Infrared Changes Research Articles

Impact of Vegetation Structure on Drought Indices Based on MODIS Spectrum

The drought indices based on MODIS spectral reflectance data are widely used for drought characterization and monitoring in agricultural context. Based on the PROSAIL model and MODIS observational data in Shandong in 2010, the present paper studied the impact of vegetation structure of leaf area index and physiological growth cycle on MODIS spectral drought index. The results showed that the reflectance of three MODIS bands in spectrum of near-infrared and shortwave infrared changes significantly with leaf water content of vegetation. Therefore, the five kinds of MODIS spectral drought index constructed by those MODIS bands can be used to monitor the leaf water content of vegetation. However, all drought indices are affected by leaf area index. In general, the impact is serious in the case of low LAI values and is weakened with the increase in LAI value. The study found that physiological vegetation growth cycle also affects the magnitude of MODIS spectral drought indices. In conclusion, the impact of vegetation structure must be carefully considered when using MODIS spectral drought indices to monitor drought. The conclusion of this study provides a theoretical basis for remote sensing of drought monitoring.

The antenna system of Rhodospirillum rubrum: Radical formation upon dark oxidation of bulk bacteriochlorophyll

11. Such near infrared changes are very similar to those observed upon light-induced or dark oxidation of photoreaction center bact- eriochlorophyll (the primary donor of bacterial photosynthesis), i.e., a bleaching at 865 nm and increase in optical density at 1245 nm [2]. Besides, the oxidized primary donor exhibits an ESR signal with a Gaussian lineshape, a g-value of 2.0025 and a peak-to-peak derivative linewidth of 9.5 G 131. In view of the similarities existing between the near infrared changes that follow oxidation of antenna and photoreaction center bacteriochlorophylls, it seemed interesting to investigate whether the oxi- dized antenna pigment is a paramagnetic species which can also be detected by ESR spectroscopy. As reported here, a nearly Gaussian ESR signal with a g-value of 2.0025 and a linewidth of 3.8 G appears to be due to the oxidized bacteriochlorophyll con- stituent which exhibits the 1230-nm band. Such a constituent seems to account only for - 1/3rd of total antenna bacteriochlorophyll and has an ap- parent midpoint redox potential of -555 mV (pH 8.0). A preliminary report of this work has been presented in [4].