Effects of different phosphorus levels on tiller bud development in hydroponic Phyllostachys edulis seedlings.

An appropriate amount of phosphate fertilizer can improve the germination rate of bamboo buds and increase the bamboo shoot output. However, the underlying biological mechanisms of phosphate fertilizer in bamboo shoot development have not been systematically reported. Herein, the effects of low (LP, 1 μM), normal (NP, 50 μM) and high (HP, 1000 μM) phosphorus on the growth and development of Phyllostachys edulis tiller buds were first investigated. Phenotypically, the seedling biomass, average number of tiller buds, and bud height growth rate under the LP and HP treatments were significantly lower than those under the NP treatment. Next, the microstructure difference of tiller buds in the late development stage (S4) at three P levels was analyzed. The number of internode cells and vascular bundles were significantly lower in the LP treatments than in the NP treatments. The relative expression levels of 8 phosphorus transport genes, 8 hormone-related genes and 4 bud development genes at the tiller bud developmental stage (S2 ~ S4) and the tiller bud re-tillering stage were analyzed with RT-qPCR. The results showed that the expression trends for most phosphorus transport genes, hormone-related genes and bud development genes from S2 ~ S4 were diversified at different phosphorus levels, and the expression levels were also different at different phosphorus levels. In the tiller bud re-tillering stage, the expression levels of 7 phosphorus transport genes and 6 hormone-related genes showed a downward trend with increasing P level. REV expression level decreased under LP and HP conditions. TB1 expression level increased under HP condition. Therefore, we conclude that P deficiency inhibits tiller bud development and re-tillering, and that P depends on the expression of REV and TB1 genes and IAA, CTK, and SL synthesis and transporter genes to mediate tiller bud development and re-tillering.