Tohoku Journal of Crop Science

The concept of the constancy of accumulated effective temperature to the growth in paddy rice plants was examined under the controled environment for several rice cultivars which had different local adaptability. The results obtained were summerized as follows: 1. The constancy of accumulated effective temperature was maintained in varieties adapted to cold Hokkaido district to some degree. For the varieties adapted to the warm district of Japan, however, the concept was not applicable. 2. Influence of daylength must be taken into account when we examine the accumulated effective temperature always. 3. As to the accumulated effective temperature required for the expansion of successive leaves, there was no marked difference between cold and warm district varieties. 4. Under the low temperature condition, there was significant difference of total number of leaves on the main culm between varieties of cold and warm district of Japan. 5. In any cultivars, the constancy in later vegetative growth period, young ear formation to heading, was more notable than that in early period of growth, germination to young ear formation.

View full abstract

To study the influence of temperatures of the air condition upon the tillering of the rice plant, an experiment was made with six varieties including Japonica and Indica. The plants were cultured in growth cabinets, and the day length was controled as 12 hours, the light intensity being 22,000lux. The experimental plots used were 18.5°, 24.5° and 30.5°C. in the mean air temperature. The number of tillers decreased with rise of the air temperature in all of the varieties tasted, and this phenomenon was due to decrease of the secondary and tirtiary tillers, while the number of the primary tillers was unchanged. Difference of the growth habit of varieties gave different grades of the decrease of high position tillers with rise of the temperature, i.e. the decrease was conspicuous in varieties of the heavy panicle type.

View full abstract

Norin-17 rice plants were grown in 4 growth cabinets (day-night temperatures, 30-25°, 25-20°, 20-15°, 15-10°C), combined with SL (strong light; natural daylight plus a 5000f.c. lamp), WL (weak light; covered by a vinyl blind having 1/3intensity of natural light), HH (high air-humidity, 70-80%R.H.) and LH (low humidity, 50-60%R.H.). The growth such as plant height, leaf appearance rate, leaf number, and dry weight all increased as temperature increased, with a higher leaf-blade ratio and T/R ratio. Concentrations of both nitrogen and carbohydrate increased as temperature decreased, especially so of the former at leaf-blade in protein-N, at leaf-sheath plus stem in soluble-N, and markedly so of the latter at leaf-sheath plus stem in crude starch. Growth was promoted slightly by HH with a higher T/R ratio and a greater accumulation of nitrogen. SL very much increased dry matter, nitrogen and carbohydrate accumulations especially so at higher temperatures, although with a decrease of leaf-blade ratio and T/R ratio.

View full abstract

Show abstractHide abstract

To clarify the influence of seed weight on the early vegetative growth of seedlings in several grasses and what extent the difference of early growth can be explained by difference in seed weight especially when two or three species of grasses are in mixed culture where those are mutually, different mean seed weight, decrease in seed reserve substances followed by the germination and dry matter increase in seedling were examined for 9 grass species 15 varieties. Results obtained are as follows: 1) Comparing two varieties belong to the same species, heavy seed weight variety which has much seed reserve substances consumes them more rapidly than light seed weight variety. Dry matter increase in the former seedling is, therefore, quantitatively much more than in the latter. The relative growth rate (RGR) of dry weight of light seed weight variety is, conversely, higher than that of heavy seed weight variety. Consequently, it is suggested that variety which has originally light seed weight has possibility to restore its inferiority in seedling growth immediately after it takes to germinate because the RGR of young seedling of light seed weight variety is higher than that of heavy seed weight variety. About a month after germination, however, the difference of RGR between varieties become to disappear and thereafter the RGR's of both variety become to same value in their time course. It is fact that the initial seed weight affects positively the vegetative growth of grasses over a conciderably long period. 2) Among species which have originally different seed weight, on the contrary, the difference of seedling vigor (dry matter increase) between species does not necessarily be ascribed to the difference in their seed weight.

View full abstract

Download PDF (318K)

Register with J-STAGE for free!