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温暖地におけるコムギの一穂粒数の成立過程を定量的に評価するため, 圃場で栽培したチクゴイズミの主茎の葉, 小穂および小花の分化数を走査型電子顕微鏡で調査し, それらの分化数の推移に有効積算温度を基準としたモデル式を適用した. なお, 小穂や小花の数に影響を与えると考えられる窒素の追肥処理を行ったが, いずれの調査項目にも処理間差は認められなかった. 葉と小穂の分化数の推移に線形スプラインモデルを適用した結果, 分化速度は0.0181 [葉 (°C d)-1] と0.0995 [小穂 (°C d)-1], 分化期間は葉と小穂の順に374°C dおよび149°C dと推定された. 一穂あたり分化小花数の推移には, 小花が直線的に増加する分化初期に直線回帰式を適用したのを除き, Gompertzの生長モデルを適用した. 小花の分化開始期は494°C d, 分化数の最大値は116個で, その時期は821°C dであった. 小穂別の小花の分化数と有効積算温度との関係には直線回帰式を適用し, これを基に小穂別の小花分化開始期, 小花分化速度, および最終生存小花分化期など, 小穂あたり粒数の成立に関係する諸形質を推定した. 収穫期の小穂あたり粒数は穂の中央部が多く, 穂の基部側と先端側に向けて次第に減少したが, その分布に最も密接に関係していたのは小花分化開始期であり, 小花分化開始期が早いほど小穂あたり粒数が多かった. また, 穂の基部から先端に向けて, 小花分化速度は次第に遅く, また最終生存小花分化期は次第に遅れる傾向を示したが, 小穂位置によるこれらの変異や小穂あたり粒数との関係について考察した.

The effect of the selection for leaf color in early generations on the grain-protein content and some other brewing characteristics in late generation was investigated in the crosses of Ooseto with Yamadanishiki and Ooseto with Matuyamamii. The leaf color (SPAD) values at heading time in the F2 population showed a normal distribution. The broad-sense heritabilities of leaf color estimated from F2 variance were 0.517 in the cross of Ooseto with Yamadanishiki and 0.397 in the cross of Ooseto with Matuyamamii. The selection for leaf color at heading time toward dark color (H group) and light color (L group) was continued from the F2 generation to F5 generation. In F6 lines, the mean value of the protein content of the H group was significantly higher than that of the L group. Plant length was longer and 1000 grain weight was lighter in the H group than in the L group. Days from transplanting to heading was shorter and the percentage of white core rice was higher in the H group. There was a significant correlation between the leaf color and the protein content. However, some lines in the H group had a higher protein content than the others at the same level of leaf color. The F5-F6 parent-offspring correlation of the leaf color was significant. From those results, it is considered that the leaf color at heading time in early generation can be used as a criterion for the selection for protein content.

To find useful indexes for the selection of new rice varieties having a high harvest index, the correlation of harvest index (HI) with morphological characteristics and leaf color was examined using 60 Japanese varieties (J group) and 20 high-yielding varieties bred in Asian countries (H group). In the J group, HI showed a positive correlation with leaf color (SPAD value, SV) and a negative correlation with plant length (PL) at the heading time. In the H group, HI showed a positive correlation with SV, but the correlation coefficient between HI and PL was not significant. The correlation berween HI and culm length (CL) was similar to that between HI and PL. HI showed a negative correlation with ear length (EL) in the J group, but significantly positive correlation in the H group. There was a significantly positive correlation between EL/CL and HI in the H group. A multiple regression analysis was conducted to clarify the relationship berween morphological characteristics and HI. A significant multiple correlation coefficient was obtained between HI and SV (X1), PL (X2) or EL/CL (X3). The ratio of standard partial regression coefficient of X1, X2 and X3 to HI was 54:15:31. Consequently, it is considered that these morphological characteristics are useful indexes to select varieties with a high harvest index.

