Air temperature and the source–sink ratio (SSR) during anthesis are key factors that affect fruit set of sweet pepper (Capsicum annuum). In a greenhouse production setup using hydroponic and heating systems, air temperature and the SSR may show negative and positive correlations with fruit set, respectively.
However, the combined effects of air temperature and the SSR on fruit set are unclear; therefore, this information will provide insights into environmentally controlled fruit production under increasing air temperatures caused by climate change. Researchers aimed to clarify the relationship between the fruit set ratio and SSR during anthesis across a wide range of air temperatures. Sweet pepper cultivar Artega was grown in a greenhouse with optimal-to-high (19–30 °C) daily average temperatures (i.e., mild heat stress). In the experiments replicated three times (206-day, 131-day, and 120-day growth periods), the plants were grown using hydroponic systems with environmental controls. Based on plant growth and aboveground environmental data, we calculated the SSR and average air temperature for 1 to 7 days after anthesis (DAA) in each flower sample and investigated correlation coefficients (r) between the fruit set ratio and SSR for 1 to 7 DAA. The fruit set ratio was positively correlated with the SSR for 1 to 7 DAA (P ≤ 0.05). However, the regression curve comprising 22 to 30 °C represented a lower fruit set ratio under a high SSR compared with the curve comprising 19 to 22 °C; for example, 8 g·g−1 as the SSR for 1 to 7 DAA corresponded with fruit set ratios of 0.5 and 0.2 fruits/flowers under optimum and high temperatures, respectively.
The experiment performed under mild heat stress conditions showed a significantly lower fruit set ratio than that under optimum temperatures (P ≤ 0.05). In conclusion, mild heat stress, despite sufficient photosynthate supply, would increase flower abortion in sweet pepper.
Homma, M., Higashide, T., & Isozaki, M. (2026). Mild Heat Stress Accelerates Flower Abortion in Sweet Pepper (Capsicum annuum L.) Independent of the Photosynthate Supply. Journal of the American Society for Horticultural Science, 151(6), 555–567. https://doi.org/10.21273/JASHS05634-26
Source: ASHS
Frontpage photo:
© Jinaritt Thongruay | Dreamstime
Publication date:
Mon 19 Oct 2026
