Expression of the α-amylase gene RAmy3D was studied in aerobic, hypoxic, and anoxic conditions using the rice cultivars Suweon 287 and Nipponbare by in situ hybridization. In the aerobic condition, the initial expression of RAmy3D in the scutellar epithelium and its later expression in the aleurone layer were consistent with the previous reports. However, hypoxia delayed the expression of RAmy3D in the scutellar epithelium, and blocked expression in the aleurone layer. In anoxia, RAmy3D expression in cv.Nipponbare was similar to that in hypoxia, but that in cv.Suweon 287 was significantly suppressed 4 d after seeding. These results suggest that the expression of the RAmy3D gene is also affected by anoxia. Considering the results of our previous report together, RAmy3D-encoded isoforms in anoxia may be mainly regulated at the post-transcriptional level. A possible process in the regulation of RAmy3D expression in germinating seeds is discussed.

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Japonica rice(Oryza sativa L., cv.Notohikari)was transformed by the use of aluminium borate whiskers(ABW) to deliver DNA into the scutellar tissues of embryos isolated from mature seeds. DNA delivery was mediated by mixing ABW and plasmid DNA. Some parameters of DNA delivery employing ABW were determined in the tissues based on the transient expression of β-glucuronidase(GUS) reporter gene. The optimum condition was established as the mixing of 290 μL buffer containing 64 mg ABW and 25 μg DNA and 20 tissues for 30 min. Under this condition, we tried to introduce the phosphinothricin acetyl transferase(bar)gene whose product confers resistance to the bialaphos into the tissues, together with the GUS gene, and obtained bialaphos-resistant calli. Transgenic rice plants were regenerated from one of them. The integration of GUS gene and bar gene were confirmed by GUS histochemical assay and polymerase chain reaction(PCR) analysis, respectively. Southern hybridization analysis also confirmed the integration of bar gene. These results suggest that a simple and inexpensive DNA delivery procedure via ABW can be useful to produce transgenic rice plants.

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Seven-day-old rice seedlings(Oryza sativa L.cv.Kinuhikari)were subjected to anaerobic stress and their proteins were analyzed using SDS-polyacrylamide gel electrophoresis. Anaerobic stress caused only minor changes in the pattern of proteins in the shoots, but disappearance of many protein bands in the roots. Three anaerobic stress proteins(ANPs; 36-, 40- and 87-kD protein)were selectively induced in both roots and shoots of the seedlings, and 36-kD ANP was identified as the glycolytic enzyme, glyceraldehyde-3-phosphate dehydrogenase(GAPDH) by limited N-terminal amino acid sequencing. Activities of GAPDH in the shoots and roots were increased by the stress for over 24 h, and were 3.4- and 6.2-fold greater than those in non-stressed seedlings at 24 h, respectively. These results suggest that anaerobiosis induces the production of ANPs including GAPDH in the seedlings, which may allow the seedlings to survive under the stress condition.

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The effects of various constant temperatures(4, 9, 14, 19, 24, 29, 34, and 38°C)on the germination of winter wheat seed(Triticum aestivum L.cv.'Koyuki')in a dark condition were studied. The maximum germinatin percentage was 98% at 24°C. The speed of germination was fastest at 29°C. These results indicate that the most suitable temperature for germination was in the range of 24 to 29°C. α-Amylase expression during germination was also high at higher temperature, and maximum expression occurred at 29°C, although a high temperature of 38°C prevented the synthesis of α-amylase. The close correlation between germination and α-amylase activity at various temperatures indicates that α-amylase is an essential factor for the temperature-dependent germination of wheat seed. In contrast, accumulation of proline increased at a lower temperature, and was the highest at 4°C. We also studied the effects of gibberellin(GA₃) and proline, a compatible osmotica in alleviating the effect of low and high temperature stresses. Pre-soaking treatment with GA₃ and proline was effective in promoting germination and increasing α-amylase expression at a low(4°C)and high(38°C)temperature. These results suggest that GA₃ and proline exhibit positive effects on stress alleviation through the stimulation of α-amylase expression.

