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