Larkum, AWD, Collett, LC & Williams, RJ 1984, 'The standing stock, growth and shoot production of Zostera capricorni aschers. in Botany Bay, New South Wales, Australia', Aquatic Botany, vol. 19, no. 3-4, pp. 307-327.
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Zostera capricorni Aschers. occurs at many shallow sites in Botany Bay, with the exception of one 5-km section of exposed sandy beach; however, bed distribution is very patchy. Details are given for shoot and underground biomass (g fresh weight), shoot density, leaf length and leaf width at 20 representative sites around the Bay. Z. capricorni was found to grow best between -0.2 and -1.0 m, with a lower limit between -2.0 m (northern side) and -3.2 m (southern side). The mean percentage cover was determined for six large areas in the bay. Shoot biomass (g dry weight) was found to be logarithmically related to percentage cover, whereas shoot density (numbers m-2) was linearly related to percentage cover. Large seasonal changes occurred, with a winter die-back characterised by a 4-fold reduction in shoot biomass and a 2-fold reduction in shoot numbers. Flowering occurred from September to April. An equation is presented for determining the total above-ground stock for an area. The total summer above-ground stock of the bay was estimated at 18 ± 8.1 tonnes for a total area of beds of 309 ha. Mean annual leaf production was estimated to be 5.22 ± 0.52 gDW m-2 day-1 for a representative healthy bed at 0.3 m depth, and leaf plus flower production was 5.86 ± 0.59 gDW m-2 day-1. The total above-ground production for all the beds of the bay was estimated to be 512.7 ± 51.3 tonnes year-1, i.e. 1.66 ± 0.17 tonnes ha-1 year-1. © 1984.
RITCHIE, RJ & LARKUM, AWD 1984, 'CHLORIDE TRANSPORT INENTEROMORPHA INTESTINALIS(L.) LINK', New Phytologist, vol. 97, no. 3, pp. 319-345.
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SummaryRates of36Cl−labelling, efflux and uptake were measured onEnteromorphaplants grown in sea‐water (547 mM Cl−), and also in brackish water medium [Artificial Cape Banks Spring Water (ACBSW), 25.5 mM Cl−, 20.4 mM Na+ and 0.5 mM K+]. Efflux experiments showed that, inEnteromorphaplants grown in seawater, light did not affect Cl−fluxes at the plasmalemma and tonoplast. Typical experiments exhibited two exchanged phases but a significant number (8/32) exhibited a single exchange phase; this was more likely to occur in darkness. Influx experiments also showed no effect of light on the tonoplast flux. Transfer of plants grown and labelled in seawater to low salinity medium caused a rapid loss of36C1−label; however, this was related to the change in osmotic potential of the medium rather than to changes in [Cl−o] or [K+0]. Exchange of36Cl−did not depend on [K+o] in seawater. Cyanide decreased36Cl−uptake in the dark but not in the light. In low salinity medium (ACBSW),36Cl−labelling and the plasmalemma flux inEnteromorphaplants were independent of light; however, the intracellular compartmentation of Cl−differed between light and dark. The tonoplast flux was also greater in the light. Intracellular Cl−was about 300 mmol kg−1in seawater plants and about 159 mmolkg−1in ACBSW plants. The cytoplasmic Cl−concentrati...
RITCHIE, RJ & LARKUM, AWD 1984, 'SODIUM TRANSPORT INENTEROMORPHA INTESTINALIS(L.) LINK', New Phytologist, vol. 97, no. 3, pp. 347-362.
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SummarySodium transport was studied in the marine euryhaline alga,Enteromorpha intestinalisin seawater (465 mM Na+and in low salinity medium [Artificial Cape Banks Spring Water (ACBSW), 25.5 mM Cr, 20.4 mM Na+, 0.5 mM K+]. The intracellular Na+concentration ([Na+1]) ofE. intestinaliswas so low that it was difficult to detect using chemical and22Na+methods. Consequently, intracellular Na+fluxes were also difficult to measure. Most of the Na+of theEnteromorphatissue was bound to the fixed negative charges of the cell wall and this binding has, in previous studies, led to great overestimates of the intracellular Na+of this plant‐Data of22Na+labelling gave lower estimates of the Na+1] than a rinsing technique using isotonic Ca(NO3)2. The overall mean [Na+1] of seawater plants was only 5.5 ± 1.4 mM, with a value of 0.623 ± 0.163 mM Na+in ACBSW plants. With one exception, all the seawater22Na+experiments indicated a single intracellular exchange phase, i.e. a separate vacuolar phase could not be detected. The data on plants grown at low salinity could be interpreted as having either a single intracellular phase or two intracellular phases because of the problem of cell wall Na+exchange. No significant difference was found in total22Na+uptake or exchange fluxes in the light and dark in seawater‐grown plants but the...
Tyerman, SD, Hatcher, AI, West, RJ & Larkum, AWD 1984, 'Posidonia australis Growing in Altered Salinities: Leaf Growth, Regulation of Turgor and the Development of Osmotic Gradients', Functional Plant Biology, vol. 11, no. 2, pp. 35-35.
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The marine angiosperm Posidonia australis Hook f. is always submerged and the leaf cells are able to exchange ions, gases and water with the surrounding seawater. The base of the youngest lamina is surrounded by sheaths from older leaves and a gradient in cell osmotic pressure existed from the base of the lamina enclosed within the sheath to the emerged zone at the top of the sheath. For plants grown in seawater, the cells at the base of the lamina had an osmotic pressure of 1.34 MPa (seawater = 2.54 MPa); the osmotic pressure increased with distance along the lamina to the emerged lamina value of 3.09 MPa. The osmotic gradient was accounted for by cell concentration gradients of Na+ (73 mol m-3 increasing to 412 mol m-3), K+ (91 mol m-3 increasing to 279 mol m-3) and Cl- (62 mol m-3 increasing to 578 mol m-3). Gradients also existed in the cell concentrations of sucrose and amino acids. It is proposed that, within the solution enclosed by the sheath, a standing osmotic gradient is created by ion uptake from the sheath solution. Leaf growth was unaffected by salinities from 13‰ to 57‰ and net photosynthesis was unaffected by reduction in salinity from 34‰ to 19‰. The cells of the leaves and rhizome adjusted their osmotic pressure by changes in Na+, K+ and Cl- concentrations such that turgor varied only between 0.67 and 1.52 MPa over a range in external osmotic pressures from 0.83 to 3.89 MPa. The tolerance of P. australis to changes in salinity in the absence of severe physical disturbance is due, largely, to the sheath and to the osmotic pressure gradient.
