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1.
TATSUYA INAMURA 《Weed Biology and Management》2003,3(1):1-7
The loss of final tuber weight of Eleocharis kuroguwai Ohwi by shading during the early tuber formation period (TFP) is overcome by exposure to unshaded daylight thereafter (late TFP). In the present study, the growth parameters that contribute to the dry matter increase (DMI) per day of tubers in the late TFP were examined. DMI of the tuber during the late TFP was determined by that of the whole plant and the ratio of the DMI of the tuber to that of the whole plant during this period. The ratio of the DMI of the tuber to that of the whole plant during the late TFP was significantly correlated with the DMI of the whole plant during the first 14 days of the late TFP. During the late TFP after the exposure to unshaded daylight, DMI of the whole plant correlated with the surface area of the stem (SAS) and net assimilation ratio (NAR), and the SAS correlated with the stem dry weight (DW) and specific stem-surface area (SSA). SSA negatively influenced NAR, but NAR was increased by unshading. During the late TFP after shading, the effect of the decrease of the stem DW due to shading on the DMI of the whole plant was mitigated by the large SAS and high NAR. These results indicate that the growth parameters that contribute to the DMI of tuber during the late TFP after exposure to unshaded daylight are SAS and NAR just after unshading, and SSA during this period. 相似文献
2.
In order to explore the methods of recovering native grasses into exotic vegetation, the response of riparian vegetation to the removal of the above‐ground shoots and/or litter of Solidago gigantea in a flood plain in Hokkaido, northern Japan, was investigated. The four treatments were: the removal of the above‐ground shoots of S. gigantea (A); the removal of the litter of S. gigantea (L); the removal of both the above‐ground shoots and litter of S. gigantea (AL); and a control (C). The vegetation cover and S. gigantea cover decreased in the A and AL treatments and increased in the L and C treatments. The understory plant cover increased in the A and AL treatments, but did not change in the L and C treatments. The increases in the understory cover in the A and AL treatments were associated with increases in Phalaris arundinacea. The seedling emergence of P. arundinacea was promoted by AL. In a greenhouse, the S. gigantea litter tended to decrease the seed germination of P. arundinacea. The AL treatment also increased the abundance of the other exotic plant, Solidago altissima. The continuous removal of the above‐ground shoots and litter of S. gigantea long term is effective for promoting the recovery and emergence of native riparian grassland vegetation. However, this method also promotes the recovery of other exotics. 相似文献
3.
SHINSUKE TOMITA EIJI NAWATA YASUYUKI KONO TATSUYA INAMURA YOSHIKATSU NAGATA CHAIRAT NOICHANA AKKADET SRIBUTTA 《Weed Biology and Management》2003,3(2):68-76
In north-east Thailand where rainfed paddy cultivation is commonplace, direct dry seeding is replacing transplanting to increase the frequency of successful plantings and to save labor. The present study shows the impact of this change on paddy vegetation from agricultural and ecological viewpoints. One hundred and seventy-nine paddy fields from a wide range of climatic, topography, soil and hydrological conditions were used in this study. Authors visited these fields every 3 weeks during the rainy seasons of 1996–1998 to collect data about water conditions, rice growth, progress of cultivation, paddy vegetation and roughness (unevenness) of the soil surface. Analysis of this data revealed that direct dry seeded fields are resource-poor and have a wider range of water conditions within a field than transplanted fields due to a rougher soil surface. This results in lower productivity of total vegetation for rice growing in direct dry seeded fields. However, weed productivity was not significantly different between the direct dry seeding and transplanted fields. Direct dry seeded fields have more species-rich vegetation and greater diversity than the transplanted fields. Previous planting methods for particular fields did not influence productivity and diversity of paddy vegetation. It is concluded that the use of direct dry seeding increases biomass production of rice and the diversity of the paddy vegetation. The present results also suggest that an analytical framework be used to integrate agricultural and ecological studies of paddy vegetation in order to harmonize agricultural productivity with biological diversity. 相似文献
4.
