Interactive effects of elevated [CO₂] and drought on cherry (Prunus avium) seedlings II. Photosynthetic capacity and water relations

Abstract

Cherry seedlings (Prunus avium) were grown from seed for two growing seasons in three ambient [CO # ] ("350 µmol mol −" ) and three elevated [CO # ] (ambient j"350 µmol mol −" ) open-top chambers, and in three outside blocks. A drying cycle was imposed in both the growing seasons to half the seedlings : days 69-115 in the first growing season, and in the second growing season days 212-251 on the same seedlings which had already experienced drought. Stomatal conductance was significantly reduced in elevated [CO # ]-grown, unstressed seedlings in both the first and second growing seasons, but was not caused by a decrease in stomatal density. Droughted seedlings showed little or no reduction in stomatal conductance in response to elevated [CO # ]. However, stomatal conductance was highly correlated with soil water status. Photosynthetic rate increased significantly in response to elevated [CO # ] in both water regimes, leading to improvement in instantaneous transpiration efficiency over the whole duration of the experiment, but there was no relationship between instantaneous transpiration efficiency and long-term water use efficiency. The A max was strongly reduced in the second growing season, but unaffected by [CO # ] treatment. Although photosynthetic rate was not down-regulated, Rubisco activity was decreased by elevated [CO # ], possibly because of the increased leaf carbon : nitrogen ratio which had occurred by the ends of the two growing seasons. Elevated [CO # ] did not improve plant water relations (for example, bulk leaf -water potential, osmotic potentials at full and zero turgor, relative water content at zero turgor, bulk modulus of elasticity of the cell) and thus did not increase water-stress tolerance of cherry seedlings.Key words : cherry, elevated [CO # ], instantaneous transpiration efficiency, nitrogen, Rubisco, water relations, water stress. Drought is a major factor limiting plant productivity in large areas of the world, where it affects growth of both agricultural and forestry species and also influences distribution and composition of vegetation. The steady increase in greenhouse gases might lead in future to higher temperatures and greater evaporative demands ; drought occurrences will be more frequent, intense, and erratic, and will possibly affect regions not currently subjected to drought. Important issues are raised, such as how growth in elevated [CO # ] is affected by evaporative *Author for correspondence (e-mail centrit!nserv.icmat. mlib.cnr.it).demand, water supply and drought, and whether increased growth in elevated [CO # ] could be offset by adverse influences of drought on the soil-plantatmosphere continuum.Drought resistance involves a range of cellular and metabolic adaptations which affect plant water relations. Elevated [CO # ], by causing a decline in stomatal conductance (g s ), might reduce transpiration rate (E ), leading to an increase in plant water potential and a delay in the onset of drought. Moreover, it is reasonable to suppose that less nega...

Plant water relations at elevated CO2– implications for water‐limited environments

“…A similar lack of response in leaf water potential to elevated [CO 2 ] was observed by Ferris & Taylor (1994) and Ellsworth (1999), albeit in the latter study with loblolly pine, a significant response might not have been expected given that no effect of atmospheric [CO 2 ] on stomatal conductance was observed. Although it is not surprising that some studies report no effect of elevated [CO 2 ] on leaf water potential, it is interesting that a few recent studies have shown that leaf water potentials may actually be lower (more negative) in plants grown at elevated [CO 2 ] (Centritto et al 1999b;De Luis et al 1999). The mechanisms that contribute to these effects are not known.…”

“…Thus, CO 2 enrichment studies that link plant and soil-based processes should be encouraged. (Centritto et al 1999b) A common expectation from many, albeit not all, studies that address the physiological response of plants to elevated [CO 2 ] is that stomatal conductance will be reduced. In herbaceous species, these reductions can approach 27-40% (Morison 1985;Field et al 1995), whereas in some coniferous species the response may be considerably less (Teskey 1995;Tissue et al 1997;Ellsworth 1999).…”

“…1993;Tschaplinski, Norby & Wullschleger 1993;Centritto et al . 1999b;Ellsworth 1999;Tognetti, Raschi & Jones 2000a).…”

Stomatal density and stomatal index as indicators of paleoatmospheric CO2 concentration

“…Clifford et al, 1995;Heckenberger et al, 1998;Pa Èa Èkko Ènen et al, 1998). Some studies, however, report no response (Estiarte et al, 1994;Dixon et al, 1995;Pritchard et al, 1998;Centritto et al, 1999). No studies report a decrease.…”

Potential impacts of climate change on water availability for crops in the Okanagan Basin, British Columbia

“…A second limitation is the possible effect of elevated CO 2 on stomatal conductance, resulting in reduced transpiration and demand for water (Drake et al 1997). Although there is little direct, experimental evidence that fruit trees display reduced transpiration in response to elevated CO 2 (Centritto et al 1999(Centritto et al , 2002, there is considerable evidence that grasses and other annual C3 crops transpire less in elevated CO 2 atmospheres (Morison 2001). Such reductions in water demand may be as high as 20-30%, although a study of potential effects of climate change on US agriculture determined that un-irrigated field crops (corn, wheat, alfalfa) grown in the Pacific Northwest and western mountainous regions had relatively low decreases in transpiration by the end of the current century (approximately 8%) compared with other regions (Izaurralde et al 2003).…”