Photosynthesis in culms of non-foliar organs and effect of light on culm development of Moso bamboo (Phyllostachys edulis)

Photosynthesis of non-foliar organs helps plants improve their survivability. Moso bamboo (Phyllostachys edulis) is well-known for its great green culm, and the effect and mechanism underlying remains largely unclear. Firstly, we found that the culm had photosynthetic capacity, and its correlation with culm development stage in this study, the photosynthetic performance of bamboo shoot (culm with light 20 d) is higher than that of culm-forming bamboo (culm with light 5 a). However, the photosynthetic capacity of culms was much less than the respiratory capacity, photosynthetic products cannot be accumulated. Secondly, light was conducive to the growth of bamboo materials, promoting cell wall thickening and lignin accumulation, and the expression of transcripts of cellulose synthesis (PheCESA4.1, PheCESA4.2) and lignin synthesis (Phe4CL1.1, Phe4CL1.2) genes decreased significantly after shading. Furthermore, light affected the height growth rate of bamboo shoots, which promoted the elongation of developed internodes, and shading inhibited the continual elongation of developed internodes and initiated the elongation of multiple undeveloped internodes. Finally, shading greatly increased the length of undeveloped internode of bamboo shoots and provided a new strategy for the directional cultivation of long internode of bamboo. This study provided new insights into the photosynthetic capacity of non-foliar organs and the effect of light on the growth and development of non-foliar organs, which laid a foundation for further studying the rapid growth and development of Moso bamboo.