Seaweed Fronds Of Asexual Reproduction

Porphyra conducts asexual reproduction by monospores production. In the field Porphyra cultivation we noticed that there was difference in monospore production among different cultivated Porphyra strains and the difference has existed for many years. The study compared the difference in monospore production among 4 cultivated strains of Porphyra yezoensis and their genetic distance with RAPD. The result showed that the furthest genetic distance is between the strain which can produces fewest monospores and the strain which can produce most monospores among the 4 strains. It indicates that monospore production is related to heredity. The effects of temperature, the developmental phases of the thalli on monospores production was studied too. The lowest temperature for monospore formation in lab was different from that in the sea( they were 12 0C and 7--8 ~C respectively). After beginning to form monospores when they were about 0.2mm long, the leafy thalli produced monospores all through their life in suitalbe temperature(l 70C). Carpogonia on the edge of the mature leafy thallus could be discharged and geminate in the same way as monospores did. 2. There are many reports that cells (protoplasts) separated from the thalllus of Porphyra are able to develop into normaL leafy thalli just as monospores do. So it is conceivable that the cells may become monospores before they germinate. To make clear whether the separated and cultured cells undertake the same or similar ultrastructure changes during culture and germination as monoospores do in their formation and germination, The ultrastructural change of them was observed. The result shows that the ultrastructure development of separated and cultured cells did not have the characteristic feature of monospore formation, such as production of small and large fibrous vesicles, but was accompanied by vacuolation and starch mobilization which is similar to the monospore germination. It may suggest that the production of small and large fibrous vesicles in developing monospores may play a role in their release, but may not be involved in their subsequent adhesion to the substrate. Excised fragments from the inner part of matured blades of 8 cultured strains of Porphyra yezoensis ,Psuborbiculata, P Oligospermatangia, P haitanensis and young Pyezoensis was cultured in temperature 15 0C, lightintensity3Oi-imol photon m2 s?and light period 12:l2LDto get juvenile blades. In spite of most of the cells are necrotic in the culture, the fragments except the ones from P haitanensis regenerated their young 3 sound blades in different forms: (I) Marginal cells formed a packet of cells with a common covering. Each of the cells developed into young blades in situ or after being discharged; (II) Scattering survived marginal and (or) inner cells round themselves, and discharged protoplasts which then germinated, some of the round cells has regenerated wall; (3) scattering survived cells developed into callus-like clumps that differentiated young plantlets. (4) Marginal cells in fragments from young blades germinated to leafy seedlings without further cell divide after regenerated wall. The forms to differentiate into plantlets were related with strains and species.