Impact of the CO2 requirement on plant water use

✍ Scribed by Richard W. Tinus

• Publisher: Elsevier Science
• Year: 1974
• Weight: 758 KB
• Volume: 14
• Category: Article
• ISSN: 0002-1571
• DOI: 10.1016/0002-1571(74)90013-2

✦ Synopsis

Land plants lose large quantities of water, because they must expose their photosynthetic tissue to the air to obtain CO2. Succulents which absorb CO2 at night and C4 plants which lack photorespiration are more efficient than C3 plants in carbon fixation per unit of water lost. Plant-water-use efficiency of C3 plants can be increased by growing in greenhouses at elevated CO 2 levels, conditions which conserve moisture and suppress photorespiration. Antitranspirants may be useful under certain conditions. Perhaps water-use efficiency can be increased by breeding.

INTROD UCTION

Every beginning biology student learns that water plus CO2 in the presence of light and chlorophyll yields sugars. This simple equation not only describes photosynthesis, but explains why land plants are such voracious consumers of water. Plants have evolved perforated lamellar structures distributed on a ramified framework which guarantees maximum tissue exposure to air and sunlight. The inevitable high water loss is the price the plant must pay to satisfy its requirements for atmospheric CO2 and sunlight energy.

Water loss is relative, however, and some plants are much more efficient than others in terms of water consumed per unit of dry matter produced. I hope to show why this is so in terms of CO2 metabolism, and what might be done to alter plant productivity in our favor.