Berry culture and 13C stable isotope tracer experiment
At veraison, softened green berries (V. vinifera L. cv. Cabernet
Sauvignon) were excised from the rachis, and sterilized with a dilute
solution of sodium hypochlorite (1%), then with ethanol (70%), and
finally rinsed twice with deionized water. The sterilized berries were
cut around the peduncle and aseptically incubated on filter paper in
a Petri dish. A 4.5 ml filter-sterilized aqueous [13C]phenylalanine
solution (0.3 M sucrose, 1 mM L-[1-13C]phenylalanine) was applied
to the berries, and the berries were then incubated at 25 C under
fluorescent light at approximately 40 lmol m2 s1. After 1 week
of culture, the berries were placed on a new Petri dish containing
a 0.3 M sucrose solution. Thereafter, the berries were cultured
without phenylalanine at 15, 25, and 35 C under fluorescent light
at approximately 40 lmol m2 s1. After 0, 2, 5, and 7 d of
temperature treatment, the berries from each dish were collected. As
stated above, the berries were peeled, frozen immediately in liquid
nitrogen and stored at 80 C until use. Experiments were
triplicated, with each replicate consisting of six or seven berries
in a Petri dish.