DELAY OF SWEET OSMANTHUS FLOWER SENESCENCE BY PROTEASE INHIBITORS AND PLANT GROWTH REGULATORS

Abstract

Sweet osmanthus (Osmanthus fragrans Lour.), is a well known ornamental plant native to East Asia for its unique scent. However, the short flowering span restricts its ornamental and economic values. Visible senescence of petals was preceded by a significant increase in petal protease activity. The vase life, contents of free amino acids and soluble proteins and protease activity of sweet osmanthus petals were evaluated by treating with protease inhibitors/activators, 6-BA and ABA. The results showed that the protein degradation and petal protease activity were partly inhibited by treatments of metalloprotease inhibitors EGTA (10 mM) and cysteine protease inhibitors ZnCl2 (1 mM), and the vase life was also prolonged 22 and 12 hours respectively. On the other hand, the treatments of proteases activators dithiothreitol (2 mM) and MgSO4 (2 mM) had an opposite effect of EGTA and ZnCl2. The treatments of 6-BA (1 mg/L) inhibited petal protease activity and prolonged the vase life of sweet osmanthus about 10 hours. The treatment of ABA (5 mg/L) shortened the vase life about 10 hours. The level of free amino acids in plants treated with 6-BA (1 mg/L) was lower than that with ABA (5 mg/L), whereas the content of soluble proteins with the treatment of 6-BA (1 mg/L) was higher than that with ABA (5 mg/L). The present study demonstrated significant delay of petal senescence when petal protease activity was inhibited, which could be applied for improving ornamental and economic value of sweet osmanthus practically.