Control of arabitol formation in Schizophyllum commune development

Summary Dikaryotic cells of S. commune synthesized polyols throughout the life cycle when grown on glucose, cellobiose, or cellulose. Basidiospores contained arabitol and mannitol which were depleted during germination. The mannitol content of the young germlings rose to normal levels within a day; arabitol accumulation remained depressed for 5 to 7 days and then returned to normal levels characteristic of vegetative cells. Individual homokaryons differed in their production of intracellular polyols, which, unlike germlings, remained constant with cultural age. Homokaryon (str. 699) produced low levels of arabitol but high levels of glycerol while another homokaryon (str. 845) was the reverse. Mixtures of these homokaryons as well as the dikaryon (699×845) produced arabitol and glycerol levels intermediate between the parent homokaryons. High concentrations of glucose did not change the nature of the polyols produced. Arabitol formation could be induced prematurely in germlings or elevated in the dikaryon by growth on acetate or ethanol. Both homokaryons responded to growth on acetate with elevated arabitol production; acetate induction of arabitol formation was repressed in all types of cells if glucose were added simultaneously with acetate. Maltose, cellobiose, and trehalose also stimulated arabitol formation in young germlings, suggesting that glucose repression was the cause of decreased arabitol formation in basidiospore germlings. There was no correlation between the formation of arabitol and the derepression of isocitrate lyase or change in specific activities of alkaline and acid phosphatase in germlings grown on various carbon sources.     

Comparing salinity tolerance in early stages of the sporophytes of a non-indigenous kelp (Undaria pinnatifida) and a native kelp (Saccharina latissima)

The short-term effects of low salinities on the survival of germlings of an introduced kelp Undaria pinnatifida and a native kelp Saccharina latissima were assessed under laboratory conditions. This experiment was designed to compare the differential stress tolerance to salinity of the early life history stages of sporophytes of these two kelps that co-occur on European Atlantic coasts. Germlings (young sporophytes) of both species were exposed for 4 days to salinities ranging from 31 (control) to 26, 21, 16, 11, and 6 psu. Afterwards, they were post-cultured in control seawater (31 psu) for another 4 days to corroborate the viability of injured germlings. Results showed that germlings of the introduced kelp were less resistant to low salinity, surviving to as low as 16 psu; whereas the germlings of the native kelp survived in salinities as low as 11 psu. Despite the observed differences, both species are relatively tolerant to low salinity. Our observations also indicated that, at least in a short term, gametophytes of both species were able to survive in salinities as low as 6 psu. The significance of low-salinity tolerance to the distribution of these kelps and for their offshore cultivation is discussed.     

Growth and photosynthetic responses of Ulva lactuca (Ulvales,Chlorophyta) germlings to different pH levels

In ocean ecosystems, fluctuations in seawater pH affect CO₂ fluxes, fundamentally influencing the metabolism of marine algae, especially during the early stages of macroalgal development. In this study, short-term exposure tests (minutes) and prolonged culture experiments (eight days) were performed at different pH levels to investigate the growth and photosynthetic responses of Ulva lactuca (Ulvales, Chlorophyta) germlings. Both acidified and alkalized seawater significantly depressed algal photosynthesis during short-term exposure tests. Prolonged culture in acidified or alkalized seawater also notably decreased photosynthesis rates and growth rates of U. lactuca germlings, but increased energy consumption and lipid peroxidation, indicating damage to the germlings. Our results suggested that both lowered and increased pH levels of seawater exert significant physiological stress on U. lactuca germlings.     

