Percentage Of Ripened Grains Research Articles

Effect of nitrogen application during ripening period on photosynthesis and dry matter production and its impact on yield and yield components of semidwarf iniica rice varieties under water culture conditions

A water culture pot experiment was conducted to analyze the effects of N application during the ripening period (RP) on photosynthesis, dry matter production, and its impact on grain ripening and yield in two semidwarf indica type varieties viz. Gui Zhao 2 (GZ) and BR3 (BR) compared with a japonica type variety Koganemasari (KO) under four N rates viz. 0 (N0), 10 (N10), 20 (N20), and 40 (N40) mg L−1. Results showed that N application enabled to maintain a higher leaf area and delay leaf senescence in both indica and japonica type varieties but the decrease in the rate, of leaf area was higher in the former than in the latter and the rate was reduced with increasing N rates. Flag leaf photosynthesis and SPAD values of N treated plants were higher throughout the RP, showing the presence of a significant correlation either for each variety or all the varieties together. Higher photosynthetic rate was supported by higher leaf chlorophyll (SPAD value basis) content, stomatai conductance, and N concentration in leaf blades. Top dry matter content increased with increasing N rates mainly due to mean leaf area rather than NAR except for BR during RP but it was higher in KO than in GZ and BR. Reduction of shoot weight due to translocation of dry matter to panicles during RP was suppressed by N rates both in GZ and BR while shoot weight increased in the N-treated plants in KO. The dependency of KO on current photosynthates for panicle weight was found to be almost hundred percent while the contribution of stored carbohydrates in shoot before heading to panicle weight in GZ and BR was in the range of 4-27 and 33-54%, respectively and the rest was contributed by current photosynthates. The percentage increased with increasing N rates. Percentage of ripened grains (PRG) increased with increasing N rates in GZ and BR due to the increase in dry matter production and in the photosynthetic rates of apex leaves, despite the larger spikelet number and larger hull size. However, KO showed almost no variation although it had the highest PRG among the varieties. Brown rice yield followed the same pattern as that of PRG in GZ and BR and the highest yield was produced by BR followed by GZ and KO. These results suggest that N application during RP was more effective in increasing yield in the semidwarf indica type varieties than in the japonica type variety.

Effect of Winter Weeds on Growth and Yield of Direct-Seeded Rice in No-tillage Dry Paddy Field.

The effects of winter weeds on the growth and yield of direct-seeded rice (Oryza sativa L. cv. Akebono) were evaluated in a no-tillage dry paddy field where Alopecurus aequalis Sobol. var. amurensis (Komar.) Ohwi was uniformly dominant, in Kurashiki, Okayama, Japan, in 1994 and 1995. Winter weeds significantly inhibited the growth and spikelet production of rice plants as compared to those in the control plots, which were established by herbicide application. The reduction in the spikelet number finally resulted in a 12.6 to 15.6% yield reduction, although the percentage of ripened grains of rice increased somewhat because of the inhibition of the spikelet number by winter weeds. Rice yields in the weedy and control plots increased in different ways according to the increase in straw weight. The number of spikelets on the rice plants in the control plots increased as straw weight increased. In contrast, the percentage of ripened grain on the rice plants in weedy plots increased as straw weight increased. A higher rate of fertilizer greatly recovered the growth and yield of rice in weedy plots. This result suggests that the basal dressing of fertilizer at a higher volume would reduce the frequency of herbicide application for winter weeds.

Effect of Competition in a Hill to Seedling Number per Hill on Yield Components and Yield in Paddy Rice.

日本晴(1984年), ホウレイ(1985年)を30cm×15cmおよび30cm×30cmの栽培密度のもとで一株植付本数1, 4, 7本あるいは4, 7本に手植し, 分げつの発現時期を3～4時期に分け, 発現時期ごとに分げつの生存率, 穂の諸形質を検討した. 一株植付本数が多いと穂数はやや多かったが, 平均一穂籾数, 平均登熟歩合は低下した. しかし千粒重には影響がみられなかった. 発現時期によって分けた穂の一穂籾数, 登熟歩合, 有効茎歩合は, 栽植密度, 植付本数に関係なく, 伸長第一節間径と正の相関関係にあり, 茎の生長量と関係したと考えられた. 一方同一栽植密度の伸長第一節間径は, その分げつの発現したときの一株茎数(発現時一株茎数)に同時期に発現した分げつを加えた一株茎数つまりその分げつの生長開始時の一株茎数と負の相関関係にあった. さらに分げつ発現率も発現時一株茎数が多いと少なく, 登熟期の葉色も一株植付本数が多いと淡かった. したがって一株植付本数が多いと一株茎数が多くなり, そのことによって有効茎歩合, 分げつ発現率が低下して穂数増加の効果が小さく, さらに一穂籾数, 登熟歩合が低下するため, 7本植のように一株植付本数が多すぎるとかえって収量が低下することが明らかとなった.

