Extraction and assay of amylases (only in 2009) Freeze-dried root tissue (50 mg) was suspended in 1.0 ml of extraction buffer [50 mM 4-(2hydroxyethyl)piperazine-1-ethanesulphonic acid-KOH, 5.0 mM MgCl2, 1.0 mM EDTA, and 2.5 mM dithiothreitol; pH 7.5] and kept on ice for 10 min with repeated vortexing.After centrifugation (26,000 g for 15 min at 4ºC) the resulting supernatant was used as the enzyme extract. Total amylolytic activity was determined as described by Steup (1990) and by Bernfeld (1955).Two-fold diluted enzyme extract (50 µl) was mixed with 200 µl of assay buffer (0.1 M 4-morpholine ethanesulphonic acid-KOH, pH 6.2 plus 2 mM CaCl2) containing 1% (w/v) soluble starch (Zulkowsky starch; SIGMA-Aldrich) and incubated for 15 min at 30ºC in a water bath. To determine the extent of hydrolysis of soluble carbohydrates in the enzyme extract,starch was omitted from the assay buffer.The enzyme reaction was stopped by adding 250 µl of alkaline colour reagent,as described by Steup (1990), and the absorbance was measured spectrophotometrically at 546 nm.A calibration curve of maltose was prepared (1 ml samples of which contained 2 mg soluble starch and 0 – 1.5 µmol maltose). Maltose reacted with the alkaline colour reagent and was processed as described above.Total amylase activity was expressed in µmol maltose mg–1 DW min–1.