Selection and characterization of a high-temperature tolerant strain of <Emphasis Type="Italic">Porphyra haitanensis</Emphasis> Chang et Zheng (Bangiales,Rhodophyta)

Porphyra haitanensis is one of the most economical nutritive marine algae; however, its production and quality are significantly jeopardized by high temperatures. Selection of heat-resistant strains will greatly reduce the economic risks and benefit to the nori industry. Three previously isolated and improved strains with a high yield were screened at 28°C and identified, of which one strain, ZS-1, showed significantly improved heat tolerance. Upon further characterizing of the cultures of the ZS-1 strain and the wild-type (WT) strain at 28°C and 30°C, the ZS-1 conchospore germlings survived at rates of 69.9% and 59.6%, while the WT conchospore germlings survived at significantly lower rates of 15.9% and 6.7%, respectively, over a period of 15 days. Furthermore, ZS-1 conchospore germlings divided at significantly higher rates of 100% and 88.6% compared to the WT conchospore germlings with 90.4% and 63.8%, respectively. When the 35-day-old conchospore germlings were transferred from the optimal temperature of 24°C to higher temperatures of 28°C and 30°C, the ZS-1 blades sustained growth over a 25-day period without decay and increase of blade lengths with a factor of 18.5 and 10.3 times, respectively. The blade lengths of the WT germlings only increased by a factor of 1.7 and 0.9 times and began to decay after being cultured for 15 days at 28°C and 30°C. At 24, 28, and 30°C, the ZS-1 blades grew 3.4, 8.6, and 8.0 times faster than those of the WT. Evidently, ZS-1 is a fast-growing and heat-resistant strain compared to the WT strain and may offer an alternative for the nori industry.     

DISTRIBUTION AND SALINITY ADAPTATIONS OF BANGIA ATROPURPUREA (RHODOPHYTA), A PUTATIVE MIGRANT INTO THE LAURENTIAN GREAT LAKES1

In a survey of the distribution of Bangia atropurpurea (Roth) Ag. along the north and east shorelines of the Laurentian Great Lakes, it was observed that this species was concentrated in the lower lakes. Asexual reproduction by monospore formation was the only form of reproduction in these populations. First generation germlings derived from these spores grew in a wide range of salinities from 1 to 26‰, but the rate was inversely proportional to salinity. In addition, acclimation of parent plants to freshwater or marine media prior to sporulation affected growth rates of first generation germlings placed into a series of salinities. By the second and third generation, germlings with a lineage of seawater showed a preference for the higher salinities, 19 and 26‰ Plants collected in Lake Ontario exhibited no decline in photosynthetic rate as salinity was raised by 13‰ for 15 min. At 26‰ the rate was reduced by half and thylakoids were disrupted in the region of the pyrenoid. On the other hand, third generation plants with a history of seawater attained maximum photosynthetic rates at 26‰ and contained a normal thylakoid organization. Three chromosomes were observed in these plants, which agrees with some of the previous findings for marine Bangia. Origins and taxonomic status of Bangia growing In the Great Lakes are discussed in light of these findings.     

Control of macroalgal blooms at early developmental stages: Pilayella littoralis versus Enteromorpha spp.

Although blooms of opportunistic fast-growing macroalgae now occur frequently in coastal ecosystems affected by eutrophication, their initiation and control is little understood. Most previous studies have focused on the ecophysiology of adult algae only. We show that spores and/or germlings may represent critical stages in the life cycles and mass-developments of co-occurring opportunistic macroalgae in the Baltic (Pilayella littoralis and Enteromorpha spp.). We investigated the overwintering of spores, timing of germination, subsequent growth, and grazing on spores and germlings, in order to explain the initiation of mass blooms and species dominance patterns. In the field, Enteromorpha spp. showed 10- to 50-fold higher abundances of overwintering microscopic forms (up to 330 individuals cm⁻²) than P. littoralis. Moreover, we found continuous production of spores (up to 1.2 million settling spores m⁻² h⁻¹) from April to October in Enteromorpha spp., while there was evidence of only a short reproductive period in Pilayella. However, in spring, germlings and adults of P. littoralis appeared earlier in the field and reached a 10-fold higher biomass than Enteromorpha spp. In factorial laboratory experiments including temperature and light, there were clear differences in timing of germination. P. littoralis germinated at 5°C whereas Enteromorpha spp. required temperatures of 10–15°C for germination. In contrast, we detected only minor differences in growth response among adults of P. littoralis and Enteromorpha spp. Germination, not growth of adults, appeared to be the ecophysiological bottleneck for initiating mass spring development. Following the spring Pilayella bloom, Enteromorpha germlings occurred massively in the field (April–September), but rarely developed into adults. In laboratory feeding experiments we tested whether crustacean mesograzers common in summer may control development of Enteromorpha germlings. Both germination of settled spores and growth of germlings were reduced by 93–99% in the presence of grazers (Idotea chelipes and Gammarus locusta). Thus in addition to ecophysiological constraints, grazers, if present, may play a decisive role in the early life stages of macroalgal mass developments. These results mirror patterns of overwintering of seeds, germination control, seed and seedling predation in terrestrial plant communities. Received: 7 March 1998 / Accepted: 18 November 1998     

