Abstract

Switchgrass (Panicum virgatum L.) is widely adapted throughout North America, but its productivity tends to decline with increasing latitude. Little is known about its genetic potential to photosynthetically acclimate to suboptimal growth temperature, although such potential could be useful to enhance productivity. To examine this, a growth chamber study was conducted with two lowland (Alamo and Kanlow) and two upland (Cave in Rock and Sunburst) ecotypes grown under day/night air temperatures of 32/24°C and later switched to 22/14°C. Photosynthesis, growth, and carbohydrates were analyzed before and after temperature switching. Photosynthesis was greater in lowland than upland cultivars at 32°C air temperature. After switching to 22/14°C and allowing plants to adjust, photosynthesis declined with little difference among cultivars. Moreover, photosynthetic capacity among cultivars slightly decreased or remained similar compared to before the temperature switch. However, after switching to 22/14°C, Alamo gained the most dry matter (3.9 g plant⁻¹), which was 69, 82, and 152% greater than that of Sunburst, Kanlow, and Cave in Rock, respectively. Total nonstructural carbohydrates increased at 22/14°C, but Alamo showed the least change and no difference in leaf sucrose/starch ratio following the switch. Maintenance of carbon metabolism favoring growth, but not photosynthetic acclimation, may be a key to enhancing switchgrass productivity under suboptimal growth temperatures.

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