In order to understand the physiological and biochemical reasons of leafcolor transformation in Loropetalum chinense var. rubrum,three types of L. chinense var. rubrum, Zihei (black purple), Zihong(red purple)and Hongzhe(red_ochre), and L. chinense were taken as materials. The contents of chlorophyll, carotenoid and soluble sugar, and activity of phenylalanine ammonialyase (PLA) in the leaves were measured from early March to June. The results showed that the contents of chlorophyll, carotenoid and soluble sugar increased gradually during the leafcolor changing from red to green, but there were obviously differences among types of Zihei, Zihong and Hongzhe. Anthocyanins contents in Zihe and Zihong leaves maintained high level, so their leaves still kept red when they got mature in early June. Phenylalanine ammonialyase (PLA) activity decreased, and had positive relationship with anthocyanin contents. Some measures such as shading or watering to lower air temperature could be taken to maintain leaves of L. chinense var. rubrum fresh red during summer.
