N. D. Hallam's research while affiliated with Monash University (Australia) and other places
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Publications (30)
The development of digestive glands in pitchers of three species of Nepenthes (N. alata Blanco, N. tobaica Danser, and N. ventricosa Blanco) was studied by LM and SEM, and the presence of digestive enzymes was examined by enzyme cytochemistry. Pitchers at various developmental stages were studied, corresponding to prepitcher inflation, early pitche...
The Droseraceae exhibit a range of“germination patterns which are of possible taxonomic usefulness at the sectional and higher levels. Three patterns were observed in the family: phanerocotylar (Drosera subgen. Drosera and Regia); cryptocotylar (subgen. Ergaleium and Rorella); and a new category, hemi-cryptocotylar, where both cotyledon apices rema...
Droseraceae germination and leaf gland and microgland character state patterns were re-examined in the light of new molecular phylogenetic relationships. Phanerocotylar germination is basal in the family, with cryptocotylar germination having evolved at least twice; once in Aldrovanda, and again in Drosera within the Bryastrum/Ergaleium clade. Glan...
The genus Durvillaea currently has four recognized species found along many exposed, rocky coastlines of the temperate to sub-Antarctic regions in the Southern Hemisphere. We propose that the current species distributions are related primarily to vicariance events and subsequent speciation associated with the breakup of Gondwana between 40 and 100...
Species of the family Seirococcaceae have been described as producing an oogonial collar and egg stalk. Oogonial collar, stalk and egg structure were investigated in Phyllospora comosa (Labillardiere) C. Agardh using light and electron microscopy techniques. Fertilization was observed using videomicroscopy. Oogonia develop a layered wall and an 'oo...
Morphology and development of Phyllospora comosa juveniles, and adult apical growth was investigated using light and electron microscopy and histochemistry. Juvenile plants followed a pattern of adhesion and development consistent with other fucoids, and at ten weeks a three-sided apical cell was produced at the plant apex. Serial sectioning of adu...
Durvillaea potatorum illustrates a high degree of morphoplasticity both within and between populations. Populations illustrate an average morphology which is consistent with both their hydro-dynamic environment and geographic location. There is a broad scale longitudinal division of the species into an eastern and a western morphotype, superimposed...
Analysis of the age composition of a given species within a community is fundamental to any study of population dynamics and to the subsequent analyses of community interactions such as competition, succession and productivity. A problem exists in that calendar age often provides little information on the role played by any given individual plant w...
The larger brown marine algae are extremely difficult to prepare for electron microscopy. Most previous papers have illustrated artifacts such as negative contrast membranes, myelin figures of disturbed membrane systems, vesiculation of the cytoplasm and effects resembling plasmolysis. Although no single fixation and infiltration technique produces...
The differences in the morphology of adult plants of Durvillaea potatorum from five sites of differing exposure to wave force, have been quantified. Plants from higher wave exposure environments have thicker laminae and are longer with more braids and have short, thick stipes. Plants from lower wave exposure environments have thinner laminae and ar...
Apical cells are lenticular in longitudinal section and triangular in transverse section, are larger than those surrounding them and have less dense contents compared with the surrounding cells. The apical cell usually divides longitudinally repeatedly and new cells resulting from these divisions continue to divide longitudinally and transversely....
Monthly observations were made on the annual sequence of conceptacle initiation, development, maturation, and senescence in Durvillaea potatorum using techniques of light and electron microscopy. Conceptacles are initiated by oblique divisions of meristoderm cells which, as growth proceeds, result in the formation of clusters of branching files of...
Six potato virus Y isolates from Victoria and Queensland were characterized on the basis of host plant reactions. Four isolates from potato produced symptoms in indicator plants and potato cultivars consistent with those caused by the PVYO group. Two isolates from tobacco produced necrotic symptoms on some tobacco cultivars characteristic of the PV...
Transmission and scanning electron microscope studies of broccoli florets affected by head rot, at various stages of disease development, strongly indicated a bacterial etiology for the disease. Nevertheless, the different species of bacteria isolated from diseased heads, using standard techniques, failed to reproduce symptoms in pathogenicity test...
Light, scanning and transmission electron microscopy have been used to study the initiation of apical growth, the development of constrictions and branching in Hormosira banksii (Phaeophyta). In the early stages of embryogenesis, a single apical cell arises from a cell lying at the base of the apical hairs which grow out of the primary cryptostoma....
doi: 10.2216/i0031-8884-24-2-147.1
Leaves of the resurrection plant Xerophyta villosa appear to become desiccation tolerant while they dry on the intact plant. After a small decline during moderate water stress,
the polyribosome content of attached leaves appears to rise at 50% relative water content (RWC) to almost double the content
in controls, before it finally declines to zero...
Anatomical, ultrastructural, ecological and physiological aspects of the relationship between the common brown alga, Hormosira banksii, and the obligate epiphyte Notheia anomala are described. The highest frequencies of infection by N. anomala occur in sexually mature H. banksii in tide-pool populations. Male and female H. banksii are equally affec...
Following fertilization Hormosira zygotes rapidly acquire an adhesive surface coating that firmly attaches them to the substratum. It is not until 14–16 h after fertilization that rhizoids appear and these attach both by mucopolysaccharides and by physical interaction with the microtopography of the substratum surface. Histochemistry of the adhesiv...
Electron microscopy demonstrated gross changes to organelles during dehydration, particularly
in chloroplasts which lose thylakoids. Plastoglobuli increase in size as internal chloroplast membranes
develop into vesicles. An increase in polysomes and in rough endoplasmic reticulum after moderate
stress suggested the possibility of increased protein...
