Effects of red plastic films and fluorescent light (as control) on the contents of chlorophyll,alkaloids and the expression of biosynthesis pathway genes in the leaves of Catharanthus roseus aseptic seedlings were studied.The results showed that chlorophyll content in leaves was higher under red films than that under fluorescent light on the first 30 d,and the chlorophyll content under red films decreased significantly after 3 d (P<0.05).The ratio of chlorophyll a/b was lower than control.The content of vindoline (VIN) and catharanthine (CAT) firstly increased a little and then decreased compared with control.The content of vinblastine (VBL),as a coupling product of VIN and CAT increased gradually and reached the highest on the 15th day (0.028 0±0.005 1) mg/g in shade culture.The plastic films induced the high expression of alkaloids biosynthesis pathway genes (Tdc,Str,Dat and D4h).The results indicated that plants under shade treatment with red films were positively regulated by physiological metabolisms.