Drought tolerant of one- year- old seedlings 5 clones of Populus deltoides Bartr. ex Marsh

In this study, Populous deltoides seedlings were exposed to drought stress for four months. Cuttings of poplar clones were collected from the terminal shoot in the Chamestan Research Station, Mazandaran Province, Iran. Cuttings were planted in plastic pots under the control environment of Ghaemshahr Horticultural Research Station in June. After three growing months, seedlings of uniform height were chosen. Then potted seedlings included treatment 20 under the control environment in five clone levels (P.d.63/10, P.d.63/51, P.d.73/51, P.d.69/55, P.d.77/51) and four drought stress levels (four periods of irrigation, 3, 6, 9, 12 days) with three replicates were investigated using a factorial experiment under randomized complete block design. Results showed that water stress affected and reduced growth, survival, seedling growth (plant height, diameter, leaf area), biomass, net photosynthesis, and transpiration. However, P.d.69/55 clone seedling growth was appropriate in addition to optimal survival. However, comparisons amongst clones showed that the maximum rate of survival was achieved in 63/10 clone, but growth was less than that of 69/55 and 63/51 clones. Avoidance mechanisms in different clones caused the resistance of seedlings to drought. But among clones, P.d.69/55, P.d.63/51, P.d. 63/10 were relatively tolerant of drought. This study showed that the 9-day irrigation interval was the most suitable treatment for P. deltoids clones, also 77/51 clone was drought-susceptible with a 12-day irrigation interval. These results suggest that a selection of these clone seedlings for drought tolerance when water is limited with sandy loam soil in order to seedling production in nursery and wood cultivation conditions in the north of Iran. Thus particularly applies for 69/55 clone, which is also used the 9-day irrigation interval.