| In the present study, the experimental ecology and physiological methods wereconducted to investigate the effects of three factors, including high salinity, exogenousabscisic acid (ABA) and cryopreservation by vitrification on seed dormancyofeelgrass Zostera marina.The optimum salinity conservation and maximum storagetime of seeds was determined, and the mechanism of high salinity had been discussed.The mechanism of exogenous ABAextending eelgrass seed dormancy and its impacton seed germination capacity was preliminarily studied as well. The relationshipbetween vitrification dehydration time and the seed moisture content was conductedaccording to the impact of vitrification on eelgrass seedsand initially explored thefeasibility of vitrification cryopreservation in eelgrass seeds. The findings of theresearch not only provided information and support for the conservation of eelgrassseeds, but also technically supported for the use of seed in seagrass bed restoration.The main results were summarized as follows:1. Salinity is one of the limiting factors affecting seeds’ dormancy among manyseagrass species, but the mechanism of the dormancy is not well-known. In order tofind the effect of high salinity (30,40,50,60,70) on seed dormancy of eelgrassZostera marina from October2012to October2013, the methods of direct andgradual salinity increase (5plus and10plus) on seed dormancy were evaluated. Todetermine the seed optimum salinity conservation and maximum storage time, thepreservation experiments were surveyed for280days. Different concentrations ofNaCl and PEG-6000(polyethylene glycol) was used to simulate different ionconcentrations and osmotic pressure, combined with the change of nutrients underhigh-salinity conditions to explore the mechanismof high-salinity on germination ofeelgrass seeds. The results showed that the direct salinity increase was moreconducive to long-term storage. There was a significantly decreaseof cumulate germination rate with increased salinity, and the vigor and germination ability wasdiminishing with the extension of storage time. Under high salinity conditions, theoptimal salinity was60and the maximum storage timewas196days to50%of seedviability. The dormancy of eelgrass seeds promoted by high salinity was mainly dueto osmosis stress, which inhibited imbibition of seeds and mobilization of reserves.The soluble sugar could also play an important role in resisting salinity stress.2. Abscisic acid can inhibit germination and induce dormancy of seeds. There aremany researches about extending seed dormancy by exogenous ABA, however,seagrass seeds have not been reported. Five concentrations of exogenous ABA (0,1×10-5,5×10-5,1×10-4,1×10-3mol/L) were treated to eelgrass seeds.The cumulativegermination rate, physical activity and nutrition of seeds were calculated andmeasured to study the effects of exogenous ABA on seeds dormancy andregermination. The results showed that10-4mol/L exogenous ABA could extend seedsdormancy up to60days without affecting the seeds vitality. By inhibiting seedsimbibition to control the metabolism of reserves, less than20%of seeds germinatedforced byexogenous ABA, which showed eelgrass seeds were in deep dormancy.3. Three key factors of cryopreservation by vitrification, i.e., cryoprotectivesolution application, dehydration time of vitrification solution, and rapid freezing,were installed to study the effects of cryopreservation by vitrification on the viabilityof Zostera marina seeds. Cryoprotective solution application and dehydration timehad no significant effects on the viability of the seeds. Cryoprotective solutionapplication and dehydration time had no significant protective effects on the viabilityof the seeds, which showed that vitrification couldnot effectively reduce moisturecontent of the seeds. When exposed to rapid freezing, the viability of the seeds wassignificantly lower than that of the control.It suggested rapid freezing had damagedthe seeds viability. Then the relationship between dehydration time and seedsmoisture content were conducted according to the influence of silica rapiddehydration on eelgrass seeds. Through the conductivity changed after dehydration, asuitable reaction time had been found by adjusting the dehydration time. The resultsshowed that eelgrass seed moisture and silica dehydrating time met the function W=38.895e-0.005T, R2=0.97. The dehydration seed conductivity decreased at first andincreased subsequently with time, and after recover for4days, seed conductivitywassignificantly lower than dehydrated seeds.The results summarized that ilicadehydration15-60min after30min vitrification dehydration could not affect theviability of seeds in cryopreservation. |
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