Paper Reviewed
Cho, A.R., Chung, S.W., and Kim, Y.J. 2020. Flowering responses under elevated CO2 and graded nutrient supply in Phalaenopsis Queen Beer 'Mantefon'. Scientia Horticulturae 273: 109602, doi.org/10.1016/j.scienta.2020.109602.

Crassulacean acid metabolism, or CAM, plants comprise only 3 to 4% of all plant species and are unique in that they fix carbon at night instead of during daylight hours. When it comes to CO2 enrichment studies, much remains to be learned concerning their response to elevated levels of atmospheric carbon dioxide.

Tackling this subject head-on, Cho et al. (2020) recently examined the flowering responses of one of the most popular CAM flowering plants, Phalaenopsis Queen Beer 'Mantefon,' to atmospheric CO2 enrichment. This species is widely cultivated in greenhouses -- particularly across Asia -- and is well known for its bright pink/red flower colors.

The plants were grown in a controlled environment for 17 weeks under a full-factorial design of two CO2 (400 or 800 ppm) and four nutrient levels (solutions of four electrical conductivities: 1, 2, 3, or 4 dS m^-1). At the reproductive stage, the scientists collected data on various flowering characteristics, including the number of flowers, flower size, flower spike length, lateral branch numbers, floral buds, days to flowering and flower color).

And what did such data reveal?

In the words of the authors, "overall, higher CO2 concentrations enhanced the growth and productivity of Phalaenopsis." More specifically, they report (1) "flower spike lengths were longer and more lateral branches were initiated under 800 ppm CO2 compared to plants cultivated under 400 ppm CO2 with and electrical conductivity of 3.0 or 4.0 dS m^-1," (2) plants subjected to 800 ppm CO2 had "greater number of floral buds and flowers than those cultivated at 400 ppm CO2, regardless of electrical conductivity," (3) days to flowering "was faster in plants cultivated under 800 ppm CO2, and (4) flower coloration "was not affected by CO2 concentration or electric conductivity level."

Commenting about their work, Cho et al. write that "altogether, these results suggest that an elevated atmospheric CO2 concentration positively affects the flower spike length and the number of lateral branches, floral buds, and flowers of Phalaenopsis and also indicate that nutrient levels can be adjusted to improve the growth of obligate CAM plants." Furthermore, given the reduced time to flowering at higher CO2 (by 11%), the authors add that those who utilize CO2 enrichment in the production of Phalaenopsis are "likely to improve farm household income" because a shorter flowering time translates to a quicker time to market. And a quicker time to market means more opportunities over a given time period to earn income selling this plant.