In order to raise highly palatable rice cultivars in the Huabei region, palatability characteristics were compared between 10 cultivars grown in Tianjin district(Tianjin cultivars)and 10 new and old Japanese cultivars (Japanese cultivars). The score of overall eating-quality in the sensory test on cooked rice was the highest in the Japanese cultivar Koshihikari and the lowest in the Tianjin cultivar Jinyou 9701. The average value of overall eating-quality of Tianjin cultivars was -0.42 and that of Japanese cultivars was -0.04. By using the score of overall eating-quality, all cultivars were classified into 3 groups i.e., H group(g+0.35), M group(+0.35∼-0.35)and L group(l-0.35). Among the Japanese cultivars, Koshihikari, Kinuhikari and Okuhikari belonged to the H group, Shinriki, Aikoku and Norin 18 to the L group, and the other cultivars to the M group. In Tianjin cultivars, only Huayu 13 belonged to the H group. Jinzhu 1, Jindao 779 and Jinyou 29 belonged to the M grouo, and all others to the L group. There were no significant differences among groups in amylose content, protein content and maximum viscosity. Amylose contents and protein contents of Jindao 779 and Huayu 13 were close to those of Koshihikari and/or Kinuhikari. From these results, it was concluded that although the Tianjin cultivars had satisfactory physicochemical properties, they wae inferior in overall eating-quality in the sensory test. This may be because only a few Tianjing cultivars possess a low amylose content, low protein content and high maximum viscosity in combination. However, Jindao 779 and Huayu 13 possessed comprehensively good characteristics, and these cultivars are expected to be very useful breeding materials for raising new palatable cultivars in the Huabei region.

The relationships between the early growth after transplanting and several seedling characteristics of 10 high-yielding varieties bred in Asian countries(H group)were compared with those of 10 Japanese varieties(J group). There were sighnificant differences between the seedlings of the two groups in plant length, root dry weight and the percentage of endosperm consumption. Plant length was shorter, root dry weight was heavier and the percentage of endosperm consumption was higher in the H group than in the J group. The seedling character index(SCI)shown by(the seedling age in leaf number)×(the ratio of top dry matter weight to plant length)of the H group was higher than that of the J group. The relationship between the number of days affer sowing(X)and the leaf number of seedling(Y1)was shown by Y1=a1+b1X and the relationship between X and the percentage of endosperm consumption(Y2)by Y2=100-a2·exp(-b2X). There was no significant difference between the H and J groups in the constant b1(leaf number increase coefficient, LNG), but the constant b2(endosperm consumption coefficient, ECC) of the H group was significantly higher than that of the J group. SCI was positively correlated with LNC and ECC. Top dry matter weight(TW)and leaf area(LA)at 28 days after transplanting were greater in the H group than in the J group. Significant positive corrlations were found between SCI and TW, LA, From these results, it was considered that the high yielding varieties with higher SCI have large LA and superior early growth affer transplanting.

The varietal difference in bleeding rate was investigated using 10 Japanese varieties(J group)and 10 high-yielding varieties of rice bred in Asian countries(H group). The relationship between bleeding rate and yied characters was examined. Bleeding rate at the heading time(BR1)and maturing time(BR2)ranged from 2.20 to 3.92, and from 1.50 to 2.62(g h-1 hill-1), respectively. There were no significant differences in BR1 and BR2 between the two groups. The reduction rate of bleeding rate(RRB)during the ripening period shown by 1-BR2/BR1 was significantly higher in the H growp than in the J group. BR1 was not signifcantly correlated with the number of the phytomers(TPN), but showed a significant positive correlation with BR1/TPN. BR1 also showed a significant positive correltion with the shoot dry weight at the heading time. There was a significant positive correlation between RRB and the decline of leaf color(DLC)during the ripening period. Moreover, a significant negative correlation was found between RRB and the percentage of ripened grain. These results imply that the variety with a higher RRB and DLC has a lower ripening ability.

