Effects of CO2 Concentration on the Rate of Photosynthesis

Effects of CO2 Concentration on the Rate of Photosynthesis

Whenever there is an increase of CO2 in the atmosphere, plants respond by reducing stomatal conductances, hence, water loss is reduced. This result in greater soil moisture content in ecosystems rich with CO2, this increases plant growth

In a review of studies conducted over the prior decade, Pospisilova and Catsky (1999) compiled over 150 individual plant water use responses to atmospheric CO2 enrichment. They found that elevated CO2 increased rates of net photosynthesis in about 85% of the reported studies, while reducing stomatal conductances and rates of transpiration in approximately 75% of the cases analyzed. Consequently, atmospheric CO2 enrichment increased plant water-use efficiency in more than 90% of the experiments that were conducted; and it reduced total water uptake in more than 50% of the studies, while slowing the development of water stress as indicated by plant water potential data. As a result Pospisilova and Catsky concluded that plants growing in future atmospheres of higher CO2 concentration "will probably survive eventual higher drought stress and some species may even be able to extend their biotope into less favourable sites."

In a subsequent experiment, Wullschleger et al. (2002) studied sweetgum trees growing in FACE plots maintained at an atmospheric CO2 concentration of 540 ppm and found them to display a 14% reduction (relative to trees growing in ambient air) in seasonal stomatal conductance at the canopy level, which significantly reduced their rates of transpiration during the growing season. In fact, Wullschleger and Norby (2001) quantitatively demonstrated that elevated CO2 reduced season-long stand transpiration by approxi...

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...nges in soil structure and soil biota of nutrient-poor grassland. Global Change Biology 9: 585-600.

Pospisilova, J. and Catsky, J. 1999. Development of water stress under increased atmospheric CO2 concentration. Biologia Plantarum 42: 1-24.

Wullschleger, S.D. and Norby, R.J. 2001. Sap velocity and canopy transpiration in a sweetgum stand exposed to free-air CO2 enrichment (FACE). New Phytologist 150: 489-498.

Wullschleger, S.D., Gunderson, C.A., Hanson, P.J., Wilson. K.B. and Norby, R.J. 2002. Sensitivity of stomatal and canopy conductance to elevated CO2 concentration - interacting variables and perspectives of scale. New Phytologist153: 485-496.

http://www.co2science.org/subject/t/summaries/transpiration.php

http://wizznotes.com/biology/transport-in-plants/factors-affecting-transpiration

http://water.me.vccs.edu/courses/SCT112/lecture3_2b.htm