Selection of flood-tolerant Populus deltoides clones for reforestation projects in China

Morphology, physiology, and growth of 16 poplar clones ( Populus deltoides Marsh.) were investigated during a 42-day flooding experiment. Three treatments were applied: watered, flooded to 3 cm above the soil surface, and completely submerged. Although all plants survived the entire 42-day period, leaf initiation was inhibited by flooding and chlorosis and abscission occurred. Leaf size, leaf area, and number of leaves were reduced for all flooded plants relative to watered plants. Flooding inhibited root growth and caused some deterioration of the original root system. Other responses to flooding included formation of hypertrophied lenticels and adventitious roots on submerged portions of stems, decreased chlorophyll a fluorescence, decreased transpiration rate, and increased leaf diffusion rate. There was no significant difference in leaf water potential between flooded and watered plants. Based on data of all measured values and by means of cluster analysis, the clones can be divided into three types. Type 1 clones (ST197, ST91, ST163, ST75, ST165, ST260, ST259, LU) were resistant to flooding. Type 2 clones (ST264, 800, CL723, CL552) were moderately tolerant to flooding, and Type 3 clones (ST261, ST238, ST202, ST229) were flood intolerant.