The Structure and Development of the Reproductive Organs and Carposporophyte in two British Species of Gelidium

The structure and development of the reproductive organs andcarposporophyte are described for two British species of Gelidium,G. latifolium (Grev.) Born. & Thur. and G. pulchellum (Turn.)Kütz. The gonimoblast does not develop directly from theunchanged carpogonium, as was thought by Kylin, but a swollenmultinucleate cell of irregular outline is formed first, eitherfrom the carpogonium alone, or by the fusion of the carpogoniumand certain neighbouring cells; the gonimoblast develops fromlong, non-septate processes of this multi-nucleate cell. Thesignificance of the fusion of the carpogonium and certain vegetativecells is discussed in relation to the various definitions ofthe auxiliary cell which have been proposed. It is concludedthat an auxiliary cell does not occur in Gelidium.     

Intrageneric differences in cystocarp structure in Gelidium and Pterocladia

Unilocular cystocarps, with ostioles opening to one frond surface, have traditionally distinguished Pterocladia from Gelidium, described as having bilocular cystocarps, with ostioles opening to both surfaces; however, unequally developed locules have been described in Pterocladia and differences in cystocarpic architecture between Pterocladia capillacea and the type species of the genus, P. lucida, have been recently found. As heterogeneity in cystocarp architecture raises questions of basic intergeneric distinction, a survey of reproductive morphology of species in both genera is presented in this study. Six morphologically-different types of cystocarps are distinguished among the five species of Pterocladia and the seven species of Gelidium examined.     

Physiological responses of Pterocladia and Gelidium (Gelidiales,Rhodophyta) from the Azores,Portugal

Manometric studies were conducted on Pterocladia capillacea, Gelidium latifolium and Gelidium spinulosum from the Azores, Portugal to determine optimal values of temperature, light and salinity for growth. Physiological responses were considered in relation to vertical distribution patterns of these species commonly observed throughout the Azores. Optimal parameters for the growth of Pterocladia capillacea, Gelidium latifolium and G. spinulosum were 17 to 25 °C, a photon flux density between 200 and 300 µmol m^–2 s^–1 and salinities of 25 to 35.     

Gelidium cultivation in the sea

Gelidium fronds were grown in the sea under a variety of experimental conditions: on rigid, damped and tensioned test farms of various designs, in calmer and more turbulent habitats, at various depths, with and without commercial fertilizer supply. Initially, the effectiveness of a given cultivation strategy was based on the survival and growth of the fronds, here termed bio-assay mariculture. Ambient seawater temperature, nutrient availability, hydrodynamics and other environmental parameters were measured periodically. In-the-sea irrigation of test plants with commercial fertilizers was apparently effective, at least with some farm designs, and when ambient nutrient levels were low. Under optimal conditions, achieved through experimental manipulation of farm design, specific growth rates of over 2% per day were recorded. However, considerable variation in growth rates and in plant performances was observed. It was not always possible to correlate these variations with design modifications or other experimental parameters. In view of these findings, we have reviewed our initial bio-assay approach, namely the assumptions about the design and operation of farm structures and their interactions with the water and the fronds. Methods were developed to quantify these interactions. We advocate a quantitative, hydrodynamic approach in developing an effective cultivation strategy for gelidioid algae and are optimistic about progressing from test-to-commercial scale farms in the near future.     