Case Studies on High Yields of Paddy Rice in Jiangsu Province, China. I. Characteristics of grain production.

Analysis of the characteristics of grain production of 965 gm-2 obtained by Shan You 63 (F1 hybrid rice) in 1991 was carried out Absorption of nitrogen reached 21 gm-2 up to the time of heading, and a large capacity of grain yield (50, 360 spikelets per m2) was obtained. Efficiency of increase in spikelet number per m2 by absorbed nitrogen up to heading was essentially the same as in west Japan. Mean Leaf Area Index 10 days before heading became exceptionally large (10.18). A large amount of translocation of accumulated assimilation products before heading improved the percentage of ripened grain. Increase in translocation of assimilated products stored in the culm and leaf before heading may remarkably increase yield in China.

Studies on Varietal Difference in Yielding Ability in Rice. I. Varietal difference in yield structure.

In order to investigate the breeding objective on the improvement of rice yield, the yield structures were analyzed and compared among a hundred varieties. By using the mean specific gravity (S), all varieties were divided into two types, I (S : above 1.10) and II (S : under 1.10). And by using the translocating ratio of reserves from the culm and leaf to the grains (T) on yield (Y), they were also divided into three types, A (T/Y : under 19.8%), B (T/Y : 19.8∼35.0%) and C (T/Y : above 35.0%). A hundred varieties were classified into five types that had different yield structures by combining with I, II and A∼C classes. The IC type having the highest yield was very large in the capacity of unhulled rice (NV), high in S and T/Y, but not so large in the assimilates produced after the full heading date (ΔW) and the lowest in ΔW/NV. In this type, S was higher than the other types at the same level of the percentage of ripened grain. It was conjectured that the most important breeding objectives to improve the yield were the magnification of NV for IA type, the incrase of T for IIA type, the magnification of NV and the increase of ΔW for IB and IC types and the increase of ΔW for IIB type, respectively.

Studies on dry matter and grain production of F1 hybrid rice in China. II. Characteristic of grain production.

In order to make clear the high yielding capacity of the F1 hybrid rice in China, the characteristics of grain production was examined by the yield components analysis and with reference to the source of contents accumulated to the grain during the ripening period with the same varieties used in the previous paper. It became obvious from the yield components analysis that there was a highly positive correlation between total number of spikelet per unit land area and brown rice yield (Fig. 1). High yield in the F1 hybrid rice was largely depended on spikelet number (ca. 40, 000/m2) as compared with common rice varieties. The total number of spikelet in the F1 hybrid rice was due to increased spikelet number per one panicle rather than panicle number per one hill. The F1 hybrid rice showed comparatively high percentage of tilled-spikelet (ca. 80%) in spite of its huge number of spikelet. This was caused by higher ratio of LAI to total number of spikelet (Source-Sink ratio) during the ripening period. Generally, brown rice yield is decided by the total amount of photosynthetic products, a carbohydrate stored in culm and leaf sheath before flowering, and of assimilate accumulated during the ripening period. In this experiment, the ratio of the storage translocated from the culm and leaf sheath to the spikelet was larger in the F1 hybrid than in common rice varieties. In addition, there was a highly positive correlation between translocated storage and brown rice yield (Fig.4). This fact suggests that a comparatively high percentage of ripened-grain in the F1 hybrid rice was attributed to the amount of storage. It can be concluded from the results mentioned above that high yield of F1 hybrid rice was realized by both factors: 1) remarkable large number of spikelet and 2) comparatively high percentage of ripened grain, which was attained by the high ratio of the storage translocated from the culm and leaf sheath and by high LAI during the ripening period.

Studies on the Influence of Cultural conditions to Rice Quality, especially Amount of Protein Content in Rice Kernel

In this studies we investigated influence of cultural conditions to amount of protein content in rice ripened kernel. The results are summarized as follows; 1) Conditions of many panicle formation per square meter, such as heavy nitrogen fertilization and dense planting, induced to low percentage of ripened grain, and grow small kernels. 2) Injury of root and leaf-blade, and lodging, also induced low percentage of ripened grain and small kernels. 3) Above different conditions grow as same as small kernels, and small kernels are usually protein rich kernels in this studies. The correlation coefficient between net solidity of rice kernel and amount of protein content of kernel was r=-0.903**. 4) According to our previous report, early variety usually formed protein rich kernels than late variety.

