| Sargassum polycystum is one of the subtropics marcoalgae of Phaeophyta, which mainly distributes in India, Philippines, Malayia, Vietnam and Naozhou island, Weizhou island, Hainan island of China. In China, there is a longtime history for application of S.polycystum, especially in food and medicine fields. In recent years, the application has been developed further, becoming one kind of good food for sea cucumber and abalone in the field of aquaculture feedstuff, meanwhile, becoming the material source for extracting sodium alginate in industry. The developing of aquaculture and industry brings the increasing of market demand of S.polycystum.While the supply of S.polycystum mostly relied on the wild al.gae, the artificial culture of S.polycystum was rare. With the gathered amounts increased, the wild resources of S.polycystum were destroyed seriously, which made the contradiction of supply and demand increased further, and the ecological. environments were also destroyed. Based on these reasons, people began to pay more attentions to the study of S.polycystum recently.Previously, there are few research about ecology and artificial. seedling of S.polycystum, so many basic scientific had poor research and the skill of artificial seedling not be well master. Those issues would impeded the developed of application val.ue of S.polycystum. Therefore, it is necessary to systematic study the process of sexual reproduction, the method of artificial seedling and ecology characteristic, which will promote the commercialized development of S.polycystum.In the paper, experimental material, S.polycystum, was collected from inshore of Haitou town of Danzhou city in Hainan.The main results are- as follows:(1) Through the method of field and indoor-culture observation, this study gave a systematical observation on S.polycystum as follow: the characteristics of male and female receptacles, the differentiation of the fertilized egg, rhizoid formation, the growth of the young seedling. The results showed that: the reproduction season of S.polycystum was around May to June per year, the shape of mature female receptacles usually flat, divaricate and zigzag of its top; male receptacles usually as cylinder-shaped and one or two divaricates. When the temperature was came to 28?, eggs and sperms were released form receptacles. About 5 h after fertilization, zygote began to split for per 2 h-4 h once. It was took 24 h for zygote to formed into blastocyst cell; the narrow end of the seeding can formed into short and lucency kick of rhizoid that grows rapidly. About 24 h, the length of rhizoid can surpass the seeding length and has stronger adhesion. Cultivation for 2 weeks,the seeding began to differentiation, stem base formed cylinder-shaped branch. As increasing quantity and length of the branch, the protophyll were formed and the blade edge of seeding appears zigzag-shaped after cultivation about 65 d. While under laboratory condition, the seeding of S.polycystum nearly stop growth.(2) The preliminary artificial seedling experiments were carried out in the laboratory.Results of artificial breeding showed that: Drying in shade of the mature S.polycystum and temporary rearing in nursery pond can collected the seedling; under microscope found that the seedling with rhizoid. Cultivation for 35d, the length of S.polycystum reached to 2.5-3 mm, the average density of seedling were 2-3 per cm2; Selected the healthy, strong and larger density of seedling turned to Zhejiang Dongtou Sargassum cultivation sea area to culture. After 60 days of cultivation, the length of S.polycystum reached to 7 cm, the average density of seedlings was 2 per cm2. Creeping branch was formed, the seedling preliminary has the morphological feature of S.polycystum.(3) The effects on vegetative growth and pigment accumulated of S. polycystum were carried out based on different temperature, light intensity, salinity and light quality. The results showed that: the four kinds of environmental factors have significant difference on growth of S. polycystum(P<0.05). The suitable environmental condition for S. polycystum:temperature 15-25?, the optimal was 23?, light intensity 20-80 ?mol·m-2·s-1, salinity 20-40‰, the optimal was 32‰; the highest growth rate of S. polycystum was under white light treatment and then blue light, under the yellow light treatment was negative growth.Light intensity has significant difference on chlorophyll a and carotenoid of S.polycystum(P<0.05), other environmental factors influence was not significant(P>0.05). As the increase of the light intensity, the content of chlorophyll a and carotenoid was on the decline. The four kinds of environmental factors have none significant difference on chlorophyll c (P>0.05). |
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