A physiological approach for pre-selection of Eucalyptus clones resistant to drought

Abstract

Abstract: Water deficit is one of the abiotic stresses that most affects the growth and survival of Eucalyptus. Mechanisms used to tolerate water-limited environments influence the distribution of Eucalyptus species in their natural environment. Here, we take a physiological approach to pre-screen Eucalyptus plants for tolerance to drought. Ten different clones of E. urophylla and E. grandis × E. urophylla that are known to show contrasting responses to water deficit under field conditions, were grown in Clark’s nutrient solution (WW, well-watered) and with polyethylene glycol (-1.0 MPa) to simulate water deficit (WD). Clones responded differently to drought with differentiated photosynthetic limitations in drought-treated clones. Photosynthetic rates, stomatal conductance, transpiration and internal CO2 concentrations were reduced in all genotypes under stress conditions. Clone i144 had a smaller reduction in the evaluated physiological traits, also showing increased root growth in WD-treated plants. Clones 3367 and i224, thought to be moderately tolerant, also followed these patterns. Clones gg157, 1568 and 1641, all of which are moderately sensitive under field conditions, reduced most of the physiological characters evaluated. However, clone gg157 demonstrated increased root system growth, even during short periods of water stress. Clones i042 and i182 were deemed drought-susceptible, with large reductions in photosynthesis and growth, despite showing a high increase in abscisic acid content presumably as a defense mechanism. Interaction between A (photosyntetic rate), E (transpiration rate), ETR/A (electrons transport rate/photosynthetic rate) and SDM/ RDM (shoot dry matter/root dry matter) demonstrated the most significant differences between WD-treated clones and offer great potential for use as selection criterion for water deficit-tolerant genotypes.