HIROHIKO KAGAWA HIDEKI TANAKA TATSUYA UNUMA HIROMI OHTA KOICHIRO GEN KOICHI OKUZAWA 《Fisheries Science》2003,69(2):234-241
ABSTRACT: The in vitro effects of 17,20β-dihydroxy-4-pregnen-3-one(DHP) and prostaglandins (PGE1 , PGE2 , PGF1α ,PGF2α ) on ovulation in the Japanese eel Anguillajaponica were examined. Oocytes with follicle layers at themigratory nucleus stage (approximately 850–900 µmdiameter) were removed using a polyethylene cannula from artificiallymatured fish. At concentrations of 10 and 100 ng/mL,DHP was found to induce both germinal vesicle breakdown and ovulation.The prostaglandins, except for PGE1 , effectively inducedovulation of previously matured oocytes by DHP treatment in vitro .Prostaglandin F2α was the most effective. Asignificant increase in ovulation rate was observed even at a concentrationof 0.01 µg/mL PGF2α .Indomethacin blocked the in vitro ovulation induced by DHPand addition of PGF2α reversed indomethacin-blockedovulation. Actinomycin D and cycloheximide blocked DHP-induced ovulationand PGF2α reversed the effects of both inhibitors. Theseresults indicate that DHP induces ovulation through endogenous prostaglandinsynthesis in the follicle layers of the Japanese eel. 相似文献
5.
Expression of pancreatic enzyme genes during the early larval stage of Japanese eel Anguilla japonica 总被引:1,自引:0,他引:1
TADAHIDE KUROKAWA TOHRU SUZUKI HIROMI OHTA HIROHIKO KAGAWA HIDEKI TANAKA TATSUYA UNUMA 《Fisheries Science》2002,68(4):736-744
ABSTRACT: To reveal the ontogeny of pancreatic exocrine function in the early larval stage of eel, cDNAs encoding major pancreatic enzymes, trypsinogen, amylase and lipase were identified from the Japanese eel Anguilla japonica and their expression pattern in larvae was analyzed. The cloned eel trypsinogen precursor consisted of 224 amino acids and showed 82.2% identity to trypsinogen-2 of winter flounder Pleuronectes americanus . The eel amylase precursor consisted of 512 amino acids and showed 77% identity to winter flounder amylase. Eel pancreatic lipase was composed of 470 amino acids and had 58.3% of identity to human pancreatic lipase. In the eel larvae, mRNA expression of trypsinogen and amylase was first detected at 6 days post-hatching (d.p.h.), and the expression level increased between 7 and 8 d.p.h. In contrast, mRNA expression of lipase was first detected at 8 d.p.h. Eel larvae start to feed actively at 8 d.p.h. Thus, it was indicated that eel pancreas starts to synthesize digestive enzymes at 6 d.p.h. and acquires full function by the onset of exogenous feeding at 8 d.p.h. 相似文献
6.
ABSTRACT: We examined the stomach contents of 26 Baird's beaked whales caught off the coast of Japan by small-type coastal whalers. The main prey for these whales was rat-tails and hakes in the western North Pacific. Pollock and squids were also important food in the whales collected from the southern Sea of Okhotsk. The prey species found in the stomachs of the whales were almost identical to those caught in bottom-trawl nets at depths greater than about 1000 m in the western North Pacific, which suggests that the Baird's beaked whale forages for prey at depths of about 1000 m or more. Baird's beaked whales in the western North Pacific migrate to waters of 1000–3000 m in depth, where demersal fish are abundant. This implies that Baird's beaked whales migrate to waters where demersal fish, especially rat-tails and hakes, are abundant. Although there is limited information on the feeding habits of ziphiid whales, they are generally thought to prefer squid. The present data suggest that demersal fish are also important prey for ziphiid whales. 相似文献
7.
TATSUYA KAJI MASAAKI KODAMA HIROSHI ARAI MASATOMO TAGAWA MASARU TANAKA 《Fisheries Science》2002,68(6):1212-1218
ABSTRACT: Striped bonito Sarda orientalis larvae and juveniles were reared in a laboratory from hatching to 14 days post hatching, and the development of their digestive system was investigated histologically. On day 2 (first feeding day), the larval-type digestive system was differentiated. On day 3, a blind sac with densely distributed gastric glands developed and pyloric ceca appeared, suggesting that the digestive system was attaining adult-type structure. The yolk was completely absorbed on day 4. Bonito larvae preyed on rotifers and/or Artemia nauplii on day 2, but almost the whole gut was occupied by fish larvae from day 4. In the striped bonito, the adult-type digestive system was established right after first feeding, and this precocious development was well synchronized with the appearance of piscivory. 相似文献
8.
