Effect of Nitrogen and Potassium Fertilizer on Photosynthetic Characteristics of Different Varieties Lettuce

The effect of nitrogen and potassium fertilizer on photosynthetic characteristics of different varieties lettuce was studied in pot experiment.The results indicated that the photosynthetic rate(Pn) of lettuces was increased by adding nitrogen fertilizer and it was also increased with the intensity of light.The higher Pn was observed in Dabaijia and Guasihong,and the lowest was in Doubletip.There was little effect of nitrogen and potassium fertilizer on photosynthetic characteristics of Doubletip.The higher photosynthetic characteristic of Guasihong was obtained in N15K15,N20K10 and N20K10 treatments under lower,middle and higher intensity of light,respectively,but for Dabaijia the higher positive photosynthetic characteristic was in N20K10,N15K15,N15K15 under three light intensities.N20K10+C treatment increased Pn,Gs(Stomatal conductance),Ci(Internal CO2 concentration) and Tr(Transpiration rate) in Dabaijia under lower and higher intensity of light,but under middle light intensity the effect was little on the four factors.The effect of nitrogen and potassium fertilizer on photosynthetic characteristics of lettuce under different light intensity was different with the varieties of lettuce.