Elevated CO 2 and nitrogen availability have interactive effects on canopy carbon gain in rice

• Published in: The New phytologist Vol. 161; no. 2; pp. 459 - 471
• Main Authors: Anten, N P R, Hirose, T, Onoda, Y, Kinugasa, T, Kim, H Y, Okada, M, Kobayashi, K
• Format: Journal Article
• Language: English
• Published: England 01-02-2004
• Subjects: rice (Oryza sativa); free-air CO2 enrichment (FACE); photosynthesis; global change; nitrogen; leaf area index; model; canopy structure
• ISSN: 0028-646X; 1469-8137
• DOI: 10.1046/j.1469-8137.2003.00943.x

•  Here we analysed the effects of CO
(C
) 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
(c. 200 µmol mol
above ambient, using the free-air CO
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
) and apparent quantum yields than ambient plants, when measured at their own growth CO
. C
elevation reduced the total leaf N in the canopy (N
) but had no effect on LAI, and the average leaf N content (N
/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
under elevated than under ambient C
. This indicates that there is an N × C
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
elevation.