Takanari, an indica cultivar of rice (Oryza sativa L.), is one of the Japanese cultivars with the highest yield. Although previous studies have indicated that Takanari has a greater photosynthetic capacity in canopy top leaves, which is achieved partly by its higher nitrogen (N) content per leaf area, N distribution at the whole-canopy level has not been studied. We addressed following questions: (i) Does Takanari have a higher N uptake rate? (ii) Does Takanari have more leaf N in the whole canopy? (iii) Does Takanari have higher leaf N content per leaf area in the whole canopy? (iv) Does Takanari reallocate more N from old to canopy top leaves? We studied N distribution in stands of Takanari and a popular japonica rice cultivar Koshihikari. Difference in the total plant N and leaf N per plant between Takanari and Koshihikari was small. Whereas Takanari had a lower leaf N per plant N than Koshihikari, Takanari had a steeper vertical gradient of leaf N content than Koshihikari. The slope of vertical distribution of leaf N content (KN) was positively correlated with the light extinction coefficient (KL) in each cultivar. Whereas the KN–KL relationship of Koshihikari was similar to that of the general trend found in a recent meta-analysis, Takanari had a significantly higher KN value than others when compared at a given KL. The KN values in Takanari were considered to be closer to the optimal KN than those in other species, which may contribute to higher productivity and higher N use efficiency in canopy photosynthesis.
ASJC Scopus subject areas
- Agronomy and Crop Science