The yielding abilities of rice varieties were examined among three groups : 10 European and American varieties (E group), 20 Japanese varieties (J group), and 16 high-yielding varieties bred in Asian countries (H group). Each yield capacity (NV) was expressed as a product of the number (N) and the volume (V) of unhulled rice. The vield contents (CW+ΔW) were expressed by the sum of reserved carbohydrates in the rice plant at the full heading date (CW) and the dry matter production amount during the ripening period (ΔW). The (CW+ΔW)/NV was regarded as the source-sink ratio. The average yield (Y) was highest in H group and lowest in E group. Both NV and CW+ΔW of H group were highest among the three groups. But ΔW of H group was not so large in comparison with that of J group. The (CW+ΔW)/NV of H group was lower than that of J group because the increase of NV was greater than that of CW+ΔW in H group. The transfer ratio of yield contents [Ef:Y/(CW+ΔW)] was highest in H group. The specific gravity of unhulled rice (S:Y/NV) of H group was as high as that of J group. These results suggest that the high yielding ability of H group is mainly attributable to its large NV and CW, and also to its high Ef. Consequently, it is considered that an enhancement of source-sink ratio with the increment of ΔW is necessary to improve the yield potential in H group.

The influence of different transplanting times on the grain yield and palatability of rice were analyzed by meteorological factors. The prediction of optimum transplanting time for both grain yield and palatability were also investigated. The grain yield showed a significant positive correlation with the number of grains per m2. The number of grains per m2 showed a significant negative correlation with the mean daily temperature before heading time. The relation between the grain yield (Y) and 3 meteorological factors (i.e., the mean daily temperature of period from transplanting time to heading time (T1), the mean daily temperature (T2) and the mean daily solar radiation (S1) of ripening period) was expressed as a following formula: Y=[-0.483(T2-22.936)2+74.838]S1-1.329T1·S1. The estimated grain yield calculated from this formula was close to the real grain yield. Amlose content and protein content had significant negative correlations with the mean daily temperature of the ripening period. From these results, we estimated that the optimum transplanting time for both grain yield and palatability was in early May.

This experiment was carried out in order to examine the influence of transplanting time on the growth of rice plants in Kagawa Prefecture, Japan. A rice cultivar, Kinuhikari, was transplanted at 3-4 different times from 1992 to 1995. The number of days required for first tiller appearance(DFTA), the number of days from transplanting to heading time (DTH) and the number of days from heading to maturation(DHM) were investigated in relation to temperature.The relation between DFTA(Y1) and the mean temperature for 5 days after transplanting(X1) was expressed by means of the following equation;Y1=197.35×elY2=-2.56X2+0.76X3+118.86···(2) DHM(Y3)was expressed by the mean temperature for 30 days after heading(X4)as follow;Y3=-2.1X4+89.2···(3) Therefore, we estimated that the safe transplanting time in Kagawa Prefecture is during the second five days of May.Also, heading time and maturation can easily be estimated by equations(2) and (3), respectively.

Four field-grown potato cultivars, Irish Cobbler, May Queen, Dejima and Nishiyutaka, were subjected to measurements of leaf nitrate reductase (NR) activity (in vivo assay) and the distribution of nitrogen during growth and development. Varietal differences in NR-activity averaged over a season were observed : Highest activity was Nishiyutaka (6.08 NO2- μmol h-1 g-1 fresh weight) and lowest was May Queen (4.92 NO2- μmol h-1 g-1 fresh weight). Slightly high NR-activities were observed during the 30 days of early growth in all cultivars, and as growth proceeded, they tended to fall. The NR-activity was positively correlated with the percentage total leaf nitrogen, and with nitrogen accumulated in the leaf. The NR-activity had no correlation with total dry matter or tuber dry matter. The accumulation of nitrogen in the leaves declined with age, whereas it increased in the tubers regardless of the cultivar. At the end of the season, all cultivars except Nishiyutaka accumulated almost the same level of nitrogen in the tubers. A significant linear correlation (r=0.749***) was found between the natural logarithm of SPAD reading (relative chlorophyll content) and NR. Harvest indices for nitrogen showed that the partitioning of nitrogen to the tubers was higher in Irish Cobbler and May Queen than in Dejima and Nishiyutaka. There was no evidence to conclude that NR-activity has a direct effect on dry matter production in potato.

