The Orang-dish During The Development Of Its Physiological Basis

Bangia Lyngb. is a red algal genus and contains a higher nutrient value and better taste than the well-known commercial seaweed, the sister genus Porphyra. Bangia sp. has been cultured in Putian (Fujian province, China) since 1990s, however, the culture technique is still poor. Improvement of seaweed culture technique relies on the full illustration of its developmental characteristics. This study was focused on the development of Bangia sp., the relating photo-physiological characteristics under environmental stress such as desiccation and hyposalinity, and the phylogenetic relationship between a freshwater group from Niangziguan spring (Shanxi province) and the marine groups.Phenotype of pigment is expressed and separated during the first two divisions of a pigment mutant of conchospore. The initial four cells of the developing sporelings constituted a linear genetic tetrad and the variegated color pattern of a grown-up thallus could be traced directly to the linear order. A mature thallus is diecious and the sex is determined by genotype. The characteristic structure of a full differentiated female cell is the prototrichogyne, with the development being triggered by environment conditions and time of fertilization. Archeospore is the main asexual spore type in the gametophyte phase, while under unfavorable conditions, endospores and resting cysts are also produced. Moreover, the thallus can differentiate rhizoidal structure at the fragmentation site and develop into a new thallus.High temperature is unfavorable for thallus development and temperature range of 15-20oC is optimal. The best temperature and photoperiod combination for asexual reproduction is 20oC, 8:16h L:D cycle and that for sexual reproduction is 15oC, 12:12h L:D cycle.The photo-physiological characteristics of developing spores (conchospore and zygotospore), sexual reproductive units (spermatangium and zygotosporangium) and conchocelis show that the actual PSII photosynthetic efficiency (Y(II)) is closely related to the integrality of photosynthetic organs and their location in cell but the cell type. The healthy rhizoidal cell, immature spermatium cell and immature zygospore cell all present high Y(II) level. However, Y(II) is largely reduced due to the alteration of chloroplast from large stellate central-located to parietal peripheral-located and formation of the large central vacuole (during zygotospore germinating) and fibrous vesicles (during the last stage of spore or spermatium maturing). Y(II) is almost indiscernible in the just released conchospore, however the transcriptional level of rbcL is surprisingly high, indicating that the expression of enzymes involved in photosynthesis is triggered as the conchospore is released from shell matrix into seawater so as to make good preparations for spore germination.Y(II) of gametophytes is still high under desiccation and hyposalinity stress. A fully desiccated (without further loss of thallus weight) thallus can gain the initial Y(II) level when put back into seawater for several minutes. Some of the thalli survive 7 days in 100% freshwater medium. The results reveal the physiological advantages of this species to occupy the rigorous higher intertidal zone.The freshwater Bangia population (FWB) reproduces asexually throughout the life cycle. Thallus morphology and number of chromosomes (4) is the same to the marine populations (SWBs). The rbcL-rbcS spacer sequence reveals 5bp variation between FWB and SWBs, while only 1bp variation from European and North American freshwater groups, indicating that all freshwater groups may originate from a common ancestor.