Does the origin of Eucalyptus species influence their response to water regime changes?

Abstract

Eucalyptus has been cultivated worldwide because of its good adaptability to different climatic conditions and ease of use in plant breeding programs. However, environmental stress such as drought is unavoidable, affecting the yield of this crop and making the search for genotypes more adapted to these situations, extremely important. The aim of this study was to characterize the physiological responses of young plants in six Eucalyptus species that originated from contrasting environments and then subject them to three water regimes consisting of 40, 60 and 80% field capacity (FC). For this, 180-day-old seedlings were transplanted to pots, where they were kept for 85 days in a greenhouse. After the adoption of water regimes, the net photosynthesis (A), transpiration (E), stomatal conductance (g_s) and leaf water potential (Ψ_w) were analyzed. Significant differences were found in all the physiological characteristics evaluated. There were reductions in the A, E, g_s and Ψ_w for all species as the water stress intensified. At 40% FC, E. tereticornis was the only one for which plant death occurred. Among the six Eucalyptus species studied, E. saligna was the most tolerant to water stress followed by E. urophylla and E. camaldulensis, while E. tereticornis was the most sensitive, and it was preceded by E. brassiana and E. grandis. The interspecific comparative study enabled the identification of the most contrasting species in terms of water stress tolerance, providing support to studies aimed at obtaining drought-tolerant clones.