International Journal of Horticulture, 2025, Vol.15, No.5, 218-233 http://hortherbpublisher.com/index.php/ijh 227 On the one hand, if sugarcane is mildewed or mechanically damaged after harvest, a certain amount of ethylene will be produced, which may trigger a softening process similar to that of fruits, making the sugarcane stem pith tissue loose and easy to collaps. This needs to be avoided during storage and transportation. On the other hand, moderate ethylene signals may help fresh sugarcane maintain its juiciness and palatable texture during maturity. Studies have shown that the fruits of peach mutants (hd mutations) that do not produce ethylene remain hard and crisp throughout the fruit, but soften after exogenous ethylene is applied. By analogy, the slight increase in endogenous ethylene levels during the ripening of fresh sugarcane may promote the action of some wall-relaxing enzymes (such as PG and β-glucanase), making the fiber tissue slightly softer from extremely hard, thereby improving the chewing experience. Of course, this speculation has not yet been directly supported by experiments, and further research is needed on the role of ethylene in sugarcane storage and ripening. It is worth mentioning that ethylene has extensive crosstalk with other hormones. For example, ethylene and auxin interact with each other in organ abscission and cell elongation; and ABA cooperates in maturation and senescence (Tipu and Sherif, 2024). In the regulation of sugarcane quality, the combined effects of multiple signals should also be considered. In general, although sugarcane is not a typical ethylene-driven softening tissue, key factors in the ethylene signaling pathway may implicitly affect cell wall metabolism. Through exogenous 1-MCP (ethylene receptor inhibitor) or adjusting the expression of ethylene synthesis genes, it may be possible to achieve a certain regulation of sugarcane texture in the future. 5.3 Light and temperature effects on quality-related gene networks The effects of environmental factors on the sweetness and texture of sugarcane have long been proven in production practice: good light and suitable temperature can significantly increase the sugar content and stem fullness of sugarcane, while unfavorable environments (such as weak light, heat/cold stress) often lead to reduced sugarcane yield and quality (Mehdi et al., 2024a). Light directly determines the source intensity by affecting photosynthesis, which in turn affects the accumulation of sugar in the reservoir. Sufficient sunlight can increase the photosynthetic rate of sugarcane leaves and provide more assimilated products for the stems. It is reported that from the end of sugarcane tillering to the elongation stage, if there is sufficient sunlight (more than 7~9 hours of sunshine per day), the growth and sugar accumulation of the plants are significantly accelerated; on the contrary, if there is continuous rain or short-day season, the stems become thinner and softer, and the sugar accumulation is significantly reduced. This is related to the fact that the expression of sucrose synthesis-related enzymes under light is regulated by circadian rhythm: sufficient light can upregulate the activity of enzymes such as SPS in leaves during the day and promote the output of sucrose. At the same time, it may regulate the activity of SuSy and invertase in stems at night through sugar signals, so that more sucrose can be stored in time (Zhao and Li, 2015). If there is a long-term lack of light, the plant will mobilize the stored sugar in the stem for growth, which is manifested as a decrease in sugar content and poor mechanical strength. Therefore, in sugarcane cultivation, reasonable dense planting and avoiding shading are particularly important to ensure the sugar content and quality of a single stem. Temperature affects the formation of sugarcane quality by affecting the activity of metabolic enzymes and membrane stability. Sugarcane is a C4 crop, and its photosynthesis and growth are most vigorous at around 30 ℃. High temperature or low temperature stress will interfere with its normal metabolism. High temperature (for example, daily temperature continues to be above 35 °C~40 °C) will accelerate respiration and may cause an increase in the sucrose cycle decomposition rate, resulting in impaired net sugar accumulation. At the same time, high temperature can also induce the expression of heat shock proteins and stress resistance genes, which often adjust carbon flow to defense pathways (such as proline synthesis, soluble sugar as osmotic protectants, etc.) rather than storage pathways. Mehdi et al. (2023) showed that under heat stress gradually increased to 45 °C, the sucrose content and pure sugar yield of the two sugarcane varieties decreased significantly, and high temperature treatment caused the expression of sucrose metabolic enzymes (including SPS and multiple invertases) to be significantly reduced.
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