Estimation of a thermal time in individual cucumber (Cucumis sativus L.) fruit under Japanese greenhouse production

Cucumbers (Cucumis sativus L.) can exhibit growth imbalance among individual fruits, which is caused by the duration of fruit growth and fruit abortion.
These phenomena are influenced by environmental factors and sink organs.
Although predicting sink organs that are constantly fluctuating is difficult, we assumed that when immature fruits are harvested, as in Japanese cucumber cultivation, the sink is stable, and the duration of fruit growth is easy to estimate.
The effects of temperature, solar radiation during fruit development, and the number of fruits at anthesis on the thermal time of fruits from anthesis to harvest during greenhouse cultivation were investigated.
The number of fruit sets fluctuated until about 2000°C a day after transplanting, after which it showed a stable trend.
The thermal time was highly negatively correlated with mean temperature (p<0.01) and mean cumulative solar radiation (p<0.01) but not with the number of fruits (p=0.72). Subsequently, an equation was developed based on the average daily temperature and daily cumulative solar radiation to estimate the thermal time.
Validation based on the equation showed good correlations (r=0.99, p<0.01) between the observed and estimated results for the fruits at 31-60 nodes (1700-3600°C day after transplanting). These results indicate that temperature and solar radiation are important factors for predicting the duration of cucumber fruit development under a stable fruit set.

International Symposium on New Technologies for Sustainable Greenhouse Systems: GreenSys2023

K. Maeda, K. Nomura, D. Ahn

fruit development, hydroponics, fruit set, environmental control, cumulative temperature

https://doi.org/10.17660/ActaHortic.2025.1426.10