Photosynthetic responses of greenhouse ornamentals to interaction of irradiance, carbon dioxide concentration, and temperature

Authors: ATKINS, IAN - University Of Wisconsin; Boldt, Jennifer

Submitted to: Journal of the American Society for Horticultural Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/15/2021
Publication Date: 1/21/2022
Citation: Atkins, I.K., Boldt, J.K. 2022. Photosynthetic responses of greenhouse ornamentals to interaction of irradiance, carbon dioxide concentration, and temperature. Journal of the American Society for Horticultural Science. 147(2):82-94. https://doi.org/10.21273/JASHS05115-21.
DOI: https://doi.org/10.21273/JASHS05115-21

Interpretive Summary: Greenhouses are used to provide a controlled environment for growing plants. Growers can provide heat, supplemental lighting, and supplemental carbon dioxide to optimize the growing environment. This is especially critical in winter and spring, when it is cold outside and ambient sunlight is minimal. However, it is expensive, both in terms of cost and resource use, to modulate the growing environment. Therefore, it is important to develop models that can predict how plants will respond to changing conditions and select a combination of set points that optimize growth and resource use efficiency. We developed photosynthetic light and carbon dioxide response curves for three crops (calibrachoa, petunia, and verbena) grown to three light intensities and for three crops (geranium, pepper, and sunflower) grown at three temperatures. From this, we developed models that integrated the responses into plots that growers can use to make better-informed decisions about managing greenhouse conditions.

Technical Abstract: Supplemental lighting, temperature control, and carbon dioxide (CO2) enrichment can improve the productivity of greenhouse crops, but climate control systems can also be expensive to operate. To balance operating costs with any increase in productivity, growers need to be able to predict how a crop will perform as a function of photosynthetically active radiation (PAR) intensity, CO2 concentration, and temperature. The objective of this study was to explore the response of net photosynthetic rate (Pn) to PAR intensity and CO2 concentration, for plants acclimated to different growth environment temperatures or light intensities. We measured Pn at all combinations of 14 irradiances and four CO2 concentrations of calibrachoa (Calibrachoa ×hybrida Cerv. ‘Superbells Lemon Slice’), petunia (Petunia ×hybrida Hort. Vilm.-Andr. ‘Supertunia Mini Strawberry Pink Veined’), and verbena (Verbena ×hybrida Voss ‘Superbena Royale Whitecap’) grown at three light intensities, and of geranium (Pelargonium ×hortorum L.H. Bailey ‘Maverick Red’), pepper (Capsicum annuum L. ‘California Wonder’), and sunflower (Helianthus annuus L. ‘Pacino Gold’) grown at three different temperatures. Sunflower, pepper, and geranium were fit to a model representing Pn as a function of PAR intensity, CO2 concentration, and leaf temperature. Photosynthetic light response curves, at each CO2 concentration, were fit for each species and growth environment using a nonrectangular hyperbola. These models can be used to identify multiple combinations of PAR intensity, CO2 concentration, and leaf temperature that would result in equivalent rates of photosynthesis, allowing the most cost-effective combination to be chosen.