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The growth efficiency(GE), specific dark-respiration rate(Rs) and crop growth rate(CGR) of rice plants grown in the field with applications of nitrogen fertilizer at 0, 11 and 17 g per m² were examined every two weeks in 1996 and 1997. Rs was the highest at the rooting stage, and decreased rapidly until the heading time and gradually thereafter. The nitrogen concentration(NC) of the plant also decreased during ontogeny. NC at each growth stage varied with the amount of nitrogen supply, but Rs did not. This suggests that NC did not directly influence Rs. Alinear relationship was observed between NC and Rs determined for all growth stages as a whole. However, the slope of the NC-Rs regression line greatly varied with the growth stage. The value of GE, CGR/(CGR+R)(R, respiratory loss), was within a range of 60-70% during the early growth stage independent of nitrogen supply, but that during the grain-filling period was lowered by increased nitrogen supply. The nitrogen fertilization increased phytomass and grain yield, accompanied by the increase in respiratory loss. In 1997, a larger amount of carbohydrates was consumed for respiration than in 1996, due to higher atmospheric temperatures during the grain-filling period, and GE at the later stage in 1997 was lower than that in 1996. This means that the increased respiratory loss at high temperatures may be a cause of GE depression.

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Hematoxylin staining of root(hematoxylin staining method) and the growth response to Al added to the soil in pots(growth-response method)were used to select Al-tolerant sorghum. Twenty-two sorghum genotypes were screened by the hematoxylin staining method, and twelve genotypes selected were evaluated again by the growth-response method. Five genotypes(G4, H11xC8, Real 60, SPA2, and SPAD)showed consistent Al tolerance by both screening methods. Genotype C9xH13 was susceptible to Al. A significant correlation(r=0.666^**)was observed between the score of hematoxylin staining method and that of relative root length(RRL). The value of RRL also showed a significant correlation with the score of hematoxylin staining(r=0.622^*). The roots of genotypes that were not stained by hematoxylin tended to have a long root in the soil with Al added.

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A new nurturing method was studied using pieces cut from storage roots to reduce the time-consuming and laborious works(raising, preparing, and transplating of cut sprouts), which accounts for about 60% of the total working hours in sweet potato production by the conventional method. The experiments were conducted in 1997 and 1998 using 1- and 10-g(fresh weight)cut pieces from storage roots(cultivar; Koganesengan). Five kinds of growth regulators were applied at the concentrations ranging from 0 to 200 mg L^-1 to promote rooting and shooting from the pieces. After the treatment with growth regulators, the pieces were subjected to an antiseptic curing treatment, and then incubated on wet vermiculite at 30°C. Rooting was effectively induced by IAA, and shooting by ABA, within one to two weeks. The plantlets were developed from 10-g pieces with periderm after the treatment with ABA, and were nurtured for 10, 30 and 50 days. They vigorously grew with no transplanting injury after being planted in the field in early May. They were harvested in late October and were compared for shoot growth and productivity with the control(the conventional method using cut sprouts). The plantlets nurtured for 50 days achieved the highest yield and the best qualities and did not show the thickening of mother roots obserbed in direct planting using whole storage roots. In conclusion, the new nurturing method is superior to conventional methods in both productivity and quality. However, there are still several problems to be solved, such as low shooting rate and so on.

