpenes decreased by 44%, whereas some oxygenated sesquiterpenes (globulol, epiglobulol and ledol) were doubled, and 1,8-cineole content was enhanced by 28.3%.

Chemical Defenses in Eucalyptus Species: A Sustainable Strategy Based on Antique Knowledge to Diminish Agrochemical Dependency

A large number of tree species from different genera have being used world over for their timber resources. Most of them produce roundwood for sawmill and commercial valuable derivatives such as those related to pulp and paper, hardboard and particleboard industries (FAO 2011b). Species within Fabaceae, Pinaceae, Myrtaceae, Cupressaceae, Araucariaceae, Meliaceae, Fagaceae, and Proteaceae families are exploited by those industries.

Influencia de factores climáticos en las fechas de inicio de floración y brotación de clones de álamo en el Delta del Paraná, Argentina

Se estudia el efecto conjunto de diferentes factores climaticos sobre el inicio de floracion y brotacion de distintos clones de alamo a traves de tecnicas de analisis multivariado. Se analizaron seis clones de Populus deltoides de amplio cultivo en Argentina y los registros fenologicos se realizaron durante seis anos. La informacion agrometeorologica comprendio fotoperiodo, horas de frio (temperaturas iguales o menores a 7 °C), precipitaciones y temperatura, evaluada con el modelo de grado-dia. Se analizaron cuatro temperaturas base y dos fechas de inicio de suma de temperaturas. Se utilizaron metodos estadisticos univariados y multivariados. La suma de temperaturas a partir del 1 de julio, sobre una temperatura base de 4 °C, es el factor de mayor influencia para el inicio de las fenofases. En menor grado tambien afectan las horas de luz, las precipitaciones y las horas de frio. Se discute la importancia relativa de los distintos factores climaticos en relacion al origen geografico del Populus deltoides.

Establecimiento de Pinus taeda en la provincia de Corrientes (Argentina): efecto del herbicida metsulfurón-metil sobre el crecimiento y la sobrevivencia de los plantines

Con el objetivo de evaluar el efecto del uso del herbicida metsulfuron-metil en plantaciones de Pinus taeda (pino taeda) se analizaron la sobrevivencia, el dano del herbicida sobre las plantas y el crecimiento de los plantines en un ensayo realizado en Gobernador Virasoro (norte de la Provincia de Corrientes, Argentina). Se analizaron tres dosis de metsulfuron-metil (30, 60 y 90 g/ha) y dos zonas de aplicacion del herbicida sobre los plantines forestales (cobertura total sobre la copa y dirigido a la base de la planta). Ademas, se evaluo la aplicacion de glifosato y un tratamiento sin control de malezas. Los herbicidas se aplicaron 30 dias despues de la plantacion. La altura y el diametro a nivel del cuello se evaluaron al inicio del ensayo, 60, 120 y 180 dias despues de aplicado el producto; la sobrevivencia y el estado sanitario de los pinos a los 60 dias. No se observo efecto fitotoxico sobre el pino, mostrando las plantas aspecto vigoroso y color verde intenso. El lugar de localizacion del herbicida sobre la planta no produjo diferencias en crecimiento. La aplicacion de herbicidas produjo mayor crecimiento que el control enmalezado. Con dosis de 60 y 90 g/ha de metsulfuron-metil las plantas mostraron mayor diametro y altura, siendo estos resultados similares al tratamiento con glifosato.