Diferenças na resposta a défices hídricos e a baixas temperaturas em dois clones de Eucalyptus globulus Labill. com contrastante sensibilidade à secura

Abstract

Doutoramento em Engenharia Florestal - Instituto Superior de AgronomiaWe evaluated responses to water deficits and low temperatures in two Eucalyptus globulus Labill. clones with contrasting drought sensitivity. Our aim was to identify morphological, physiological and biochemical markers of stress resistance mechanisms. In response to water deficit and chilling, CN5 clone (drought-resistant) sustained a higher root growth and displayed greater carbon allocation to the root system than ST51 clone (drought-sensitive). In addition, under drought and low temperature conditions, CN5 ramets maintained higher leaf water potential (better water status) and decreased leaf osmotic potential significantly more than the drought-sensitive ST51 ramets. Differences in the response to drought in root biomass, coupled with changes in hydraulic properties, accounted for the clonal differences in drought tolerance, allowing CN5 ramets to balance transpiration and water absorption during drought and thereby prolong the period of active carbon assimilation. Moreover, in response to low temperatures, CN5 clone exhibited a higher capacity to acclimate in a shorter period than ST51. We conclude that Clone CN5 has greater plasticity in terms of adaptive traits than ST51, allowing its plantation range to increase to sites subject to seasonal droughts or sudden frosts