However, these experimental conditions, which are different

from natural growing environments (field conditions) in combination with the border effects H 89 molecular weight associated with small plots, have been shown to modify the responses of plants to increasing [CO2] [21] and [22]. FACE experiments, conducted in fully open-air field conditions without altering microclimatic and biotic variables, represent our best simulations of the future high CO2 environment. Over the last decade, only two large-scale (12 m × 12 m plots) replicated rice FACE experiments have been conducted worldwide (1997–2006). Both experiments used a similar FACE technology and employed the same target [CO2], 570 μmol mol− 1[23], [24] and [25]. There have been reports on the effects of elevated [CO2] and N supply on the growth, nutrient uptake, root development, and yield of inbred japonica cultivars [13], [14], [25], [26], [27], [28] and [29], but no simulated prediction for root number and length has been made. Compared with conventional rice cultivars, hybrid rice cultivars exhibit better

tillering ability, thus a relatively check details higher growth rate. The effects of FACE and N on root growth may be different. In the present study, the hybrid rice cultivar Shanyou 63, the most widely used hybrid rice variety in China for the past 15 years [30], was used to study the effects of FACE under two N levels on root number and length, and the results were used for model development. The models may provide information for root growth control and high-yield cultivation of rice. The experiment was conducted in Xiaoji, Yangzhou, Jiangsu, China (32°35′5″ N, 119°42′

E) in 2005 and 2006. The farm used in this study had fluvisol soil (local name, Qingni soil) with annual mean precipitation of 980 mm, evaporation of 1100 mm, temperature of 14.9 °C, total sunshine hours of 2100 h, and frostfree period of 220 d. The physical and chemical properties of the soil were as follows: soil organic carbon (SOC) 18.4 g kg− 1, DNA ligase total N 1.45 g kg− 1, total P 0.63 g kg− 1, total K 14 g kg− 1, available P 10.1 mg kg− 1, available K 70.5 mg kg− 1, sand (0.02–2.00 mm) 578.4 g kg− 1, silt (0.002–0.020) 285.1 g kg− 1, clay (< 0.002 mm) 136.5 g kg− 1, and pH 7.2. The FACE system comprised six FACE plots located in different fields with similar soil and agronomic histories. Of these plots, three were allocated for FACE experiments (hereafter called E-[FACE]) and another three for ambient treatments (hereinafter called A-[FACE]). To reduce the influence of CO2 emission, the distance between E-[FACE] plots and A-[FACE] was more than 90 m. Each E-[FACE] plot was designed as an octagon with a largest diameter of 12.5 m. In the E-[FACE] plots, pure CO2 gas was released from peripheral emission tubes and the [CO2] was about 570 μmol mol− 1. The FACE treatment was controlled by a computer system.