Soil and water warming accelerates phenology and down-regulation of leaf photosynthesis of rice plants grown under free-air CO2 enrichment (FACE).

Minaco Adachi,Hiroshi Fukayama,Hirofumi Nakamura,Toshihiro Hasegawa,Ryoji Sameshima,Takeshi Tokida,Masumi Okada,Toshinori Matsunami,Hidemitsu Sakai

doi:10.1093/pcp/pcu005

Abstract

To enable prediction of future rice production in a changing climate, we need to understand the interactive effects of temperature and elevated [CO2] (E[CO2]). We therefore examined if the effect of E[CO2] on the light-saturated leaf photosynthetic rate (Asat) was affected by soil and water temperature (NT, normal; ET, elevated) under open-field conditions at the rice free-air CO2 enrichment (FACE) facility in Shizukuishi, Japan, in 2007 and 2008. Season-long E[CO2] (+200 µmol mol−1) increased Asat by 26%, when averaged over two years, temperature regimes and growth stages. The effect of ET (+2°C) on Asat was not significant at active tillering and heading, but became negative and significant at mid-grain filling; Asat in E[CO2]–ET was higher than in ambient [CO2] (A[CO2])–NT by only 4%. Photosynthetic down-regulation at E[CO2] also became apparent at mid-grain filling; Asat compared at the same [CO2] in the leaf cuvette was significantly lower in plants grown in E[CO2] than in those grown in A[CO2]. The additive effects of E[CO2] and ET decreased Asat by 23% compared with that of A[CO2]–NT plants. Although total crop nitrogen (N) uptake was increased by ET, N allocation to the leaves and to Rubisco was reduced under ET and E[CO2] at mid-grain filling, which resulted in a significant decrease (32%) in the maximum rate of ribulose-1,5-bisphosphate carboxylation on a leaf area basis. Because the change in N allocation was associated with the accelerated phenology in E[CO2]–ET plants, we conclude that soil and water warming accelerates photosynthetic down-regulation at E[CO2].

Highlights

Human activities have increased the concentration of atmospheric carbon dioxide ([CO2]) from the pre-industrial level of 280 mmol molÀ1
The light-saturated leaf photosynthetic rate (Asat) measured at each growth [CO2] condition decreased as the crop growth stage advanced (Fig. 1a–c)
The light-saturated photosynthetic rate (Asat) increase due to E[CO2] was slightly higher at elevated soil and water temperatures (ET) than at normal temperatures (NT) (25% vs. 16%, respectively, at active tillering, and 42% vs. 35% at heading), but the interaction between [CO2] and temperature was not significant

Summary

Introduction

Human activities have increased the concentration of atmospheric carbon dioxide ([CO2]) from the pre-industrial level of 280 mmol molÀ1. Does rising [CO2] drive changes in the global environment (e.g. in temperature and precipitation), it promotes leaf-level photosynthesis and thereby can increase biomass production and grain yield of crops (Long et al 2004). This CO2 fertilization effect is one of the few expected positive impacts of climate change on crop production (Parry et al 2005), including that of rice, the most important global food crop that feeds more than half of the world’s population. We need to better understand the interactive effects of elevated [CO2] and

Objectives

Methods

Results

Discussion

Conclusion