Molecular Plant Breeding 2025, Vol.16, No.4, 241-249 http://genbreedpublisher.com/index.php/mpb 246 systematically study the effects of humidity on melon growth and sugar accumulation (Jeenprasom et al., 2019). When the temperature is high in summer, there are also studies that use atomization systems and air circulation fans to increase humidity while cooling down, in order to simulate the management methods in real production. 8.2 Measurement of sugar content, enzyme activity, and fruit quality Brix, central sugar content and total sugar content of the fruit are commonly used indicators for judging sugar accumulation (Jeenprasom et al., 2019). Diao et al. (2022) found that the activities of sugar metabolism enzymes such as sucrose phosphate synthase and sucrose synthase would also be measured to understand how sugar is synthesized and accumulated. Jeenprasom et al.’s experiment in 2019 found that under low humidity (normal conditions), the single fruit weight and Brix value of melons were higher than those treated with high humidity (fogging). However, after moderately increasing the humidity under the atomization system, the fruit weight and sugar content actually rose. The fruit weight increased by approximately 300 g, and the Brix increased by 1.5. This indicates that an appropriate increase in humidity is beneficial to fruit quality. Wang et al. (2022) also indirectly adjusted soil moisture by covering it with degradable film, promoting sugar accumulation and quality improvement. 8.3 Practical insights for growers on optimizing humidity regimes Several studies suggest that when growing melons in greenhouses, the air humidity should be well controlled. Too high humidity will reduce the sweetness and quality of fruits. However, in hot weather, temporarily increasing humidity can reduce heat damage and promote sugar accumulation. The water content of the substrate is best controlled around 100% of the field capacity. If there is too much water, the fruit quality will decline (Jeenprasom et al., 2019). The combined use of degradable films and intelligent prediction systems is helpful for more precise regulation of greenhouse humidity, thereby increasing the yield and sugar level of melons (Wang et al., 2022; Jeon et al., 2024). 9 Challenges and Research Gaps 9.1 Integration of environmental control with plant physiology Nowadays, many studies mainly focus on how humidity affects the quality of melon fruits, such as their sweetness. However, there is still insufficient understanding of the relationship between humidity and some physiological processes within plants, such as the activity of sugar metabolism enzymes and the synthesis of ethylene. Studies have found that changes in temperature and humidity can affect the contents of soluble sugar and sucrose synthase in melon fruits, but it is not very clear how these changes cooperate with cell wall enzymes and ethylene signaling (Diao et al., 2022). In addition, it is not quite clear at present how to precisely act on these molecular regulatory links by adjusting environmental conditions to enable fruits to accumulate sugar more efficiently (Gao et al., 2023; Yang et al., 2025). 9.2 Lack of long-term and multi-environment field trials At present, many studies are conducted in greenhouses and the experimental time is relatively short. There is not yet sufficient long-term field trails on melons grown under different climates, soil conditions and planting methods. For instance, the current data on whether humidity control is effective in different varieties, seasons or irrigation methods is not comprehensive enough (Diao et al., 2022; Buczkowska et al., 2023). So it is still very difficult to formulate a universal, stable humidity management solution suitable for large-scale promotion at present. 9.3 Need for predictive models linking humidity profiles to sugar outcomes Although many people have noticed that humidity can affect sugar accumulation, there is still no model that can accurately predict the impact of humidity changes on sugar. Most studies have only made qualitative descriptions and have not integrated multi-faceted information such as environmental data, enzyme activity and gene expression into a mathematical model (Diao et al., 2022; Gao et al., 2023; Yang et al., 2025). In the future, it can be considered to utilize big data and molecular physiological indicators to establish predictive tools, which can help regulate humidity more precisely and make the sugar content of melons increase more stably.
RkJQdWJsaXNoZXIy MjQ4ODYzNA==