NEAR-INFRARED SPECTROSCOPY: A PROMISING SENSOR TECHNIQUE FOR QUALITY ASSESSMENT OF ORNAMENTAL CUTTINGS

The nitrogen (N) and carbohydrate (CH) status are crucial for storage stability and capacity of adventitious root formation (ARF) of cuttings. To utilise this knowledge in quality assurance within the supply chain for ornamental young plants a rapid, cheap and – if procurable – non-destructive method for measuring N and CH status is required. Near Infrared Spectroscopy (NIRS) may fulfil these requirements. To investigate NIRS-feasibility to assess cutting quality based on total contents and fractions of N and CH, Chrysanthemum and Pelargonium stock plants were cultivated at graduated N fertilization levels. Cuttings were harvested and allocated in two sub-samples: one to take NIR spectra without any sample preparation to predict N and CH status and one to be rooted under normal light conditions in a greenhouse and under constant low light conditions in a climate chamber. Finally, total contents and fractions of N and CH predicted by NIRS were correlated with ARF-ratings. Results showed with Chrysanthemum and Pelargonium that even slight N-deficiency limited rooting significantly, while increasing N contents of cuttings promoted ARF in both environments. For cuttings with an above-average total N content, ARF significantly increased with rising CH levels of leaves only in case cuttings were rooted under constant low light in a climate chamber but not if cuttings were rooted under similar light conditions as provided for stock plants. This correlation was closer for Pelargonium than for Chrysanthemum. The present study shows that NIRS is a promising sensor technique to enhance quality assessment systems for ornamental cuttings.