Effect of dark respiration on dry matter production of field-grown rice cultivars-comparison of growth efficiency between Nipponbare and Takanari.

摘要

Rice cv. Takanari and Nipponbare were given 11 or 17 g N/m2. The crop growth rate (CGR) and leaf area index (LAI) were higher in Takanari throughout the growing season. The higher CGR was due to the maintenance of NAR [net assimilation rate] at thesame level as in Nipponbare in spite of the increase in LAI. The higher the N rate, the higher 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 a gradual decrease thereafter. The Rs in the whole plant and stems was higher in Takanari than Nipponbare at the early stage, but was almost equal during the grain-filling period. The N concentration and Rs of the whole plant showed similar changes, 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 N rate. The GE during the grain-filling period was higher in Nipponbare than in Takanari and with normal rather than high N. It was concluded that GE decreased at the later stage of plant growth due to an increase in respiratory loss.