Short-term elevated temperature and CO2 promote photosynthetic induction in the C3 plant Glycine max, but not in the C4 plant Amaranthus tricolor

The continuous increases of atmospheric temperature and CO2 concentration will impact global photosynthesis. However, there are few studies considering the interaction of elevated temperature (eT) and elevated CO2 (eCO(2)) on dynamic photosynthesis, particularly for C-4 species. We examine dynamic photosynthesis under four different temperature and [CO2] treatments: (1) 400 ppm Chi 28 degrees C (CT); (2) 400 ppm Chi 33 degrees C (CT+); (3) 800 ppm Chi 28 degrees C (C+T); and (4) 800 ppm Chi 33 degrees C (C+T+). In Glycine max L., the time required to reach 50% (T-50%A) and 90% (T-90%A) of full photosynthetic induction was smaller under the CT+, C+T, and C+T+ treatments than those under the CT treatment. In Amaranthus tricolor L., however, neither T-50%A nor T-90%A was not significantly affected by eT or eCO(2). In comparison with the CT treatment, the achieved carbon gain was increased by 58.3% (CT+), 112% (C+T), and 136.6% (C+T+) in G. max and was increased by 17.1% (CT+), 2.6% (C+T) and 56.9% (C+T+) in A. tricolor. The increases of achieved carbon gain in G. max were attributable to both improved photosynthetic induction efficiency (IE) and enhanced steady-state photosynthesis, whereas those in A. tricolor were attributable to enhanced steady-state photosynthesis.