Objective In this study, 10 Sect. Aigeiros clones of Populus were used as experimental materials to study the changes of growth, physiological and biochemical characteristics under drought stress, analyze the drought resistance ability of different clones, and screen out excellent clones with strong drought resistance, with the aim of providing basis for the selection of poplar varieties on dry sites.
Method The drought stress was simulated by pot experiment, and four water gradients were set up to measure the changes of nine indexes of ten clones under different degrees of water deficiency, to investigate the effects of different degrees of drought stress on the growth and physiological indexes of each clone.
Result Under continuous drought stress, the differences in seedling height increment, ground diameter increment and biomass increment among the 10 clones were significant, among which the clones 1733 and 1627 were significantly different from the control 2025. The chlorophyll content of clones, except for clone 1716, showed a trend of increasing and then decreasing, with a small increase in mild drought and a decrease in moderate and severe drought. The cell membrane permeability of the leaves in each clone showed an increasing trend with the continuation of drought time, and under severe drought stress, the cell membrane permeability increased to the maximum, with the largest increase in clones 1716 and 1722, and the smallest increase in clones 1733 and 1641. The malondialdehyde content showed a pattern of change, in which it first increased and then decreased, and was the highest content in moderate drought; the superoxide dismutase (SOD) and peroxidase (POD) activities first increased and then decreased, and the activities were the highest under moderate drought, and compared with normal water supply, clones 1627 and 1733 showed the greatest elevation of SOD activity, and clones 1733 and 1641 showed the greatest elevation of POD activity. The accumulation of osmoregulatory substances gradually increased with increasing drought severity, and under severe drought, the clones 1627 and 1733 had the highest free proline (Pro) content and the highest increase, which were significantly different from the control 2025. Principal component analysis showed that under severe drought stress conditions, the 10 clones were 1733, 1627, I-107, 1641, 1640, 1725, 1723, 2025, 1716 and 1722 in order of their drought resistance.
Conclusion The variation of each index of the 10 clones under drought stress is different. Based on the result of principal component analysis, it is tentatively concluded that the clones 1733 and 1627 have strong drought tolerance and can be used as test materials for further studies in arid site.