Assay of a-amylase
Activity of a-amylase was estimated following the method
described by Bernfeld (1955). One gram of germinating seed was
ground in 10 mL of 0.1 M acetate buffer, pH 4.75, homogenized
for 30 min, and centrifuged at 10,000 rpm for 10 min at 4 C. The
supernatant was used for the enzyme assay. Enzyme extract
(0.25 mL) was taken and diluted to 1 mL. One milliliter of a 0.01%
(w/v) starch solution was added and incubated for 60 min at
37 C. Two milliliters of DNS reagent (1% dinitrosalicylic acid dissolved
in 0.2 M NaOH and 30% sodium potassium tartrate) were
added and kept in a boiling water bath for 5 min. After cooling in
water, absorbance was measured at 540 nm. For the controls,
1 mL double-distilled water was used in place of the enzyme
extract. A standard graph was prepared using glucose, and the
amount of amylase present in the samples was calculated from
the standard curve and expressed as mg glucose/g fresh weight.
All measurements were conducted in triplicate.