Analysis on difference of dry matter production between rice cultivars with different plant height in relation to gas diffusion inside stands.

Abstract

The differencc in yield, dry matter production, and physiological and ecological characters were studied between Tainung 67, a high-yielding cultivar (long-culm and ear-weight type) in Taiwan, and Nippon-bare, a Japanese standard cultivar (short-culm and ear-number type). The yield and dry matter production were higher in Tainung 67 than those in Nipponbare. Both net assimilation rates and mean leaf area indices were higher in Tainung 67 than those in Nipponbare, after heading time when the plant length was much higher in Tainung 67 than that in Nipponbare. The causes of the difference in net assimilation rates between two cultivars were examined by measuring canopy structure. The characteristics of canopy structure related to an increase in dry matter production in Tainung 67 were compared with those of Nipponbare. (1) smaller leaf area density in spite of larger leaf area index owing to larger plant height, (2) good light-intercepting characteristics indicated by a little sraller light extinction coefficient and larger leaf angles against horizontal, (3) higher evaporation rate inside stands in spite of larger leaf area index, (4) higher CO2-concentration inside the stands during daytime in spite of larger leaf area index and the same or higher leaf photosynthetic rate. On the basis of these results, we pointed out that it was necessary for the breeding of high-yielding rice cultivars to give full consideration to the use of these characteristics in long-culm and ear-weight type cultivar when an increase in dry matter production is attempted on condition that physical, physiological and morphological characteristics of the culm and sheath must be studied to improve lodging resistance in cultivars with large plant height.