Molecular data reveals two new species of Hypnea (Cystocloniaceae, Rhodophyta) from India: Hypnea indica sp. nov. and Hypnea bullata sp. nov.

We used three molecular markers (COI-5P, rbcL and UPA) to investigate the diversity of Hypnea spp., an economically important red algal genus, collected from India. Our concatenated tree (COI-5P and rbcL) supported the monophyly of two new species, Hypnea indica sp. nov. and Hypnea bullata sp. nov. H. indica diverged from its closest two sister species, Hypnea cervicornis and Hypnea tenuis (by 15.9 and 11.2%, respectively, in COI-5P; and 3.4 and 3.2% in rbcL). We describe H. indica as a new species characterised by an erect, percurrent main axis with spine-like branchlets in acute angles, straight and forked apices, axial cells surrounded by large periaxial cells or two cells similar in size to the axial cell, and the presence of lenticular thickening in the cross-section of the thallus. H. bullata diverged from its closest sister species, Hypnea brasiliensis (by 10.9% in COI-5P and 3.3% in rbcL). H. bullata is characterized by a prostrate thallus up to 1.5 cm in height, highly anastomosed, with an axial cell surrounded by similar sized, or smaller, periaxial cells, tetrasporangia present near the base of branchlets, and the presence of lenticular thickening.

The availability of filament ends modulates actin stochastic dynamics in live plant cells

A network of individual filaments that undergoes incessant remodeling through a process known as stochastic dynamics comprises the cortical actin cytoskeleton in plant epidermal cells. From images at high spatial and temporal resolution, it has been inferred that the regulation of filament barbed ends plays a central role in choreographing actin organization and turnover. How this occurs at a molecular level, whether different populations of ends exist in the array, and how individual filament behavior correlates with the overall architecture of the array are unknown. Here we develop an experimental system to modulate the levels of heterodimeric capping protein (CP) and examine the consequences for actin dynamics, architecture, and cell expansion. Significantly, we find that all phenotypes are the opposite for CP-overexpression (OX) cells compared with a previously characterized cp-knockdown line. Specifically, CP OX lines have fewer filament–filament annealing events, as well as reduced filament lengths and lifetimes. Further, cp-knockdown and OX lines demonstrate the existence of a subpopulation of filament ends sensitive to CP concentration. Finally, CP levels correlate with the biological process of axial cell expansion; for example, epidermal cells from hypocotyls with reduced CP are longer than wild-type cells, whereas CP OX lines have shorter cells. On the basis of these and other genetic studies in this model system, we hypothesize that filament length and lifetime positively correlate with the extent of axial cell expansion in dark-grown hypocotyls.

Acoustic Monitoring of Hydraulic Fracture Propagation in Pre-Fractured Natural Rocks

Active acoustic monitoring can capture two types of fracture behavior in rock samples, opening and closure of an existing fracture and tip movement of a propagating fracture. The first type is related to wave transmission across the fracture interface. The second one is related to the travel times of waves that diffract at the fracture tip. A series of experiment has been conducted with an acoustic system that has transducers mounted on the loading frames of a tri-axial cell situated in the Rock Mechanics Laboratory, TUDelft, the Netherlands. The existing fractures are formed by cleaving the rock samples into layers and putting them back together. The propagating fractures were created by hydraulic fracturing via bore-hole injection. The tests in this study featured both cleaved and hydraulic fractures, and aimed to characterize the interaction between them. This paper focus on the data processing that is adapted to these special tests and comparison between the monitored and recovered fractures.

Ceramium juliae (Ceramiaceae, Ceramiales), a new red algal species with distinctive spines from eastern Australia

Ceramium juliae sp. nov. (Ceramiaceae, Ceramiales, Rhodophyta) is described from subtidal habitats on the southeast coast of Australia. Plants are prostrate on the basal parts of the brown algae Cladostephus spongiosus and Halopteris platycena and the red alga Chondria succulenta and reach lengths of no more than 8 mm. Individual axes grow to widths of 160 �m, are dichotomously to alternately branched and have markedly involute apices. Each axial cell produces six periaxial cells, each of which produces a distinctive spine. The first-formed spine becomes multiseriate, as does the second-formed which lies on the opposite side of the filament. Four uniseriate spines are then formed, two on each side of the axis, to make a total of six spines per cortical node. Tetrasporangia are cut off from the periaxial cells and occur one per cortical segment. Comparisons are made with other spined Ceramium species as are the generic characteristics of the genus Ceramium with relation to Centroceras, Ardreanema, Campylaephora, Corallophila and Reinboldiella.

Morphogenetic determination of the axial cells of Antithamnion plumula (Ceramiaceae, Rhodophyta): early identification of the nature of the whorls

Antithamnion plumula axial cells are either "cladomophoric" (bearing a lateral cladom) or "pleuridiophoric" (with pleuridia only). The time required for their formation (generation time) and their length were the two variables used for their early characterization. The data presented show that (i) the generation time (approximately 10 h) of the pleuridiophoric axial cell, which immediately succeeds a cladomophoric axial cell, is significantly longer than that observed for all the other axial cells (6–7 h); (ii) the initial cell length (approximately 9 μm) of the cladomophoric axial cells is significantly greater than that of the pleuridiophoric axial cells (approximately 6 μm); and (iii) during the first stages of cell elongation (when the distance to the apex does not exceed 12 cells), the difference in size between the axial cells remains significant; the lateral budding of the cladomophoric cell occurs earlier than that of the pleuridiophoric cell. Thus, the cladomophoric axial cells can be distinguished from the pleuridiophoric axial cells very early. Their state seems to be determined by that of the apical initial cell that generates them. The transition between two successive tagmas is always characterized by a significantly longer generation time. Key words: plant morphogenesis, Rhodophyta, Antithamnion plumula, ramification, apical growth, generation time.

Morphological and taxonomy of Bostrychia and Stictosiphonia (Rhodomelaceae/Rhodophyta)

The genus Bostrychia Montagne s.l. is reassessed. Two genera are recognised. Bostrychia and Stictosiphonia J.D. Hooker et Harvey, differing from eachother by the number of tiers of pericentral cells per axial cell, the mode of cortication and the number of indeterminate axes. These genera are described and keys are provided to all species. Bostrychia consists of 11 species. One of which, B. tenussima R.J. King et Puttock, sp. nov., is newly described from New Zealand and temperate Australia. Detailed descriptions are given for the other six species, B. harveyi, B. moritziana, B. pinnata, B. radicans, B. simpliciuscula and B. tenella, that occur in the Australasian region. Taxonomic notes are provided for the type of species. B. scorpiodes, which is restricted to western Europe, and three lesser known species, B. callipters, B. montahnei and B. pilulifers, from the Central and South American regions. Stictosiphonia is resurrected and emended. This genus consists of six species, two of which have tropical distributions, S. kelanensis (Grunow ex Post) R.J. King et Puttock, comb. nov. (southern and eastern Asia and northern Australia) and S. tangatensis (Post) R.J. King et Puttock, comb. nov. (eastern Africa and northern Australia). The remaining four species, S. hookeri, S. vaga, S. arbuscula (J. D. Hooker et Harvey) R.J. King et Puttock, comb. nov. and S. gracilis R.J. King et Puttock, sp. nov., have a southern Australian, New Zealand or subAntarctic distribution.