Light microscope and fine structural studies of the gametes of Hormosira banksii show the antherozoids as typical Fucales biflagellate gametes with a posterior whiplash flagellum and an anterior flagellum with mastigonemes. The oospheres are enclosed in a plasma membrane, are highly vacuolate and contain abundant phenolic inclusions.Antherozoids at...
Air-dry viable leaves of Xerophyta villosa, fixed in non-aqueous fixatives, show disorganization of the cytoplasm and loss of cristae, grana and thylakoids, but retention of intact double membranes around plastids and of intact nuclei. Some reorganization of cell fine structure takes place while the leaves are rehydrating: cristae reappear in the m...
Talbotia elegans (Velloziaceae) is a desiccation-tolerant plant whose dry leaves contain chlorophyll. The plastids of dry viable leaves retain some semblance of thylakoid structure and organization but are in a loose array. This contrasts with desiccation-tolerant plants that lose chlorophyll during dehydration and reduce the chloroplast to pro-pla...
Citations
... Drosera meristocaulis has type T2 biseriate and T11-12 multiseriate sessile trichomes (Seine and Barthlott, 1993;Länger et al., 1995). Conran et al. (2007) stated that the trichome patterns found in D. meristocaulis are ambiguous, as they can be observed in members of both the Drosera and the Bryastrum clade (sensu Rivadavia et al., 2003), and that only in combination with the germination pattern could the phylogenetic position of sect. Meristocaulis be verified. ...
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... Morphological variants of the species can occasionally occupy different depths, however. For example, solidbladed morphotypes of D. antarctica, that can extend several meters into the subtidal zone, have been recorded (sometimes, historically, as distinct species) from subantarctic environments including Gough Island (see Hay 1994), Macquarie Island (see Klemm and Hallam 1988a), Falkland Islands (M. Clayton pers. ...
... Most of the mitochondrial cristae also disappear during the process of desiccation, while the remaining ones seem to decompose within 30 min after rewetting in X. villosa. This is exhibited by a loss of almost 50% of insoluble or structural proteins which is found to be very less observed (generally c. 10%) in HDT plants (Gaff and Hallam 1974). ...
... In the Sargassum apex, a new leaf will develop its own apical cell, and further cells along the meristoderm between this and the primary apical cell will follow suit, each giving rise to another organ on each branch 31 . All meristodermal cells have a meristematic ability which could indicate that any cell from this cell layer could "switch on" and become an apical cell and start producing its own bud 25 . This is not dissimilar to the specification seen in ferns for the production of new leaves from the epidermis 8,62 . ...
... Many modern algae develop reproductive cells (e.g., gametes and spores) within mother cells before their release at maturation (Alves et al., 2012), and some algae (e.g., fucalean brown algae) can develop reproductive cells within spherical cavities (known as conceptacles; ca. 0.1-0.6 mm across) that occur as raised superficial structures (Clayton et al., 1987). In particularly, fucalean conceptacles, when compressed, would morphologically resemble the dark structures (Xiao et al., 1998). ...
... In general, D. antarctica shows a pattern of seasonal variation of reproduction, with the maximum reproductive individuals in winter and with few or no reproductive individuals occurring during summer (Klemm and Hallam 1988b;Hay 1994;Collantes et al. 2002;Tala et al. 2016Tala et al. , 2019. However, a recent long-term study suggests that populations of D. antarctica from subantarctic Chile (> 54°) are reproductive throughout the year and reach their maximum reproductive peaks in autumn, declining gradually towards summer ). ...
... The body of parenchymatous brown algae is built through the meristematic activity of an apical cell 21,22 . In the Fucales, the apical cell presents as three or four sided in transverse view and divides from these faces [23][24][25][26][27][28][29] . In some cases, the apical cell is thought not to divide but rather stimulate the cells around it to do so 26 ). ...
... Specialized digestive glands for prey digestion and nutrient uptake are usually sessile or stalked multicellular structures derived from the epidermis (Fig. 4; Thornhill et al., 2008). Their ultrastructure revealed a labyrinthine-like cell wall organization, lack of chloroplasts, numerous mitochondria and the extensive development of a secretory system. ...
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... A number of alginate epimerases, both membranebound and extracellular, then act on, and progress along, the polymannuronate chain, undergoing M to G epimerisation in specific regions of the polymer in different patterns (Larsen 1981). In fucoids, changes in the M/G ratio of thalli of different ages follow a similar pattern, with older tissues generally richer in G units (Cheshire and Hallam 1985;Indergaard and Skjak-Braek 1987;McKee et al. 1992;Minghou et al. 1984), reflecting the action of C-5 epimerase over time. As with S. muticum, observation of the life cycle of Undaria pinnatifida showed an increase in alginate production from spring to mid-summer (Skriptsova et al. 2004). ...
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... A few studies have measured standing stocks of Tasmanian seaweeds, again focussing on large brown seaweeds. The highest known standing stock is 68 kg ww m −2 in the low intertidal (0 m) for Durvillaea potatorum (probably mixed with D. amatheiae) at Eaglehawk Neck, which compares to 20 kg m −2 at 2 m depth; the lower biomass at 2 m was due to a high density of small, young seaweeds compared to a lower density of large, mature seaweeds at 0 m (Cheshire and Hallam 1988). Standing stocks at 14 m depth at George III Reef were 36 kg m −2 (Sanderson 1990a). ...