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Soybean(Glycine max[L.]Merr.)seed storage proteins consist of subunits that differ in amino acid profile, the β-subunit of 7S protein being essentially devoid of the S-containing amino acids, methionine and cysteine. Our objective was to examine the interaction of N and S nutrition on the relative abundance of these storage protein subunits in soybean seed. 'Kenwood' soybean was grown in hydroponic culture, and during vegetative growth(V2-R4.5)N was provided as 5 mM KNO₃ to plants grown under sulfur-deficient(0.004 mM Na₂SO₄)or sulfur-sufficient(0.4 mM Na₂SO₄)conditions. During seed fill(R4.5-R7)N was supplied as 5 mM KNO₃ or 2.5 mM urea. Each N group was given S treatments of 1)no sulfur, 2)0.4mM Na₂SO₄, 3)0.2 mM L-cystine, or 4)0.4 mM L-methionine. Effects on seed protein quality of S deficiency during vegetative growth were essentially overcome by supplying sulfate as late as R4.5. Total protein and seed storage protein were increased with urea as N source, but urea also increased the β-subunit. Provision of reduced S as methionine essentially suppressed β-subunit production, but cystine did not, suggesting that cystine did not influence methionine level in the seed. We also report the accumulation of two as yet unreported proteins which occur at extremes of S nutrition: (1)a putative β-subunit of 7S protein occurring in the embryonic axis under S-deficiency; and (2)a ca.14kD protein in cotyledon tissue under provision of L-methionine. Though S and N did interact to a limited extent to influence seed protein composition, major effects were from S or N acting individually.

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Increase in seedling vigor is necessary to improve the yield of early-maturing spring wheat with a limited growth period. The importance of coleoptile tillers in increasing seedling vigor has been suggested. However, most previous studies on the development of coleoptile tillers have been made with only a limited number of varieties and under controlled environmental conditions. In this study, we examined difference in the development of coleoptile tillers among early-maturing varieties of wheat under field conditions. We observed large differences among varieties in the percentage of plants with coleoptile tillers, ranging from 5.6% in Haruyutaka to 60.1% in Bandouwase. The percentage of plants with coleoptile tillers was closely correlated with the number of leaves developed on the main stem. The dry weight of the plants with coleoptile tillers was heavier than that without coleoptile tillers(by 34.8% in Fukuwase komugi). However, in some varieties, the dry weight of the plants with coleoptile tillers was similar to that of plants without coleoptile tillers. The increase in dry weight per plant seemed to be achieved by the production of either a few heavy tillers or many light tillers.

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Deep penetration of an axile root is one of the important factors that allow crops to form deep root systems. In this study, the nodes from which the deepest penetrated roots had emerged were examined at the heading stage in upland rice and maize grown in large root boxes and in the field. Both experiments were designed to measure the direction, length, and rooting nodes of each root. In maize, the growth angles of axile roots increased with vertical elongation as rooting nodes acropetally advanced. The roots that emerged from the lower nodes, namely from coleoptilar to the second node, exhibited conspicuously horizontal elongation in the field, reaching 2.3 m in width at the maximum. The roots that emerged from higher than the fifth node were too short to penetrate deeply. Thus, these roots became the deepest root in less or no probability under field conditions. On the other hand, the fourth nodal root, which had an intermediate growth angle and length, had the highest probability. In upland rice, the deepest roots emerged from the nodes lower than the forth node on the main stem in the root boxes. In the field, however, the deepest roots emerged at later stages, that is, the roots from the middle nodes on the main stem and from the low nodes on the primary and secondary tillers were the deepest roots. Five out of nine of the deepest roots were from the prophyll nodes in three field-grown upland rice. The deepest roots from the same plant were estimated to have emerged and grown at approximately the same stage.

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The fractal dimension(D) is the main concept of fractal geometry. D may have the potential to describe morphology in overall terms for root systems quantitatively. However, it is often difficult to discriminate root systems possessing a common D but having a different morphological appearance. We tested the potentiality of multifractal analysis as a tool for characterizing the morphology and architecture of root systems, and applied this method for discrimination of such root systems having similar Ds. We adopted mass fractal measure and determined Ds for small area(local fractal dimension, D_local)at different locations of root systems. The multifractal spectrum indicated that D_local varied with the location on the roots, suggesting that root systems possess a multifractal structure, the complexity is unevenly distributed, and its characteristic can be partly described with the D_local spectrum. The skewness and kurtosis of histogram of D_local varied among species, even when they possess root systems with a common D which was determined by the box-counting method as an overall morphology of the system(global D). The spectrum of D_local was further analyzed in relation to topological parameters. We found significant correlation between topological index and skewness as well as between topological index and kurtosis. These suggest that the variation of D_local spectrum can be an indication of variability of architecture in a locally restricted area of root system. The multifractal analysis can be applicable and it has a potential for discriminating and characterizing root systems having a common global D, but with different morphology.

