The
enzymes that metabolize sucrose translocated from leaves
to
sink tissues are sucrose synthase (EC 2.4.1.13) and acid invertase
(-fructofuranosidase,
EC 3.2.1.26), which are present in vacuoles
(soluble
form) and cell walls (insoluble form) in many higher plants.
Cell
wall acid invertase plays a role of converting sucrose into hexoses
after sucrose is translocated from the phloem to the apoplast
(
Roitsch
and Gonzalez-Garcia, 2004), and this enables petals to take
up
more sucrose from the phloem. Vacuolar invertase also plays
an
important role in biological function associated with sucrose metabolism. It presumably hydrolyzes sucrose to supply hexoses
necessary
for cell growth and development (Tymowska and Kreis,
1998;
Tang et al., 1999).