The popularity of white asparagus (Asparagus officinalis L) spears is mainly due to its unique flavour and its high concentration of health promoting compounds. Physical elicitors that activate plant defence systems are known to cause an increase of antioxidant compounds in plant tissue, such as phenolic compounds, and their corresponding enzymes (e.g. phenylalanine ammonia- lyase, {[}PAL, EC 4.3.1.5], peroxidase {[}POD, EC 1.11.1.7]). The objective of this work was to evaluate the impact of UV-B on PAL and POD kinetics, as well as to characterize the resulting changes in flavonoid composition in the different morphological sections (apical and basal) of harvested asparagus spears. For this purpose, spears of the cultivar `Gijnlim' were irradiated with either 0.54 kJ m(-2) or 1.08 kJ m(-2) of UV-B. In order to follow the temporal dynamics of the UV-B treatments, analysis were performed after 2 h and 22 h of adaptation. Results revealed changes in the polyphenol composition, and in the activity of related enzymes (PAL POD), in the different morphological parts of asparagus spears as mediated by UV-B dosage at the different adaptation times. The flavonol quercetin-4'-O-monoglucoside showed the most pronounced UV-B response because its concentration increased with increasing UV-B dosage. Furthermore, POD activity of both segments tended to increase with higher UV-B dosage. In contrast, PAL activity in the base segment tended to decrease with higher UV-B irradiation, while PAL activity in tips remained unaffected. However. PAL and POD activities were mainly influenced by the adaptation time. While PAL decreased with the duration of adaptation time, POD showed an opposite behaviour. The presented results revealed the complexity of the antioxidant defence system of asparagus, which is discussed in detail. Crown Copyright (C) 2012 Published by Elsevier Ltd. All rights reserved.