Elevated CO₂ and nitrogen availability have interactive effects on canopy carbon gain in rice

Abstract

Summary• Here we analysed the effects of CO 2 (C a ) elevation and nitrogen availability on canopy structure, leaf area index (LAI) and canopy photosynthesis of rice ( Oryza sativa ).• Rice was grown at ambient and elevated C a ( c. 200 µmol mol − 1 above ambient, using the free-air CO 2 enrichment, FACE) and at two N availabilities. We measured leaf area, area-based leaf N contents and leaf photosynthesis, and calculated net daily canopy photosynthesis.• FACE plants had higher light-saturated rates of photosynthesis ( P max ) and apparent quantum yields than ambient plants, when measured at their own growth CO 2 . C a elevation reduced the total leaf N in the canopy ( N leaf ) but had no effect on LAI, and the average leaf N content ( N leaf /LAI) was therefore reduced by 8%. This reduction corresponded well with our model predictions. Leaf area index increased strongly with N availability, which was also consistent with our model.• Calculated canopy photosynthesis increased more strongly with N leaf under elevated than under ambient C a . This indicates that there is an N × C a interactive effect on canopy carbon gain. This interaction was caused by the increase in LAI with N availability, which enhanced the positive effect of the higher quantum yield under C a elevation.

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

“…It has been shown that predicted LAI values are strongly correlated with measured LAIs (Anten et al 2000). Anten et al (2004) applied the concept of optimal LAI to stands of rice grown under free air CO 2 enrichment (FACE). In this experiment, LAI increased with increasing nitrogen availability but was not affected by elevated CO 2 .…”

“…However, the increase in LAI by elevated CO 2 was only 6-8%, both in the experiment and the prediction, suggesting that nitrogen availability is the most important factor for leaf development even under elevated CO 2 . Anten et al (2004) further analysed the canopy photosynthetic rates in the rice stands. There are clear indications that the positive effect of elevated CO 2 on canopy carbon gain increases with nitrogen availability (Fig.…”

“…Second, nitrogen uptake increases under elevated CO 2 only when nitrogen availability is high, and not when it is low (Stitt and Krapp 1999). Anten et al (2004) proposed a mechanism of an interactive effect of nitrogen and CO 2 that is independent of the above two factors. When nitrogen availability is low, the canopy is relatively open and most leaves receive relatively high light.…”

“…Under these conditions the enhanced quantum yield under elevated CO 2 will have an increasingly positive effect on canopy photosynthesis (see Fig. 5e in Anten et al 2004).…”

Effects of Elevated Atmospheric CO2 on Photosynthesis, Growth and Biomass in Shorea platycarpa F. Heim (Meranti Paya)

“…Oikawa et al (2013) reported that elevated CO 2 did stimulate the LAI in the soybeans cultivars but the LAI was also being regulated by the leaf production rate and leaf loss. The effects of (CO 2 ) on LAI are probably modified by N availability, which strongly controls leaf area growth (Anten et al 2003). The LAI of plants in elevated CO 2 might be affected by the insufficiency of N uptake.…”