• 한국작물학회지
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• 제45권5호
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• pp.282-287
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• 2000

Soybean [Glycine max (L.) Merrill] crops, grown in a rice soybean rotation, can suffer when grown in soil with excessive moisture. The objective of this work were to determine the reduction in growth and yield, responses of vegetative and reproductive growth of soybean to excessive soil moisture achieved by prolonged irrigation. Responses of different cultivars were determined at growth stages from V6 to R8 to clarify the sensitive growth stages or characteristics to excessive soil moisture. Cultivar differences in response to excessive soil moisture condition were conspicuous in seed dry weight and harvest index (HI) but not in the response of seed number or pod number per plant. The timing of irrigation causing the condition of excessive soil moisture influenced the vegetative or reproductive traits. Soybean plants were more affected by irrigation commencing at the pre-flowering than at the post-flowering stage. Post-flowering irrigation did not reduce growth of vegetative organs significantly; in fact the growth of stems and leaves was facilitated by the prolonged irrigation commencing at flowering. Differences between cultivar response to prolonged irrigation were assumed to relate to the reduced amount of assimilates translocated to the reproductive organ.

• 한국수산과학회지
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• 제39권6호
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• pp.472-479
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• 2006

The sexual maturity and reproductive cycle of the common squid, Todarodes pacificus captured from the East Sea, Korea, between January 2004 and January 2006, were investigated by documenting changes in the gonadosomatic index (GSI), gonad development, and oocyte size frequency distribution. The GSI of females began to increase in July, reached a maximum in August, and then gradually decreased. The GSI of males increased from July to March. Using gonad histological observations, we identified four oocyte developmental stages. The changes in GSI and gonad tissue resulted in the classification of the annual reproductive cycle into the following four successive stages: immature (April to June), growing (June to July), mature (July to August), and ripe and spawning (August to March). According to the oocyte diameter size frequency distribution in the ovary, this species appeared to have asynchronous oocyte development and one spawning time.

• Animal cells and systems
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• 제8권1호
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• pp.33-40
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• 2004

Reproductive cycle and spawning rhythm with lunar cycle of the ascidian, Halocynthia hilgendorfi ritteri were investigated by histological examination. The specimens were sampled in the coastal waters of Yongdam, northwest of Jeju Island, Korea, from November 2001 to January 2003. H. hilgendorfi ritteri is a synchronous hermaphrodite; the gonads are located in the mantle. The reproductive cycle can be grouped into the following successive stages in the ovary: growth (February to June), vitellogenesis (April to September), mature (July to December), spent (November to February), and recovery (December to April). Likewise, in the testis, the stages observed were: growth (October), mature (October to December), spent (November to February), and resting (January to September). Major spawning probably occurs between November and January, when water temperatures decrease. The histological observations of the gonads suggested that this species is a multiple spawner during the spawning period. Spawning occurred between the new moon and full moon, and again between the full moon and new moon, suggesting that the spawning rhythm is influenced by the lunar cycle.

• 한국수산과학회지
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• 제52권5호
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• pp.496-510
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• 2019

We investigated the reproductive characteristics of the sweetfish Plecoglossus altivelis, including changes in the gonadosomatic index (GSI), frequency of gonad developmental stages, and abundance of drifting larvae, in three streams (Gangjeong, Yeonoi, and Ongpo) on Jeju Island from May 2004 to December 2005. The GSI values of female P. altivelis in all Jeju streams began to increase in September and reached a maximum in October and November. Peak GSI values in males occurred in Gangjeong from October to November, in Yeonoi from November to January, and in Ongpo from September to October. The gonadal development of P. altivelis was classified into four stages: growth (March to October), maturity (September to December in females; July to December in males), spawning (September to January), and degeneration (October to March in females; after November in males). Drifting larvae were collected from October to January. These results suggest that the main spawning activity of P. altivelis in Jeju streams occurs from October to November. The information about the reproductive characteristics of P. altivelis obtained in this study is critical to fishery management for this species.

