Effects of ammonium to nitrate ratio on vase life and stem strength of gerbera cut flowers

Abstract

The postharvest quality of gerbera cut flowers a major floricultural commodity is largely limited by stem bending and abbreviated vase life. Although nitrogen form is a critical preharvest variable, the optimum ammonium‑to‑nitrate (NH₄⁺/NO₃⁻) ratio for extending postharvest longevity has not been established. This study demonstrates that a moderate NH₄⁺/NO₃⁻ ratio of 20:80 was associated with the longest vase life and greatest stem rigidity among the treatments tested by enhancing calcium uptake and improving plant water relations. In a controlled study with two cultivars (‘Stanza’ and ‘Double Dutch’), the 20:80 ratio was associated with the longest vase life (14.20 days) and greatest stem strength among the treatments tested, whereas a high-ammonium ratio (60:40) reduced vase life by 28.3% and stem strength by up to 32.2%. This reduction was closely associated with decreased concentrations of calcium in the stem and lower RWC in the leaves. Cultivar choice was also critical, with ‘Double Dutch’ accumulating more calcium and exhibiting the best postharvest performance. Our results suggest that calcium-mediated stem integrity may be a key mechanism connecting nitrogen form to postharvest quality, although further research is needed to confirm this hypothesis. We demonstrate a direct, practical approach, based on the 20:80 NH₄⁺/NO₃⁻ ratio to minimize financial loss in commercial floriculture. In addition, our data provide a physiological basis for using N form to enhance Ca‑dependent stem integrity in cut flowers, offering a practical strategy to help reduce postharvest losses in gerbera production.