Soluble sugars

Total soluble sugar content was determined at heading stage in the 2016–2017 season by anthrone sulfuric acid extraction according to the method in [20]. An anthrone reagent was prepared with 0.2 g anthrone, 8 mL absolute ethyl alcohol, 30 mL distilled water and 100 mL sulfuric acid. A total of 100 mg dry weight powder of the flag leaf was boiled for 1 h, cooled, and filtrated, after which 0.5 mL of the extract was mixed with 4.5 mL of the anthrone reagent. The absorbance was measured at 625 nm using glucose as a standard, and the results were expressed by μM g⁻¹ dry matter.