MORE EFFICIENT PLANTS: A Consequence of Rising Atmospheric CO₂?

Abstract

KEY WORDS: CO2 and plants, CO2 and photosynthesis, CO2 and stomata, CO2 and respiration, plants and climate change ABSTRACTThe primary effect of the response of plants to rising atmospheric CO 2 (C a ) is to increase resource use efficiency. Elevated C a reduces stomatal conductance and transpiration and improves water use efficiency, and at the same time it stimulates higher rates of photosynthesis and increases light-use efficiency. Acclimation of photosynthesis during long-term exposure to elevated C a reduces key enzymes of the photosynthetic carbon reduction cycle, and this increases nutrient use efficiency. Improved soil-water balance, increased carbon uptake in the shade, greater carbon to nitrogen ratio, and reduced nutrient quality for insect and animal grazers are all possibilities that have been observed in field studies of the effects of elevated C a . These effects have major consequences for agriculture and native ecosystems in a world of rising atmospheric C a and climate change. CONTENTS

Projected Dryland Cropping System Shifts in the Pacific Northwest in Response to Climate Change

“…All future periods and RCP scenarios produced more yield than the baseline period, and RCP 8.5 had higher yield gains than RCP 4.5 as a result of higher atmospheric CO 2 (Drake et al, 1997) counteracting greater warming. Compared to the historical baseline, the 50% probability total grain yield by the 2070s is projected to increase 23-37% for RCP 4.5 and 35-71% for RCP 8.5 depending on the AEC, with CC showing the greatest absolute increase and CF showing greatest relative increase compare to baseline yields.…”

Response of central Siberian Scots pine to soil water deficit and long‐term trends in atmospheric CO2concentration

“…In controlled experiments, more often than not, some form of ''acclimation'' develops. This may involve, for example, changes in stomatal conductance or reduced photosynthetic capacities or changes in plant allocation patterns [e.g., Bowes, 1993;Drake et al, 1997;Idso and Idso, 1994;Lee and Jarvis, 1995;Lloyd and Farquhar, 1996;Long et al, 1996]. It remains uncertain, however, if the results derived from controlled experiments are sufficient to predict successfully plant responses in their ''natural'' environment characterized by a gradually increasing [CO 2 ].…”

Carbon balance, partitioning and photosynthetic acclimation in fruit-bearing grapevine (Vitis vinifera L. cv. Tempranillo) grown under simulated climate change (elevated CO2, elevated temperature and moderate drought) scenarios in temperature gradient greenhouses

“…Interactive effects of elevated CO 2 , water stress and temperature have 16 been rarely examined in the past (Lloyd and Farquhar, 2008). Elevated CO 2 decreases 17 stomatal conductance and transpiration rates (Drake et al, 1997;Del Pozo et al, 2005).…”