Seasonal changes in the effects of free‐air CO₂ enrichment (FACE) on growth, morphology and physiology of rice root at three levels of nitrogen fertilization

Abstract

Over time, the relative effects of elevated [CO 2 ] on the aboveground photosynthesis, growth and development of rice (Oryza sativa L.) are likely to be changed with increasing duration of CO 2 exposure, but the resultant effects on rice belowground responses remain to be evaluated. To investigate the impacts of elevated [CO 2 ] on seasonal changes in root growth, morphology and physiology of rice, a free-air CO 2 enrichment (FACE) experiment was performed at Wuxi, Jiangsu, China, in 2002-2003. A japonica cultivar with large panicle was exposed to two [CO 2 ] (ambient [CO 2 ], 370 lmol mol À1 ; elevated [CO 2 ], 570 lmol mol À1 ) at three levels of nitrogen (N): low (LN, 15 g N m À2 ), medium (MN, 25 g N m À2 ) and high N (HN, 35 g N m À2 ). Elevated [CO 2 ] increased cumulative root volume, root dry weight, adventitious root length and adventitious root number at all developmental stages by 25-71%, which was mainly associated with increased root growth rate during early growth period (EGP) and lower rate of root senescence during late growth period (LGP), while a slight inhibition of root growth rate occurred during middle growth period (MGP). For individual adventitious roots, elevated [CO 2 ] increased average length, volume, diameter and dry weight early in the season, but the effects gradually disappeared in subsequent stages. Total surface area and active adsorption area per unit root dry weight reached their maxima 10 days earlier in FACE vs. ambient plants, but both of them together with root oxidation ability per unit root dry weight declined with elevated [CO 2 ] during MGP and LGP, the decline being larger during MGP than LGP. The CO 2 -induced decreases in specific root activities during MGP and LGP were associated with a larger amount of root accumulation during EGP and lower N concentration and higher C/N ratio in roots during MGP and LGP in FACE vs. ambient plants. The results suggest that most of the CO 2 -induced increases in shoot growth of rice are similarly associated with increased root growth.

Ammonia Volatilization from Rice Paddy Soils Fertilized with15N-Urea Under Elevated CO2and Temperature

“…However, to take full advantages of the CO2 fertilization effect, management of soil N availability has been shown to be very crucial [4][5][6][7] . Urea is the most extensively used fertilizer (accounted for 40% of total synthetic fertilizer consumption in the world), and is very susceptible to loss particularly via ammonia volatilization 8) .…”

Effects of elevated [CO2] on stem and root lodging among rice cultivars

“…In this study, we did not obtain an accurate count of the roots due to the huge roots number. Yang demonstrated that under elevated [CO 2 ], the increase of the number of adventitious roots, and the root volume and root dry weight per plant were similar (about 30%) at 80 days after transplanting [17]. The findings suggested that under elevated [CO 2 ], the increase in root biomass was mainly attributable to an increase in root number.…”

“…Studies confirmed that during rice growth, after stem lodging, root lodging is the next greatest lodging risk, and also proved that the larger roots system and thicker crown roots in subsoil were the very important characteristics for anti-lodging for root [15,16]. Although most studies approved that elevated [CO 2 ] promoted root growth, and increased the root volume, root biomass of rice [17,18], no study has examined the risk of root lodging under elevated [CO 2 ].…”

“…The two chambers were used to impose two CO 2 levels: 680 µmol mol -1 CO 2 (elevated) and 400 µmol mol -1 CO 2 (ambient) during day and night. The chambers have been used for elevated [CO 2 ] experiments of rice since 1996 [17]. Each chamber, measuring 4 m × 2 m × 2 m (L × W × H), has two stainless-steel containers (1.5 m × 1.5 m × 0.3 m, L × W × H) filled with water to hold the pots.…”

Fenced cultivation of water hyacinth for cyanobacterial bloom control

“…The parameters, such as volume, TSA (total root surface area), AAA (active absorption area), and AAA/TSA of roots were are considered to be crucial in root function (Yang et al 2008). The present study provides clear experimental evidence which states that all the four parameters in Downwind sites were significantly lower than those values obtained in Upwind sites.…”