Cell wall structure of the agarophytes Gracilaria tikvahiae and G. cornea (Rhodophyta) and penetration by the epiphyte Ulva lactuca (Chlorophyta)

Use of light, transmission, and scanning electronmicroscopes revealed that the epidermal cell wall ofthe red algal agarophytes Gracilaria tikvahiaeMcLachlan and G. cornea J. Agardh consists of adecklamelle and outer and inner wall layers. The twospecies differed, with G. cornea having asignificantly thicker outer wall and a more diffusedecklamelle. After induction, the zooids of Ulvalactuca would attach to glass slides and the twospecies of Gracilaria via an adhesion pad. Within a few days, 3–5 celled germlings penetrated thedecklamelle and outer wall layer of both basiphytes. By the time the epiphyte germlings reached the 15celled stage, they had penetrated the inner walllayer. The differences in epidermal cell wallconstruction between the two basiphytes may play arole in the ability of zooids of U. lactuca toattach in nature where epiphytization of G.cornea is infrequent.     

New life cycles of <Emphasis Type="Italic">Porphyra katadae</Emphasis> var. <Emphasis Type="Italic">hemiphylla</Emphasis> in culture

Porphyra katadae Miura var. hemiphylla Tseng et T. J. Chang, a species distributed around the Liaodong and Shandong Peninsulas of China, produces gametophytes from late winter to early spring. These are monoecious with male and female reproductive tissues in distinct halves or sectors. Vegetative tissues from sectors expected to differentiate into sexual tissue were cultured in the laboratory. Male and female reproductive organs, as well as conchocelis and blades, were differentiated from these tissues. The male and female reproductive tissues were in patches and mixed on the cultured tissue pieces. This was quite different from the wild-type sectored individuals. The F₁ conchospore germlings also produced monospores, carposporangia, spermatangia and conchocelis. These carposporangia and spermatangia were in patches and were mixed on the F₁ fronds. The results imply that P. katadae var. hemiphylla is possibly sex-differentiated rather than sex-determined. This is the first report of such a dimorphic life history in the genus Porphyra.     

Modeling variation in interaction strength between barnacles and fucoids

The strength by which species interact can vary throughout their ontogeny, as environments vary in space and time, and with the density of their populations. Characterizing strengths of interaction in situ for even a small number of species is logistically difficult and may apply only to those conditions under which the estimates were derived. We sought to combine data from field experiments estimating interaction strength of life stages of the barnacle, Semibalanus balanoides, on germlings of Ascophyllum nodosum, with a model that explored the consequences of variability at per capita and per population levels to the abundance of year-old algal recruits. We further simulated how this interaction affected fucoid germling abundance as the timing of their respective settlements varied relative to one another, as occurs regionally across the Gulf of Maine, USA. Juvenile S. balanoides have a weak estimated per capita effect on germlings. Germling populations are sensitive to variation in per capita effects of juvenile barnacles because of the typically large population sizes of the latter. However, high mortality of juvenile barnacles weakens the population interaction strength over time. Adult barnacles probably weakly facilitate fucoid germlings, but greater survival of adults sustains the strength of that interaction at the population level. Germling abundance is positively associated with densities of adult barnacles and negatively associated with that of juvenile barnacles. Metamorphosing cyprid larvae have the strongest per capita effect on germling abundance, but the interaction between the two stages is so short-lived that germling abundance is altered little. Variation in the timing of barnacle and A. nodosum settlement relative to one another had very little influence on the abundance of yearling germlings. Interactions between barnacles and germlings may influence the demographic structure of A. nodosum populations and the persistence of fucoid-dominated communities on sheltered rocky shores in New England. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Reproductive patterns of Caloglossa species (Delesseriaceae, Rhodophyta) from Australia and New Zealand: multiple origins of asexuality in C. leprieurii. Literature review on apomixis, mixed-phase, bisexuality and sexual compatibility

