Effect Of FACE On Root Growth Of Rice And Its Relation With Yield Formation

Global atmospheric CO2 concentration is increasing from 280 to since pre-industrial times and it is projected to reach levels of 450~550μmol mol-1 within year 2050. The enhancement of atmospheric CO2 concentration commonly caused the climate change and affected the rice crops production. This study was carried out in the platform for FACE study, located in Wuxi (31°37'N, 120°28'E), China, using Wuxiangjing 14 as tested rice cultivar. The CO2 concentration in FACE treatment was 570μmol mol-1, with 370μmol-mol-l as ambient (AMB). The main purpose of the experiment was to study the effects of elevated CO2 concentration on root growth of rice and its relation with yield formation. Results showed as follows:(1)The number of adventitious roots per hole, the length of adventitious roots per hole, the roots volume per hole and the dry weight of roots per hole under FACE condition were significantly higher than those under AMB at tillering, jointing and heading stages; FACE treatment could significantly increase the diameter per adventitious root which were generated during effective tillering and unproductive tillering period, while the diameter per adventitious root generated during stem elongating and panicle bearing period became more and more thinner under FACE condition, which resulted in no significant differences existed between the diameter per adventitious roots under FACE and those at AMB at heading stage; The number of adventitious roots per hole, the length of adventitious roots per hole, the roots volume per hole and the dry weight of roots per hole under FACE were significantly higher than those at AMB at heading stage, which was chiefly resulted from the larger increment of those root traits stimulated by FACE during effective-tillering and unproductive-tillering period. While no obvious stimulation due to FACE were detectable for those root traits growth during stem elongating and panicle bearing period.(2)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. 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. 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.(3)In three year's experiment, the number of panicles, filled grain percentage and 1000-grain-weight in FACE, average value of the data in 2001, 2002 and 2003, increased 17.42, 4.16 and 1.72 percent, respectively, while number of spikelets per panicle decreased in FACE treatment with 6.78 percent. Compared with AMB, Grain output in FACE treatment increased 11.14, 15.80 and 14.22 percent in 2001, 2002 and 2003, respectively, which was chiefly resulted from the larger increment of the number of panicles. The number of panicles and grain yields were significantly correlated with the number, the length of adventitious roots per hole and the roots volume, the dry weight of roots per hole. Among those root traits, the number of adventitious roots and the dry weight of roots per hole were the main traits which...