Study On Scanning Electron Microscopy And Infrared Spectra

Rust is a serious disease of broad bean in Southwest of China, which caninfluence the quality and output of the crop. The study on broad bean disease is ofgreat importance to crop protection and disease prevention. In this dissertation, broadbean leaves with aecidiospores were observed by scanning electron microscope(SEM). The healthy and rust leaves were studied by Fourier transform infraredspectroscopy (FTIR) combine with statistic anslysis.Five kinds crop leaves with aecidiospores were observed by scanning electronmicroscope (SEM). Five crops were wheat, faba bean, Allium sativum, Zea mays, andAllium fistulosum. Most spores shape in irregular ellipsoid and exine with spines andgerm pore. Aecidiospores of different crops can be distinguished by spore wallsculpture. Based on analysis of SEM，three major different spore wall sculpture(psilate, granulate, regulate) were observed. According to the difference in themorphology of spore, different rust pathogens can be distinguished by SEM.Fourier transform infrared spectroscopy (FTIR) was used to study rust andhealthy broad bean leaves. The results show the infrared spectra of samples aremainly composed of the absorbtion of protein and polysaccharides. The originalspectra of healthy and rust samples are very similar. While the second derivativespectra show obvious differences in the region of1200-950cm-1between rust andhealthy leaves. The second derivative spectra from1200to950cm-1were used toperform hierarchical cluster analysis. The cluster accuracy rate is94%among healthyand rust leaves from the same geographical area. The cluster accuracy rate is88.75%for the leaf samples from different areas.In order to investigate the effect of rust on secondary structure of protein ofbroad bean leaves, the secondary structure contents were caculated by curve fittinganalysis according to the spectra from1700to1550cm-1. The results indicated-sheet,-helical and-turn contents decreased in the rust leaves, which suggest thatthe amount of protein decreases after the leaves affected by rust.Our study show that FTIR combing with chemometrics could identify diseased and healthy broad bean leaves and could analysis leaves’s content changes caused bydiseases.