Effects of CO(2) and O(2) on Photosynthesis and Growth of Autotrophic Tobacco Callus

Gas exchange measurements were made on plants from two natural populations differing in salt tolerance of Andropogon glomeratus, a C₄ nonhalophyte, to examine the effect of salinity on components responsible for differences in photosynthetic capacity. Net CO₂ uptake and stomatal conductance decreased with increasing salinity in both populations, but to a greater extent in the inland (nontolerant) population. The intercellular CO₂ concentrations increased with increasing salinity in the inland population, but decreased in the marsh (tolerant) population. Water use efficiency decreased as salinity increased in the inland population, and remained unchanged in the marsh population. Carboxylation efficiency decreased and CO₂ compensation points increased with increasing salinity in both populations, but to a lesser extent in the marsh population. Carboxylation efficiencies were higher with 2% relative to 21% atmospheric O₂ in salt stressed plants, suggesting that a decrease in the carboxylation:oxygenation ratio of ribulose 1,5-bisphosphate carboxylase/oxygenase was partly responsible for the decrease in photosynthetic capacity. Populational differences in photosynthetic capacity were the result of greater salinity-induced changes in carboxylation efficiency in the inland population, and not due to differences in the stomatal limitation to CO₂ diffusion.     

Ionic and Water Relations Responses of Two Populations of a Non-Halophyte to Salinity

Bowman, W. D. 1988. Ionic and water relations responses of twopopulations of a non-halophyte to salinity.–J. exp. Bot39: 97–105 Salinity-induced changes in the ionic and water relations inplants from two naturally-occurring populations of the C₄ non-halophyteAndropogon glomeratus were measured to detect differences inthe capacity to adjust osmotic potentials and in ion contentpotentially responsible for the osmotic adjustment Pressure-volumecurves and leaf ion content were measured in plants from twopopulations, salt marsh and inland, after long-term exposureto three salinity levels. Osmotic adjustment and decreases inthe bulk tissue elasticity occurred to a similar extent in bothpopulations with increasing salinity. Cl^– concentrationsincreased with increasing salinity in both populations, whereasleaf Na⁺ concentrations increased only in the inland population,but were higher at all salinities in the marsh population. K⁺concentrations changed little with increasing salinity. Prolineconcentrations increased only at the highest salinity level,and did not difler significantly between populations. Theseresults suggest a role for Na⁺ uptake and regulation in osmoticadjustment in the marsh population, contrasting with studiesof salt tolerance in other nonhalophytic grasses     

Physiological responses in two populations of Andropogon glomeratus Walter B.S.P. to short-term salinity

Summary Andropogon glomeratus is a C₄ nonhalophytic grass which exhibits population differentiation for tolerance to short-term salinity exposure. To investigate possible physiological mechanisms whch enable salt-tolerant individuals to survive short-term inundation, gas exchange and water relations parameters were measured before and during a 5-day watering treatment of half-strength synthetic seawater in plants from a tolerant and a non-tolerant population. Photosynthetic recovery was followed for 10 days after the salinity treatment. Photosynthetic CO₂ uptake was substantially inhibited in both populations. Stomatal conductances decreased and intercellular CO₂ concentrations increased, indicating non-stomatal factors were primarily responsible for the decrease in CO₂ uptake. After termination of the salinity treatment photosynthetic capacity increased more rapidly in the tolerant population and reached the pretreatment level after 6 days, whereas the nontolerant population did not recover fully after 10 days. A-Ci curves measured before and after the salinity treatment indicated a decrease in the carboxylation efficiency, and suggested a proportionately greater metabolic inhibition relative to the increase in the stomatal limitation. Osmotic adjustment occurred in a 2-day period in the tolerant population, but there was no change in the osmotic potentials or the water potential at the point of turgor loss in the nontolerant population. Thus short-term salt tolerance in the marsh population is associated with rapid osmotic adjustment and recovcry of photosynthetic capacity shortly after the end of the salinity exposure, rather than maintenance of greater photosynthesis during the salinity treatment.     

Population differentiation within Festuca rubra L. with regard to soil salinity and soil water

Summary Seed and transplanted adult plants from populations of Festuca rubra, collected from inland, salt-marsh and sand-dune sites were grown on culture solution with added sodium chloride. The growth of the populations of the three habitats was reduced differentially by salt. The salt marsh ecotype Festuca rubra ssp. litoralis was only slightly affected and the inland ecotype F. rubra ssp. rubra was severely retarded at 60 mM NaCl. The dune ecotype F. rubra ssp. arenaria had an intermediate tolerance. The tolerant ecotypes accumulated less sodium chloride as compared to the sensitive ecotype, suggesting that salt tolerance is caused in part by salt exclusion.In addition, the dune ecotype F.r. arenaria appeared to be more drought tolerant than the salt marsh ecotype. Abscission of salt-saturated leaves does not function as an adaptation to salinity in Festuca rubra.All three ecotypes accumulated proline with increased salinity. The response was most pronounced in the drought tolerant F.r. arenaria, indicating that proline accumulation is a response to osmotic stress rather than to ion-specific effects of salinity. The observed differences in salt tolerance may be explained by differential sensitivity to toxic effects of sodium chloride.The occurrence on a beach plain of closely adjacent populations of F.r. arenaria and F.r. litoralis, differing markedly in salt tolerance, is briefly discussed.     

