The effects of diurnal temperature rise on tomato fruit quality. Can the management of the greenhouse climate mitigate such effects?

In the present study, tomatoes were grown under control conditions (CT), a moderate (MT, up to 2 °C) or a higher rise in temperature (HT, up to 5 °C), and a moderate rise followed by a lower air temperature at the end of the day (ED), in order to analyze the effects of increased temperature as well as management system impact on fruit quality. Rising temperatures up to 5 °C reduced the fruit growth duration by five days and greatly reduced the fresh (29.7 %) and dry matter (30 %) accumulation rate. Increasing the temperature during the day and lowering it at the end of the day increased citric and malic acid concentrations in the fruit, therefore reducing the sugar/acid ratio. The ascorbate concentration and carotenoids increased in the fruits grown under high temperature, while phenolics concentrations did not change. Fruit water conductance was strongly reduced under HT (−37 %), and so was starch accumulation, in contrast to hexoses. Dropping the air temperature at the end of the day could help mitigate HT impacts as it slightly increased the pericarp dry matter content. It could also improve seeds quality as it increased their dry matter content. It would be interesting to consider broader changes in ED temperature to confirm its potential role in improving fruits dry matter content.