The Influence of Nitrogen on the Chlorophyll Fluorescence Parameters of Lettuce

Chlorophyll fluorescence images of lettuce in four nitrogen levels were studied to investigate the influence of nitrogen on fluorescence parameters. The results indicated that, at seedling period, Fo and Fm declined with the increase of the amount of nitrogen fertilizer. Fv/Fm had a downward trend after the first rise with the increase of the amount of nitrogen fertilizer. And the influence of nitrogen on Yield, qp, qN were not obvious. At tillering stage, Fo, Fm were on a same level in every nitrogen level. Yield, qp and ETR decreased with the increase in the amount of nitrogen. At mature stage, in addition to in the severe lack of nitrogen level, Fo and Fm reached the maximum of the whole growth period. In the normal nitrogen amount, Fv/Fm, Yield, ETR, qp were high, but qN was very low.