Abstract: This work was aimed to investigate to relations between tolerance to water deficit stress (WDS) and the activity and type of endopep tidase in different cultivars of Cut roses (Rosa hybrid). Two cultivars, ‘Samantha’with the strong tolerance to WDS, and ‘Belami’with the medium one, were used as
materials, and WDS treatment was carried out for 0 - 60 h under the conditions of 22 - 25℃, RH 30% - 60% , and 80μE·m^{- 2} · s^{- 1}. To make different p rocess ofWDS, we treated the two cultivars separately with two manners, namely flowers with and without branches in the same condition of WDS above. The results showed that, ① the decrease of flower recovery percentage was much slower in ‘Samantha’ than in‘Belami’, and was slower significantly in the flowerswith branches than without branches in a cultivar, while the opposite tendency was obtained on the increase of flower bent neck percentage during WDS. A turning point, in which recovery rate of flowers was going to be decreasing rapidly, was observed in both flowers with and without branches, and the occurrence of the turning pointwas later in ‘Samantha’ than in ‘Belami’. However, the value of water potential was almost the same in a cultivar, corresponding to the turning point of recovery rate. ② The turning point of quick climbing of free amino acid content in petals was also observed in
the flowers of both cultivars, including the two manners, with orwithout branches separately duringWDS, and these pointswere identicalwith the turning points of their recovery rate. ③WDS2induced increase of endopeptidase activity was later in‘Samantha’than in‘Belami’, and it was earlier in the flowerswith branches than without branches in a cultivar. Interestingly, the turning points of quick increase of endopep tidase activity in2duced byWDS in both cultivarswith orwithout brancheswere consistentwith the turning points of their recovery rates. ④ Changes of both metall-oproteinase and serine proteinase activities of petals induced by WDS were significantly smaller in ‘Samantha’ than in ‘Belami’. The results above suggested that the difference of tolerance toWDS between different cultivars might be related to the different changes of metallo-proteinase and serine proteinase activitives in petals induced by WDS.

Key words: Rose, Cut flower, Tolerance, Water deficit stress, Endopep tidase