Differential Responses of Populus Deltoides and Populus × Canadensis Clones to Short-Term Water Deficit

Populus spp. are among the fast-growing tree species most prone to water deficit. The use of drought-resistant clones allows mitigating the negative effects of water deficit on the establishment and the productivity of unstable irrigated plantations in dryland areas. We evaluated the responses of four Populus × canadensis (‘Conti 12’, ‘Guardi’, ‘I-214’ and ‘I45/51’) and four Populus deltoides (‘Stoneville 67’, ‘Catfish 2’, ‘Dvina’ and ‘Australiano 129/60’) clones to a short-term water stress. Three water treatments were imposed on 6-month-old plants: well-watered (WW), 5 days of irrigation withdrawal followed by rewatering (−5 + RW), and 9 days of irrigation withdrawal followed by rewatering (−9 + RW). Populus clones presented different strategies to face water deficit, resulting in variable effects on plant growth. The small-leaved clone ‘Australiano 129/60’ showed strong stomatal control and maintained a high increase in leaf area during the water-shortage period. These strategies were associated with high relative growth under both water-shortage treatments. ‘Australiano 129/60’ showed to be a drought-resistant clone with the highest growth under both water-shortage treatments, appearing to be a promising clone for production in environments prone to short-term water stress.