Effects of low atmospheric CO2 and elevated temperature during growth on the gas exchange responses of C3, C3–C4 intermediate, and C4 species from three evolutionary lineages of C4 photosynthesis

Abstract

This study evaluates acclimation of photosynthesis and stomatal conductance in three evolutionary lineages of C(3), C(3)-C(4) intermediate, and C(4) species grown in the low CO(2) and hot conditions proposed to favo r the evolution of C(4) photosynthesis. Closely related C(3), C(3)-C(4), and C(4) species in the genera Flaveria, Heliotropium, and Alternanthera were grown near 380 and 180 μmol CO(2) mol(-1) air and day/night temperatures of 37/29°C. Growth CO(2) had no effect on photosynthetic capacity or nitrogen allocation to Rubisco and electron transport in any of the species. There was also no effect of growth CO(2) on photosynthetic and stomatal responses to intercellular CO(2) concentration. These results demonstrate little ability to acclimate to low CO(2) growth conditions in closely related C(3) and C(3)-C(4) species, indicating that, during past episodes of low CO(2), individual C(3) plants had little ability to adjust their photosynthetic physiology to compensate for carbon starvation. This deficiency could have favored selection for more efficient modes of carbon assimilation, such as C(3)-C(4) intermediacy. The C(3)-C(4) species had approximately 50% greater rates of net CO(2) assimilation than the C(3) species when measured at the growth conditions of 180 μmol mol(-1) and 37°C, demonstrating the superiority of the C(3)-C(4) pathway in low atmospheric CO(2) and hot climates of recent geological time.

Photosynthesis of C3, C3–C4, and C4 grasses at glacial CO2

“…In addition, the C 4 grasses had higher photosynthesis under ambient and glacial [CO 2 ] relative to their C 3 and C 3 –C 4 counterparts (Figs 1A, 2A). Similar responses were observed for other C 3 , C 3 –C 4 , and C 4 species exposed to 180 μl CO 2 l –1 and 380 μl CO 2 l –1 (Ward et al , 1999; Cunniff et al , 2010; Pinto et al , 2011; Vogan and Sage, 2012). …”

“…Growth at low [CO 2 ] may cause acclimation of the stomatal response that is not necessarily captured during short-term gas exchange measurements. However, a number of studies found no evidence of differential stomatal acclimation between C 3 and C 4 plants (Cunniff et al , 2010; Vogan and Sage, 2012). Hence, there does not seem to be a consensus regarding the relative stomatal sensitivity to short- or long-term changes in [CO 2 ] between C 3 and C 4 plants, which remains an area worthy of further investigation.…”

“…The C 3 –C 4 species had no PNUE advantage over the C 3 species, mainly due to the higher leaf [N] and Rubisco-N of the intermediate species (Table 4). In contrast, intermediate Flaveria species maintained higher photosynthesis and PNUE relative to C 3 congeners at ambient and glacial [CO 2 ] (Vogan and Sage, 2012). …”

“…The operation of a photorespiratory pump in C 3 –C 4 photosynthesis is expected to elicit a response to [CO 2 ] that is intermediate between C 3 and C 4 photosynthesis (Monson and Rawsthorne, 2000; Sage et al , 2012). Under low [CO 2 ], C 3 –C 4 plants have been reported to maintain greater photosynthetic rates, PWUE, and PNUE relative to C 3 species (Ku and Edwards, 1978; Bolton and Brown, 1980; Ku et al , 1991; Monson and Rawsthorne, 2000; Vogan et al , 2007; Pinto et al , 2011; Vogan and Sage, 2012). The current study seeks to determine how C 3 –C 4 species perform relative to the various C 4 subtypes at low [CO 2 ].…”

Patterns of Plant Biomass Allocation in Temperate Grasslands across a 2500-km Transect in Northern China

“…Therefore, the influence of temperature on C allocation is mainly reflected in its interaction with the limited precipitation [22], [35], [46], explaining the positive correlation between temperature and root/shoot ratios we found. Our results may also be partly explained further by the significantly positive correlation between root/shoot ratios and PET (all p <0.05) and the significantly negative correlation between root/shoot ratios and DI (all p <0.05) (Table 6).…”