2000 Volume 69 Issue 2 Pages 194-200
The dry matter production, dark respiration rate and growth efficiency of high-yielding rice cultivar 'Takanari', grown under two levels of nitrogen fertilization (11, 17 gN / m2), were compared with those of 'Nipponbare' The crop growth rate (CGR) and leaf area index (LAI) were higher in 'Takanari' throughout the growth season. This higher CGR in 'Takanari' was due to the maintenance of NAR at the same level as in 'Nipponbare' in spite of the increase in LAI. The higher the nitrogen fertilization, the higher was the CGR due to the increase in LAI. The maximum dark respiration rate (Rs) in the whole plant was recorded at the early growth stage, followed by a rapid decrease until 40 days after transplanting and decreased gradually thereafter. The Rs in the whole plant and stems was higher in 'Takanari' as compared with 'Nipponbare' at the early stage, but was almost equal during the grain-filling period. The nitrogen concentration and Rs of the whole plant changed similarly, showing a close correlation between the two characters. The growth efficiency (GE) was about 64% during the early stage and gradually decreased thereafter in both cultivars irrespective of fertilization level. The GE during the grain-filling period was higher in 'Nipponbare' than in 'Takanari' and with the normal fertilization than heavy fertilization. We concluded that GE decreased at the later stage of plant growth due to increase in respiratory loss.