• 한국수산과학회지
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• 제57권1호
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• pp.53-59
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• 2024

The reproductive biology of the Washington clam Saxidomus purpuratus, from Yeosu, Korea was investigated based on 699 individuals collected from January to December 2022. The sex ratio of this species was not significantly different from a 1:1 (male:female) sex ratio (P>0.05). Monthly changes in gonadosomatic index were analyzed to estimate the spawning season. The reproductive cycle of this species can be divided into the following stages: active (Jan.-Mar.), ripe (Mar.-Nov.), spent (Apr.-Dec.), and degenerative (Jun.-Dec.) stages. The spawning period ranged from March to December with the main periods being from April to June and from September to November. The shell length at 50% female group maturity (SL₅₀) was estimated to be 60.2 mm.

• 한국발생생물학회지:발생과생식
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• 제4권2호
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• pp.175-180
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• 2000

양산 내원사 계곡에 서식하는 난태생인 다슬기(Semisulcospira libertina libertina)를 재료로 하여 번식주기를 조사하였다. 서식지 수온은 연중 1.3~22.5$^{\circ}C$였으며, 육중량비는 수온이 상승하기 시작하는 3월에 최고값을 보였고, 8월에 최저값을 나타내었다. 난모세포의 평균 직경은 7월에 249.6$\pm$2.6 $mu extrm{m}$로 최대값을 나타냈으며, 12월에 134.3$\pm$2.8 $\mu\textrm{m}$로 연중 최소값을 보였다. 다슬기는 혹서기와 혹한기를 제외하고 주년 번식하는 종으로서, 연간 2회의 주된 번식주기를 가져, 암컷에서 분열증식기 3월ㆍ10월, 성장기 4~5월ㆍ11월, 성숙기 6~7월ㆍ12월, 배란기 8월ㆍ1월, 출산기 9~10월ㆍ3~5월, 휴지기 9월ㆍ2월, 수컷에서는 분열증식기 3월ㆍ10월, 성장기 4월ㆍ11월, 성숙기 5~6월ㆍ12월, 교미기 7~8월ㆍ1월, 휴지기 9월ㆍ2월인 것으로 판정되었다.

• Fisheries and Aquatic Sciences
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• 제14권4호
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• pp.379-388
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• 2011

The mechanism by which gonadotropin-releasing hormone (GnRH) and dopamine (DA) control gonadotropin (GTH) release was studied in male and female rainbow trout using cultured pituitary cells obtained at different reproductive stages. The mechanisms of follicle-stimulating hormone (FSH) release by GnRH and DA could not be determined yet. However, basal and salmon-type GnRH (sGnRH)- or chicken-II-type GnRH (cGnRH-II)- induced luteinizing hormone (LH) release increased with gonadal maturation in both sexes. LH release activity was higher after sGnRH stimulation than cGnRH-II stimulation at maturing stages in both sexes. The GnRH antagonist ([Ac-3, 4-dehydro-$Pro^1$, D-p-F-$Phe^2$, D-$Trp^{3,6}$] GnRH) suppressed LH release by sGnRH stimulation in a dose-dependent manner, although the effect was weak in maturing fish. The role of DA as a GTH-release inhibitory factor differs during the reproductive cycle: the inhibition of sGnRH-stimulated LH release by DA was stronger in immature fish than in maturing, ovulating, or spermiated fish. DA did not completely inhibit sGnRH-stimulated LH release, and DA alone did not alter basal LH release. Relatively high doses ($10^{-6}$ or $10^{-5}M$) of domperidone (DOM, a DA D2 antagonist) increased LH release, which did not change with reproductive stage in either sex. The potency of DOM to enhance sGnRH-stimulated LH release was higher in maturing and ovulated fish than in immature fish. These data suggest that LH release from the pituitary gland is controlled by dual neuroendocrine mechanisms by GnRH and DA in rainbow trout, as has been reported in other teleosts. The mechanism of control of FSH release, however, remains unknown.