Thallus initiation and development in the lichen Rhizocarpon lecanorinum

Ascospore germination, thallus initiation, and areole and prothallus development in the lichen Rhizocarpon lecanorinum Anders were examined using light, fluorescence and scanning electron microscopy. The ascospore germ hyphae remain very short and do not form a prothallus-like mycelium. Instead, a compact soredium-like granule develops directly from sporeling contact with a compatible species of Trebouxia . Diffuse initial stages involving non-trebouxioid algae are lacking. The onset of thallus differentiation is marked by the deposition of rhizocarpic acid in an incipient cortical layer within the apical part of the granule. As pigmentation and cortex-formation transform this structure into a typical areole, radiating prothallus hyphae are simultaneously initiated from its basal margin. Most areoles formed subsequently in the marginal prothallus lack subtending melanized hyphae and apparently stem from overgrowth by the prothallus of photobiont cells on, or in, the substratum. Apothecia reach maturity in thalli as small as 2 mm in diameter. It is proposed that the lack of diffuse hyphal growth in sporelings and telescoped morphogenesis of R. lecanorinum are part of a life history strategy geared to precocious, heavy investment in ascospore production. The R. lecanorinum – Trebouxia symbiosis has a number of features which make it well-suited for further studies of the life history and development of prothallus-forming crustose lichens with sexually reproducing mycobionts.     

Water Distribution in Foliose Lichen Species: Interactions between Method of Hydration, Lichen Substances and Thallus Anatomy

Three lichens (Neofuscelia pokornyi, N. pulla and Xanthoriaparietina) from a semi-arid habitat were examined using low-temperaturescanning electron microscopy to evaluate the effects of hydrationmethod, lichen substances and thallus anatomy on the water distributionof hydrated thalli. In theNeofuscelia species, extracellularwater within the thallus was observed in association with cracksin its otherwise impervious upper cortex, while X. parietinashowed abundant extracellular water between medullary hyphae.Spraying the thalli followed by maintenance for 14–20h in a water-saturated atmosphere led to the disappearance ofthe external water film in X. parietina but not in the Neofusceliaspecies. Surface water was abundant in specimens of all speciesimmediately after spraying for 15 min. No extracellular waterwas observed inside the thallus 14–20 h after spraying,but after rinsing with acetone its presence was detected inall three species. Hydric strategy correlated with cortex hygroscopicity:X. parietina, an aero-hygrophytic species, had a more hygroscopicupper cortex than theNeofuscelia species, which are substrate-hygrophytic.The hygroscopicity of the upper cortex was linked with the amountof extracellular water in the thalline interior. Differencesbetween X. parietina and Neofuscelia in the polarity and distributionof their lichen substances agreed with species differences inthe presence and distribution of free water both as a film overthe surface and inside the thallus. Lichen substances appearto play a role in the maintenance of air-filled intrathallinespaces in species whose anatomy, habitat, or both, favour water-loggedconditions. Copyright 2000 Annals of Botany Company Lichen, water relations, semi-arid, lichen substances, LTSEM, thallus anatomy, extracellular water, Neofuscelia pokornyi(Körb.) Essl., Neofuscelia pulla(Ach.) Essl., Xanthoria parietina(L.) Th. Fr     

Positive Phototropism in the Thallus of Bryopsis plumosa

Positive phototropism in the thallus of the marine coenocyticgreen alga Bryopsis plumosa was investigated in terms of themode of bending, the photosensitive zone and the effectivenessspectrum. The bending occurred as a consequence of a differencein growth rate between the illuminated and the shaded sidesof the thallus. Elongation on the shaded side was stimulatedwhile that on the illuminated side was inhibited. However, theoverall elongation rate was barely affected. Illumination witha fine beam revealed that a zone from approximately 80 to 120µm below the tip was the most photosensitive. The effectivenessspectrum showed that blue light (<550 nm) was most effective,with light at 467 nm having maximal effectiveness. (Received November 29, 1994; Accepted May 29, 1995)     

