At the end of the annual horticultural
production cycle of greenhouse-grown crops, large quantities of residual
biomass are discarded. Here, we propose a new value chain to utilize
horticultural leaf biomass for the extraction of secondary metabolites.
To increase the secondary metabolite content of leaves, greenhouse-grown
crop plants were exposed to low-cost abiotic stress treatments after
the last fruit harvest. As proof of concept, we evaluated the production
of the flavonoid rutin in tomato plants subjected to nitrogen deficiency.
In an interdisciplinary approach, we observed the steady accumulation
of rutin in young plants under nitrogen deficiency, tested the applicability
of nitrogen deficiency in a commercial-like greenhouse, developed
a high efficiency extraction for rutin, and evaluated the acceptance
of the proposed value chain by its key actors economically. On the
basis of the positive interdisciplinary evaluation, we identified
opportunities and challenges for the successful establishment of horticultural
leaf biomass as a novel source for secondary metabolites.