Photoacoustic Study of Fungal Disease of Acai (Euterpe oleracea) Seeds

Abstract

Photoacoustic spectroscopy is introduced as a promising experimental technique to investigate fungus infected Acai (Euterpe oleracea) seeds. Photoacoustic spectra of healthy and infected Acai seeds with the fungus Colletotrichum gloeosporioides were recorded firstly in the modulation frequency range of 5 Hz to 700 Hz, while keeping the wavelength of excitation radiation of a Xe arc-lamp constant, to ascertain the depth of penetration of infection within the seed and secondly, at variable wavelength (wavelength scanning) in the interval 250 nm to 1,000 nm, while keeping the modulation frequency constant. In the former, the photoacoustic signal strength from the infected seed was found higher than that of the healthy one, and has been associated with the appearance of new biomolecules associated with the pathogen infection. In the latter, characteristics peaks and bands were observed in the range from 650 nm to 900 nm ascribed to organic compounds with carboxylates and amines (functional groups) forming the typical metabolic structures of the fungus.

Thermal analysis and artificial vision of laser irradiation on corn

“…One of the PT techniques is the photoacoustic spectroscopy (PAS), used to study the optical and reflectance properties in different areas of knowledge, obtaining optical properties in biological materials, having relation to color, quality and state of degradation [9][10][11]. By using PT techniques, different crops such as wheat, acai, and corn seeds have been studied to obtain various optical and thermal properties [9,10,12,13]. These techniques may be used as a diagnostic, to obtain features of seeds.…”

The Optical Absorption Coefficient of Maize Seeds Investigated by Photoacoustic Spectroscopy

“…13 In another application, PAS (from 5 to 700 Hz) was used to investigate healthy Acai seeds (Euterpe oleracea) that were later infected with Colletotrichum gloeosporioides, fungus. 14 Another potential application of PAS is that of biostimulation which implies the irradiation of seeds (either raw or in combination with the photosensitizers) by a lowpower laser light. [15][16][17][18][19][20] Some reports indicated that the effects of laser irradiation are more pronounced if the seed is dyed.…”