Effects of different lights on seed germination, seedling growth and HY5 gene expression of three pine species

In order to explore the regulatory mechanism of different light quality on seed germination and seedling growth of pine trees, the main afforestation trees of barren mountains at different altitudes in Yunnan, namely Pinus kesiya var. Langbianensis, Pinus yunnanensis and Pinus densata Mast., were selected as the research objects. The relevant parameters of three pine trees, seed germination, seedling growth and biomass accumulation were determined by using RL, BL and WL (CK) as the light sources. Furthermore, the relationship between hypocotyl elongation and HY5 expression was analyzed. The results showed that RL can promote the seed germination (germination rate, germination potential, average germination time and germination index) and seedling growth (seedling height) of three pine trees, which increased by 23.70% and 14.02% for P. kesiya, 11% and 11.61% for P. yunnanensis, 9.37% and 11.35% for P. densata, respectively. However, the chlorophyll content of needles in three pine seedlings (P. kesiya, P. yunnanensis and P. densata decreased by 15.30% and 8.78%, respectively) was reduced under the RL, and RL had no significant effects on biomass accumulation. The chlorophyll content and biomass accumulation of three pine seedlings were increased under BL, which increased by 3.27%, 11.72% and 2.28% in P. kesiya, P. yunnanensis and P. densata, respectively. On the other hand, it inhibited the seed germination and seedling growth of P. yunnanensis and P. densata, but promoted the growth of P. kesiya. The hypocotyl elongation was negatively correlated with HY5 expression in three pine seedlings under RL and BL light. The seed germination and seedling growth of P. kesiya showed RL > BL > WL under different light quality, while that of P. yunnanensis and P. densata showed RL > WL > BL.