Spatiotemporal temperature distribution in the canopy of summer-to-autumn flowering chrysanthemum under different zone cooling methods

Avoiding high-temperature stress effectively can ensure sufficient plant production in hot seasons. Therefore, we proposed the use of zone cooling to decrease the temperatures around the chrysanthemum canopy using a heat pump and duct at the bottom (base cooling), top (top cooling), and above (above-top cooling) the canopy. The spatiotemporal distribution of temperatures (air, leaf, and stem temperatures) was measured under the various zone cooling treatments applied, and compared with those under the treatments which were not subjected to cooling (no cooling) and were entirely cooled (entire cooling). The air temperature around the targeted cooling regions and some plant temperatures declined substantially under the base and top cooling treatments at night, but such a decline was not observed with the above-top cooling treatment. During the day, the cooled region under top cooling was directly affected by solar radiation, but this region was unaffected under the base cooling treatment. The cold air was maintained at the bottom. The results indicate that solar radiation substantially influenced spatiotemporal temperature distribution. Moreover, base cooling was found to be the most effective method during both day and night. Thus, this study examines the spatiotemporal temperature distribution under zone cooling methods in the chrysanthemum canopy, thereby advancing our understanding of the fundamental knowledge required for the establishment of a practical zone cooling system.