Effects Of Different Nitrogen Forms On Growth And Camptothecin Content Of Camptotheca Acuminata

Camptotheca acuminata Decne with the anticancer substance Camptothecin in the leaves.is a unique tree species in China.In this paper,the two-year-old Camptotheca acuminata seedlings were used as experimental materials,and the pure ammonium sulfate??NH₄?₂SO₄?and potassium nitrate?KNO₃?were used as the nitrogen fertilizer for fertilization.The control?CK?,ammonium nitrogen?NH₄⁺-N?and nitrate were set.The effects of camptotheca seedlings growth.chlorophyll content,chlorophyll fluorescence parameters,camptothecin content,TSB and TDC enzyme activities,and expression of camptothecin-related genes were mainly studied.?1?Compared with CK,different NH₄⁺-N and NO₃^--N treatment levels significantly promoted the growth of seedling height,ground diameter,leaf length and leaf area of Camptotheca acuminata?P<0.05?,NH7.5 and NO7.5 was significantly higher than that of other similar treatments.Appropriate addition of NH₄⁺-N in NO₃^--N is beneficial to the growth of Camptotheca acuminata.When the ratio of T2?NH₄⁺-N and NO₃^--N is 30:70?,seedling height,ground diameter,leaf length and leaf area was the largest.Under the single NH₄⁺-N and NO₃^--N fertilization treatment,the growth was decreased.?2?Under different levels of NH₄⁺-N and NO₃^--N treatment,the chlorophyll content and photosynthetic characteristics of the leaves were significantly increased,and the chlorophyll content,F_v/F_m,F_v'/F_m',?PSII and qP of NH7.5 and NO7.5 were significant.Compared with the rest of the treatment?P<0.05?,the chlorophyll content and light and characteristics decreased significantly when the nitrogen content was continuously increased?P<0.05?,and the leaves of Camptotheca acuminata were significantly inhibited by light.The addition of NH₄⁺-N and NO₃^--N could promote the synthesis of chlorophyll,but the difference of chlorophyll content and chlorophyll fluorescence between different NH₄⁺-N and NO₃^--N treatments was not significant?P>0.05?,T2?NH₄⁺-N:NO₃^--N is 30:70?,which is most beneficial to the chlorophyll synthesis in the leaves of Camptotheca acuminata.?3?Appropriate low nitrogen stress could effectively promote the synthesis of camptothecin.The results of this experiment showed that the content of camptothecin of NH2.5 and NO2.5 is significantly higher than that of the other treatments on the 30th day of treatment?P<0.05?..The content of camptothecin reached the maximum on the 30th day with different NH₄⁺-N:NO₃^--N treatment,and the content of camptothecin was the highest in T2?NH₄⁺-N:NO₃^--N is 30:70?.The synthesis and accumulation of lower camptothecin decreased significantly?P<0.05?.?4?Under different NH₄⁺-N and NO₃^--N treatment levels,the difference of TSB activity was not significant?P>0.05?,reached the maximum on the 30th day,and then decreased significantly after stabilization.NH2.5 and NO2.5 was higher than the rest of the treatment.The TDC activity was significantly different?P<0.05?.NH2.5 and NO2.5 treatment was significantly higher than that of other similar treatments,and the TDC activity decreased with the decrease of NH₄⁺-N and NO₃^--N treatment levels.There was no significant difference in TSB activity between different NH₄⁺-N:NO₃^--N treatments?P>0.05?,TDC activity was significantly different?P<0.05?,and T2?NH₄⁺-N:NO₃^--N was 30:70?TSB and TDC activity is higher than the rest of the treatment.?5?Under the treatment levels of NH₄⁺-N and NO₃^--N,the expression levels of CaTSB and CaTDC1 reached the maximum at the 30th,and then decreased significantly.The expression of CaTSB and CaTDC1under the treatment of NH2.5 and NO2.5was significant.Compared with the other similar treatment levels,the expression level of CaTDC2 was lower than that of CaTDC1,but higher than that of CK treatment.The expression of CaTSB and CaTDC1 reached the maximum at the 30th day after different NH₄⁺-N:NO₃^--N treatment,and the expression of CaTSB and CaTDC1under the treatment of T2 was significantly higher than that of the same treatment.CaTDC2 reached the maximum at the 105th day.In summary,the two-year-old camptotheca acuminata;of NH7.5,NO7.5 and T2,growed the best.NH2.5,NO2.5 and T2 treatments are most conducive to the accumulation of camptothecin,and the suitable NH₄⁺-N stress could promote the synthesis of camptothecin,At 30 days,and obtain the highest camptothecin content.