Localization of hydrogen peroxide (H₂O₂) accumulation during the interaction between rice and Xanthomonas oryzae pv. oryzae (X. oryzae pv. oryzae) was observed by histochemical analysis and electron microscopy. The changes that occurred in an avrXa7 mutant strain of X. oryzae pv. oryzae including the decreased production of endogenous H₂O₂, impacted on the mean level of H₂O₂ accumulation during the interaction with the plant. The results of catalase and aminotriazole treatments indicated that the changes of H₂O₂ accumulation during the interaction are induced by the impairment of endogenous H₂O₂ accumulation in X. oryzae pv. oryzae. These results suggested that bacterial pathogen is a potential source of the H₂O₂ accumulated in the interaction between rice and X. oryzae pv. oryzae.

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This technical report describes a gradient system for characterizing the vertical gradients of CO₂, H₂O, and air temperature within and above the canopy of plants. The system is low in cost and easy to use. The instruments were fitted and placed in one box with a total weight of about 10 kg. The box can be carried and moved from one site to another. The features of this apparatus are high frequency sampling cycle as short as 1 min per cycle for all six measurement levels and fast response gas analyzer for measurement as short as 10s per level. Two exhaust pumps, one sampling pump, six 3-way solenoid valves, and flow meter were used to insure simultaneous flow rate of air in all tubes from all measurement levels. This system transfers data from the data-logger directly to the add-in Spreadsheet of Microsoft Excel by using an Ethernet cable to automatically convert digital data to scientific units in less time. This system also allows the use of multiple micro-environmental sensors that can be sampled at the same time. It is useful not only for agricultural ecosystems but is also adequately sensitive and rapidly responds to the gas analyzer with a modifiable flow rate meter for use in forest ecosystems. This system also has potential for use in the measurement of CO₂, H₂O, associated environmental elements, and CO₂ storage flux within the canopy of plant, and other processes including a CO₂ sink and source.

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Anthocyanins play beneficial roles in plant growth and development such as the reduction of photo-oxidative damage to leaf cells. Tartary buckwheat contains two anthocyanins, namely, cyanidin-3-O-glucoside and cyanidin-3-O-rutinoside, which are accumulated in the stems and leaves. In order to clarify which type of anthocyanin is accumulated at different nodal positions, we investigated the type of anthocyanin and their contents in buckwheat stems using HPLC. The anthocyanins detected were identified as cyanidin-3-O-glucoside and cyanidin-3-O-rutinoside by comparison with the retention times and co-chromatography with the standard solutions. The contents of cyanidin-3-O-glucoside and cyanidin-3-O-rutinoside at the proximal stem position were higher than those at the distal stem position. The ratio of each anthocyanin to total anthocyanin varied with the nodal positions. An outdoor study suggested that UV stress might influence the ratio of each anthocyanin to total anthocyanin. Consequently, we investigated these ratios in a growth chamber. The growth chamber study suggested that the ratio of cyanidin-3-O-rutinoside to total anthocyanin was higher under UV conditions than under non-UV conditions. These results indicate that cyanidin-3-O-glucoside accumulates in a small amount and that cyanidin-3-O-rutinoside accumulates in a large amount in young organs that suffer from strong UV stress. Cyanidin-3-O-rutinoside may have a UV-protective effect and tartary buckwheat may accumulate cyanidin-3-O-glucoside and cyanidin-3-O-rutinoside systematically to afford effective protection against UV stress.

