Non-destructive detection of variations in nitrate metabolism within vegetables by FANOVA

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Lettuces (Lactuca sativa L., cv. "Greenwave") were cultivated in a growth chamber and visible-near infrared absorption spectra were measured from each lettuce at every 20 minutes continuously for 14 days. The time course of the nitrate concentration of the lettuces could be measured by substituting the absorption spectra into a developed mathematical model. It was shown that at first the nitrate concentration increased with the increase of the days after planting and then decreased at a certain date. Analyzing the spectra by FANOVA, the functional effect of the nitrate concentration at 978 nm showed the noticeable daily variation. The date, which the peak of variation occurred in the functional effect, coincided with the date at which the nitrate concentration begun to decrease. It was found that the date, which the variations in nitrate metabolism began, could be detected non-destructively by analyzing the daily variation of the functional effect of the nitrate concentration.