Modification of the response of photosynthetic productivity to rising temperature by atmospheric CO₂ concentrations: Has its importance been underestimated?

Abstract

Abstract. Climate change will include correlated increases in temperature and atmospheric CO2 concentration (Ca). Rising temperatures will increase the ratio of photorespiratory loss of carbon to photosynthetic gain, whilst rising Ca will have an opposing effect. The mechanism of these effects at the level of carboxylation in C3 photosynthesis are quantitatively well understood and provide a basis for models of the response of leaf and canopy carbon exchange to climate change. The principles of such a model are referred to here and used to quantitatively examine the implications of concurrent increase in temperature and Ca. Simulations of leaf photosynthesis show the increase, with elevation of Ca from 350 to 650 μmol mol‐1, in light saturated rates of CO2 uptake (Asat) and maximum quantum yields (φ) to rise with temperature. An increase in Ca from 350 to 650 μmol mol‐1 can increase Asat by 20% at 10°C and by 105% at 35°C, and can raise the temperature optimum of Asat by 5°C. This pattern of change agrees closely with experimental data. At the canopy level, simulations also suggest a strong interaction of increased temperature and CO2 concentration. Predictions are compared with the findings of long‐term field studies. The principles used here suggest that elevated Ca will alter both the magnitude of the response of leaf and canopy carbon gain to rising temperature, and sometimes, the direction of response. Findings question the value of models for predicting plant production in response to climate change which ignore the direct effects of rising Ca and the modifications that rising Ca imposes on the temperature response of net CO2 exchange.

Simulação do desenvolvimento da batata cultivar asterix em cinco cenários de mudanças climáticas em Santa Maria, RS

“…Plantas com metabolismo C3 são mais beneficiadas pelo aumento da concentração de CO 2 atmosférico do que plantas com metabolismo C4 (TUBIELLO et al, 2000;SIQUEIRA et al, 2001;STRECK, 2005). No entanto, se o aumento da concentração de CO 2 for acompanhado de aumento da temperatura do ar, poderá não haver aumento no crescimento e produtividade das culturas devido ao encurtamento do ciclo (WIEGAND e CUELLAR, 1981;SIONIT et al, 1987;HUNT et al, 1991;BUTTERFIELD e MORISON, 1992;SHAYKEWICH, 1995, SIQUEIRA et al, 2001) e aumento da respiração (fotorespiração e fase escura da respiração) (ROSENBERG et al, 1983;LONG, 1991;VU et al, 1997;TAIZ e ZEIGER, 2004). Portanto, em estudos de impactos das mudanças climáticas sobre os agroecossistemas, devese dar especial atenção ao efeito do aumento de temperatura (aquecimento global) no desenvolvimento vegetal e assim caracterizar mudanças no ciclo das culturas em diferentes cenários meteorológicos.…”

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

“…Grapevine photosynthesis, as in other C 3 species, is limited by CO 2 (Mullins et al, 1992;Bindi et al, 1996). Any CO 2 increase therefore may enhance CO 2 23 fixation rates (Long, 1991). However, plants may experience photosynthetic acclimation when exposed to elevated CO 2 in long-term experiments, which decreases 1 photosynthesis capacity below its maximum potential (Jifon and Wolfe, 2002;Long et 2 al., 2004;Erice et al, 2006b).…”

Effects of experimental warming and drought on biomass accumulation in a Mediterranean shrubland

“…The projected temperature rise could affect plant growth due to changes in photosynthetic rate, CO 2 losses by respiration, enhanced photorespiration and VOC production which present different responses depending on the temperature range (Long 1991;Huntingford et al 2000;Peñuelas and Llusià 2002). In the Mediterranean area, warming effects are expected to be dependent on the season.…”