Abstract:

To study the changes of freezing tolerance and its physiological basis of annual leaves and
shoots of Rosa beggeriana and R. fortuneana，the cold hardiness was estimated by the semi-lethal
temperature（LT50），which was assessed by electrolyte leakage rate with Logistic equation，the
accumulation of starches in stems was observed by periodic acid-shiff staining and the contents of relative
water，malondialdehyde，soluble sugars，proline，ABA and activities of SOD，POD and CAT were
measured. The results showed that the freezing tolerances of leaves of two Rosa species were similar，but
the shoots of R. beggeriana exhibited stronger cold hardiness than that of R. fortuneana. Compared with R.
fortuneana，R. beggeriana accumulated more soluble sugars at the beginning of cold acclimation，which
transported to shoots and stored as starch under the possible signaling regulation by increased ABA content before defoliation and hydrolyzed as soluble sugars at the midwinter to sustain osmotic balance，and
depended on higher activity of SOD to maintain redox balance，while the higher content of proline and
POD activity observed in the shoots of R. fortuneana could not sustain the osmotic and redox balance，
which led to more damage of membrane lipid peroxidation and weaker hardiness eventually.

Key words: Rosa beggeriana, R. fortuneana, freezing tolerance, overwintering