Effects of auxin and methyl jasmonate on cut rose petal growth through activation of acid invertase

Petal growth associated with flower opening depends on cell expansion caused by water influx. To understand the mechanism of flower opening and to develop a method for improving cut flower quality, we investigated the changes in the amount of soluble carbohydrates and invertase activities in rose (Rosa ‘Meivildo’) petals using attached and cut flowers, and the effects of α-napthylacetic acid (NAA) and methyl jasmonate (MeJA) on cut flowers. Cut rose flowers were harvested at the tight bud stage (TB), or mature bud stage (MB), which is the commercial harvest stage, and 2 days after TB. Cut flowers were immediately treated with deionized water or 1% (w/v) glucose. Fresh weight (FW) and the levels of soluble carbohydrates in petals in cut flowers were lower under postharvest conditions than those of attached flowers during flower opening. Although invertase activities in petals of attached flowers increased drastically during TB and MB, those in the petals harvested at TB did not increase under postharvest conditions. These results suggested that sucrose metabolism, including invertase activity, could be an important factor in cut rose flower opening to a greater extent after harvest. In addition, we tried to control flower opening by affecting invertase activities in petals of cut rose flowers. Cut flowers treated with NAA opened faster and those treated with MeJA opened later than in controls. Levels of soluble carbohydrates and invertase activity in petals were also changed by these treatments. In flowers treated with NAA, activities of both vacuolar and cell wall invertases increased 1 day after treatment and then decreased through to the end of the treatment, although activities in control flowers never increased after harvested. By contrast, cell wall invertase activity in MeJA treated flowers increased 1 day later than with the NAA treatment and remained at a relatively high level until 4 days after treatment compared to the controls. Our results suggest that inducing invertase activity in postharvest conditions may important for the quality of cut roses.