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Tomato(Lycopersicon esculentum Mill.cv.Know-You 301)shoots were grafted onto the rootstock of the same species or Salanum mammosum and grown in nutrient solution. After the grafted tomato plants developed 4-5 leaves, the uppermost fully expanded leaves were used to determine net photosynthetic rate(P_N), transpiration rate and leaf water potential(Ψ_L)under control(unstressed)and -0.5 MPa water deficit(mannitol was added to nutrient solution). Both PN and leaf conductance(G_L)were reduced under water deficit. However, tomato plants grafted onto S.mammosum rootstock had higher Ψ_L, P_N and G_L than those grafted onto tomato rootstock under water deficit. This result demonstrates that S.mammosum roots had a greater ability in water uptake under water deficit. Under +0.2 MPa pressure, the root of S.mammosum showed a higher exudation rate than that of tomato. However, the former showed a lower exudation rate than the latter under -0.5 MPa water deficit. It was concluded that the greater ability of water uptake in S.mammosum rootstock under water deficit is related to a lower hydraulic conductivity, which promotes passive, rather than active water uptake.

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The difference in the number of pollen grains may be the primary factor determining the resistance to cool weather at the young microspore stage in rice(Oryza sativa L.)cultivars. To confirm this hypothesis, we compared the number of pollen grains among the cultivars or lines with various cool-weather resistance. The cultivars or lines used in the experiments were mainly released or grown in the Tohoku district(the northern part of the mainland of Japan). The number of pollen grains showed high correlation with the degree of cool-weather resistance, but considerably varied with the cultivar or line, even in the group having the same cool-weather resistance. Each group with different cool-weather resistance was divided into two subgroups, implying the existence of another genetic factor determining the resistance. The number of pollen grains in the plants cooled at the young microspore stage showed higher correlation with the degree of the cool-weather resistance than that in the control plants without exposure to low temperature. The correlation between the pollen number and spikelet sterility was also analyzed using the data of Satake and Shibata(1992, Jpn.J.Crop Sci.61: 454-462), who primarily used the cultivars in Hokkaido(the northernmost island of Japan). The results were basically the same as those obtained in the present experiments. These results confirmed the hypothesis that the variation in the number of pollen grains is a primary factor of the resistance to cool weather at the booting stage in the cultivars in the northern part of Japan. The results also suggested the existence of another genetic factor determining the resistance.

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The effect of a long term of soil compaction on dry matter production(DMP) and water use in rice cultivated under limited water supply during the reproductive stage is unknown. Our objectives were to determine which of the transpiration(Tr) or water use efficiency(WUE) is dominant in determining DMP under compacted and desiccated soil conditions. When irrigation in the period around the reproductive stage was terminated in artificially compacted and non-compacted fields, the rate of suppression of DMP by soil compaction was similar in the three rice cultivars, but DMP was higher in drought resistant cultivars having deep root density at the heading stage. Six cultivars were grown in pots of 1.0 m in depth containing the soils of three levels of soil bulk density(SBD). Water supply was restricted by keeping the water table in the pot deep without irrigation during the reproductive stage. DMP and Tr in all cultivars decreased with increasing SBD, and a close relationship was seen between DMP and Tr. WUE was thus a fairly stable factor for all cultivars examined. Tr was positively correlated with root length density and was relatively maintained at a high SBD in drought-resistant cultivars having a higher root length density. We concluded that water shortage under compacted soil conditions during reproductive stage suppressed the DMP, and DMP suppression accompanied a reduction of Tr due to poor root development rather than the reduction of WUE. In the drought-resistant cultivars reduction of DMP was relatively small due to their higher developed root systems that allowed high water absorption from the deep layers in the compacted soil.

