The 2010 ASHS Annual Conference

Carbon dioxide assimilation rates and total carbon fixed in plant tissue were assessed in a variety of species commonly grown in interior environments.  Quantitative data was obtained under a) controlled conditions simulating a typical range of irradiance levels encountered indoors (10, 20, or 30 μmols/m²/s); and b) in situ conditions in interiorscapes.  Under the former, plants were grown for ten weeks and their photosynthetic rates were assessed before and after this period.  Species varied in their daily carbon gain (net amount of carbon fixed by each plant in a 24-hour period) and their carbon use efficiency (fraction of carbon fixed in gross photosynthesis and incorporated into biomass), with Spathiphyllum and Aglaonema, exhibiting higher values compared to Scindapsus, Philodendon, Sanseveria, Ctenanthe, or Ficus benjamina.  Carbon content was lower in herbaceous species (e.g. Scindapsus aureus, 38% of dry mass) compared to woody ones (e.g. Ficus benjamina, 43%).  A positive relationship between duration and irradiance level of the acclimatization period was found for all species, which in turn impacted photosynthetic rates in subsequent interior environment.  A positive relationship between plant age and amount of carbon fixed was also found.  All species exhibited positive carbon gain under simulated irradiance levels, although some species (e.g. Spathiphyllum, had significantly higher values (up to 3.5 grams of carbon dioxide per week).  In situ, plants exhibited varying photosynthetic rates and carbon gains, largely dependent on irradiance level.  Predictably, a positive correlation was found between irradiance level and amount of carbon incorporated into biomass.  In general, a large plant and/or species with higher amount of woody tissue in their above- or belowground organs (e.g., 14-ft arboreal plant), removed more carbon over time, compared to a small and/or herbaceous species.  This study is the first to provide quantitative data of carbon assimilation under interiorscape environments.  Data from this as well as past research supports the view that under typical interiorscape irradiance levels, carbon assimilation in plant tissue represents a carbon gain.  Interiorscape plants have been documented to remove volatile organic compounds (VOCs) and this aspect has been used by the industry to promote the health benefits of indoor plants.  Carbon dioxide assimilation provides corollary information to the VOC removal and a more complete assessment of plants’ benefits to the indoor environment.  While the impact of ambient CO₂ removal may be modest, it represents a positive benefit that has the potential to further enhance the purchase and use of indoor plants.