Abstract: Based on the long-term nutrient balance experiment conducted in Yucheng Comprehensive Exp. Sta-tion of CAS,the effects of nitrogen,phosphorus and potassium on the photosynthetic characteristics of summer maize were investigated respectively in this study. Four treatments,namely NP,NK,PK and NPK used as comparison,are selected. In order to study the photosynthetic characteristics of summer maize in the long -term nutrient deficiency conditions,the chlorophyll fluorescence parameter,photosynthetic rate,light response curve and CO₂ response curve of summer maize leaves are measured. The results showed that phosphorus deficiency and potassium deficiency would lead to the increase of initial fluorescence ( Fo). Phosphorus deficiency and nitrogen deficiency would lead to the decrease of the maximal photochemical efficiency ( Fv/Fm) and actual photochemical efficiency (Φ_PSⅡ) and elec-trons transfer efficiency ( ETR),while the lack of potassium alone had no significant effect on the above indicators. Compared with the photosynthetic rate under the conditions of an adequate supply of NPK,the deficiency of potassi-um has not reduce the photosynthetic rate significantly,while the deficiency of nitrogen and phosphorus has lead to an significant decrease of the photosynthetic rate,especially phosphorus deficiency conditions the photosynthetic rate has decreased by 32.86%.The variation of photosynthetic rate follows the same trend of Φ_PSⅡ and ETR variation. The results of statistical analysis showed that there is significant linear correlation relationship between photosynthet -ic rate and Φ_PSⅡ and ETR.The correlation coefficients are as high as 0.986 and 0.988,respectively.By analyzing the light response curve and CO₂ response curve,it is concluded that the impact of nitrogen deficiency on the maxi-mal photosynthetic rate,saturation light intensity and saturation CO₂ concentration is more significant than the im-pact of phosphorus deficiency.

Key words: Summer corn, Nutrition deficiency, Chlorophyll fluorescence, Photosynthesis rate

CLC Number: 

• S513