The instantaneous photosynthetic rate (Pn), transpiration rate (E), and stomatal conductance (gS) were measured for 33 outdoor-grown Capsicum varieties (varying in species of origin and indigenous habitat) between 29 July and 22 Aug. 2017 using a portable gas exchange meter. Cuvette leaf temperature (Tleaf) and relative humidity (RH) were recorded at that same time. Pn differed from 3.6 to 3.7 for ‘Malawi Piquante’ and ‘Korean Long Green’ peppers to 16.3 mmol CO2/m2/s (fixed) for ‘Thai Hot’ peppers. The gS differed from 0.01 to 0.05 among 13 varieties to 0.28 mmol H2O/m2/s for ‘Thai Hot’ peppers. E differed from 0.43 to 0.59 among three varieties to 4.14 to 4.20 mmol H2O/m2/s for ‘CGN 22091’ and ‘Peruvian Purple’ peppers. Water use efficiency (WUE; Pn/E) varied from 2.92 to 3.43 among three varieties to 5.10 to 7.20 for 16 other varieties. C. annuum derived varieties had higher Pn (9.4 mmol CO2/m2/s fixed) than varieties derived from other species (4.5–8.6 mmol CO2/m2/s fixed). Varieties originating from dry climates had higher Pn (12.5 mmol CO2/m2/s fixed) than those originating from temperate or tropical climates (8.0–8.8 mmol CO2/m2/s fixed). Tleaf (27 to 33 8C) and RH (38% to 39% and 57% to 59%) differed among varieties. Pn was positively correlated with gS, E, and RH and was negatively correlated with WUE. We found that Capsicum Pn, E, and gS varied more than has been previously reported, and our data suggested that Pn, gS, and E data of outdoor-grown peppers should be used only when selecting parents for a breeding program (unless progeny is intended for greenhouse production).
Bibliographical noteFunding Information:
Received for publication 8 Jan. 2019. Accepted for publication 9 Jan. 2019. The authors acknowledge and appreciate the financial support of the IRSIP Program of the Higher Education Commission of Pakistan, the Minnesota Agriculture Experiment Station, the Floriculture and Nursery Research Initiative administered by USDA-ARS, Society of Allied Florists American Floral Endowment (SAF/AFE), and the Horticulture Research Institute (HRI), and the Floriculture Research Alliance members who support University of Minnesota Research (Altman Plants, Rocket Farms, Green Circle Growers, and Smith Gardens). J.E. is the corresponding author. E-mail: erwin001@ umn.edu.
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