The supernodulating variety “Sakukei 4”, which has improved growth and yield, was recently developed. To evaluate its physiological traits related to the high productivity, we compared dry matter production, nitrogen (N) accumulation and N utilization in Sakukei 4 with those in the parental normally nodulating varieties, Enrei and Tamahomare, and a nonnodulating line, En1282, in pot experiments. The seed yield of Sakukei 4 was similar to that of Enrei and Tamahomare. Leaf area and relative ureide abundance in xylem sap were maintained for longer growth period in Sakukei 4 and Tamahomare than in Enrei. The total amount of nodule N2 fixation at maturity was also larger in Sakukei 4 and Tamahomare than in Enrei and En1282. In En1282 and Enrei, a larger part of N accumulated in leaves and stems before seed maturation was translocated to seeds during seed filling. However, Sakukei 4 and Tamahomare, more N tended to remain in leaves and stems at maturity. These observations suggested that the physiological traits of dry-matter accumulation and N utilization in Sakukei 4 were quite similar to those in Tamahomare, despite the difference in nodulation. N use efficiency for dry matter production (NUED) was lower in Sakukei 4 than in Enrei and Tamahomare, probably due to the energy cost for sustaining a greater number and mass of nodules. This observation indicated that the low NUED of Sakukei 4 impairs its productivity and seed yield, and therefore Sakukei 4 could not exceed Enrei or Tamahomare in seed productivity.
The effects of temperature during the ripening period on digestible protein contents of the rice grains of a seed-protein mutant rice cultivar LGCsoft were examined. The plants were grown under a natural condition until the booting stage, and then in temperature-controlled greenhouses set at 24.0ºC, 28.0ºC, and 30.6ºC (mean temperature). The protein compositions and the protein contents of the rice grains were analyzed quantitatively. The protein compositions in the LGCsoft grains varied with the temperature condition. The ratio of the digestible to total protein was higher in high-temperature conditions, and that of difficult-to-digest proteins, especially 13 kDa prolamin was lower in high-temperature conditions. The protein compositions in a normal-type cultivar Nihonmasari, which was the original cultivar of LGCsoft also varied with the temperature. However, the effect of temperature on the ratio of the digestible to total protein was larger in LGCsoft than in Nihonmasari. The ratios of the digestible protein in the grains under 24.0ºC and 30.6ºC conditions were 74.3% and 81.3%, respectively, in Nihonmasari. On the other hand, they were 52.0% and 63.1%, respectively, in LGCsoft. In LGCsoft, the total protein content of grains was 70.6-72.5 mg g-1, and it was affected only slightly by temperature during the ripening period. Therefore, the digestible protein content of grains under 24.0ºC and 30.6ºC conditions was 36.7 mg g-1 and 45.7 mg g-1, respectively, in LGC soft. It was clarified that the digestible protein content was higher at elevated temperatures because of the increased ratio of digestible to total protein.
The partial pressure of CO2 in air decreases with the increase in altitude. Therefore, increase in molar concentration of CO2 is smaller at higher altitudes than at lower altitudes for increases in molar fraction of CO2. This study aimed to predict the effect of global CO2 increase on net photosynthetic rate of spring wheat (Triticum aestivum L.) at high altitudes. The net photosynthetic rate of spring wheat grown in Lhasa (3688 m above sea level), China, was compared with that of the same cultivar grown in Sapporo (15 m above sea level), Japan. At the current level of CO2, it was significantly lower in Lhasa than in Sapporo, and stomatal conductance, chlorophyll content (SPAD value) and apparent quantum yield were similar in both locations. The interaction of CO2 level and altitude was suggested; the amount of increase in net photosynthetic rate caused by increase in CO2 was smaller at high altitudes than at low altitudes. Lower CO2 partial pressure at higher altitude could explain the difference in net photosynthetic rate between altitudes, and the interaction of CO2 level and altitude.
In crop rotations that include rapeseed (Brassica napus L.), the growth of the crops following rapeseed is sometimes inhibited. The aim of this study was to assess the role of glucosinolates (GSLs) in the inhibitory effect. Three cultivars with zero erucic acid content (Asakano-natane, Kizakino-natane, Nanashikibu: single-low cultivars) and one cultivar with zero erucic acid and low GSL contents (Kirariboshi: double-low cultivar) were grown. The GSL contents differed greatly depending on plant part, stage of development, and cultivar. Progoitrin and gluconapin were detected mainly in the seeds of the single-low cultivars. Their contents either did not change or increased slightly during the reproductive stage. The double-low cultivar Kirariboshi contained almost none of either progoitrin or gluconapin in any part during the reproductive stage. Glucobrassicanapin, glucobrassicin, and gluconasturtiin were detected, mainly in the roots, of all four cultivars, and tended either to decrease or to remain steady as plants matured. Dense stands of rapeseed seedlings that had germinated from seeds dropped at harvest grew together with the subsequent crop. The GSL contents in the leaves and roots of these seedlings were high. These results suggest that the GSLs in the seeds of single-low cultivars, in the roots of both types at harvest, and in the leaves and roots of volunteer seedlings are the candidate cause of the generally observed phenomenon of inhibited growth of the crop following rapeseed.
