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.

Leaf photosynthesis of Betula albosinensis seedlings as affected by elevated CO2 and planting density

“…Thus, we suggest that photosynthetic acclimation implies a reallocation of N from the photosynthetic machinery to other parts of the plant at elevated CO 2 . Many previous studies have also reported that A in the leaves is determined by the amount of leaf N and its partitioning between the photosynthetic and non-photosynthetic proteins, and among the various photosynthetic components (Woodward, 2002;Hikosaka, 2004;Hikosaka et al, 2005). Our results showed that elevated CO 2 reduced the initial activity of leaf Rubisco by 37.0% at the low planting density, and by 33.1% at the high planting density.…”

Carbon dioxide enrichment by composting in greenhouses and its effect on vegetable production

“…The problem is exacerbated in the middle of the day when plants experience their maximum rate of photosynthesis and high demand for CO 2 . Sufficient CO 2 concentrations are crucial to sustain vegetable production (Hikosaka et al, 2005;Fierro et al, 1994;Buddendorf-Joosten and Woltering, 1994). In the present study, large quantities of CO 2 were generated through microbial fermentation in greenhouses containing CRAM units.…”

Effects of experimental warming on growth, biomass allocation, and needle chemistry of Abies faxoniana in even-aged monospecific stands

“…Competition with neighboring plants is one of the most important biotic factors limiting plant growth. Plants in a stand compete with each other for resources, and competition alters morphological and physiological traits of plants (Hikosaka et al 1999(Hikosaka et al , 2005Nagashima et al 2003). These alterations, in turn, result in changes in the microclimate and resource acquisition in the stand, and consequently influence the growth and development of individuals (Hikosaka et al 1999;Nagashima et al 2003).…”

“…We analyzed how warming over 6 years influenced growth, biomass allocation, needle chlorophyll concentrations, and carbohydrate status of individuals in a stand. Since light competition is critical for the survival and growth of individuals in dense stands and forest understory (Hikosaka et al , 2005Wang et al 2006), we postulated the following two hypotheses: (1) warming benefits individuals in the stand and causes changes in biomass allocation patterns, and (2) warming causes adjustments in morphology and physiology that allow improved capture of light to support seedling growth.…”