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Effects of Elevated CO2 on Water-Stressed Peach Seedlings
Centritto, M., Lucas, M.E. and Jarvis, P.G.  2002.  Gas exchange, biomass, whole-plant water-use efficiency and water uptake of peach (Prunus persica) seedlings in response to elevated carbon dioxide concentration ands water availability.  Tree Physiology 22: 699-706.

What was done
After having been grown at atmospheric CO2 concentrations of 350 and 700 ppm for one full year in two "growth tunnels," peach (Prunus persica) seedlings were transferred to pots and placed in open-top chambers having the same CO2 concentrations for an additional three months.  During the final four weeks of the study, half of the seedlings in each CO2 treatment were allowed to "dry-down", thus allowing the researchers to investigate the interactive effects of elevated CO2 and water stress on photosynthesis and growth in this deciduous fruit tree.

What was learned
Elevated CO2 stimulated rates of net photosynthesis by about 60% in the well-watered seedlings.  Under drought conditions, however, the relative photosynthetic stimulation increased to as much as 180%, leading to CO2-induced increases in seedling dry mass of 33 and 31% for well-watered and water-stressed seedlings, respectively.  The larger percentage enhancement of net photosynthesis in the water-stressed seedlings essentially ameliorated the negative effect of water stress on growth.  In addition, elevated CO2 increased whole-plant water-use efficiency by 51 and 63% in the well-watered and water-stressed seedlings, respectively.  This enhancement resulted solely from the CO2-induced increases in photosynthesis, and not from reductions in stomatal conductance or total water use.

What it means
As the air's CO2 content increases, peach seedlings likely will exhibit increased rates of net photosynthesis and biomass production.  In addition, they will likely be better able to deal with intermittent periods of water shortage, without compromising overall productivity and growth.  Thus, peach production will likely increase as the atmospheric CO2 concentration continues to rise.

Reviewed 23 October 2002