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We tested the hypothesis that elevated CO₂ concentration [CO₂]-induced enhancement of biomass production of soybean is greater in a genotype that has a higher nitrogen (N) fixation capacity. Furthermore, we analyzed the interactive effects of N fertilization, temperature and [CO₂] on biomass production. Three genetically related genotypes: Enrei (normally-nodulating genotype), Kanto 100 (supernodulating genotype), and En1282 (non-nodulating genotype) were grown in pots, with or without N fertilizer for two years (2004, 2005). They were then subjected to two different [CO₂] (ambient and elevated (ambient+200μmol mol^-1))×two temperature regimes (low, high (low+4∼5ºC)). Top dry weight at maturity was the greatest in the elevated [CO₂]×high temperature regime, irrespective of genotype and N fertilization. The [CO₂] elevation generally enhanced N acquisition and dry matter production during the vegetative growth stage, and the enhancement was more pronounced in the nodulating genotypes (Enrei and Kanto 100) than in the non-nodulating genotype (En1282), indicating that N supply through N fixation contributes to elevated [CO₂]-induced biomass production in soybean. However, the relative responsiveness of biomass production to elevated [CO₂] was not necessarily higher in the supernodulating genotype than the normally-nodulating genotype. The N utilization efficiency to produce biomass was inferior in the supernodulating genotype than in the normally-nodulating and non-nodulating genotypes. These results did not fully verify the hypothesis that elevated [CO₂]-induced enhancement of biomass production of soybean is greater in a genotype with a higher N fixation capacity.

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Water scarcity and salinity are important limitations for agricultural production in semi-arid region. The purpose of this research is to study the interaction between the effects of water salinity and deficit irrigation on yield as grain per pot and yield components in greenhouse conditions. The irrigation treatments were continuous flooding (control), intermittent flooding (intervals of 1 or 2 d); W_o, W_1, and W₂, respectively. The salinity levels of irrigation water were 0.6 (control), 1.5, 3.0, 4.5 and 6 dS m^-1 in year of 2005 and 0.6 (control), 1.5, 2.5, 3.5 and 4.5 dS m^-1 in the year of 2006, which are referred to as S_o, S_1, S₂, S₃ and S₄, respectively. A local cultivar (Kamphiroozi) was planted in pots in a greenhouse in 2005 and 2006. The results indicated that grain weight per pot was not significantly different between continuous flooding and intermittent flooding at 1-d intervals. The volumetric water contents of soil before each irrigation in the intermittent flooding at 1- and 2-d intervals were 0.36 and 0.34 cm³ cm^-3 with a corresponding matric head of -431 cm and -594 cm, respectively. The grain weight per pot was not reduced significantly by salinity level of 1.5 dS m^-1 in W_o and W₁, while it decreased significantly at salinity levels higher than 2.5 dS m^-1 in W₂. With increasing irrigation water salinity levels from S_o to S₁, the straw weight per pot increased significantly. Generally, increased irrigation water salinity reduced 1000-grain weight, but water stress mitigated the reduction of 1000-grain weight by salinity. With increasing irrigation salinity beyond threshold (1.5 dS m^­-1), deficit irrigation resulted in significantly higher number of spikelets per panicle compared with flooding irrigation. Increased salinity with deficit irrigation resulted in a higher percent of unfilled grain. With increasing salinity level of irrigation water beyond the threshold values (1.5 dS m^-1) the deficit irrigation resulted in a lower percent of unfilled grain. respectively. The reduction of average grain weight per pot per unit increase of salinity of saturation extract was 14.5% per dS m^-1 in continuous flooding, and 11.0% per dS m^-1 in intermittent flooding (1-d and 2-d intervals) in the two years of study. The average reduction of grain weight per pot per unit increase in irrigation water salinity was 38.0% per dS m^-1 in continuous flooding, 17.0% per dS m^-1 in intermittent flooding (1-d and 2-d interval) during the two years of study. Finally, it is concluded that with saline water at 2.5–3.0 dS m^-1, intermittent irrigation is preferable for rice production and with saline water at 3.5 dS m^-1  or higher continuous flood irrigation failed to produce grains, but intermittent irrigation produced some grains whose weight per pot was about 50% of that in non-saline irrigation water.

