2.8. Carbohydrate analysis
Sucrose was measured using a Waters 600E high-performance
liquid chromatograph (Millipore, UK) [28]. A carbohydrate column
and a 2410 refractive index monitor were used. The mobile phase
used was 75% acetonitrile and ultra water (75:25). The mobile rate
and temperature of the column were set at 1.0 mL min−1 and 35 ◦C,
respectively. Water Millennium software (Millipore, UK) was used
to manage the data.
2.9. Antioxidant enzyme activity and antioxidant determination
2.9.1. Antioxidant enzyme activity determination
Each 0.5 g of leaf material was homogenized in 3 mL 25 mM
HEPES buffer (pH 7.8) containing 0.2 mM EDTA and 2% (w/v) PVP.
The homogenate was centrifuged for 20 min at 12,000
×
g, and the
supernatant was used for enzyme analysis. All operations were
performed at a temperature range of 0–4 ◦C.