Caracterización de clones de Eucalyptus grandis e híbridos interespecíficos con antecedentes de estrés hídrico a través de parámetros fotosintéticos y morfológicos

Climate change and the increasing frequency of drought events represent a growing challenge for forest production, affecting tree growth and productivity. Therefore, studying and identifying drought-tolerant clones that can recover and resume growth provides valuable information for selecting better-adapted clones. The purpose of this study was to determine variations in photosynthesis and morphology of four clones of Eucalyptus grandis and their interspecific hybrids after a prolonged period of water stress and a seven-month rehydration phase. The study included two Eucalyptus grandis clones (G1 and G2) and two hybrids (E. grandis × E. camaldulensis and E. grandis × E. tereticornis), with a total of 24 trees grown under controlled greenhouse conditions. These plants were subjected to two treatments: control condition (CC) and recovered condition (CR). In CR, the plants underwent a four-month water stress period followed by a seven-month rehydration phase. Photosynthetic and morphological variables were evaluated, including quantum yield of photosystem II (ΦPSII), net assimilation rate (An), stomatal conductance (gₛ), height, root dry weight, shoot dry weight, among others. Analysis of variance revealed no significant differences in maximum net assimilation between treatments, even though significant differences were observed in gₛ and some morphological variables. Clone G2 exhibited higher gₛ in the recovered condition, suggesting potential adaptation during the stress period. The quantum yield of photosystem II (ΦPSII) and other photochemical phase variables showed no significant differences during treatments, while morphological variables indicated that the control treatment outperformed the recovered treatment. This suggests that rehydration did not fully reverse the effects of water stress.  In conclusion, the evaluated clones exhibited similar behavior in the measured parameters, and the recovery period enabled partial recuperation. It is suggested that shorter recovery periods and continuous measurements at the onset of rehydration could help identify early recovery mechanisms. Additionally, investigating xylem anatomical traits is recommended to gain a better understanding of gₛ variations and their relationship with hydraulic conductivity.