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The effects of soil compaction under water deficit conditions during the reproductive stage on the grain yield of rice were examined with various cultivars. In a field experiment, three rice cultivars were grown in compacted and non-compacted upland conditions and irrigation was terminated at the early reproductive stage. The grain yield and total dry weight(DW) at maturity was similarly reduced by soil compaction regardless of the rank of the cultivars in drought resistance. However, the yield was superior in the cultivars that showed higher yield and DW under non-compacted conditions. In greenhouse experiments, six rice cultivars were grown in the pot of 1.0 meter in depth containing soil at three levels of soil bulk density(SBD), and water supply was reduced by lowering the water table during the reproductive stage. The effects of SBD on DW and grain yield were similar among six cultivars. In both field and pot experiments the yield reduction was predominantly caused by a smaller number of spikelets, with greater reduction of DW than the reduction of harvest index. We concluded that soil compaction reduced rice grain yield by decreasing the number of fertile spikelet that was mainly caused by the suppression of DW and partly by sterility due to water deficit regardless of cultivar. There was no clear difference among the cultivars in the yield response to soil compaction, but the local drought-resistant cultivars, which showed a relatively superior yield and DW under the non-compacted upland condition, showed a higher yield even on compacted soil.

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The combined effects of high nitrogen supply, cool temperature regimes and shading on factors related to fertility in rice plants were investigated. High nitrogen supply during the period from the spikelet differentiation stage to the young microspore stage caused a decrease in the number of microspores per anther. High nitrogen supply plus cool treatment at the young microspore stage(12°C for 3 or 4 days)resulted in a conspicuous decrease in the number of engorged pollen grains per anther. Shading also decreased the number of microspores and pollen grains. The lowest numbers of microspores and pollen grains were observed in a treatment combining high nitrogen supply with shading and cooling. The number of pollen grains shed on the stigma and germinated pollen grains were decreased by cooling. These results suggested that the lower fertility due to high nitrogen supply combined with cooling resulted from 1)decrease in number of microspores, 2)large decrease in number of pollen grains per anther, and 3)decreases in number of pollen grains and germinated pollen grains on the stigma.

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White heads and silicon deposition in spikelets were observed in three rice varieties(IR28, IR4595-4-1-13 and Mangasa), which were different in vulnerability to white heads under salinity conditions. Plants were grown in three-liter pots with two nitrogen fertilizer levels(HN: high nitrogen and LN: low nitrogen)and subjected to salinity by submerging the soil in a 100mM sodium chloride solution from booting to seven days after panicle emergence. White heads occurred in IR4595-4-1-13 and Mangasa but not in IR28 under the salinity condition, and the vulnerability to white heads was higher with the HN treatment than the LN treatment. Silicon deposition in spikelets, measured by energy-dispersive X-ray analysis with a scanning electron microscope, was correlated to the vulnerability to white heads. White heads inhibited flower opening and thus induced high sterility. It was concluded that low silicon deposition in spikelets was responsible for the occurrence of white heads under salinity conditions in rice.

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Developmental plasticity in lateral roots may be one of the key traits for the growth of rice plants under soil moisture fluctuations. We aimed to examine responses in seminal root system development to changing soil moisture for diverse rice cultivars. Special attention was paid to the two different types of lateral roots; the generally long, thick L type capable of branching into higher orders, and the non-branching S type. Plants were grown in half-split polyvinyl chloride tubes fixed with transparent acrylic plate for root observation under glasshouse conditions. When plants were grown first under drought conditions, then rewatered, the seminal root system development in terms of dry weight and total length was promoted as compared with plants grown under continuously well-watered conditions in IRAT 109 and Dular, drought tolerant cultivars. Promoted production of L type lateral roots mainly contributed to the development of the longer seminal root system. Plants exposed to soil submergence before they were grown under drought conditions did not show such promoted responses in these two cultivars. However, in KDML 105, a drought tolerant cultivar, the production of especially L type laterals was substantially promoted under drought and rewatered conditions. Honenwase was characterized by the shallow root system and great reduction in root system length when soil moisture becomes limited. These facts show that genotypic variations exist in the plastic response of rice seminal root system and that the L type lateral root plays a key role in manifestation of this plasticity.

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