Plant responses to elevated CO₂ concentration at different scales: leaf, whole plant, canopy, and population

Abstract

Elevated CO 2 enhances photosynthesis and growth of plants, but the enhancement is strongly influenced by the availability of nitrogen. In this article, we summarise our studies on plant responses to elevated CO 2 . The photosynthetic capacity of leaves depends not only on leaf nitrogen content but also on nitrogen partitioning within a leaf. In Polygonum cuspidatum, nitrogen partitioning among the photosynthetic components was not influenced by elevated CO 2 but changed between seasons. Since the alteration in nitrogen partitioning resulted in different CO 2 -dependence of photosynthetic rates, enhancement of photosynthesis by elevated CO 2 was greater in autumn than in summer. Leaf mass per unit area (LMA) increases in plants grown at elevated CO 2 . This increase was considered to have resulted from the accumulation of carbohydrates not used for plant growth. With a sensitive analysis of a growth model, however, we suggested that the increase in LMA is advantageous for growth at elevated CO 2 by compensating for the reduction in leaf nitrogen concentration per unit mass. Enhancement of reproductive yield by elevated CO 2 is often smaller than that expected from vegetative growth. In Xanthium canadense, elevated CO 2 did not increase seed production, though the vegetative growth increased by 53%. As nitrogen concentration of seeds remained constant at different CO 2 levels, we suggest that the availability of nitrogen limited seed production at elevated CO 2 levels. We found that leaf area development of plant canopy was strongly constrained by the availability of nitrogen rather than by CO 2 . In a rice field cultivated at free-air CO 2 enrichment, the leaf area index (LAI) increased with an increase in nitrogen availability but did not change with CO 2 elevation. We determined optimal LAI to maximise canopy photosynthesis and demonstrated that enhancement of canopy photosynthesis by elevated CO 2 was larger at high than at low nitrogen availability. We also studied competitive asymmetry among individuals in an even-aged, monospecific stand at elevated CO 2 . Light acquisition (acquired light per unit aboveground mass) and utilisation (photosynthesis per unit acquired light) were calculated for each individual in the stand. Elevated CO 2 enhanced photosynthesis and growth of tall dominants, which reduced the light availability for shorter subordinates and consequently increased size inequality in the stand.

Response of 12 weedy species to elevated CO2 in low‐phosphorus‐availability soil

“…However, more and more studies have shown that other environmental factors (e.g. soil fertility, soil water availability) could regulate plant responses to rising CO 2 (Oren et al 2001;Prior et al 2003;Hikosaka et al 2005). Wand et al (1999) and Ward et al (1999) showed that soil water and nutrient stress reduced the response of C 3 , but not C 4 plants, to CO 2 .…”

Including the dynamic relationship between climatic variables and leaf area index in a hydrological model to improve streamflow prediction under a changing climate

“…This could influence the water balance by increasing evapotranspiration and decreasing runoff. In addition, at the canopy scale, the evapotranspiration effect of increased LAI can be masked by shading among leaves, soil cover and raised canopy humidity (Hikosaka et al, 2005;Bunce, 2004). A study that considered both effects suggested that the fertilization effect of rising CO 2 is larger than the stomatal pore reduction effect, and the net effect is decreases in runoff (Piao et al, 2007).…”

Pollen performance of Raphanus sativus (Brassicaceae) declines in response to elevated [CO2]

“…Elevated [CO 2 ] may cause short-term increases in vegetative growth due to higher rates of CO 2 assimilation, and these increases in growth might translate into an increase in male fitness. This positive response might decrease over time if there is a downward regulation of photosynthesis or if other resources become limited (Conroy and Hocking 1993;Geiger et al 1999;Urban 2003;Hikosaka et al 2005). To address these issues, we examined how [CO 2 ] affected male components of fitness in wild radish over several months.…”