Differential physiological performance of two Eucalyptus species and one hybrid under different imposed water availability scenarios

Abstract

Eucalyptus forest reproductive material responded differently to the imposed water scenarios through different water resistance mechanisms. Eucalyptus is amongst the most planted genera in the world. The focus of this study was to evaluate the ability of different forest reproductive material to withstand the occurrence of drought under different possible climate scenarios, both experienced by plants in the field: a long-term water deficit period (WS) and a short-term water deficit period followed by recovery, in comparison with a well-watered condition. The performance of two Eucalyptus species (Eucalyptus globulus and Eucalyptus nitens) and one hybrid (Eucalyptus globulus × Eucalyptus cypellocarpa), under such conditions, was assessed through several morphological and physiological traits. Under prolonged water stress, E. globulus, which experienced the lowest water potential values, suffered a decrease in CO2 assimilation rates as a result of stomatal limitations that, together with high oxidative damage, led to growth impairment. It also exhibited the slowest recovery from a short-term water stress period. The hybrid reacted to the prolonged water stress period through an active antioxidant system which allowed a higher photosynthetic assimilation rate and overall growth. Though it experienced a decrease in CO2 assimilation rate, due to non-stomatal limitations, E. nitens was able to maintain its growth under a prolonged water deficit period. Furthermore, under short-term drought stress followed by recovery, E. nitens was able to completely recover its gas-exchange parameters and increase overall growth production conferring a physiological advantage under the tested conditions. Our data demonstrate that, under the experimentally imposed water stress scenario, plants have different adaptive mechanisms to cope with continuous water deficit and recovery after a short-term stress situation.