Responses of Leaf Cuticles to Rice Blast: Detection and Identification Using Depth-Profiling Fourier Transform Mid-Infrared Photoacoustic Spectroscopy.

Cuticle is the first barrier for rice to resist blast fungus on the surface of the leaf. Studies on how the rice leaf cuticle responds to rice blast and attempts to perform early detection of rice blast are limited, and these two issues were explored in this study via depth-profiling Fourier transform infrared photoacoustic spectroscopy (FTIR-PAS). Rice leaves with four different scales of injury (healthy leaves as CK, asymptomatic leaves from mildly diseased seedlings as S1, infected leaves with fewer than five lesions as S2, and infected leaves with more than 10 lesions as S3) were scanned by three moving mirror velocities 0.32, 0.47, and 0.63 cm/s for the depth profiling of the rice leaf surface. The response patterns were acquired via chemometrics to analyze the variations of the chemical group absorptions in the different layers of a sample and in the same layer between different samples. Results showed that the leaf cuticle tended to be thicker and the relative content of fatty alcohols and cutin, unsaturated compounds, and aromatics in the cuticle increased when rice seedlings were infected by blast fungus. Together with the principal component analysis, the probabilistic neural network was applied to identify the samples in early stages (CK and S1), which reached an accuracy of 90% for the samples in the greenhouse and 82% for the samples in the field. Thus, depth-profiling FTIR-PAS was good at analyzing the variation in cuticle layers and showed great potential in the early detection of rice blast or other diseases in different species.

Rapid Determination of Nitrogen Isotope Labeled Nitrate Using Mid-Infrared Attenuated Total Reflectance Spectroscopy / 分析化学

The nitrate-N content in KNO3 solution and soil was rapidly predicted using techniques of mid-infrared spectroscopy, in which 15 NO-3 and 14 NO-3 were distinguished and predicted. The results showed that the characteristic band of nitrate in solution and soil was 1200-1500 cm-1 , and compared with 14 NO-3 , the red shift of characteristic band of 15 NO-3 was about 35 cm-1 . In the characteristic band of nitrate, absorption band increased with the nitrate nitrogen concentration with less interference absorption. The linear regression was made between the first principal component of characteristic band and nitrate-N content, and correlation coefficient was more than 0 . 9840 , indicating that the technique of mid-infrared attenuated total reflectance spectroscopy could be applied for rapid monitoring of nitrate in solution and soil. Meanwhile, based on the red shift characteristic of 15 NO-3 absorption band, the method of partial least squares were involved to predict the nitrate-N of different N-isotope labeled in solution and soil, resulting that all the prediction models reached excellent levels. For 14 NO3-N and 15 NO3-N in solution, the correlation coefficients ( R2 ) were 0. 9980 and 0. 9982 respectively, and ration performance to standard deviations ( RPD ) were 6. 44 and 4. 76, respectively. While for 14 NO3-N and 15 NO3-N in soil, the correlation coefficients ( R2 ) were 0. 9794 and 0. 9679, and RPD were 5. 75 and 4. 78, respectively. Therefore, the technique of mid-infrared attenuated total reflectance spectroscopy can be applied for rapid monitoring different N-isotope labeled nitrate in solution and soil, to provide a new in situ and fast time method to study nitrification process in soil.