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High-yielding rice varieties require a large accumulation of N in panicles. The objectives of this study were to clarify the change in N allocation during the ripening period (Exp. 1) and to quantify the contribution of N absorbed during the ripening period to panicle N at maturity (Exp. 2) in the high-yielding variety Takanari in comparison with that in Nipponbare as a control. In Exp. 1, ¹⁵N-labeled N (¹⁵N) was applied at heading to investigate the distribution of newly absorbed N as well as the allocation of plant N. In Exp. 2, split ¹⁵N application was performed during the filling period to estimate the above contribution. In Exp. 1, the allocation of plant N and absorbed ¹⁵N to the panicles was larger and that to the leaves was smaller in Takanari than in Nipponbare during the ripening period, although Takanari accumulated more N at maturity. The difference in N allocation suggested that the difference in N demand in panicles would be larger than that in N uptake. In Exp. 2, the varietal difference in the grain filling duration was observed: Nipponbare accumulated little N in the panicles after 28 d after heading (DAH), while Takanari accumulated about a quarter of its panicle N during that time. An estimate showed that in Takanari, 13.5% of the panicle N was derived from N absorbed after 28 DAH. These results suggest that the utilization of newly absorbed N until a later period after heading is important for the achievement of high yields.

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Rice productivity is related to the ability of plants to adapt to heat stress. The heat-tolerant cultivars ‘Nikomaru’ and ‘Chikushi 64’ and heat-sensitive cultivar ‘Hinohikari’ were grown at 30ºC and 25ºC for 49 days after flowering. At 30ºC, only a few white immature kernels were produced in ‘Nikomaru’ and ‘Chikushi 64’, but about 22% of grains had immature kernels in ‘Hinohikari’. The high temperature(30ºC) caused no significant changes in grain dry weight, water content, and the NMR T₁ value during the early ripening stage in ‘Nikomaru’ and ‘Chikushi 64’. It also did not affect grain development, especially with respect to the nucellar epidermis, in ‘Nikomaru’ and ‘Chikushi 64’, but caused clear cessation of development of the nucellar epidermis at 14 days after flowering in ‘Hinohikari’. In addition, high temperature decreased the amylose content and increased hardness vs. adhesion ratio of cooked rice in both ‘Nikomaru’ and ‘Chikushi 64’ resulting a softer, less sticky texture, but not in ‘Hinohikari’. The maximum viscosity and breakdown values were increased, and final viscosity decreased at 30ºC in all three cultivars. These results suggested that starch in the endosperm of grains changed from a fluid state to a doughy state more slowly in ‘Nikomaru’ and ‘Chikushi 64’ than in ‘Hinohikari’, in which the water content and NMR relaxation time decreased, and transported assimilates accumulated slowly during grain development.

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To understand the function of oxygen-evolving enhancer proteins (OEEs) in PSII, we cloned the complete nucleotide sequence of three OEE genes from Salicornia europaea cultured in a 3% NaCl solution and determined the effect of salt treatment on the expression levels of the OEE genes. The three OEE proteins were 89-74% identical to those of spinach. The expression of OEE1 gene was increased by NaCl treatment but not changed in OEE2 and OEE3. Therefore, the increases in the expression levels of Salicornia OEE1 gene may be important in maintaining the PSII activity in the presence of NaCl.

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In NADP-malic enzyme (NADP-ME) type C₄ plants, MC chloroplasts have well-developed grana, whereas BSC chloroplasts are generally characterized by highly reduced grana. In the previous study, salt treatment induced granal development in BSC chloroplasts of Zea mays, an NADP-ME type C₄ plant. Therefore, we examined the effects of salinity stress on the granal structure of BSC chloroplasts in seven other C₄ species belonging to the NADP-ME type. The plants were grown in soil and after a certain period of time, they were treated with 3% NaCl for 5 d. Ultrastructure and quantitative properties of chloroplasts at the middle part of leaf tissues were investigated. In BSC chloroplasts of all the C₄ species, almost no structural damage was observed, but the development of granal stacking was induced under salinity condition. Granal indices and appressed thylakoid density of BSC chloroplasts in the salt-treated plants were higher than those in the control plants. In all the species, the structure of MC chloroplasts was more or less damaged by salt stress; thylakoids were swollen and chloroplast envelope was disorganized. These results suggest that the granal development in BSC chloroplasts and the high damage of MC chloroplasts are common features of NADP-ME type C₄ plants under salinity stress.

