The Effect of Chlorophyll Concentration of Paddy Rice on the Fluorescence Spectrum

In order to enhance the monitoring of paddy growth, utilize the fertilizer more efficiently, increase crop yield and improve the quality of grain, thus the system of laser-induced fluorescence (LIF) was built. The system was designed to study the relationship between the rice leaf chlorophyll content and fluorescence ratio. In this paper, the samples came from the second upper leaves of paddy in shooting stage and the cultivated area was located in Jianghan plain of China. Firstly, the Kjeldahl method combined with the formula which was described by Zivcak et al. was utilized to calculate the chlorophyll content of paddy, then the fluorescence spectrum of paddy leaf with different chlorophyll content by the instrument of laser-induced fluorescence (the wavelength of excitation 355 nm). Fluorescence spectra of paddy leaf with different chlorophyll content were collected and then a fluorescence spectra database was established. It is discussed that the relationship between the ratio of fluorescence (F740/F685 is the ratio of fluorescence intensity of 740 nm dividing that by 685 nm) and the chlorophyll content of paddy. It is found that the effect of chlorophyll content on the fluorescence spectral characteristics is evident. The results demonstrated that it has the tightly positive correlation between the fluorescence ratio (F740/F685) and chlorophyll content of paddy leaf. The determination coefficient (R2) can reach up to 0.901 3 and 0.912 5 at tillering stage and shooting stage, respectively. The experimental analysis showed that the LIF technology has the advantages of convenient, quick and nondestructive, and it has the potential for quantitative monitoring of crop growth.