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

Highlights

• Fruit water conductance strongly decreased under high temperature.

• Rising temperature reduced starch accumulation in contrast to hexoses.

• Rising temperature reduced the fresh and dry matter accumulation in tomato fruit.

• The ascorbate and carotenoid concentrations increased under high temperature.

• A broader change in ED temperature is necessary to assess its role on fruit quality.

Abstract

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.

Introduction

Under glasshouse, different cultural practices and climate management strategies can be used to modulate plant growth conditions in order to obtain the required fruit yield and quality. Among those, temperature control is a useful method for growers to modulate plant growth when other factors such as light, nutrients and water are not limiting (Guichard et al., 2001).

Over the last few decades, several studies have been devoted to identifying the minimal temperatures allowing a high yield of tomatoes while limiting the energy costs of heating. Night temperature has long been known to be the determining factor in tomato fruit setting, with optimum temperatures ranging from 15 °C to 20 °C. In addition, the variation of daily temperature patterns may affect the plant and fruit growth and metabolism, and ultimately, the fruit quality (Adams et al., 2001; Hurd and Graves, 1985; Truffault et al., 2015; Van der Ploeg and Heuvelink, 2005). In the near future, climate change will cause an increase in temperature, which can affect crop yield, due to a reduced fruit set, and change fruit quality (Garg and Cheema, 2011). Increasing temperature generally increases the fruit growth rate but also accelerates fruit maturation and ripening so that fruit weight at harvest can be reduced (Adams et al., 2001; Fleisher et al., 2006). Temperatures at the daily scale can affect water and carbon fluxes within the plant. Walker and Ho (1977) reported that increasing fruit temperature favored sugars allocation to the fruits. Similarly, a rapid decrease in air temperature at the end of the day is used by growers to favor assimilate partitioning to the fruits. The tomato fruits dry matter content is not affected by temperature increase from 18 °C to 23 °C (Heuvelink, 1995). However, growing plants at higher temperatures (increasing temperature from 25/14 °C to 30/12 °C, day/night respectively) enhances the tomato fruits dry matter content (Rosales et al., 2011). These changes in dry matter content also reflected changes in the tomato fruits composition (Dorais et al., 2010; Rivero et al., 2001). Rosales et al. (2011) reported that sugars content increased at high temperatures (30−35 °C) while organic acids decreased. Robertson et al. (1995) found a maximum plateau of tomato lycopene concentration between 18 and 26 °C. Similarly, Brandt et al. (2006), Krumbein et al. (2006), and Dannehl et al. (2012) reported that the lycopene content in tomatoes increases with increasing temperature and reaches its maximum concentration at 25 °C. Temperatures below 12 °C strongly inhibit lycopene biosynthesis and temperatures above 32 °C stop the process (Dumas et al., 2003), affecting the activities of enzymes in the metabolic pathway and consequently, the fruit carotenoid composition (Gautier et al., 2008). Likewise, phenolic compounds (e.g. chlorogenic acid, rutin and naringenin) increase with increasing mean temperatures (Dannehl et al., 2012). In contrast, increasing the temperature from 27 to 32 °C reduces ascorbate accumulation (Gautier et al., 2008). Thus, high temperature could also have a significant impact on the quality of fruits due to changes in primary or secondary metabolism (Moretti et al., 2010).

In this sense, in the present work, we intend to study the consequences of different climates (moderate to larger temperature increase) in order to mimic a possible future scenario under climate change. The data obtained may help in the interpretation of the effects of diurnal temperatures in the development and dry mass allocation as well as in the quality and composition of tomatoes. It is imperative to acquire such knowledge since a moderate or larger temperature increase may have different effects.