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.
Rates of 36Cl− labelling, efflux and uptake were measured on Enteromorpha plants 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, in Enteromorpha plants 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 of 36C1− 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 of 36Cl− did not depend on [K+o] in seawater. Cyanide decreased 36Cl− uptake in the dark but not in the light. In low salinity medium (ACBSW), 36Cl− labelling and the plasmalemma flux in Enteromorpha plants 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−1 in seawater plants and about 159 mmolkg−1 in ACBSW plants. The cytoplasmic Cl− concentration ([CI−0]) based on compartmental analysis was about 200 mM in Enteromorpha plants in seawater and ACBSW medium. Use of this [Cl−0] value and the Nernst equation suggests active Cl− uptake in plants in both seawater and ACBSW. However it is unlikely that the cytoplasmic [Cl−] is above about 70 to 100 mM since many cytoplasmic enzymes are inhibited by high [Cl−0]. Taking this lower estimate of [C1−0], the Nernst criterion suggests passive accumulation of Cl− across the plasmalemma in seawater but active transport would be likely in plants in ACBSW medium. Where separate plasmalemma and tonoplast fluxes were detectable, plasmalemma fluxes were hi...
Sodium transport was studied in the marine euryhaline alga, Enteromorpha intestinalis in 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]) of E. intestinalis was so low that it was difficult to detect using chemical and 22Na+ methods. Consequently, intracellular Na+ fluxes were also difficult to measure. Most of the Na+of the Enteromorpha tissue 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 of 22Na+ 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 seawater 22Na+ 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 total 22Na+ uptake or exchange fluxes in the light and dark in seawater‐grown plants but there may have been a light effect on low salinity plants. The Na+ flux in Enteromorpha plants in seawater was about 3 nmol m−2 s−1 and in low salinity plants was about 0.2 nmol m−2 s−1. Sodium in Enteromorpha is far from electrochemical equilibrium (more than –100 mV) in plants in both seawater and ACBSW medium so that Na+ is actively excluded from the cells. The plasmalemma has a very low Na+ permeability (seawater, 3 pm s−1; ACBSW plants, either 3 or 100 pm s−1 depending on which compartmentation model is accepted). Copyright © 1984, Wiley Blackwell. All rights reserved
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.', Australian Journal of Plant Physiology, vol. 11, no. 1-2, pp. 35-47.
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Leaf growth was unaffected by salinities from 13-57per mille and net photosynthesis was unaffected by reduction in salinity from 34per mille to 19per mille. 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 0.67-1.52MPa over a range in external osmotic pressures from 0.83-3.89MPa. The tolerance of P. australis to changes in salinity in the absence of severe physical disturbance is largely due to the sheath and to the osmotic pressure gradient. -from Authors