红毛菜发育过程及其生理基础

红毛菜（Bangia Lyngb.）属于红藻门，与紫菜属同属红毛菜科，其味道和营养都优于紫菜。目前红毛菜栽培产业已在我国福建莆田展开，但栽培技术还有待提高。海藻栽培技术的发展和成熟依赖于对其生长发育过程的认识。本研究针对红毛菜发育过程及相关光合生理展开，并初步探讨了一采自山西娘子关泉淡水红毛菜群体（FWB）的系统地位。 色素突变标记的壳孢子萌发特征表明最初两次分裂产生的4细胞决定了完整植株的形态建成。成熟植株，为雌雄异体。雌性生殖器果胞的标志性分化结构为原始受精丝，环境因子是促发原始受精丝发展的外部因素，其膨大程度随受精的延迟而增大。原孢子是主要的无性生殖孢子类型，在不良环境中，藻体也会形成内生孢子或休眠包囊，或者藻体断裂后重新形成完整的植株。 红毛菜的生长发育很大程度上受环境因子的控制。高温不利于配子体的发育，15-20 ºC比较适宜。红毛菜无性繁殖的最适温度-光照组合为20 ºC-8 h，有性繁殖为15 ºC-12h。 不同发育阶段，PSII实际光合效率（Y(II)）与细胞的健康状况以及光合器官完整性及其在细胞内的分布有关，而与细胞的类型关系不大。健康的假根细胞、已分化未成熟的精子以及果孢子细胞均具有很高的Y(II)。色素体由中间位变为围周位，中央大液泡（营养藻丝）和大小纤维囊泡（成熟孢子与精子）的产生，使得细胞Y(II)降低。刚放散的壳孢子Y(II)很低，说明在壳孢子由贝壳基质释放到自由水体过程，光合作用受到一定程度抑制；而2h后，Y(II)开始恢复，rbcL的转录水平非常高，为孢子的萌发储备物质和能量需求。 在失水和低盐胁迫下，藻体均维持较高的Y(II)。干出处理至藻体重量不再变化，复水后Y(II)可回复初始水平。海生红毛菜在100％淡水培养基中（约20ºC）培养7天后，部分雄性藻体依然活着。从而体现了红毛菜位居高潮带的生理优势。 FWB终生行无性繁殖，藻体形态与发生以及染色体数目（4条）与海生群体没有区别。而rbcL-rbcS Spacer序列显示，红毛菜海生群体（无性和有性）具有完全相同的序列，而FWB与它们有5bp差异，但是与欧洲、北美地区的淡水群体仅1bp不同，初步说明所有淡水红毛菜群体具有共同的原始起源。

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.