Relationship Between Leaf Nitrogen Content and Fluorescence Parameters in Rice

The fluorescence parameters of the 1st, 2nd, 3rd and 4th leaves from the top of culms in two rice varieties (Huajing 2 and Wuxiangjing 9) were measured with FMS-2 at different growth stages under three nitrogen levels, and the leaf nitrogen contents were correspondingly determined by destructive sampling and chemical assay. The leaf nitrogen contents and fluorescence parameters changed significantly with nitrogen levels, tending to increase with the nitrogen application rates. The fluorescence parameters exhibited a parabolic shape over the growth progress, initially increased until heading and then decreased to the lowest from heading to maturity stages. The distributions of fluorescence parameters on main culm in all treatments were L1L2L3L4 (L1, L2, L3 and L4 mean the 1st, 2nd, 3rd and 4th leaf from the top). For the same variety, leaf nitrogen contents at different leaf positions were significantly correlated to fluorescence parameters, with better performance in Huajing 2 than in Wuxiangjing 9. With combined rice varieties, leaf nitrogen contents at different leaf positions were linearly related to fluorescence parameters ΦPSⅡ and qP. Different regression equations should be used to estimate leaf nitrogen contents at different leaf positions with ΦPSⅡ and qP. The results indicated that fluorescence parameters ΦPSⅡ and qP could be potentially useful for estimating leaf nitrogen content in rice.