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Title:   Author  item
                                            Boldt, Jenniferitem
                                            ERWIN, JOHN - University Of Minnesotaitem
                                            FISHER, PAUL - University Of Florida
  Submitted to: HortScience
                                    Publication Type: Abstract Only
                                    Publication Acceptance Date: 4/25/2014
                                    Publication  Date: 9/1/2014
                                    Citation: Boldt, J.K., Erwin, J.E., Fisher, P.R. 2014. Development of photosynthetic response curves and their integration into a decision-support tool for floriculture growers. HortScience. 49(9):S389(Abstract).Interpretive Summary:
                                Technical Abstract: Irradiance, CO2, and temperature are critical inputs for photosynthesis and crop growth.  They are also environmental parameters which growers can control in protected horticulture production systems.  We evaluated the photosynthetic response of 13 herbaceous ornamentals (Begonia × hiemalis, Begonia semperflorens, Catharanthus roseus, Cyclamen persicum, Euphorbia pulcherrima, Gerbera jamesonii, Impatiens hawkerii, Impatiens wallerana, Osteospermum × hybrida, Pelargonium x hortorum, Petunia × hybrida, Verbena × hybrida, and Viola × wittrockiana) to irradiance, temperature, and CO2.  Initial growth chamber conditions were 20 °C air temperature, 300 μmol·m-2·s-1 irradiance, and a 14 h photoperiod.  Single leaf photosynthetic measurements were measured on one fully mature, non-shaded leaf per plant (5 to 7 plants per species).  Cuvette set points matched chamber conditions, except for the variable of interest.  Photosynthetic irradiance and CO2 response curves were fit to the data using a non-rectangular hyperbola, and temperature response curves were fit using an asymmetric (Landsberg) function.  Light compensation points varied between 24 and 52 μmol·m-2·s-1, light saturation values ranged from 156 to 597 μmol·m-2·s-1, and apparent quantum efficiency varied between 0.033 and 0.087.  Maximum rates of net photosynthesis (Amax) at saturating irradiance varied between 5.0 and 10.5 μmol CO2·m-2·s-1, and they were 5% to 90% greater than net photosynthetic rates (An) at ambient irradiance.  At saturating CO2 concentrations, Amax ranged between 8.2 and 17.2 μmol CO2·m-2·s-1.  CO2 compensation points ranged from 6 to 146 μmol CO2·mol-1 air, and CO2 saturation values ranged from 538 to 2219 μmol·mol-1.  Rates of An were 31% to 153% greater at twice ambient CO2 concentrations.  The optimal temperature (Topt), corresponding to Amax, ranged from 11.1 °C to 30.8 °C.  Simulation software has been developed for these species, providing growers and greenhouse managers with a decision-support tool that allows them to estimate the impacts altering irradiance, temperature, or CO2 will have on photosynthetic rate.


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