Short-term phosphorus deficiency induces flavonoid accumulation in the lamina of pak choi: A finishing treatment that influences inner quality

Plants that suffer phosphorus (P) deficiency acclimate to these inconvenient conditions by synthesizing flavonoids. These metabolites have features that are useful to withstand a mild P deficiency, e.g. antioxidative properties for reactive oxygen species scavenging. Moreover, flavonoid accumulation in photosynthetically active leaf tissue shields the chloroplasts from excessive light energy, doing so by intercepting photons. This is relevant because lack of P feedback inhibits photosynthetic electron transport chain, a process that would give rise to toxic amounts of reactive oxygen species. The idea of the presented study was to subject pak choi to a short P deficiency in order to induce accumulation of the human health-promoting flavonoids a few days before harvest. Pak choi was selected because it is a widely consumed leafy vegetable that has the genetic capacity to synthesize flavonoids. First, plants were hydroponically cultivated with sufficient P. Eight days before harvest, P was omitted from the nutrient solution. In result, the lamina of fully-grown harvested leaf enriched in eight flavonoids, among them quercetin, kaempferol and flavone structures. However, the entire shoot lost water. This is a problem because this means a reduction of marketable yield. Of note, P concentrations were not yet reduced in the lamina of the fully-grown harvested leaf that accumulated the flavonoids. This is indicatory for systemic stress signals that transmit information for example of a P deprivation to distant tissue.

Automated summary

Plants suffering from phosphorus deficiency produce flavonoids to adapt to the conditions, which provide antioxidative properties and protect the chloroplasts from excessive light energy. A study aimed to induce the accumulation of flavonoids in pak choi before harvest by subjecting it to a short P deficiency. The experiment resulted in increased flavonoid content in the harvested leaf but also caused water loss in the entire shoot, leading to reduced marketable yield.