Rapid and non-destructive measurement of nitrogen status in ornamental cuttings by near infrared spectroscopy as part of a quality assessment system in supply chains of young plant production.

摘要

The role of nitrogen (N) in adventitious root formation of leafy cuttings is discussed extensively for different ornamental species. To date, this knowledge is rarely used for a quality assessment system in young plant production. Analysis of the growing medium or nutrient solution of stock plants provides indirect and limited information of the N-status of cuttings yielded form these stock plants and N analyses of cuttings (e.g., by Kjeldahl or Dumas methods) are time consuming and expensive. In the present study, we explored the potential of near infrared spectroscopy (NIRS) as a fast and non-destructive alternative to time consuming N analysis. Cuttings of Pelargonium x hortorum, Pelargonium x peltatum and Chrysanthemum x grandiflorum from commercial production and from stock plants cultivated at different levels of N-supply at the Forschungsanstalt fur Gartenbau Weihenstephan have been used for calibration. NIR spectra were taken from intact, fresh cuttings using a Zeiss NIR diode array spectrometer. Four N-fractions (amide-N, nitrate-N, amino-N, protein-N) and total-N were analysed as reference using a modified Kjeldahl procedure. Additionally, sums of extractable N-fractions (enf-N=amide-N+nitrate-N+amino-N) and organic bound N-fractions (onf-N=amide-N+amino-N+protein-N) were calculated. The dataset was 241 samples in total, 161 samples were used for calibration and 80 samples were used to build the validation set. Best prediction power was achieved for protein-N with a standard error of prediction (SEP) of 1.92 mg N g dry weight (DW)-1 and a R2 of 0.89, total-N (SEP=2.89 mg N g DW-1; R2=0.88) and onf-N (SEP=2.60 mg N g DW-1; R2=0.88). Amide-N, nitrate-N, amino-N and enf-N showed a poorer accuracy with R2 between 0.65 and 0.75, but results may be usable for quality screening. Results reveal that especially protein-N, total-N and onf-N can be predicted by NIRS accurately and non-destructively within seconds. This makes NIRS a promising tool for quality assessment of ornamental cuttings.