2.7. Determination of chlorophyll and carotenoid
Chlorophyll(Chl) were extracted fromthemature leaves of eight
plantlets within each treatment. A total of 20 mg lettuce samples
(shoot FW) were groundinamortar. The ground were washedusing
80% acetone and subsequently filtered, the residues were washed
again with 80% acetone and re-filtered until the leaf turned white.
Both filtrates were mixed, and distilled water was added to a total
volume of 10 mL. The optical density of the extract was measured
with a UV-1200 spectrophotometer (MAPADA, Shanghai, China) at
663 nm (OD 663) for chlorophyll a (Chl a), 645 nm (OD 645) for
chlorophyll b (Chl b), and 470 nm (OD 470) for carotenoid (Car).
Concentrations of the chlorophyll and carotenoid were determined
using the following equations (Lichtenthaler and Wellburn, 1983):