Phosphorus Utilization Mechanism Of Phyllostachys Edulis In Response To Different Phosphorus Status Under Simulated Nitrogen Deposition

Soil phosphorus（P）environment plays an important role in plant growth.But in recent years,plants have been also facing the aggravation of atmospheric nitrogen（N）deposition.It is of great significance to explore the response of plants to N deposition under different P conditions.We selected Phyllostachys edulis（P.edulis）seedlings as materials and N&P as change factors in this experiment.Three N levels [N: 0（No N）,30（Low N）,60（High N）Kg N·hm^-1·a^-1] and three P levels [P: 2.99（Low P）,20（Suitable P）,40（High P）mg·Kg^-1] were set respectively to carry out a one-year pot controlled experiment for studying the effects of simulated N deposition on seedling growth and mechanism of P utilization at different P status.The results showed that:1)Stem height,ground diameter,leaf area and total biomass of seedlings were all significantly reduced in P deficiency while root-shoot ratio was significantly increased by 1.40 times.Most of growth characteristics in high P environment were not significantly different from that in suitable P.After simulated N deposition,most growth traits were promoted under three P conditions and the positive effect of high N was stronger.New tissue received a more obvious promotion than that of old tissue.What’s more,simulated N deposition accelerated the withering of old leaves on old branchs of seedling in low P.2)The total P acquisition efficiency（PAE）of seedlings in low P was significantly reduced by 70.8% compared with that of suitable P and the P accumulation of each part was also significantly decreased.The P reabsorption efficiency（PRE）of new stem and new leaf were significantly decreased by 60.2% and 26.9% respectively.On the contrary,the P utilization efficiency（PUE）was significantly increased by 1.34 times.The P loss rate（PL）was significantly increased by 54.9%.With simulated N deposition,PAE and PUE in three P environments were significantly increased and high N had a stronger effect.The PL was significantly increased by 54.9% and 26.3% in low P respectively resulting from low N and high N.3)The acid phosphatase（APase）activity of root and new leaf,stimulating by low P stress was significantly increased while it in soil with high P significantly decreased 34.4% compared with that of suitable P.Simulated N deposition further increased soil APase activity in low P,but inhibited it in new leaf.4)The content of inorganic P and ester P of new leaf in P limitation were both significantly decreased.The Ca_2^-P and Al-P concentration in low P soil were significantly decreased by 77.4% and 60.4%,respectively.However,Ca_2^-P and Ca_10^-P content were both significantly increased under high P.N inputs resulted in a decrease of inorganic P concentration in three P status.A significant raise of ester P and a significant depression of nucleic P were found in low P.Ca_2^-P and Al-P in low P group were significantly increased by influence of simulated N deposition.5)Through high-throughput sequencing on total RNA in roots of low P treatment and low P with high N,2766 up-regulated（low P with high N/low P）genes and 1483 down-regulated genes were screened.Besides,14 genes selected from the functional enrichment of up-regulated genes were found to be significantly correlated with positive regulation of cellular response to P starvation.In general,our results suggested that short-term simulated N deposition had a compensatory effect on the growth of P.edulis seedlings under low P stress.From the outside,seedlings could accelerate the withering of old leaves from old branches and improve the APase activity to activate P in soil.From the inside,the PUE were increased,and the distribution proportion of inorganic P,ester P and nucleic P in the new leaves were optimized.The expression of 14 genes related to cellar P starvation was up-regulated to maximize the acquisition and utilization of P.Also,N inputs had a positive effect on the absorption of excessive P in P.edulis seedlings in high P environment.