Abstract: In order to provide a scientific basis for rational application of nitrogen fertilizer,the effects of different forms of nitrogen on photosynthetic capacity of millet seedlings were studied. The experiment studied the application of nitrate nitrogen(NO₃^--N),ammonium nitrogen(NH₄⁺-N) and ammonium nitrate(NH₄NO₃) on the growth and PSⅡ photosynthetic characteristics in leaf of the millet seedlings under low nitrogen conditions. The results showed that the application of different forms of nitrogen significantly promoted the growth of millet seedlings. Under the treatment of NO₃^--N and NH₄NO₃,the PSⅡ reaction center activity,electron transfer efficiency and photosynthetic capacity of millet seedlings were significantly higher than NH₄⁺-N,and NH₄NO₃ only slightly less than NO₃^--N. Under NH₄⁺-N treatment,parameters including Fm,Fv/Fm,Fv/Fo,PI_total and PI_ABS in leaves of millet seedlings were significantly lower than NO₃^--N and NH₄NO₃,and had no obvious difference comparing with the CK,namely the application of single NH₄⁺-N failed to improve the PSⅡ performance of millet seedlings under low nitrogen stress. Under NO₃^--N and NH₄NO₃ treatment,V_J,V_I and V_K were lower than CK in different extent,but there was no difference in NH₄⁺-N and CK which indicated that NO₃^--N and NH₄NO₃ treatment promoted the OEC activity of PSⅡ electronic donor side and the ability of transmitting electron of PSⅡ receptor side of millet seedlings. There was no significant difference between V_L under different treatments,indicating that the thylakoid structure of millet seedling leaves were not sensitive to low nitrogen. Based on these results,NO₃^--N should be mainly used for millet nitrogen fertilizer application in low nitrogen area,or used the combined application of NO₃^--N and NH₄⁺-N to avoid the application of single NH₄⁺-N.

Key words: Millet, Nitrogen form, Chlorophyll fluorescence characteristics, PSⅡ

CLC Number: 

• S143.1

• Q945.79