Abstract:

A free-air CO₂ enrichment experiment was conducted at Anzhen city, Wuxi，Jiangsu, China, to study the effect of free-air CO₂ enrichment [FACE, 200 μmol·mol^-1 higher than Ambient(AMB)] on root growth dynamics, using the Japonica cultivar Wuxiangjing 14. Results showed that：(1) The peak value of total absorption area per unit dry weight of root and active absorption area per unit dry weight of root under FACE reached 10 days earlier than those at ambient air; and FACE treatment significantly decreased the total absorption area per unit dry weight of root, active absorption area per unit dry weight of root and the amount of a-NA per unit dry weight of root at 18 days after transplanting and its followed different stages, while little effects of FACE were detected on root activity per hole.(2)Root activity per unit dry weight of root negatively correlated with the number of adventitious roots per hole, total length of adventitious roots per hole, roots volume and dry weight of root per hole at 28 days after transplanting and its followed different stages. The larger the root production, the lower the root activity per unit dry weight. (3) For the most part，root activity per unit dry weight of root positively correlated with N content of rice plant, and negatively correlated with C/N ratio. According to available study results, the authors speculated that the largeness of biomass accumulated at early growth stages, lower N content in rice plant and higher C/N ratio appear to be the primary causes of significant decrement of root activity per unit dry weight of root under FACE condition.

Key words: Rice, Free-air CO₂ Enrichment, Root activity, N content, C/N ratio