Genomics and Applied Biology 2026, Vol.17, No.1, 26-36 http://bioscipublisher.com/index.php/gab 29 (Bhattarai et al., 2017). This indicates that once the gas in the rhizosphere is restricted, it will affect the aboveground part through stomatal regulation and assimilation rate. In other words, if the ridge height is too low, the drainage is slow, and CO₂ is prone to accumulate, even if the leaves appear vigorous, the photosynthetic efficiency and assimilate output may still be hindered by the underground conditions. On the contrary, when the ridge height is appropriately raised and the aeration is improved, the net photosynthetic level is more likely to be maintained, and the assimilate supply is more stable. Such differences can often be observed in production: for the same variety and fertilization, the plots with appropriate ridge height have stable leaf color, are less prone to premature aging in the later stage, and can continue to supply carbon during the expansion period; while the plots with poor ridge shape and low ridge height are prone to “root suffocation” after rain, and then fall into the cycle of “rapid growth - premature aging - small tubers” (Villordon et al., 2019). This is consistent with the technical advice that emphasizes preventing waterlogging in the later stage, timely drainage, and promoting expansion. 3.3 Synergistic relationship between aboveground growth and underground root enlargement For sweet potatoes to achieve high yields, it is not dependent on any single aspect, but rather on whether the “source” and “sink” can cooperate well: continuous leaf output, and the successful transportation of assimilates to the roots and their conversion into starch. Many physiological studies have already pointed out that once soil aeration is improved, the transportation of assimilates to the roots will be more smooth, and the proportion of dry matter in the roots will also increase (Bhattarai et al., 2017). Recent field results have made this point more specific - in treatments with looser soil and better aeration, the yield and economic coefficient of the roots increased by 27.03%-38.74% and 6.30%-13.05% over two years; conversely, the compact treatment resulted in significant reduction in yield. ^13C labeling also showed that under loose conditions, the efficiency of root input was higher (Colombi et al., 2018). When these phenomena are viewed from the perspective of ridge height, a possible solution can be proposed: when the ridge height is moderate, the topsoil is more loose and oxygen is replenished faster after rain, allowing the assimilates to flow more smoothly between the “stem base - root”; when the ridge height is too low and encountering waterlogging or compaction, the receiving capacity of the root “sink” decreases, and assimilates are retained in the stems and leaves. A common example is “vigorous vines but thin roots”. Therefore, discussing the optimal range of ridge height is essentially about creating structural conditions to maintain the activity of the “sink” end, rather than simply making the ridge higher. 4 The Effect of Ridge Height on the Swelling Process of Sweet Potato Tubers 4.1 Differences in the initiation and expansion stages of root tubers at different ridge heights The swelling of the root tuber is not achieved overnight, and can be roughly divided into the initiation period and the rapid swelling period. In the previous stage, the key lies in root differentiation, whether it can form root segments that can be transformed into tubers, and have a more obvious response to soil aeration and soil temperature (Villordon et al., 2014); In the period of rapid expansion, the influencing factors turn to whether the water is stable and whether the assimilates can be continuously supplied. The technical opinion mentions that the root tubers begin to swell 30-40 days after planting and are most sensitive to water at this time. It is required to strengthen management and prevent later waterlogging, which actually corresponds to this stage difference. The role of ridge height in the two stages is not exactly the same: during the start-up period, a moderately high ridge, especially when combined with mulching, is beneficial for heating and ventilation, and the root system is built quickly with low risk of root blockage; But in the rapid expansion period, if the ridge is too high and lacks irrigation, it is easy to lose moisture, slow down the expansion speed, and increase the risk of potato cracking. From the perspective of energy metabolism, soil with good ventilation conditions is more conducive to aerobic respiration and ATP supply of root tubers, laying the foundation for starch synthesis (Colombi et al., 2018). This also explains why the ventilation status during the start-up phase can affect the “potential upper limit” of subsequent expansion.
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