SPECTRAL IMAGING IN THE EVALUATION OF THE CHLOROPHYLL CONTENT IN WHEAT PUBLISHEDF. SALA, M. BOLDEA, I. GERGEN
The objective of our research was to evaluate the nutritional status expressed through thechlorophyll content in wheat crops, by using the analysis of the digital images taken in the visiblespectrum. The study is based on observations of different colors expressed by plants in the visiblespectrum, following a different nutritional status. These data about colors were associated and correlatedwith the chlorophyll content. The biologic material was represented by Alex variety of wheat (Triticumaestivum ssp. Vulgare). The nutritional stress which generated the variation in the chlorophyll contentwas induced by controlled nitrogen fertilization, in doses between 0 – 200 kg active substance ha -1 withfour levels of PK 0 – 150 kg active substance ha -1 . Chlorophyll content of wheat plants was determinedwith a portable chlorophyll meter (Konica Minolta SPAD 502 Plus) to measure absorbance leaves redand near infrared region. Determination of chlorophyll was done in the same time to capture digitalimages. Capturing digital images made with a Nikon D80 at uniform parameters for all variants. Thedigital images, captured in the visible spectrum, were analyzed from the point of view of their colorspectrum by nonlinear perceptual representation systems RGB, HSB and HSL. Chlorophyll contentranged from 40.26 ± 1.36 (SPAD units) from control variant (P 0 K 0 N 0 ) and 55.57 ± 0.55 (SPAD units) atP 150 K 150 N 200 variant. After the correlative analysis of the numerical values resulted on color channels(H,S,B and H,S,L) and chlorophyll, we obtained correlations with high significance level (verysignificantly negative correlation between the chlorophyll content and color channel B HSB , r = -0.930).Multi-parameter analysis of the variables, accomplished through cluster analysis and data groupingbased on Euclidean distances, places the experimental variants according to the fertilization level. Theirdisposition is also correlated with the chlorophyll content and HSB and HSL values resulted from testscarried out and from the data stored in digital images.
imagistic spectral analysis, digital image, visible spectrum, RGB, HSB, HSL, chlorophyll, wheat