Analysis of Developmental Factors Determining Yield and Its Application to Yield Prediction and Culture Improvement in Lowland Rice. : LI. Effects of top-dressing with ammonium sulfate on the grain-yield and its constitutional factors at critical periods relating to determination of each yield-constitutional factor.

Examining the effects of top-dressing with ammonium sulfate under different amounts of basic fertilizer on the grain-yield and its constitutional factors in critical periods in which the value of each yield-constitutional factor is determined, as seen in Table 1, the authors tried to establish some reasonable fertilizing methods to get good yields. The most effective stage for top-dressing to increase the value of each yield-constitutional factor was as follows (Refer to Fig. 1): (1) No. of panicles per hill……Maximum tillering stage. (2) No. of spikelets per panicle……Differentiating stage of 1st bract primordium and just before reduction division stage of P. M. C. (3) No. of spikelets per hill……Differentiating stage of 1st bract primordium. (4) Percentage of ripened grains……Just after full heading stage. (5) Weight of 1, 000 grains……Just before reduction division stage of P. M. C. The best top-dressing method to get good yields varied with the amounts of basic fertilizer and weather conditions, but it might be generalized that the top-dressing methods (Plot No. 3, 7, 4 and 5) which always cause the rice plant to increase the number of spikelets per hill or per unit area are successful in getting good yields under the conditions which make the plant get a high percentage of ripened grains, and on the contrary, the other top-dressing methods (Plot No. 6 and 1) which always cause the plant to get a high percentage of ripened grains are effective in increasing yields under the conditions which make the plant get an excessive number of spikelets per hill. And some other top-dressing methods (Plot No. 10, 9, 8, 2, 7, 4 and 5) which cause the plant to increase both the number of spikelets per hill and the percentage of ripened grain or only the number of spikelets per hill (except for Plot No. 3) were liable to get good yields under the conditions which make the plant get a medium percentage of ripened grains and a medium number of spikelets per hill.

Comparison of the Growth and Yield of Paddy-and Upland-Rice grown under Paddy-and Upland -Field Conditions

The study was begun in an effort to make clear the difference of growth and yield, especially dry matter and carbohydrate production, of paddy and upland rice crop grown under paddy-and upland-field conditions. A supplementary study of the effect of fertilizer and soil moisture contents was introduced into the experiment on the upland field plots. Experiments were carried out with paddy rice variety Fujisaka No. 5 and upland rice varieties Norin No. 12 and No. 21. The results obtained were as follows: 1. Among the factors which constitute rice yields, such factors which are determined by the time of heading as the number of ears, number of grains per ear were larger under the upland field condition than under the paddy field condition. And such factors which are influenced after heading as percentage of ripened grain, 1, 000-kernel weight were larger under the latter condition than under the former condition. 2. The ratio of the amount of carbohydrates stored by the time of heading to those of carbo-hydrates in the grain yields was higher under the upland field condition than under the paddy field condition. On the other hand, the ratio of the amount of carbohydrates produced after heading to those of carbohydrates in the grain yield was higher under the paddy field condition than under the upland field condition. 3. Therefore, the yield of upland rice grown under upland field condition was as high as that grown under paddy field condition because of their greater vegetative growth and larger amounts of carbohydrates stored by the time of heading, in spite of the low photosynthetic ability after heading. 4. Paddy ribe variety Fujisaka No. 5 showed higher photosynthetic ability than either of two upland rice varieties under both conditions after heading, thus resulted in approximately 11 per cent increase in its yield as compared with the yield of upland rice under the paddy field condition. But under the upland field condition the hulled rice yield of paddy rice was about 1, 000 kg. per hectare lower, representing an decrease of 22 per cent on the basis of the yield under paddy field condition, because of their poor growth by the time of heading. 5. At the high level of nitrogen supply, the photosynthetic ability of the both of paddy- and upland-rice after heading, was reduced, especially the reduction of the latter was remarkable. 6. In the unirrigated plot, the amount of the both carbohydrates stored by the time of heading and accumulated after heading in the grain were less. By the irrigation both of these increased, and the amount of non-reducing sugar was reduced remarkably. 7. The amount of growth of paddy rice variety Fujisaka No. 5 was smaller than that of the upland rice varieties under both condition, paddy-and upland-field. Especially under the latter condition, the ratio of the amount of carbohydrates accumulated by the time of heading and translocated to the grain to the total amount of carbohydrates in the grain was low even under irrigated condition. The content of non-reducing sugar was also low, showing that paddy rice suffered from the drought even under the soil moisture condition sufficient for upland rice growth.