Seagrasses, sea flowering plants, comprise approximately 60 species globally and are often called ‘ecosystem engineers’ because they create their own habitats by modifying the surrounding environments, which provide coastal zones with a number of crucial ecosystem services. Zostera marina (the common name ‘eelgrass’) is one of the seagrass beds-forming species distributed widely in northern hemisphere including the Korean coast, which plays a pivotal role in ecosystem as a primary producer and a nursery habitat or refuge for other marine organisms. However, due to global climate change and anthropogenic activities such as reclamation and dredging, there has recently been a drastic decline in population sizes of Z. marina in Korea. In order to develop effective conservation and restoration management programs of Z. marina populations, it would be helpful to consider all biological aspects of this species such as genetic characteristics as well as ecological and physiological features. This study first provides information on genetic diversity and genetic structure of Jeju Island and Namhae populations of Z. marina, which will contribute to the establishment of appropriate conservation and restoration management plans for future persistence of this species. Using six microsatellite markers, we investigated the level of genetic diversity and genetic structure among 10 geographic populations of Z. marina inhabiting Jeju Island (Hamdeok, Tokki-seom, Sungsan, Woljeong, Ojo) and Namhae (Gamak bay, Jindong bay, Nampo, Anggang bay, Geoje) on the southern coast of Korea. The level of genetic diversity within Jeju populations (mean allelic richness [AR]: 1.57 ~ 3.09) was found to be significantly lower than Namhae populations (AR: 3.09 ~ 4.29) (Mann-Whitney U-test, P < 0.05). These findings suggest that effective population sizes (Ne) of Jeju populations are generally smaller than those of Namehae populations. Within Jeju Island, Hamdeok population had the smallest population size (coverage: 138 m2) and the lowest genetic diversity (AR: 1.57), while Ojo population had the largest population size (coverage: 275,736 m2) and the greatest level of genetic diversity (AR: 3.09). Hamdeok population showed evidence of genetic bottleneck. These results again suggest that Ne of Jeju populations is generally low (except Ojo population). Among Jeju populations, all pair-wise comparisons of FST values (i.e., degree of genetic differentiation) were highly significant (FST = 0.0612 ~ 0.7168, P < 0.001) despite Jeju populations that were geographically closely located, indicating that these local populations are genetically divergent, probably due to a lack of gene flow among the populations. The observed strong population structure was substantiated by evidence that five genetic clusters are most likely, based on population assignment test (STRUCTURE). The Mantel test showed a positive relationship between genetic distance (FST) and geographic distance (km) across all the populations sampled (R2 = 0.4118, P < 0.05), suggesting that our data follow Isolation By Distance (IBD) model. Woljeong population revealed the highest level of FST values compared to other populations within Jeju Island in IBD. STRUCTURE and factorial correspondence analysis (FCA) further showed that some Woljeong individuals included genotypes of Namhae populations. Population size of Woljeong (coverage: 310m2) was approximately 50 % smaller than that of Sungsan (coverage: 841m2); however, extent of its genetic diversity (AR: 2.39) was even higher than that of Sungsan population (AR: 1.77). We speculated that Woljeong population underwent a transplantation from Namhae populations with relatively higher level of genetic diversity. FST values within Namhae populations were relatively lower (compared to within Jeju Island) despite the populations that were geographically more distant. It means that level of gene flow is higher among Namhae populations than among Jeju populations. Z. marina is known to have different life histories by water depth. In subtidal zone (deep water depth) populations predominantly undertake sexual reproduction through seeds such as annual life history, whereas those of intertidal zone (shallow water depth) undertake both sexual and asexual reproductions through horizontal rhizomes i.e., perennial life history. STRUCTURE analysis showed no clear differences between shallow and deep populations at Namhae, but some FST values were statistically significantly different despite their low values. For Geoje population sampled in 2005, intertidal and subtidal populations were not significantly different (FST = 0.0045, P = 0.033), but these populations sampled in 2015 showed a significant difference (FST = 0.0328, P < 0.001). It means that genetic structure of Geoje has been changed over the 10 year period between shallow and deep populations. Overall, the Jeju and Namehae populations analyzed in the current study have relatively low levels of genetic diversity and distinct genetic compositions, which warns the message that this ecologically important species should be conserved separately in the local populations and with high priority. We propose that future conservation and restoration plans for seagrasses should consider genetic characteristics particularly because a close relationship between genetic diversity and ecological performance in marine species has been well documented.

Experiments were carried out to find out the optimum water potential, temperature, and duration for the priming of rice seeds, Oryza sativa L. (cv. Ilpumbyeo) for better germination at sub-optimal temperatures. Seeds were primed in 0, -0.2, -0.4, -0.6, -0.8, and -1.0 MPa PEG (polyethylene glycol) solutions at 25~circC . The optimum water potential for seed priming, the highest water potential at which rice seeds did not germinate, was -0.6 MPa. To find out optimum priming temperature and duration rice seeds were primed in -0.6 MPa PEG solution and 0 MPa (water as a control) for various durations at 15 and 25~circC and the seeds were germinated at 17, 20, and 25~circC . Considering germination rate and speed, the optimum priming time in water (0 MPa) was 4 days at 15~circC and 1 day at 25~circC , while 4 days was the optimum priming time in a -0.6 MPa PEG solution, regardless of the priming temperature. Priming reduced the actual time of germination, especially at sub-optimal temperatures. Priming did not affect germination rate in -0.6 MPa PEG solution at 15~circC , but overpriming reduced the final germination rate in water at 15~circC and in -0.6 PEG solution at 25~circC . Total sugars and α -amylase activity induced during the seed priming were negatively correlated with the final germination rate and there was no noted relationship with the speed or uniformity of germination.

최근들어 우리나라 국민의 식품소비 형태가 점차 고급화됨에 따라 메밀의 어린 식물체와 종실은 건강 별미식품의 원료로서 수요량은 단속 증가될 전망이다. 엽채소용으로 이용되는 메밀의 어린 식물체는 30% 이상의 단백질과 500mg / 100g 이상의 Rutin과 상당한 양의 미네랄, 비타민 함유하여 단경기 재배시 녹채소의 수량은 파종량, 파종기, 재배환경 조건에 따라서 262～2,270 / 10a로 차이가 매우 컸으며 예상조수익도 52.4～183.5만원 / 10a이었다. 엽채소용 메밀의 육묘기간을 20, 25, 30일로 하였을 경우 육묘기간이 길수록 초장, 줄기의 굵기, 잎의 수와 크기가 증대되었다. 4배체품종 신주대메밀의 생체중은 2배체품종 수원재래와 신농001에 비하여 35%가 더 무거웠으며 엽육이 두껍고 잎이 커서 상품가치가 더 좋았다.