Influence of Elevated Atmospheric CO2 Concentrations on Plant Nutrition

Abstract

The rising levels of atmospheric CO2 are likely to increase biomass production of C3 species in both natural and managed ecosystems because photosynthetic rates will be higher. The greatest absolute increase in productivity will occur when nitrogen and phosphorus availability in the soil is high. Low nitrogen does not preclude a growth response to high CO2, whereas some C3 species fail to respond to high CO2 when phosphorus is low, possibly because insufficient phosphorus is available to maintain maximum photosynthetic activity at high CO2. C3 plants response to high CO2 because the flux of carbon through the photoreductive cycle is increased and photorespiration is suppressed. This change in metabolism appears to alter the foliar nutrient concentration required to promote maximum productivity (critical concentration). Higher phosphorus concentrations are needed at elevated CO2, whereas the nitrogen requirement is reduced by CO2 enrichment. Since critical concentrations are used to evaluate nutrient status of crop and forest species and to manage fertiliser programs, they will need reassessing as the atmospheric CO2 concentration rises. Another consequence of the altered nutrient requirement at high CO2 is that the nitrogen concentrations of foliage, roots and grain are consistently lower in plants grown at elevated CO2, irrespective of availability of nitrogen in the soil. In natural ecosystems, the lower nitrogen to carbon ratio of the litter may alter rates of nutrient cycling. For farmers, the rising CO2 concentrations could cause reductions in grain nitrogen, and therefore protein content. This could have important implications for baking quality of hard wheats as well as affecting the nutrient value of grain such as rice.

Elevated Carbon Dioxide and Soil Moisture on Early Growth Response of Soybean

“…Reduction in nutrient concentration of plants due to increased [CO 2 ] concentration has been reported by earlier studies [10]- [12]. The reason attributed to the uptake of nutrient from the soil is not increased in relation to the increased net carbon assimilation may leading to changes in the nutritional quality of the crops.…”

“…Previous studies also reported reduction in leaf nitrogen concentration with elevated [CO 2 ] in different crop species [12]- [14] [82]. This reduction in nitrogen may be either due to the dilution effect as a result of greater carbohydrate accumulation [13] or due to the acceleration of plant growth, but not due to the increased nitrogen use efficiency [83].…”

“…The direct impact of rising atmospheric [CO 2 ] concentration on plants includes increase in photosynthetic rate [4]- [6], growth [7]- [9], reduction in nutrient concentration of plants [10] [11], reduction in leaf nitrogen concentration [12]- [14], increased C:N ratio [15] [16] and increased flowering and fruiting [15]- [21], and yield of agricultural crops [2] [22] [23], and is also expected to increase water use efficiency of crops [2] [4]. Productivity of most agricultural crops increases under elevated [CO 2 ] is in the range of 15% to 41% for C3 crops and 5% to 10% for C4 crops [2] [22] [23].…”

Photosynthetic Acclimation in Pea and Soybean to High Atmospheric CO2 Partial Pressure

“…The second potential indirect response to growth under high CO, concentration is a change in the relative distribution of N between the photosynthetic machinery as a whole and sinks and/or into the systems for acquiring other resources such as roots for mineral nutrient acquisition. This is suggested by the observation (Conroy, 1992) that plants from high CO, conditions always have a lower foliar Iq concentration than control plants, even when grown with abundant N supply. This was also true when foliar N concentration was expressed on a structural (rather than total) leaf dry weight basis (Rogers et al, 1993).…”

The effects of elevated CO2 and water stress on whole plant CO2 exchange, carbon allocation and osmoregulation in oak seedlings

“…Thus, it might be hypothesized that increasing atmospheric CO 2 concentration favours osmotic adjustment through enhanced carbon supply to the different plant components and increased organic solute concentrations. However, elevated CO 2 concentrations often lead to reduced total mineral ion concentrations in the plant tissues (Conroy, 1992;Overdieck, 1993 Biomass partitioning between the plant compartments was assessed by determining i) the leaf mass ratio (LMR, leaf dry mass/whole plant dry mass, g g -1 ), ii) the stem mass ratio (SMR, stem dry mass/whole plant dry mass, g g -1 ), iii) the root mass ratio (RMR, root mass/whole plant mass, g g -1 ) and iv) the root:shoot ratio (root mass/[leaf mass + stem mass]). Specific leaf mass ratio (SLA, dm 2 g -1 ) and leaf area ratio (LAR, dm 2 g -1 ) were calculated as the leaf area to leaf mass and the leaf area to plant mass, respectively.…”