• Clinical and Experimental Reproductive Medicine
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• 제21권1호
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• pp.69-76
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• 1994

The survival and pregnancy rates were compared between non-frozen embryos and cryopreserved embryos at either pronucleate or 2-4 cell stages using the freezing and thawing techniques being identical in both groups were compared with fresh embryos. 496 embryos were frozen with 1, 2-propanediol and sucrose and 117 2-4 cell stages embryos had been thawed and 79.6 and 66.0% of them respectively were survival. Clinical pregnancy rate was 19.2% for embryos frozen at the pronucleate stage and 19.0% for embryos frozen at the 2-4 cell stages while the pregnancy rate of non-frozen embryos was 21.3%. There were no significant difference in the survival and pregnancy rates of embryos frozen at pronucleate and 2-4 cell stages. The current cumulative pregnancy rate per retrieval in all cycles with frozen zygotes is 35.4 %, consid~ erably higher than observed in single transfers of embryos without cryopreservation(21.3%); predicted pregnancy rate after transfer of all frozen embryos is 43.3 %. It is concluded that firstly, the survival and pregnancy rate of cryopreserved embryos at pronucleate or 2-4 cell stages are very similar to those from their fresh embryos and non-frozen embryos and secondly, cryopreservation substantially enhances pregnancy attainment from in vitro fertilization.

• Journal of Ginseng Research
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• 제45권4호
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• pp.527-534
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• 2021

Background: Phenological studies are a prerequisite for accomplishing higher productivity and better crop quality in cultivated plants. However, there are no phenological studies on Panax ginseng that improve its production yield. This study aims to redefine the phenological growth stages of P. ginseng based on the existing Biologische Bundesanstalt, Bundessortenamt und Chemische Industrie (BBCH) scale and proposes a disease control reference. Methods: This study was conducted at the Korea Ginseng Corporation Experiment Station in Gyeonggi province, South Korea. Phenological observations were performed once weekly or twice monthly, based on the developmental stages. The existing BBCH scale with a three-digit code was used to redefine and update P. ginseng's phenological growth codes. Results: The phenological description is divided into eight principal growth stages: three for vegetative growth (perennating bud, aerial shoot, and root development), four for reproductive growth (reproductive organ development, flowering, fruit development, and fruit maturation), and one for senescence according to the extended BBCH scale. A total of 58 secondary growth stages were described within the eight principal growth stages. Under each secondary growth stage, four mesostages are also taken into account, which contains the distinct patterns of the phenological characteristics in ginseng varieties and the process of transplanting seedlings. A practical management program for disease control was also proposed by using the BBCH code and the phenological data proposed in this work. Conclusion: The study introduces an extended BBCH scale for the phenological research of P. ginseng.

• 한국수산과학회지
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• 제33권3호
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• pp.184-191
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• 2000

포항 형산강 하구에 서식하는 참재첩, Corbicula leana을 대상으로 생식세포 형성과정 및 생식주기를 조직학적으로 조사하였다. 참재첩은 자웅이체로서 난생이며, 생식소는 완숙하면 암컷은 흑갈색, 수컷은 유백색을 띤다. 생식소관은 내장낭의 간중장선 하방으로 부터 근충의 외벽근층내에 있는 섬유성 망상결체조직까지 분포되어 있다. 난소는 수지상으로 연결된 난소소관으로 구성되어 있고, 정소 역시 많은 소관상의 정소소관으로 구성되어 있는데 이들 소관의 내강상피가 생식상피 기능을 하고 있다. 성숙난모세포는 배포의 변화로 알 수 있으며, 그 크기는 $70{\~}80{mu}m$ 정도이다. 난소 및 정소의 초기 발달에는 간충조직과 색소과립세포들이 영양세포로 관여하고 있으며 난소와 정소가 발달하면서 점차적으로 사라진다. 생식소 발달은 수온과 밀접한 연관성이 있고, 비만도의 변화도 주기성이 일치하였다. 생식주기는 분열증식기, 성장기, 성숙기, 방출기, 퇴화기 그리고 회복기 둥의 연속적인 주기로 구분할 수가 있다. 산란기는 6월 하순부터 9월 중순까지이고, 산란성기는 7월과 8월이었으며 생물학적 최소형은 10.0 mm 이상으로 조사되었다.