Reproduction and life history patterns in culture of five Caloglossa speaes from Australia and New Zealand are compared. Caloglossa adhaerens King et Puttock and Caloglossa bengalensis (Martens) King et Puttock have a Polyslphonla‐type sexual life history (P‐type, isomorphic alternation of generations). Caloglossa monosticha Kamiya occurs only in Western Australia (WA) and is a P‐type. Caloglossa ogasawaraensis Okamura occurs in WA, Northern Territory (NT), Queensland (QLD), New South Wales (NSW), Victoria (VIC) and South Australia (SA) and is for the most part a P‐type in culture. A few isolates have bisexual gametophytes that are self‐compatible, while most are unisexual. Caloglossa ogasawaraensis from Adelaide, SA and from Wilsons Promontory, VIC are new records for these States. In Australia, Caloglossa postiae (King et Puttock) Kamiya et King occurs in NSW, NT and QLD. All nine isolates are P‐type. Isolates of Caloglossa leprieurii (Montagne) G. Martens from NSW, NT, QLD, Tasmania, VIC and New Zealand are P‐type except for the freshwater isolates in which tetraspore germlings do not reproduce. In some isolates mixed‐phase reproduction is seen with male gametophytes producing both viable spermatia and tetrasporangia and female gametophytes producing procarps and sori with non‐dividing sporangia. All isolates of C. leprieurii irom Spencer Gulf and Gulf of St Vincent, SA and one isolate from QLD give rise to successive asexual generations of tetrasporophytes. Based on RuBisCO spacer DNA data an asexual life history has arisen several times in the C. leprieurii complex. The literature on apomixis, mixed‐phase reproduction, bisexuality and sexual compatibility in red algae is surveyed.     

Carpospore early development and callus-like tissue induction of <Emphasis Type="Italic">Chrysymenia wrightii</Emphasis> (Rhodymeniaceae,Rhodophyta) under laboratory conditions

Morphological and culture studies of germlings derived from carpospores of Chrysymenia wrightii (Harvey) Yamada were carried out under various treatments combining temperature and irradiance. Basal, main, and tip branches were applied for inducing callus-like tissue. Focus was on how carpospores develop into germlings, how callus-like tissues are induced from explants, and how temperature and irradiance affect carpospore germination and discoid crust growth. Results show that carpospore development can be divided into three stages: division stage, discoid crust stage, and erect juvenile germling stage. Discoid crusts, even more than ten, might coalesce into a big discoid crust, and then developed into germlings. Filamentous fronds, formed on the rims of discoid crusts, exhibited in self-existence or co-existence form with germlings, could form spherical tufts if cultured separately. Filamentous callus-like tissues appeared on the tip branches after 13 days. PES is suitable for filament induction and culture, and filaments have potential use in germplasm preservation and vegetative propagation. Temperature (10, 15, 20, 25°C) and irradiance (8 and 36 μmol photons m⁻² s⁻¹) significantly influenced carpospore germination rate and discoid crust diameter. Carpospores germinated normally under 36 μmol photons m⁻² s⁻¹, 15~25°C, and maximum growth of discoid crusts was at 25°C, 36 μmol photons m⁻² s⁻¹; 10°C and 8 μmol photons m⁻² s⁻¹ did not favor carpospore germination or discoid crust growth.     

