Assimilation and metabolism of formaldehyde by leaves appear unlikely to be of value for indoor air purification

Uptake, translocation and metabolism of 14 C-labelled formaldehyde in the leaves of Epipremnum aureum (Golden Potho) and Ficus benjamina (Weeping Fig) were investigated. Plants were exposed in light and dark to 14 C-formaldehyde (500 μg m −3 ) in gas exposure chambers. The amount of 14 C-incorporation into the soluble (water-extractable) and insoluble fractions of leaves, stem sections and roots was determined. The soluble 14 C-activity was fractionated by ion exchange chromatography followed by thin-layer chromatography/autoradiography. Approximately 60–70% of the applied 14 C-formaldehyde was recovered from the plants. In the light about five times more 14 C-formaldehyde was assimilated than in the dark. The amount of 14 C-label derived from 14 C-formaldehyde, which was incorporated into acid-stable metabolites, was enhanced to an even larger extent in the light. The 14 C-activity pattern closely resembled the general labelling spectrum of photosynthates, obtained after a 14 CO 2 exposure. A substantial amount of labelled material, mostly sucrose, was translocated into the stems and roots. Our results suggest that in the light 14 C enters the Calvin cycle after an enzymatic two-step oxidation process of 14 C-formaldehyde to 14 CO 2 . The activities of the respective enzymes, formaldehyde dehydrogenase and formate dehydrogenase, were determined. Among 27 ‘leafy’ indoor decorative plants, a screening experiment revealed no outstanding species with regard to its capacity for metabolism of formaldehyde, and rate of uptake through stomata was too low to justify claims that plants contribute usefully to indoor air purification.