Influences of storage temperatures (4 and 20C) on weight loss and carotenoids and glucosinolates (GSs) contents in pakchoi leaves were investigated. The weight loss was prevented by low temperature. At 9 days of storage, the contents of chlorophylls, β‐carotene, lutein and GSs at 20C decreased to 52, 48, 26 and 47%, respectively, compared to those at 4C. At 4C, the total GS content was not significantly changed during 3 days, however increased at 5 and 7 days and returned to the beginning level at 9 days. At 20C, total GS was increased at 3 days, and then decreased gradually. The change trend of aliphatic GS was similar to that of total GS. The indolyl and aromatic GS was not significantly affected by storage temperature. The gluconapin, glucobrassicanapin and 4‐methoxyglucobrassicin contents were increased and then decreased with the time; however, the decrease processes were delayed by low temperature. PRACTICAL APPLICATIONS Pakchoi is a traditional vegetable in China and belongs to the cruciferous family which is considered to protect human against the risk of cancer, and provides benefits from numerous nutrient and phytochemical compounds with anticancer activity, such as carotenoids and glucosinolates. The contents of carotenoids and GSs might be lost due to unsuitable storage conditions before consumption, and temperature is a critical factor in vegetable storage. Hence, it is necessary to investigate the influence of temperatures on phytochemicals as well as visual quality to provide some suggestions for pakchoi storage. Our results imply that low temperature was beneficial to reduce the loss of β‐carotene, lutein and chlorophylls, maintained the visual quality and total GSs content or even slightly increased the contents of glucoalyssin, gluconapin, glucobrassicanapin and 4‐methoxyglucobrassicin at the end of experiment. We suggest that pakchoi should be packed with polyethylene bag and stored at low temperature, especially for longer time storage.

CYP83A1 and CYP83B1 are two key synthesis genes in the glucosinolate biosynthesis pathway. CYP83A1 mainly metabolizes the aliphatic oximes to form aliphatic glucosinolate and CYP83B1 mostly catalyzes aromatic oximes to synthesis corresponding substrates for aromatic and indolic glucosinolates. In this study, two CYP83A1 genes named BcCYP83A1-1 (JQ289997), BcCYP83A1-2 (JQ289996) respectively and one CYP83B1 (BcCYP83B1, HM347235) gene were cloned from the leaves of pak choi (Brassica rapa L. ssp. chinensis var. communis (N. Tsen & S.H. Lee) Hanelt) “Hangzhou You Dong Er” cultivar. Their ORFs were 1506, 1509 and 1500 bp in length, encoding 501, 502 and 499 amino acids, respectively. The predicted amino acid sequences of CYP83A1-1, CYP83A1-2 and CYP83B1 shared high sequence identity of 87.65, 86.48 and 95.59% to the corresponding ones in Arabidopsis, and 98.80, 98.61 and 98.80% to the corresponding ones in Brassica pekinensis (Chinese cabbage), respectively. Quantitative real-time PCR analysis indicated that both CYP83A1 and CYP83B1 expressed in roots, leaves and petioles of pak choi, while the transcript abundances of CYP83A1 were higher in leaves than in petioles and roots, whereas CYP83B1 showed higher abundances in roots. The expression levels of glucosinolate biosynthetic genes were consistent with the glucosinolate profile accumulation in shoots of seven cultivars and three organs. The isolation and characterization of the glucosinolate synthesis genes in pak choi would promote the way for further development of agronomic traits via genetic engineering.