Wheat cultivar Haruyutaka, bred in Hokkaido, as a cultivar with improved genetic traits for production in western Japan, had a lower grain yield when grown in Yamaguchi in western Japan than Daichinominori, native to Yamaguchi. We examined the yield and grain growth of these two cultivars in the two areas in 2005/2006, 2006/2007 and 2007/2008 to elucidate their grain filling mechanisms under the two environments. When grown in Yamaguchi, Haruyutaka had a lower grain yield due to smaller grains than Daichinominori and when grown in Hokkaido, Daichinominori had a lower grain yield due to smaller grains than Haruyutaka. The slower grain growth, especially, at the later period of grain filling was considered to be the major cause of smaller grain in both cultivars, but it was more pronounced in Haruyutaka grown in Yamaguchi. Haruyutaka and Daichinominori ceased total dry mass production earlier when grown in the non-native area, Yamaguchi and Hokkaido, respectively, resulting in less supply of current assimilation products to grain growth. When grown in Yamaguchi, the amount of post-anthesis culm reserves, water soluble carbohydrate (WSC), was smaller in Haruyutaka than in Daichinominori, while they accumulated a similar amount of WSC in Hokkaido. The pattern of remobilization of WSC to grains was similar in both areas. However, the grain filling period was significantly shorter in the non-native area. These results suggested that in the non-native environment, the grain size is decreased due to slower grain growth, mainly due to less current assimilation, and shorter grain filling period.
We analyzed the response of transcripts corresponding to ascorbate peroxidase (APX) and catalase (CAT) under salinity in the basal region of the rice leaf, which is tolerant to salinity compared with the apical region. In the NaCl treated plants, the transcript levels of CATB, CATC, APX1, APX4, APX6 and APX7 increased. The transcript level of APX2 was comparable to that of the control, but the transcript level of APX8 was slightly decreased by salinity. The activity of dehydroascorbate reductase decreased by salinity. These results suggest that the increase in CAT activity observed in our previous study is due to the enhancement of transcript levels of CATB andCATC, and the increase in the transcript level of APX1, APX4, APX6 and APX7 may contribute to maintain APX activity under salinity. The enhancement of the enzyme activities involved in regeneration of ascorbate under salinity is needed to increase APX activity and salinity tolerance in rice plants.
The effect of NaCl stress on the structure of leaf chloroplasts was investigated in several NAD-Malic enzyme (NAD-ME) and phosphoenolpyruvate carboxykinase (PCK) type C4 plant species. Seedlings of the monocot species, except Zoysia japonica, grown in 300 mL pots were subjected to salt stress by adding 50 mL of 3% NaCl solution per day to the soil for 5 d after the fourth leaf blades were fully developed. Z. japonicaand the dicot species,Amaranthus tricolor, were also treated with 3% NaCl in a similar manner from 5 wk after germination. Salt stress negatively affected the growth, chlorophyll content and chloroplast structure in all the species. At the ultrastructure level, swelling of thylakoids and disruption of envelopes were more or less observed in mesophyll cell (MC) chloroplasts after salt treatment. The structure of bundle sheath cell (BSC) chloroplasts, on the other hand, was hardly damaged under salt condition although stromal and starch areas were considerably decreased. Furthermore, salinity induced granal development in BSC chloroplasts in most species; the number of thylakoids per granum, granal indices and appressed thylakoid density in salt-treated plants were generally higher than those in control. Since the similar responses have also been reported in all NADP-ME type C4 species investigated in our previous study, the high sensitivity to salt stress in MC chloroplasts and the granal development in BSC chloroplasts by salinity were considered to be common phenomena in all three C4 subtypes.
The physicochemical properties of eight popular glutinous rice varieties (Hwasunchal, Dongjinchal, Sangjuchal, Seolhyangchal, Jinbuchal, Sangnamchal, Hangangchal, Milyang-167) in Korea were evaluated. The starch granules in Seolyangchal, Sangnamchal, Hangangchal, and Milyang-167 rice showed greater crystallization than that of the other varieties, which were more loosely packed with larger air spaces in between granules. Dongjinchal rice showed lowest amounts of potassium and calcium with 44.51 and 3029.50 ppm, respectively. This variety also exhibited the highest sugar content with 1.30–16.82µg g-1 and fastest hydrolysis rate of 771.5 mg g-1. Sangnamchal, Sangjuchal, and Jinbuchal varieties showed abundant amounts of essential amino acids and highest pasting values (73.6°C, 3.0 min). On the other hand, lowest pasting values (69.6°C, 2.7 min) and total amino acid content of 452.61 ng mg-1 were observed in Milyang-167 rice. Hwasunchal and Sangnamchal samples contained the highest concentration of unsaturated fatty acids with 760 mg g-1 and lowest level of saturated fatty acids with 230 mg g-1. The highest viscosity values were obtained in Hangangchal variety, while the lowest values were found in Jinbuchal sample. This study illustrates the wide variation in the physicochemical properties of the glutinous rice varieties analyzed. The results could serve as baseline information for the quality evaluation of rice with unique characteristics suitable for specialty food processing.
