Changes of several physiological indices in hybrid clones of Populus deltoides Bartr. ×P. ussuriensis Kom. under low temperature stress.

Cuttings of six hybrid clones of P. deltoides×P. ussuriensis were exposed to consecutive low temperatures (5 ℃, 0 to 5 days) to study the variation of several physiological indices. The results indicated that under low temperature stress, chlorophyll content and Fv/Fm values in the six hybrid clones decreased gradually; MDA content kept a gradually increasing trend; content of soluble sugar and soluble protein increased first and then declined. In addition, there were significant differences among the six clones in those physiological indices under low temperature stress, and chlorophyll content, Fv/Fm values, soluble sugar and soluble protein content in clones DU146 and DU147 were the highest, whereas MDA content and the increased multiples were the lowest, reflecting that they possessed more photosynthetic and lowtemperaturetolerant abilities; clones DU136 and DU165 were in the next place, whereas clones DU135 and DU150 were the weakest.