Resultados preliminares sobre la variación en vulnerabilidad a la cavitación por sequía en clones de Eucalyptus grandis.

TESÓN, N.; FERNÁNDEZ ME; LICATA J.

Pucón

Congreso; Congreso IUFRO 2012: "Eucaliptos mejorados para aumentar la competitividad del sector forestal en América Latina"; 2012

IUFRO (International Union of Forest Research Organizations)

Water transport is functionally linked to carbon fixation in terrestrial plants. Water inside plants is under meta-stable state due to negative pressure (tension) according to Cohesion-Tension Theory. Vulnerability to cavitation curves, i.e., those relating losses in xylem hydraulic conductivity (ks) due to water column breakage with tension inside the xylem, provide valuable information about different species and genotypes response capacity to environmental stress. The objective of this study was to evaluate the variation in drought stress tolerance of four Eucalyptus grandis clones (K, B, 2 and 4) from the Genetic Improvement Program of INTA. For this purpose, methodological adjustments were needed in order to develop vulnerability to cavitation curves in adult trees. The air-injection method was applied, which relates ks losses with cavitation induced by positive pressures in a double-ended chamber. The selected clones present contrasting wood density  (high, low) and different growth rates. The studied material was obtained from a 18 years-old clonal trial located in Concordia, Entre Ríos, Argentina (Lat.: 31°22? S; Long.: 58° 07? W; h.a.s.l.: 43 m) in deep sandy soil. Crown access was possible with a hydraulic crane. Branch samples (3 individuals per clone) were taken between April and May of 2012, Vulnerability-to- cavitation curves were developed in the basal portion (20 cm long) of secondary branches. Curves parameters (a and b) were compared between clones with ANOVA, describing the water potential at which 50% of ks is lost (P50) and the curve form. Significant differences were observed between two studied clones. The most cavitation resistant clone 2 (P50= -1,85 +/- 0,19MPa) was a high wood density clone. The least cavitation resistant clone B (P50= -1,11 +/- 0,11 MPa) was characterized by its high growth rates and low wood density. These results are in agreement with post-drought responses evaluated through growth and sapflow measurements (previous studies), which demonstrated a higher resilience in clone 2 than in clone B. High wood density clone K also presented a high resilience after a severe drought event, but it did not present clear advantages in terms of cavitation resistance. However, it presented the highest osmotic adjustment capacity of the studied clones. We concluded that vulnerability to cavitation is variable between clones and it would have an adaptive role in terms of drought resistance of E. grandis. However, alternative (and/or complementary) mechanisms exist in other plant organs which have to be evaluated in order to select drought resistant genotypes.