Extraction and characterization of agar from Australian Pterocladia lucida

Polysaccharides were sequentially extracted from Australian Pterocladia lucida at 50 °C, to give the Warm Water (WW) fraction, and at 95 °C. The 95 °C extract was further separated into gelling (GF) and thaw water (TW) fractions by freezing-thawing. Fourier Transform infrared (FTIR) spectroscopy, compositional and linkage analyses, and physico-chemical properties indicated that the GF contained an agar with nearly idealized repeating structure and low levels of sulfate and pyruvate substitution. By contrast, the WW and TW contained heterogeneous, highly sulfated galactans with relatively low levels of 3,6-anhydrogalactose and higher levels of pyruvate and glycosyl branching and impurities, such as starch and protein. The properties of the gels formed from the GF and two commercially available agars (Sigma High Gel Strength agar and Sigma Type A agar) were investigated with a texture analyser. The GF from P. lucida had a gel strength intermediate between that of the commercial agars. The gel setting temperature of a 0.8% (w/v) solution formed from the GF was 2 °C below that of comparable solutions of the two commercial agars. This revised version was published online in August 2006 with corrections to the Cover Date.     

Structure and Development of Stomata in Vegetative and Floral Organs of Three Species of Kalanchoe

The structure and ontogeny of stomata in vegetative and floralorgans of three species of Kalanchoe is described. The matureanisocytic stomata are mono-cyclic or completely or incompletelyamphicyclic, rarely paracytic, transitional between paracyticand anisocytic and with a single subsidiary cell. The developmentof all the types is syndetocheilic or mesogenous from organto organ but the mature stomatal apparatus varies from organto organ as regards the number and arrangement of subsidiarycells. Abnormal stoma with a single guard cell and arresteddevelopment were observed on all organs. An abnormal stoma witha single guard cell develops directly from the meristemoid.     

Artificial sporeling and field cultivation of Gelidium in China

The supply of Gelidium resources is dependent on collection from natural habitats. As these resources are very limited, one possible means of augmenting production is by implementation of artificial cultivation as has been done with Laminaria, Porphyra and Eucheuma. Chinese phycologists have conducted research on sporeling and field cultivation of Gelidium for many years. Trials have been made using: (1) raft cultivation based on vegetative propogation of thallus fragments, (2) cultivation based on spore-collecting and land-based tank culture to provide seedstock, (3) cultivation based on regeneration from small thallus fragments to provide seedstock. Some of these results have been promising, but development remains at the experimental stage and methods of cultivation need to be improved. This paper is an updated review of the research and development on artificial sporeling production and field cultivation of Gelidium in China.     

The Structure of the Mesophyll of Flag Leaves in Three Triticum Species

Flag leaves of Triticum urartu, T. monococcum and T. aestivumcv. Professeur Marchal were examined by light and electron microscopyand by separating cells to determine whether differences inleaf anatomy could be related to known differences in theirlight-saturated rates of photosynthesis. Mesophyll cells fromthe three species were lobed and orientated with their longaxis parallel to the veins. The longest, most-lobed cells flankedthe sclerenchyma associated with the veins. Mean cell dimensionswere greatest in Professeur Marchal, but there was no significantdifference in the ratio of the mesophyll cell surface area tocell volume amongst the three species. Flag leaves of T. urartushowed the highest rates of photosynthesis and were also thethickest, with closely-spaced veins from which many of the mesophyllcells radiated. These flag leaves also had significantly more(21.9 per cent) air-filled space, and the highest ratio (15.2)of mesophyll cell surface exposed to this air-filled space perunit leaf area. Ways in which these anatomical characteristicsmay contribute to the higher rate of photosynthesis are discussed. Triticum urartu, Triticum monococcum, Triticum aestivum, flag leaves, morphology, mesophyll     

Effect of salinity and temperature variations on Pterocladia capillacea

Summary At high salinities and high temperatures, the growth rate of Pterocladia was high, the tips of branch initials were dilated and holdfasts broadened. By the end of the fourth week bleaching of the whole plant was complete.Under low salinities and low temperatures, the rate of vegetative growth was decreased, the cuticle was thin and food reserve was centrally accumulated in the cells.Under high salinities and low temperatures, the rate of growth was greatly reduced and cells were devoid of food reserve. Defoliation of lateral branches was frequent.Under low salinities and high temperatures, the rate of growht was rather high and cells were relatively large.