Raising the degree of grain filling is an important issue for the genetic improvement of extra-heavy panicle type rice which does not always realize the high yield potential due to low degree of grain filling. The objective of this study was to analyze the variation and association of the traits related to grain filling in four cultivars, three extra-heavy panicle types and one non-extra-heavy panicle type as a control, under seven environments. The results showed wide variation among cultivars and among growing environments in most of the traits examined. In addition, significant interactions between cultivar and environment were detected. From the analyses of joint regression and genetic and environmental correlations, an extra-heavy panicle type cultivar, Milyang 23, showed a higher degree of grain filling and higher rate of grain filling (grain weight/cumulative temperature), in response to several environments with a higher temperature and longer sunshine hours under which a large amount of photoassimilates would be available to grains. On the contrary, another extra-heavy panicle type cultivar, Akenohoshi, showed a lower rate of grain filling, even under the favorable environments mentioned above, resulting in a lower degree of grain filling. The difference in the rate of grain filling between Milyang 23 and Akenohoshi might be due to the difference in the growth of individual endosperm cells, not in the number of cells, because these two cultivars had similar grain sizes. This study obviously emphasized the importance of high grain sink activity in the genetic improvement of grain filling in extra-heavy panicle type rice.
For rice cultivation in Japan, deep-flooding irrigation is used as a growth control method. To clarify the effects of deep-flooding cultivation under the different planting-pattern, we arranged conventional (Con, 22 hills m-2), narrow (Nar, 33 hills m-2) and very narrow (broadcast direct-seeding Model:BDSM, 100 hills m-2) planting plots under shallow-flooding (SF: 5 cm) and the deep-flooding (DF: 27 cm) conditions from active to maximum tillering stage and evaluated the growth, panicle weight yield, panicle components and community structure. DF was effective in controlling the weak tiller over the whole planting plots arranged. The panicle weight yield (m-2) was high in DF and high yield was kept even in BDSM. The panicle weight yield (m-2) increases in DF was based on the panicle weight (panicle-1) increased by increasing secondary rachis-branches and their grains (Con and Nar), or on the panicle numbers (m-2) increase (BDSM). Shoot nitrogen content (tiller-1), reported to have the correlation with panicle components, was high in the Con and Nar in DF, and this might contribute to the increase in secondary rachis-branch grains. In BDSM in DF, the marked decrease in the percentage of productive tillers and serious lodging observed in SF were improved. The lodging resistance value in DF was higher than that in SF over the whole planting plots. The light transmission in DF was superior to that in SF in spite of the large LAI. Thus, the growth improving effect of DF was obvious over the wide planting pattern range.
It is essential to provide experimental evidence and reliable predictions of the effects of water stress on crop production in the drier, less predictable environments. A field experiment undertaken in southeast Queensland, Australia with three water regimes (fully irrigated, rainfed and irrigated until late canopy expansion followed by rainfed) was used to compare effects of water stress on crop production in two maize (Zea mays L.) cultivars (Pioneer 34N43 and Pioneer 31H50). Water stress affected growth and yield more in Pioneer 34N43 than in Pioneer 31H50. A crop model APSIM-Maize, after having been calibrated for the two cultivars, was used to simulate maize growth and development under water stress. The predictions on leaf area index (LAI) dynamics, biomass growth and grain yield under rainfed and irrigated followed by rainfed treatments was reasonable, indicating that stress indices used by APSIM-Maize produced appropriate adjustments to crop growth and development in response to water stress. This study shows that Pioneer 31H50 is less sensitive to water stress and thus a preferred cultivar in dryland conditions, and that it is feasible to provide sound predictions and risk assessment for crop production in drier, more variable conditions using the APSIM-Maize model.
The growth and seed yields of 2 Japanese and 3 Chinese cultivars of soybeans cultivated in 2002-2005 using a drip irrigation system in the arid area of Xinjiang, China, were analyzed with respect to growth parameters and air temperature. Seed yield was very high in 2002, 2003 and 2004, but relatively low in 2005. The variation among years in seed yield clearly depended on pod number. The mean leaf area index (LAI) and crop growth rate (CGR) in 2005 was lower than those in the other 3 years. CGR showed significant positive correlations with mean LAI at the early growing stages, and with net assimilation rate (NAR) at the later growing stages. The increasing rate of pod number (IRP) was positively correlated with the mean LAI and CGR at the pod setting period, suggesting that an adequate supply of photosynthates would be required for pod setting. It was concluded that excellent growth in the years with high yields was supported by the large LAI before the pod setting periods and by high NAR and vigorous pod growth at the latter half of the growing season.