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To examine the possibility of breeding high-yielding cultivars with high nitrogen use efficiency for dry matter accumulation (NUEd) and to provide simple criteria for the selecting and breeding high-yielding cultivars with high NUEd as well as useful information for the mapping of quantitative trait loci (QTL) controlling NUEd, we cultured recombinant inbred lines (RILs) of rice hydroponically in 2000 and 2001. RILs with a higher grain yield tended to show greater total dry matter accumulation (TDMA) and higher harvest index (HI), while increasing TDMA resulted in a decrease in HI. The contribution ratio of the TDMA to grain yield (2000 : 67.3%, 2001 : 68.2%) was higher than that of HI in both 2000 and 2001. Even at the same high-yielding level, there was a significant difference in the TDMA and HI values. In both years, the contribution ratios of NUEd and total nitrogen absorption (NTA) to TDMA were about 62.0 and 38.0%, respectively. The contribution ratio of the NUEd to grain yield was higher than those of the NTA and HI in both 2000 (41.6%) and 2001 (42.9%). These results suggested that the high-yielding rice plants generally displayed high TDMA and HI values. Further increase in rice grain yield should be based on the further increase in TDMA than in HI, and to increase TDMA leading to a high grain yield, the emphasis also should be put on improving NUEd in RILs.

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Pod dehiscence (shattering) is a major source of yield loss in the mechanically harvested soybean. We examined near-isogenic lines (NILs) for a major quantitative trait locus (QTL) controlling pod dehiscence, designated as qPDH1, to reveal the mechanism underlying the effect of this QTL on shattering resistance. The degree of shattering resistance differed among the NILs; as pod dehiscence percentage after 3 hr heat treatment was under 50% and over 90% for the genotypes resistant to shattering and those susceptible to shattering, respectively. On the other hand, there were no significant differences in the length, width and thickness of pods among the NILs. Anatomical analysis of the dorsal sutures of pods, at which pod dehiscence was found to commence most frequently, revealed no marked differences between the NILs. These results suggest that qPDH1 controls pod dehiscence without markedly changing the morphology of the pods.

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In rice (Oryza sativa L.), the maintenance of high photosynthetic rate of flag leaves and the carbon remobilization from leaf sheaths after heading is a critical physiological component affecting the yield. To clarify the genetic basis of RuBisCO content of the flag leaf, a major determinant of photosynthetic rate, and non-structural carbohydrate (NSC) concentration in the third leaf sheath at heading, we carried out quantitative trait loci (QTL) analysis with 39 Koshihikari/Kasalath chromosome segment substitution lines (CSSLs) and backcross progeny F₂ population derived from target CSSL holding the QTL/Koshihikari in the field. QTLs for RuBisCO content and NSC concentration at heading were detected between R2447-C1286 and R2447-R716 on chromosome 10, respectively, by comparing Koshihikari with four CSSLs for chromosome 10 (SL-229, -230, -231 and -232). The progeny QTL for RuBisCO content and for NSC concentration at heading qRCH-10 and qNSCLSH-10-1, respectively, were detected at similar marker intervals between RM8201 and RM5708. In addition, QTLs for RuBisCO content at 14 d after heading, qRCAH-10-1 and qRCAH-10-2, were detected in regions different from that of qRCH-10. No QTL for NSC concentration at 14 d after heading was detected between RM8201 and R716, the region analyzed in this study. The QTLs qRCH-10 and qRCAH-10-1 for RuBisCO content would have additive effects. These QTLs for RuBisCO content and NSC concentration newly found using CSSLs and their backcross progeny F₂ population should be useful for better understanding the genetic basis of source and temporary-sink functions in rice and for genetic improvement of Koshihikari in terms of their functions.

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The kernels of Hattan-nishiki No. 1 and Kairyo-omachi have larger air spaces in the white-core tissue and are broken easily during the process of polishing when compared with those of Senbon-nishiki and Yamada-nishiki. The polishing characteristics of brewers’ rice kernels are closely related with the structure of the white-core tissue of kernels. In this study, the varietal differences in the starch properties of white-core tissue of brewers’ rice kernels on polishing characteristics were studied. The starch properties were studied by rapid visco analysis (RVA) and differential scanning calorimetry (DSC); the amylose content of the rice flour of each variety was also analysed. No significant differences were observed in the amylose content among the four varieties. The two RVA parameters, peak viscosity and breakdown, were higher in Hattan-nishiki No. 1 and no significant differences were observed in them among Senbon-nishiki, Yamada-nishiki and Kairyo-omachi. The DSC parameters, gelatinization onset and peak and conclusion temperatures, were higher in Hattan-nishiki No. 1, lower in Senbon-nishiki and Yamada-nishiki, and intermediate between them in Kairyo-omachi. These results suggest that the polishing characteristics of brewers’ rice kernels are related with not only the endosperm structure but also the starch property of white-core tissue, except for Kairyo-omachi.

