The close to impossible correct controlling of the temperature and light intensity is the main limiting factors of growing plants in the plastic covered greenhouses. Quality and vase life of cut flowers are mostly influenced by greenhouse temperature. Alstroemeria needs cold temperature for growth and flowering. In the current study, the such changes in vase life and flower quality as stem length, the number of flowers per inflorescence, and flower pigmentation in relation with anthocyanin concentration and Phenylalanine ammonia lyase (PAL) activity was investigated for three Alstroemeria cultivars namely: ‘Bordeaux’ , ‘Sukari’, and ‘Modena’ during the growing season in summer and autumn in plastic greenhouses.The results indicated that increase in temperature during summer resulted in declining flower quality and vase life, in contrast, cold temperature in late summer and early autumn enhances biosynthesis of anthocyanin and flower pigmentation. There were significant differences observed between Alstroemeria cultivars as regards high temperature during the summer season. In this study, high temperature induced Phenylalanine ammonia lyase (PAL) activity in petals, making one conclude that Phenylalanine ammonia lyase (PAL) enzyme might not be a key enzyme for biosynthesis of anthocyanin in Alstroemeria flowers. With increase in temperature, the number of flowers were shown to decrease in ‘Bordeaux’ cultivar.