ABSTRACT
Reducing soil temperatures could prevent quality decline of creeping bentgrass with heat stress. The objective of this study was to determine the differential effects of lowering soil temperature to different levels during the day or night on turf quality, root growth, photosynthesis, and carbohydrate distribution for creeping bentgrass (Agrostis palustris L.) in a growth chamber study. ‘Penncross’ was exposed to optimal air and soil temperature during the day and night (20/20 °C); high air and soil temperature during the day and night (35/35 °C); lowering soil temperatures during the day (20, 25, and 30 °C); and lowering soil temperature during the night (20, 25, and 30 °C) while shoots were maintained at high air temperature (35 °C) during the day and night. High air and soil temperature reduced turf quality, root weight, and canopy net photosynthetic rate and increased daily carbon consumption to production ratio. Turf quality increased with night temperature reduction to 20, 25, and 30 °C and with day temperature reduction to 20 and 25 °C; the increases was more pronounced at 20 °C than 25 and 30 °C. Root weight increased at night temperature reduction to 20 and 25 °C and day temperature reduction to 20 °C. Canopy photosynthetic rate increased following 14 d or longer exposure to lower soil temperatures during the night at 20, 25, and 30 °C and during the day at 20 and 25 °C. Daily carbon consumption to production ratio decreased with soil temperature reduction during the day or night. Lowering soil temperature during the night increased the root to shoot ratio of carbohydrate content. The results demonstrated that lowering soil temperature, particularly at night, was effective in alleviating heat injury even though air temperature was high. These results could be related to the alteration of the balance between carbon consumption and production and carbohydrate distribution in root and shoots.