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This study aimed to clarify the effects of water storage-type deep irrigation (WSDI) on the yields of various rice cultivars used in the Tohoku district of Japan. We compared a WSDI plot (DP) with a standard irrigation plot (SP) with regard to the growth, yield, and yield components of the rice cultivars grown in these plots during 4 years (2002–2005) in Sendai, Japan. In 2003, which had a cool summer, the yields in DP were considerably higher than those in SP, thus confirming that WSDI mitigated the cool summer-induced damage to rice. The yields in DP were not lower than those in SP during the other 3 years (normal climatic years), indicating that various cultivars could adapt to WSDI. Although high-yielding rice plants cultivated by well-experienced farmers under deep-water irrigation regimes have large panicles, the spikelet number per panicle and the yield in DP were not higher than those in SP. Based on the results of the comparison between the cultivation system of WSDI and that of high-yielding deep-water irrigation regimes practiced by such farmers, we speculated that to achieve a higher yield under WSDI, other cultivation techniques need to be incorporated into WSDI.

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A Chinese high-yielding large-panicle indica cultivar Yangdao 4 (YD) was examined for the response of yielding ability, sink size and percentage of filled grains (PFG), to the cultivation practice in comparison with a Japanese cultivar Hinohikari (HH) that had almost the same growth duration in 2005 and 2006. Treatments included planting density and number of seedlings hill^-1, and supplement application of fertilizer to deep layer (SAFDL). Results revealed that the average sink size of YD was 17−28% larger than that of HH due to the larger number of spikelets panicle^-1 and heavier grain weight. A significantly larger sink size was attained by the high density planting and SAFDL treatments in both cultivars, but not by changing the seedling number hill^-1. The sink size of YD responded more significantly to the cultivation practices than that of HH. The average PFG in YD was about 10% higher than that in HH in both years. The PFG in both cultivars decreased with increasing sink size, but the decreasing rate in YD was 1/3 of that in HH and its yearly fluctuation was also less in YD than in HH. Consequently, the yield of YD increased with increasing sink size in contrast to HH. The average brown-rice yield of YD (640−653 g m^-2) was 41−51% higher than that of HH (418−454 g m^-2). In comparison with HH, the stable PFG in YD at increased sink size could be attributed to the increase of carbohydrate accumulation in the panicle (ΔW+ΔT ), larger amount of NSC in the LS+C and higher NSC/sink size.

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Using a Chinese large-panicle-type high-yielding indica rice cultivar, Yangdao 4 (YD), pot experiments were carried out to determine the effects of the removal of the lower nodal primary tillers on the growth and yield-related characteristics in comparison with a Japanese cultivar, Hinohikari (HH), with almost the same growth duration. The plants with all tillers remaining (Cont), those with tillers from the 5th and higher nodes (T5) and those with tillers from the 8th and higher nodes (T8) were prepared by removing the other tillers and grown in early, normal and late cropping seasons, sowing in late April, May and June, respectively. The lowest nodal primary tillers in each group emerged earlier and the number of days from sowing to flag leaf expansion and to full heading stage was reduced in the late cropping season, especially in HH. The maximum number of stems and number of panicles were larger in HH than in YD, and tended to be higher in the order of Cont>T5>T8 plants. The average panicle weight per stem was higher in YD than in HH and higher in the order T8>T5>Cont. Panicle weight per hill was higher in YD than in HH in each cropping season and higher in early cropping season in both cultivars. Panicle weight decreased with delayed tiller emergence in YD, but not in HH. Panicle weight was more closely related to straw weight in YD than in HH. Therefore, the promotion of vegetative growth by early sowing and development of lower nodal tillers is more effective for attaining a high yield in YD than in HH.

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