Abstract: Anthocyanin，a water soluble compound is thought to be responsible for the coloration of outer scales of purple garlic. The changes in anthocyanin content in relation to enzymatic activities of phenylalanine ammonia-lyase（PAL），chalcone isomerase（CHI），and dihydroflavonol reductase（DFR）were studied in the outer scales of purple garlic‘G075’. The relationships between anthocyanin biosynthesis and environmental conditions（temperature，pH of substrate，supplement of nitrogen and phosphorus）were established. The results show that among these enzymes，the activity of CHI is positively correlated to anthocyanin content in significant level and further postulated as key limiting factor to regulate anthocyanin synthesis in the outer scales of purple garlic. The fluctuation of the CHI activity and anthocyanin content is consistent with that of the environmental conditions. These results obviously demonstrate the environmental conditions play a major role in regulating the enzyme activities of anthocyanin biosynthesis. Cool temperature in open field，acidic medium（pH 6.5），low nitrogen level（1/2 N：7.5 mmol · L^-1）and optimum phosphorus levels（P：1 mmol · L^-1）are favorable for anthocyanin synthesis in the outer scales of purple garlic.

Key words: purple garlic, outer scales, anthocyanin, activities of related enzymes, environment condition