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Water relations and gas exchange in poplar and willow under water stress and elevated atmospheric CO 2
Author(s) -
Johnson Jon D.,
Tognetti Roberto,
Paris Piero
Publication year - 2002
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1034/j.1399-3054.2002.1150111.x
Subject(s) - willow , transpiration , salicaceae , stomatal conductance , cutting , photosynthesis , turgor pressure , water use efficiency , chemistry , botany , water potential , horticulture , osmotic pressure , soil water , agronomy , biology , woody plant , ecology
Predictions of shifts in rainfall patterns as atmospheric [CO 2 ] increases could impact the growth of fast growing trees such as Populus spp. and Salix spp. and the interaction between elevated CO 2 and water stress in these species is unknown. The objectives of this study were to characterize the responses to elevated CO 2 and water stress in these two species, and to determine if elevated CO 2 mitigated drought stress effects. Gas exchange, water potential components, whole plant transpiration and growth response to soil drying and recovery were assessed in hybrid poplar (clone 53–246) and willow ( Salix sagitta ) rooted cuttings growing in either ambient (350 µmol mol −1 ) or elevated (700 µmol mol −1 ) atmospheric CO 2 concentration ([CO 2 ]). Predawn water potential decreased with increasing water stress while midday water potentials remained unchanged (isohydric response). Turgor potentials at both predawn and midday increased in elevated [CO 2 ], indicative of osmotic adjustment. Gas exchange was reduced by water stress while elevated [CO 2 ] increased photosynthetic rates, reduced leaf conductance and nearly doubled instantaneous transpiration efficiency in both species. Dark respiration decreased in elevated [CO 2 ] and water stress reduced R d in the trees growing in ambient [CO 2 ]. Willow had 56% lower whole plant hydraulic conductivity than poplar, and showed a 14% increase in elevated [CO 2 ] while poplar was unresponsive. The physiological responses exhibited by poplar and willow to elevated [CO 2 ] and water stress, singly, suggest that these species respond like other tree species. The interaction of [CO 2 ] and water stress suggests that elevated [CO 2 ] did mitigate the effects of water stress in willow, but not in poplar.