Embryology of zygote and development of germling in Sargassum vachellianum Greville (Fucales,Phaeophyta)

Sargassum vachellianum Greville is one of the most important members in the subtidal seaweed flora along the coasts of the Eastern China Sea. In order to understand the embryology of zygotes and development of germlings in S. vachellianum, we performed artificial ripening, systematically observed the morphological changes and development of the fertilized eggs and germlings, and explored the effects of culture conditions on the growth of the germlings. The receptacles matured, and eggs and sperm were released after 1–5 days of culture at 21–24 °C under 60–90 μmol photons m^?2 s^?1 (14L:10D). Once fertilized, zygotes immediately detached from the female receptacles and began to germinate. Eight nuclei in the released fresh zygote soon begun to fuse, forming a large central nucleus, and underwent two horizontal divisions to produce a small “original rhizoid cell,” which eventually formed rhizoids after several divisions, and three other cells which eventually formed landmine-like germlings after several continuous divisions. The germlings then formed rhizoids and attached onto the bottom of the flask within 12 h of culture. The growth and development of the germlings younger than 20 days were significantly influenced by the culture temperature and light, with the optimal conditions being 21 °C and 40 μmol photons m^?2 s^?1. However, for germlings older than 30 days, the optimal conditions were 24 °C and 60 μmol photons m^?2 s^?1.     

Physiological differences in the growth of <Emphasis Type="Italic">Sargassum horneri</Emphasis> between the germling and adult stages

The effects of temperature, irradiance, and daylength on Sargassum horneri growth were examined at the germling and adult stages to discern their physiological differences. Temperature–irradiance (10, 15, 20, 25, 30°C × 20, 40, 80 μmol photons m⁻²s⁻¹) and daylength (8, 12, 16, 24 h) experiments were carried out. The germlings and blades of S. horneri grew over a wide range of temperatures (10–25°C), irradiances (20–80 μmol photons m⁻²s⁻¹), and daylengths (8–24 h). At the optimal growth conditions, the relative growth rates (RGR) of the germlings were 21% day⁻¹ (25°C, 20 μmol photons m⁻²s⁻¹) and 13% day⁻¹ (8 h daylength). In contrast, the RGRs of the blade weights were 4% day⁻¹ (15°C, 20 μmol photons m⁻²s⁻¹) and 5% day⁻¹ (12 h daylength). Negative growth rates were found at 20 μmol photons m⁻²s⁻¹ of 20°C and 25°C treatments after 12 days. This phenomenon coincides with the necrosis of S. horneri blades in field populations. In conclusion, we found physiological differences between S. horneri germlings and adults with respect to daylength and temperature optima. The growth of S. horneri germlings could be enhanced at 25°C, 20 μmol photons m⁻²s⁻¹, and 8 h daylength for construction of Sargassum beds and restoration of barren areas.     

GEOGRAPHIC VARIATION IN THE LIFE HISTORY OF MASTOCARPUS PAPILLATUS (RHODOPHYTA)1

Variation in the geographic distribution of the life histories of Mastocarpus papillatus was investigated. Carpospores were isolated from 377 female gametophytes collected from eight localities on the Pacific coast of Baja California, Mexico, and California, U.S.A., and grown in laboratory culture. All carpospores from a single female gave rise either to basal discs with gametophyte-like uprights or crustose plants formerly referred to the genus Petrocelis. Early stages in the development of each type of germling were observed, and environmental factors affecting development were suggested. Based on carpospore germlings, females from each location were scored as having either the 1) sexual life history (crustose germlings) or 2) direct-development life history (discoid germlings with uprights). All females from the two southernmost locations in Baja California exhibited the sexual life history. In the three locations from the central-southern California coast, 70-95% of the females exhibited the sexual life history and the remainder exhibited the direct-development life history. In two of the three populations from the central-northern California coast, 70-90% of the females exhibited the direct-development life history and the remainder the sexual life history. In the third location from the central-northern California coast, the northernmost location sampled in the current study, 60% of the females exhibited the sexual life history and 40% the direct-development life history. The relative ecological advantages and disadvantages of the life histories are unknown as are the environmental factors that produced the ratios of sexual to direct-development females observed at each location.     

