Does Low Stomatal Conductance or Photosynthetic Capacity Enhance Growth at Elevated CO₂ in Arabidopsis?

Abstract

The objective of this study was to determine if low stomatal conductance (g) increases growth, nitrate (NO 3 2 ) assimilation, and nitrogen (N) utilization at elevated CO 2 concentration. Four Arabidopsis (Arabidopsis thaliana) near isogenic lines (NILs) differing in g were grown at ambient and elevated CO 2 concentration under low and high NO 3 2 supply as the sole source of N. Although g varied by 32% among NILs at elevated CO 2 , leaf intercellular CO 2 concentration varied by only 4% and genotype had no effect on shoot NO 3 -concentration in any treatment. Low-g NILs showed the greatest CO 2 growth increase under N limitation but had the lowest CO 2 growth enhancement under N-sufficient conditions. NILs with the highest and lowest g had similar rates of shoot NO 3 -assimilation following N deprivation at elevated CO 2 concentration. After 5 d of N deprivation, the lowest g NIL had 27% lower maximum carboxylation rate and 23% lower photosynthetic electron transport compared with the highest g NIL. These results suggest that increased growth of low-g NILs under N limitation most likely resulted from more conservative N investment in photosynthetic biochemistry rather than from low g.The availability of water varies in time and space, and plants in a given environment are expected to evolve a stomatal behavior that optimizes the tradeoff of CO 2 uptake for photosynthesis at the cost of transpirational water loss. The resource of CO 2 also varies over time, and plant fossils indicate that stomatal characteristics have changed in response to periods of high and low atmospheric CO 2 over the past 65 million years (Beerling and

Examining plant physiological responses to climate change through an evolutionary lens

“…time scales (Ehleringer and Cerling, 1995;Ward, 2005;Gerhart and Ward, 2010;Gerhart et al, 2012;Easlon et al, 2015). These findings suggest that c i /c a may have interesting evolutionary pathways, whereby this trait appears to be evolutionarily homeostatic in some cases.…”

Which plant trait explains the variations in relative growth rate and its response to elevated carbon dioxide concentration among Arabidopsis thaliana ecotypes derived from a variety of habitats?

“…In general, the photosynthesis rate is limited by the ribulose-1,5-bisphosphate regeneration rate or ribulose-1,5-bisphosphate carboxylation rate at high and low [CO 2 ]s, respectively. If the balance between the capacities of RuBP regeneration and carboxylation varies among ecotypes as indicated by previous studies (Easlon et al 2014(Easlon et al , 2015, the CO 2 response of photosynthesis should vary (Hikosaka and Hirose 1998;Medlyn 1996). Further studies are required to elucidate the underlying mechanisms.…”

Elevated-CO2 Response of Stomata and Its Dependence on Environmental Factors

“…Moreover, most studies have confirmed that elevated CO 2 may improve the water status of drought-stressed plants by reducing g s (e.g., Brodribb et al, 2009 ; Katul et al, 2010 ; Chen et al, 2015 ; Easlon et al, 2015 ), but these findings were species-dependent ( Beerling et al, 1996 ; Bernacchi et al, 2007 ; Liu et al, 2016 ). However, this case may not occur under severe or extreme drought conditions, possibly due to the depression of stomatal regulatory ability ( Xu and Zhou, 2008 ).…”