Abstract:

Foliar spraying with different concentrations of paclobutrazol was conducted to two-year-old seedlings of Populus alba×Populus berolinensis, Ulmus pumila, and Betula platyphylla under drought stress. Results showed that paclobutrazol could lower the decrease of leaf water potential and soluble protein content, increase water use efficiency of seedlings of these three species to different extent, and also had various influences on free proline content and membrane-lipid peroxidation. The synthetic evaluation of drought-resistance of seedlings from different treatments showed that the seedlings pretreated with paclobutrazol had distinct drought-resistance. Low concentrations of paclobutrazol made a great impact on the improvement of drought-resistance of P. alba×P. berolinensis seedlings, while high concentrations of paclobutrazol had a favorable regulative effect on the drought-resistance of U. pumila seedlings, and for B. platyphylla seedlings a relative good result only be obtained with paclobutrazol at the concentration of 750 mg5L^-1 .

Key words: paclobutrazol, Populus alba×, Populus berolinensis, Ulmus pumila, Betula platyphylla, drought-resistance