Response of potato genotypes (Solanum tuberosum L.) to increase in planting density was examined. Three potato cultivars (Irish Cobbler, May Queen and Dejima) and two planting densities (5 and 10 plants per m2) were employed. Increase in planting density caused the main stem length to increase and the number of branches and the leaf area per plant to decrease irrespective of the cultivar. Stolon growth and number of stolons per plant was not affected by increase in planting density, but the percentage of productive stolons was decreased by increase in planting density. During the experimental period, all cultivars showed upward trends in crop growth rate (CGR), net assimilation rate (NAR), tuber growth rate (TGR) and economic assimilation rate (EAR) under both densities. Plants under high density had higher TGR and EAR values and achieved them at an earlier stage than those under low planting densities. Increase in planting density decreased the dry weights per plant of leaves, stems and tubers but it increased dry weights per unit area. Percentage of dry matter partitioned to the tubers was high under high planting density. High density increased total and marketable tuber yield per unit area but decreased per plant yield of all three cultivars. High density markedly reduced both average tuber weight and average marketable tuber weight. Dejima outyielded the other cultivars. Range of optimum planting densities for marketable tubers will be higher for Dejima than Irish Cobbler and May Queen.

The effects of the transplanting times and the methods of feritilizer application on the yield and eating quality of rice cultivar Kinuhikari were investigated. The transplantings were made on March 28 (early season culture, ES) and on June 17 (normal season culture, NS). The methods of fertilizer application were the heavy manuring culture (HM), the standard manuring culture (SM) and the organic manuring culture (OM). 1) The averages of the daily mean temperature from the heading time to the maturing time were 26.9°C in ES and 24.6°C in NS. 2) The yield in ES was higher than that in NS. The number of grains per m2 indicated significant positive correlation with the yield and significant negative correlation with the percentage of ripened grains, respectively. The percentage of ripened grains in ES was higher than that in NS at the same lavel of the number of grains. 3) In ES, amylose content was lower but maximum viscosity and breakdown values were higher than those in NS. The order of protein content in relation to the method of fertilizer application was ; HM>SM>OM. The protein content showed significant negative correlation with the percentage of ripened grains. 4) The palatability of rice after cooking showed significant negative correlation only with protein content. In this experiment, the palatability of rice after cooking was more strongly affected by the method of fertilizer application than the transplanting time.

A glasshouse pot sand culture experiment was conducted to determine the effects of three levels of combined nitrogen-0N (0), 1N (100), 2N (200 pm) -on nitrogen nutrition, seed protein and oil content and the distribution pattern of 14C activity in the seed at different nodal position of soybean (Glycine max (L) Merr. cv. Akiyoshi). Plants were fed with 14CO2 at the vegetative, flowering, early pod filling and late pod filling stages of growth. Nitrogen content of plant organs increased with increasing level of supplied nitrogen and declined in the vegetative organs with plant growth. Combined nitrogen had no significant effect on mean seed protein and oil content. No 14C activity was detected in seeds of plants fed at the vegetative and flowering stages. More 14C was retained in seeds of plants fed at late pod filling stage than fed at early pod filling stage. Combined nitrogen had no remarkable effect on the amount and distribution pattern of 14C. Activity of 14C in seeds was in the order of secondary branches

The effects of three sowing times, from May 30 to July 20, on growth, dry matter production and seed production, were investigated in 1982 and 1983 using two soybean ecotypic cultivars, autumn and medium. 1. With a delay in sowing time, the number of days from sowing to flowering and to maturation was reduced. The stem length, the number of nodes and branches, and LAI were also decreased. 2. The productive structure at the pod-setting stage showed more photosynthetic organs in the autumn type and in plants sown earlier than in the medium type or those sown later. The light transmission coefficient (K) showed a negative correlation with SLA. 3. Such growth parameters as RGR, NAR and CGR, progressed in similar patterns, regardless of the cultivar or sowing time, but the decreases during later growth stages were more rapid with a delay in sowing time. 4. Seed yield was reduced with a delay in sowing time, resulting from the reduction in the number of pods and seeds. There was also accompanying decrease in biomass. 5. Judging from the results, a medium type cultivar, Kan-nari No. 1, did not respond enough to differences in sowing time that we easily can select an optimum time for sowing. On the other hand, the autumn type cultivar, Akiyoshi, has an optimum sowing time in warmer districts in Japan of around late June.