Effects Of Three Exogenous Factors On Zostera Marina Seed Germination

In the present study, we investigated Zostera marina seed germination under threekinds of exogenous factors. We measured Z. marina seed germination and seedlinggrowth, including cumulative germination rate, mean time of germination, index ofgermination and the content of photosynthetic pigments. Finally we confirmed thesuitable concentrations, processing time and method of disposal for Z. marina seedgermination. In addition, the changes of seed moisture and storage nutrient substancescontent were monitored in order to find out the utilization of water and storage nutrientsubstances in Z. marina seed during germination time. We also made a preliminaryanalysis of response mechanism in Z. marina seed. We combined Z. marina seedgermination and seedling growth to make a comprehensive assessment of pH,dissolved oxygen and exogenous GA effect on seed germination. These findings notonly provide technical support on seedling culturing of Z. marina, but also offer theorybasis on pretreatment methods for Z. marina seed during restoration of damagedseagrass beds. The main results are summarized as follows:1. To investigate the effect of pH concentration and treatment time on Z. marinaseed germination, seed and seedling were cultivated in the laboratory under differentpH (2,4,6,8,10,12) and soaking time (6h,12h,24h,96h). Above these treatments,the seed germination and seedling growth lasted for60days and50days respectively.For the mean time, we monitored the eelgrass seed germination and subsequentseedling cultivation data. The results showed that Z. marina seed could adapt to awider pH range (pH=4-12). At pH6and Soaking96h, Z. marina seed germinationand seedling establishment rate were both significantly improved, reached77.9%and33.8%respectively. After soaking in different concentrations of pH, the moisturecontent of seed is increase with increasing of seed soaking time, then storage nutrientsubstances began rapidly hydrolyzed, providing the physiological basis for seedgermination and seedling growth. 2. To investigate the effect of different dissolved oxygen content on Z. marina seedgermination, seed and seedling were cultivated in the laboratory under differentdissolved oxygen content (2,4,6,8,10mg·L-1). Above these treatments, the seedgermination and seedling growth lasted for60days and50days respectively. For themean time, we monitored the eelgrass seed germination and subsequent seedlingcultivation data. The results showed that Z. marina seed can tolerate low oxygenenvironment (2-6mg·L-1). Under different levels of dissolved oxygen,2mg·L-1dissolved oxygen levels has significant promoting in seed germination and seedlingestablishment, reached42.2%and17.8%respectively. Thereby it is the appropriatedissolve oxygen levels for eelgrass seed germination. With the decline in dissolvedoxygen levels, there is a significant increase in total protein and soluble sugar content,which promoted seed absorbent and accelerated the decomposition of nutrients,providing the physiological basis for seed germination and seedling growth.3. To investigate the effect of different methods to break the seed coat withexogenous GA on Z. marina seed germination, seed and seedling were cultivated in thelaboratory under different breaking way (rubbing, acid etching, alkaline etching) andGA concentrations (0,25,50,100,200,400mg L-1). Above these treatments, the seedgermination and seedling growth lasted for60days and50days respectively. For themean time, we monitored the eelgrass seed germination and subsequent seedlingcultivation data. The results showed that when exogenous gibberellins levels reach50mg L-1, Z. marina seed germination after rubbing the seed coat can be effectivelypromote, reached58.0%. The seedling establishment rate of this condition wassignificantly higher compared with the control group and non-GA group, reached30.9%. Thereby the above breaking method and GA concentration is the optimum wayfor seed germination. After breaking seed coats, exogenous gibberellins can improvethe seed germination effectively. These treatments can effectively impact waterabsorption and the synthesis of enzymes, which has a significant impact of seedgermination.4. This study found that Z. marina seed germination under suitable conditions ofthree exogenous factors can be significantly promoted, but the effects are stilldifferences. The results show that: compared with the control group, under2mg L-1dissolved oxygen content conditions, Z. marina seed cumulate germination rate has the highest rate of increase, reached51.3%, followed by friction testa+50mg L-1exogenous GA conditions and pH=6, soaking96h conditions. However, comparisonof seedling establishment rate shows Z. marina seedlings under friction testa+50mg L-1exogenous GA conditions have the highest rate of increase, reached91.1%. Z. marinaseeds under three exogenous factors have the same metabolic pattern of water imbibed.Hydrolysis of total protein and starch showed the same pattern. Under differentprocessing conditions, especially pH soaking and hypoxic conditions, soluble sugarmetabolic mode of seeds have significantly differences. Comprehensive analysis showsthese differences of Z. marina seed germination is due to the following reasons: theaccumulation of seed water imbibed, hydrolysis starting time of total protein and starch,duration time and varying amounts of soluble sugars. Among these, soluble sugars playregulatory substances on seed germination.