Stress caused by increase population density in maize produce significant yield loss. To remedy it, photosynthetic
activity maintenance even under unfavorable conditions is required. Senescence delay induced by stress in stay-green
genotypes (SG) could contribute to maintaining photosynthetic capacity. In this work we observed differences in
reflectance curves of two hybrids (SG and no SG) when population level increased. Significant differences in
chlorophyll absorption spectral region were observed. Therefore spectral signatures studies maize could help to
understanding of the physiological basis of SG character to predict the growing conditions in which these hybrids would
express their production potential.
Dynamic speckle or biospeckle is observed in biological samples illuminated by laser light. The properties and applications of this phenomenon have been treated in the literature. In this paper, we present a method of dynamic speckle analysis based on the filtering in frequency bands of the temporary history of each pixel. Butterworth filters are applied to the temporary evolution and different images are constructed showing the energy in each frequency band. Applications on vegetable specimens examples are shown.
A low cost portable spectroradiometer able to operate in the 4 bands of the satellite system Landsat MSS was developed. The radiometer was designed to measure the spectral reflectance of spatially extended targets. Spectral bands were selected with 10 nm bandwidth filters. Measurements were made during 2003, from seedtime to harvest, on an experimental plot of wheat. The culture was divided in parcels that received different treatments (seed variety, fertilizer, herbicide and fungicide). Weekly measurements with the detector at nadir and the sun near midday were made. As result of the spectral measurements of reflectance, the normalized difference vegetation index (NDVI) was calculated. As a comparison, LAI, chlorophyll concentration and diverse gravimetric determinations, were carried out. The results were analyzed by means of statistical techniques and showed a good correlation between the optical index and the culture variables. In the future the geometry of the measurement will be improved to reduce the effect of the canopy and other channel in the near infrared will be added to distinguish water and nitrogen stress.