Browsing by Author "Shvaleva, Alla L."
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- Metabolic responses to water deficit in two Eucalyptus globulus clones with contrasting drought sensitivityPublication . Shvaleva, Alla L.; Silva, Filipe Costa e; Breia, Elsa; Jouve, Laurent; Hausman, Jean-François; Almeida, Maria Helena; Maroco, João; Rodrigues, M. Lucília; Pereira, João Santos; Chaves, Maria MargaridaWe compared the metabolic responses of leaves and roots of two Eucalyptus globulus Labill. clones differing in drought sensitivity to a slowly imposed water deficit. Responses measured included changes in concentrations of soluble and insoluble sugars, proline, total protein and several antioxidant enzymes. In addition to the general decrease in growth caused by water deficit, we observed a decrease in osmotic potential when drought stress became severe. In both clones, the decrease was greater in roots than in leaves, consistent with the observed increases in concentrations of soluble sugars and proline in these organs. In roots of both clones, glutathione reductase activity increased significantly in response towater deficit, suggesting that this enzyme plays a protective role in roots during drought stress by catalyzing the catabolism of reactive oxygen species. Clone CN5 has stress avoidance mechanisms that account for its lower sensitivity to drought compared with Clone ST51.
- Responses to water stress in two Eucalyptus globulus clones differing in drought tolerancePublication . Silva, Filipe Costa e; Shvaleva, Alla L.; Maroco, João; Chaves, Maria Manuela; Pereira, João SantosWe evaluated drought resistance mechanisms in a drought-tolerant clone (CN5) and a drought-sensitive clone (ST51) of Eucalyptus globulus Labill. based on the responses to drought of some physiological, biophysical and morphological characteristics of container-grown plants, with particular emphasis on root growth and hydraulic properties. Water loss in excess of that supplied to the containers led to a general decrease in growth and significant reductions in leaf area ratio, specific leaf area and leaf-to-root area ratio. Root hydraulic conductance and leaf-specific hydraulic conductance decreased aswater stress became more severe. During the experiment, the drought-resistant CN5 clone maintained higher leaf water status (higher predawn and midday leaf water potentials), sustained a higher growth rate (new leaf area expansion and root growth) and displayed greater carbon allocation to the root system and lower leaf-to-root area ratio than the droughtsensitive ST51 clone. Clone CN5 possessed higher stomatal conductances at moderate stress as well as higher hydraulic conductances than Clone ST51. Differences in the response to drought in root biomass, coupled with changes in hydraulic properties, accounted for the clonal differences in drought tolerance, allowing Clone CN5 to balance transpiration andwater absorption during drought treatment and thereby prolong the period of active carbon assimilation.