Response Of Endoproteolytic Activity In Petals Of Two Cut Rose Cultivars To Ethylene And 1-MCP

This work was aimed to investigate the relationship between ethylene and endopeptidase during flower opening and senescence in cut rose (.Rosa hybrida) . Two cultivars sensitive to ethylene were used in the study. One was 'Samantha', whose opening process could be promoted by ethylene treatment, and the other was 'KardinaP, whose opening process could be delayed. The changes of soluble protein content and activities and kinds of endopeptidase in the petals of cut rose flowers were determined during natural opening and senescence of flowers and before or after the treatment of ethylene and its receptor inhibitor, 1-MCP. The results were as follows:1) The pH optimum for endoproteolytic activity was pHIO in both cultivars. The activity of endopeptidase was most inhibited by PMSF, a serine-proteinase inhibitor, and fewer by pepstatin, an aspartic-proteinase inhibitor and IA, a thiol-proteinase inhibitor in both cultivars. The activity of endopeptidase was slightly inhibited by EDTA, a metallo-proteinase inhibitor only in 'Samantha'.2) The total activity and specific activity of endopeptidase in petals of both cultivars, which showed unstable increases in early and full opening stages of flowers, increased sharply when the flowers were to be wilting. However, the activities of endopeptidase in 'Samantha' were almost 2 times that of '^Cardinal'. Soluble protein content in petals was generally lower in 'Samantha' than in 'KardinaF, but was higher in 'Samantha' when senescing.3) The pH optimum for endopeptidases in petals of both cultivars was not changed by treatment of ethylene and 1-MCP, but the endoproteolytic activity at pHIO was dramatically promoted by ethylene teatment. No significant effect on endoproteolytic activity was found at pHIO in 'Samantha' when treated with 1-MCP, but a momentary increase was obtained in 'KardinaP.The results above suggested that serine-proteinase might be the most important kind of endopeptidase in petals of both cultivars during flower opening and senescence, but different kinds of endopeptidases existed in petals of two cultivars. The changes of endoproteolytic activity in petals of both cultivars were probably related to flower senescence. Ethylene treatment had different effect on the opening and senescing process in 'Samantha' and 'KardinaP, which was related to its different effect on the activity of endopeptidases in both cultivars.