ARS | Publication request: Photosynthetic response of switchgrass ecotypes to fluctuating growth temperatures

Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract
Publication Acceptance Date: October 9, 2008
Publication Date: October 9, 2008
Citation: Gesch, R.W. 2008. Photosynthetic response of switchgrass ecotypes to fluctuating growth temperatures [abstract][CD-ROM]. ASA-CSSA-SSSA Annual Meeting Abstracts. ASA-CSSA-SSSA Annual Meeting. Oct. 5-9, 2008, Houston, TX.

Technical Abstract: Switchgrass (Panicum virgatum L.), a warm-season C4 grass that shows excellent potential as a bioenergy feedstock and conservation crop, is widely adapted throughout North America, but its productivity tends to decline with increasing latitude. In northern regions where growing season temperatures can fluctuate dramatically, the ability of switchgrass to adjust photosynthetically to maximize carbon assimilation under sub-optimal temperatures may enhance productivity. To test this idea, four switchgrass cultivars, two lowland (Alamo and Kanlow) and two upland (Cave in Rock and Sunburst) ecotypes were grown under a 32/24°C day/night temperature regime with a 16-hr photoperiod and later switched to 22/14°C for 15 d. Photosynthesis, growth and carbohydrates were analyzed before and after temperature switching. Photosynthesis of the lowland cultivars was greater than that of the upland varieties at 32/24°C. After switching to 22/14°C and allowing the newest expanding leaf to mature, photosynthesis was less than that before the switch, but there was no difference among cultivars. Under the lower growth temperatures, photosynthetic capacity among the cultivars tested slightly decreased or remained similar as compared to that before the temperature switch although Alamo showed increased PEPCase activity. While exposed to 22/14°C, Alamo showed the greatest dry weight gain (3.8 g plant-1). Compared to growth at the higher temperature regime, Alamo leaves showed a decrease in sucrose and hexose content; whereas, the other cultivars showed an increase when grown at the lower temperatures. The results indicate that efficient carbohydrate usage rather than photosynthetic acclimation under sub-optimal growth temperatures may be a key to enhancing switchgrass productivity.