Colchicine and the mitotic spindle of the aquatic phycomycete Allomyces

Summary Exposure of germlings of Allomyces neo-moniliformis to colchicine for 0 to 5 min after zoospore encystment was found to block 30% of germlings derived from flagellated zoospores and 55% of germlings derived from deflagellated zoospores in C-metaphase configurations at the first mitotic division. The zoospore lacks a pool of colchicine binding protein, and protein synthesis is absent during the time when colchicine first becomes effective in inducing C-metaphase. From these observations it is concluded that the microtubule subunit protein of the spindle apparatus of the first mitotic division to a large extent is derived from the depolymerization of the cytoplasmic microtubules of the zoospore. GTP, Mg²⁺, and ATP were observed to be antagonistic to the action of colchicine in vivo. It is suggested that these compounds may compete with colchicine for binding to the subunit protein in vivo. Germlings derived from flagellated zoospores are appreciably less subject to the action of colchicine in the presence of the antagonistic compounds than are germlings derived from deflagellated zoospores. This differential sensitivity to colchicine is interpreted as reflecting a difference in the quantity of microtubule subunit protein present at the time of exposure to colchicine.     

Saving Insertional Recessive Lethal Mutants of Arabidopsis thaliana

A group of 13 recessive lethal mutants was selected on the basis of the collection of Arabidopsis thaliana transgenic plants with insertions of T-DNA vector plasmid pLD3 or pPCVRN4, which was produced by agrobacterial transformation of germinating seeds. The use of media containing exogenous hormones made it possible to compensate the lethal effect, identify phenotypes, and characterize six lines of recessive lethal germlings using genetic and molecular-genetic methods.     

THE LIFE CYCLE OE SARGASSUM HORNERI (PHAEOPHYTA) IN LABORATORY CULTURE1

The life cycle of the large dioecious alga Sargassum horneri (Turner) C. Agardh was completed in unialgal culture by controlling photoperiod in relation to the phase of growth. Embryos isolated from a naturally grown female thallus gave rise to early germlings that rapidly formed blades under both short-day (9 h L) and long-day (15 h L) conditions at 20° C Shoot elongation, which followed early blade formation, occurred under the short-day conditions hut not under the long-day conditions. Functional female and male receptacles developed when thalli 8–14 cm long grown under the short-day conditions were transferred to the long-day conditions; gamete fusion occurred when male and female thalli were grown together. Fertilized oospores gave rise to normal thalli in a manner similar to that for in situ plants. Thus, the life cycle of S. horneri was completed in laboratory culture.     

Life history variation in Campanula americana (Campanulaceae): population differentiation

Genetic variation in life history traits has important consequences for life-history evolution. Here we report the results of a greenhouse experiment investigating the broad sense genetic basis of variation in life history traits within and among five populations of Campanula americana distributed along a latitudinal gradient. The populations exhibit differentiation for a number of morphological traits (seed weight, number of branches, final plant size, number of capsules) and the phenological traits, days to emergence, days to bolting, the onset of flowering, and the duration of flowering. Families within populations differed only in days to emergence and seed weight. These results suggest that the life history differences among populations are genetically based. In addition, two life history types—winter annuals and biennials—have previously been reported from natural populations of Campanula americana. This experiment identified a third type—summer annuals from the Florida population.     

THE LIFE HISTORY OF POLYSIPHONIA DENUDATA (DILLWYN) KÜTZING IN CULTURE1

The sequence of somatic phases in the life history of the red alga Polysiphonia denudata has been determined in unialgal culture, using supplemented seawater media. Tetraspores gave rise to sexual plants bearing either antheridia or carpogonia in 50 days. Fertilization occurred within 1 week and the fertilized carpogonium developed to produce the mature carposporophytic phase in approximately another week. Carpospores formed by the carposporophyte germinated to produce the tetrasporangium-bearing phase, which released tetraspores in 44 days, thus completing the life history in 3^1/2% months. No deviations from this pattern have so far been observed.