Abstract:To clarify the effect of different light quality treatment on the growth of polar, transgenic poplar line Pb29 was taken as experimental material, and full red light, full blue light, red and blue light, full white light four treatments were set by use of light emitting diode (LED) to measure the content of Cry1Ac toxic protein, morphological index, photosynthetic pigment content and chlorophyll fluorescence parameters of Pb29 under different light qualities. The results showed that the content of Cry1Ac toxic protein is the highest under the blue light and followed by the white light. Apart from the fact that leaf length/width is the highest under the blue light, the leaf number, leaf length, leaf width, the area of leaf and plant height are the highest under the red and blue light. While the content of chlorophyll b is the highest under the red light treatment, the content of chlorophyll a, chlorophyll a+b, carotenoid and chlorophyll a/b ratio are the highest under the white light treatment and followed by the red and blue light, and no significant difference was observed between white light and red/blue light. The chlorophyll fluorescence parameters (ΦPSⅡ, ETR and qP) are higher than others under the blue light and red/blue light treatments, but the Fv/Fm is greater than others under the white light and red/blue light treatments respectively. While qN is the highest under the red light treatment. Thus it can be seen that different light quality can regulate the growth of the poplar seedlings. The result in this present study will provide a scientific basis for further study on the effect of different light quality on regulating the growth and development of poplar.