Germinative and physiological performance of eucalyptus species under abiotic stress

With the increase in cultivated areas, one of the great challenges faced by eucalyptus growers is abiotic stresses, especially because new areas are often affected by water deficit. Therefore, the identification of tolerant genotypes is important to overcome this problem. Thus, the objective of this work was to characterize the germinative and physiological performance of eucalyptus species under abiotic stress. Four Eucalyptus species (E. brassiana, E. camaldulensis, E. saligna, and E. urophylla) were evaluated in two experiments. In the first experiment, the germination potential was assessed under two temperatures (25 and 35 °C) and 11 water potentials of the substrate: 0 (deionized water), -0.05, -0.10, -0.15, -0.20, -0.25, -0.30, -0.40, -0.60, -0.80, and -1.0 MPa. In the second experiment, the species were evaluated in a protected environment under two water regimes comprised by 60% and 20% of the maximum water retention capacity by the soil of the pots. Regarding germination, E. saligna was the most sensitive species to stress, showing only 48% germination on 0 MPa potential (35 °C) and under substrate water deficit it reduced 50% germination on -0.21 MPa (25 °C) and -0.16 MPa potential (35 °C). On the other hand, E. brassiana maintained germination at both temperatures and reduced half of its germination at potentials of -0.33 MPa (25 °C) and -0.32 MPa (35 °C). In protected environment, the physiological metabolism of plants decreased under lower water availability. E. saligna was the species with the highest reduction for the rate of net assimilation and efficiency in water use. In addition, E. camaldulensis showed better physiological performance under water deficit. Thus, E. brassiana and E. camaldulensis would be the most suitable species to be used for breeding program aiming to improve water deficit tolerance. E. saligna is indicated for places with a mild climate and with good water availability. The behavior of the species between the experiments showed that under certain conditions there are correspondences in performance, which indicates that this type of experiment assists in the characterization of species, especially when considering the establishment and initial plant development.