本文研究了在内蒙古饲养管理条件下,降低牛奶含菌量的方法。共进行了5个方面的试验:头几把挤出的奶中细菌含菌量的检测;容器洗净对降低牛奶含菌量的作用;鲜奶过滤对奶中细菌含量的影响,冷水浴对降低牛奶含菌量的作用;盛奶罐口径大小及奶温高低对奶中细菌含菌量的影响。奶样抹片后,用纽曼染色液染色采用直接镜捡法进行细菌计数。结果表明:刚挤出的奶含有较多的细菌,随着挤奶的延续,奶中含菌量减少,彻底洗净挤奶器具和容器可大幅度降低牛奶的含菌量;用纱布过滤鲜奶并迅速冷却可明显降低牛奶的含菌量盛奶罐口径越大,牛奶中细菌含量越高。针对以上结果采取相应的对策,可降低牛奶中细菌的含量。 相似文献
9.
Rice yield losses by competition with weeds in rainfed paddy fields in north-east Thailand 总被引:2,自引:0,他引:2
SHINSUKE TOMITA SHUICHI MIYAGAWA YASUYUKI KONO CHAIRAT NOICHANA TATSUYA INAMURA YOSHIKATSU NAGATA AKKADET SRIBUTTA EIJI NAWATA 《Weed Biology and Management》2003,3(3):162-171
Economic growth in recent years has induced a labor shortage for agriculture in north-east Thailand. Labor-saving techniques, such as the replacement of transplanting with direct seeding, have become widespread. Direct seeding methods have advantages over transplanting regarding labor savings and reductions in production risks, but may cause weed problems. Therefore, rice yield reduction by competition with weeds becomes a potential problem in this region. In the present research, the extent of weed competition in rice production from the viewpoint of resource level and disturbance intensity was studied. A large number of paddy fields from a wide range of climatic, topographical, soil and hydrological conditions were analyzed. The survey was conducted every 3 weeks, and data on paddy cultivation, weeds and water conditions were recorded. Average yield of direct seeded rice was significantly lower than that of transplanted rice. The yield decreased with resource decreases in both direct seeded (DSF) and transplanted paddy fields (TF). Although the yield was not different under resource-rich conditions, the yield of direct seeded rice was lower than that of transplanted rice under resource-medium and -poor conditions. Competition intensity was not different among resource levels or between DSF and TF. Competition intensity in all fields was between 0.02 and 0.09 on average, indicating 2–9% yield losses caused by competition with weeds regardless of resource level and disturbance intensity. This suggests that low yield of direct seeded rice under resource-medium and -poor conditions was not mainly caused by competition with weeds, whereas yield losses by weeds were observed in all field types. However, from an economical viewpoint, weeding should be applied only to limited parts of this region with stable and relatively high rice yields. 相似文献
10.
为探讨太阳热处理对小白菜根肿病的防治效果,以超级小黄白为供试材料,测定太阳热处理前后的土壤理化性质、根肿菌休眠孢子数量、土壤微生物多样性及发病率和病情指数,评价太阳热处理对小白菜根肿病的影响。研究表明:经太阳热处理后土壤0~10 cm处pH由4.96提高至5.60,根肿菌休眠孢子的浓度由1.09×106 g-1减少至5.74×105 g-1。变性梯度凝胶电泳(DGGE)结果证明,太阳热处理提高了土壤细菌微生物多样性,其中0~10 cm处和10~20 cm处土壤细菌微生物群落的香浓维纳指数分别由1.51、0.91提高到1.98、1.53,0~10 cm处根肿病的发病率由87.10%降低到49.12%,病情指数由45.24降低到16.96,防治效果明显。本研究为太阳热处理在实际农业生产中的应用及对根肿病的防治提供了理论基础。 相似文献