Abstract: Under greenhouse condition,this paper studied the effects of different concentrations CO₂ to the growth of oriental yellow poly-bud cut lily and to the two allelochemicals in lily leaves.The results showed that the optimum CO₂ concentration for Pn was 600 μmol·mol^-1.There was less impact on photosynthesis when continually supplying 600～1 000 μmol·mol^-1 CO₂ for 45 days,probably due to the photosynthesis adaptability of new bulblets.600 μmol·mol^-1 CO₂ could increase the stem height about 0.57 grades,and also had a positive effect on the growth of color bud.600 μmol·mol^-1 and 800 μmol·mol^-1 CO₂ could markedly increase the contents of polyphenols and flavonoids in lily leaves,and there was no plant leaves withered,because the appropriate concentrations CO₂ was beneficial to the Pn and to the formation and transformation of carbohydrates and allelochemicals,which increased the premunition of the plant.The contents of polyphenols and flavonoids in lily leaves reached the maximum when the concentration of CO₂ was 600 μmol·mol^-1.

Key words: CO₂, Greenhouse, Lily, Allelochemical