Interactive effects of light, temperature and cultivar on photosynthesis in evening primrose (Oenothera spp.) crops

Abstract

The photosynthetic performance of evening primrose (Oenothera spp.), a temperate oilseed crop, was assessed during the period of rapid biomass accumulation and flower bud formation. Light response curves constructed from field-grown plants harvested in late May, late June and late July were similar, suggesting that the photosynthetic capacity of evening primrose leaves is not readily susceptible to low temperatures. The maximum quantum efficiency of CO2 assimilation and light-saturated rate of CO2 assimilation data were comparable to other C3 species. Short-term changes in photosynthetic efficiency, measured as the ratio of variable to maximal chlorophyll fluorescence, Fv/Fm, were assessed on field-grown plants of five breeding lines during late May and early June, and on glasshouse-grown plants under controlled temperatures and light levels. Low temperature-dependent photoinhibition (measured as a decline in Fv/Fm) occurred in both field and controlled-environment studies. Differences were observed between breeding lines in the rate of recovery upon a return to more favourable conditions. A clear correlation between Fv/Fm and CO2 assimilation was demonstrated, suggesting that low temperature-dependent photoinhibition could lead to reduced biomass accumulation in evening primrose crops grown in cool temperate climates.