Bc1180

The contents of sucrose, fructose, and starch were determined by anthrone colorimetry [65 (link)] with minor modifications. Glucose, GSH, and GSSG contents were measured using a biochemical reagent kit (Cat#BC2500, Cat#BC1175, and Cat#BC1180, respectively; Beijing Solarbio Science & Technology Co. Ltd, Beijing, China). MeJA was determined by enzyme-linked immunosorbent assay.

One gram of homogenized cucumber fruit was mixed with 15 mL of pre-cooled 5% (w/v) trichloroacetic acid and centrifuged at 12,000 rpm for 20 min at 4°C. The supernatant was collected and AsA and DHA content (mg kg^-1) was determined as previously described (Zhang et al., 2021 (link)). DHA content was calculated as follows:
GSH and GSSG contents (mg kg^-1) were detected using the appropriate test kits (BC1170 for GSH content; BC1180 for GSSG content; Solarbio, Beijing, China) with absorbance measured at 412 nm.

A commercial kit (BC1230, Solarbio) was applied to determine AsA content based on the oxidation rate of AsA catalyzed by AAO (ascorbic acid oxidase) (spectrophotometric measurement at OD_{265 nm}). A commercial kit (BC1240, Solarbio) was applied to determine DHA content based on the production rate of AsA from DHA by DTT (1,4-dithiothreitol) (spectrophotometric measurement at OD_{265 nm}). A commercial kit (BC1170, Solarbio) was applied to determine GSH content based on spectrophotometric measurement of the product from the reaction between GSH and DTNB (5,5’-dithiobis-2-nitrobenoic acid) (OD_{265 nm}). A commercial kit (BC1180, Solarbio) was applied to determine GSSG content based on the production rate of GSH (measurement of OD_{265 nm} for the reaction between GSH and DTNB) from GSSG catalyzed by GR (GSH reductase). A commercial kit (BC0290, Solarbio) was applied to determine proline content based on spectrophotometric measurement of the product from the reaction between proline and ninhydrin (OD_{520 nm}). A commercial kit (BC0035, Solarbio) was applied to determine plant soluble sugar content based on anthrone colorimetric method (OD_{620 nm}). A commercial kit (BC0700, Solarbio) was applied to determine starch content based on the separation of starch with 80% ethanol and acid hydrolyzation to glucose, followed by anthrone colorimetric method (OD_{620 nm}) (Chen et al., 2020b (link)).