followed the procedure of Anderson et al. (1992) . Mung bean leaves (1 g fresh weight) were homogenized in 3 mL of ice-cold acidic extraction buffer [6% (w/v) meta-phosphoric acid (pH 2.8), containing 1 m m EDTA], using a Polytron homogenizer (model PT
described by Nour et al. (2010) . Chromatographic separation was performed with an HPLC system (1260 Series; Agilent Technologies, Santa Clara, CA), using 50 m m potassium dihydrogen orthophosphate buffer, pH 2.8, as a mobile phase (flow rate of 0.7 mL
ruthenium red for 20 min and observed for red color ( Jensen, 1962 ). A 1% Alcian blue 8GX solution in 3% acetic acid (pH 2.5) was applied to tissue sections for 20 min, rinsed with water, and the sections were examined for blue color under visible radiation
phase of acids was KH 2 PO 4 (18 m m , pH 2.1) and flowed at a rate of 0.8 mL⋅min −1 . Sugar and acid amounts were determined using peak areas with external standards (fructose, glucose, sucrose, tartaric acid, malic acid, and citric acid) and expressed
thawed, placed in cheesecloth, and squeezed to extract the juice from the berries. Titratable acidity and pH were measured by an 877 Titrino Plus (Metrohm AG, Herisau, Switzerland) standardized to pH 2.0, 4.0, 7.0, and 10.0 buffers. Titratable acidity was
monobasic (KH 2 PO 4 , 0.5%, w/v) at pH 2.5 with metaphosphoric acid (HPO 3 , 0.1%, w/v). The retention time of the AA peak was 2.5 min. After comparison of retention time with the AA standard, the peak was identified. The amount of total AA content in
automated titrimeter and electrode standardized to pH 2.0, 4.0, 7.0, and 10.0 buffers. Titratable acidity was determined by titrating 0.1 N sodium hydroxide to 6 g of juice diluted with 50 mL of deionized, degassed water to an endpoint of pH 8.2, with
-H refill cartridge (30 × 4.5 mm) was used for a guard column. Columns were maintained at 65 °C by a temperature control unit. Mobile phase consisted of a pH 2.28 solution of sulfuric acid and water with a resistivity of 18 M obtained from a Millipore Milli
temperature ( WSU AgWeatherNet, 2019 ). During the growing season, the average RH is 80%, while total precipitation is 39 mm per month. The soil is Skagit silt loam, a fine-silty mixed nonacid mesic Typic Fluvaquents, with 6.5 pH, 2.7% organic matter, and is
with the producers reporting research on nutrient solution formulations (mean = 3.1 ± 1.0) and nutrient solution pH (2.8 ± 1.0) being slightly to very beneficial ( Fig. 6 ). Additionally, with the majority of producers surveyed monitoring and