秦王川盐沼湿地角果碱蓬种群聚集分布格局与特征

植物种群的多尺度集聚与聚块特征变化是植物对环境协同适应的结果。运用成对相关函数与零模型方法,依据微地形的土壤盐分分布规律设置4个样地,在2 m×2 m的样方内设置400个小格子记录植物株数并取土样,分析了兰州秦王川盐沼湿地土壤盐分梯度下角果碱蓬种群(Suaeda corniculata)种群空间格局的集聚分布内在特征。结果表明:角果碱蓬种群集聚分布范围内呈现2个关键尺度的集聚现象,小尺寸聚块的集聚或叠加形成复合大尺度聚集,整体表现为嵌套双聚块分布;随着土壤盐分递减,种群集群分布中大聚块尺寸趋于增大,小聚块尺寸差异不明显;大尺寸聚块的数量明显减少,小聚块数量随种群植株数量变化,整个梯度呈现降低趋势;小聚块中植株个体平均数逐渐减少,复合大聚块中包含小尺度聚块平均数量呈降低趋势。内陆盐沼湿地土壤环境异质性背景下角果碱蓬种群集群分布中聚块特征的梯度变化,是植株个体形态与构成的调整适应,种群正负向生态关系、庇护与自疏效应梯度转换的结果。     

NaCl homoeostasis as a factor for the survival of the evergreen halophyte Armeria maritima (Mill.) Willd. under salt stress in winter

The combination of NaCl and low temperature stress makes winter a critical time for evergreen halophytes at temperate latitudes. As part of a study of ecotypic differentiation of the evergreen Armeria maritima (Mill.) Willd., inland and salt-marsh populations were compared with respect to their growth and survival, osmotic adjustment and NaCl concentrations (based on dry weight) under salt stress in pot experiments in winter. Increased leaf necrosis in all populations under salt stress indicated a higher NaCl sensitivity in winter than in summer. Plants from inland populations were more sensitive than salt-marsh populations. Inland and salt-marsh populations showed similar capacities for seasonal osmotic adjustment, high seasonal increase of praline concentration and long-term betaine accumulation. Inland and salt-marsh populations allocated Na and Cl preferentially to the shoot. In inland populations, Na and Cl accumulated to high concentrations in leaves, whereas the much lower NaCl concentration in salt-marsh populations suggested that in these plants, Na uptake was regulated to match the growth-dependent ion demand of the shoot. The prevention of NaCl accumulation in times of slow growth by a NaCl homoeostasis system seemed to be an important adaptation with respect to the survival of evergreen plants in salt marshes.     

Ecotypic differentiation within Festuca rubra L. occurring in a heterogeneous coastal environment

In order to study the genetic differentiation between Festuca rubra L. individuals growing in a heterogeneous environment, indices of salt tolerance, mean relative growth rates and the numbers of tillers formed by plants grown in a Hoagland solution, were determined. It was found that plants from salt marsh sites have a high index of salt tolerance, a high mean relative growth rate and numerous tillers; plants from coastal sand dunes are less tolerant, grow slowly and form few tillers; plants from the inland polder sites are rather salt sensitive, fast growing and form a high number of tillers. The heritability of the mean relative growth rate and the tiller number appeared to differ from zero. Apparently, these characters have been under recent selection and thus give a picture of the adaptations of individual plants to the different environments encountered. An indication of gene flow has been found, although the effect of gene flow seems to be small in the face of the force of selection. It was concluded that the distinction of three ecotypes within the species F. rubra is insufficient to describe the differentiation found. Considering the differences observed, it seems more reasonable to speak of ecotypic variation.     

What confines an annual plant to two separate zones along coastal topographic gradients?

We investigated the roles of flooding, salinity, and plant competition in creating a bimodal zonation pattern of the marsh dominant annual plant, Suaeda salsa, along coastal topographic gradients on the Pacific coast of northern China. In two consecutive years, we manipulated salinity and flooding, salinity, and competition for S. salsa seedlings that had been transplanted into the mudflat, the high marsh, and the upland, respectively. S. salsa plants that had been transplanted into the mudflat were completely eliminated in the non-elevated treatments whereas they performed much better in the 10 cm elevated treatments, regardless of salinity treatments. Although the performance of S. salsa transplanted into the high marsh did not differ between the fresh (watered) and the salt (control) treatments, S. salsa seedling emergence in the high marsh was nearly completely inhibited in the salt treatments. In contrast, a large number of S. salsa seedlings did emerge in the fresh treatments. S. salsa transplanted into the upland performed well when neighbors were removed, whereas it appeared to be strongly suppressed when neighbors were present. These data indicated that flooding, salinity, and competition all played a role in determining the zonation pattern of S. salsa. Furthermore, the importance of salinity was found to vary with life-history stage. Based on the results from these field manipulative experiments, we suggest that the marsh plant zonation paradigm may hold true for plant distributions along landscape-scale topographic gradients from mudflats to uplands in general. The relative importance of flooding, salinity, and competition, however, may vary at different elevations within a site and between sites. Handling editor: Pierluigi Viaroli     

Saline stress tolerance partly matches with habitat preference in ground‐living wolf spiders

Salinity interacts with many physiological functions and therefore probably influences the distribution of terrestrial fauna in tidal flooded salt marshes. The present study tests the hypothesis that the physiological tolerance of stenotopic wolf spiders for saline conditions at least partially determines their occurrence throughout salt‐marsh and nonsaline habitats. The duration of survival of three stenotopic wolf spider species (Araneae: Lycosidae) with different habitat preferences is compared in a controlled laboratory experiment. The forest‐dwelling Pardosa saltans, the salt‐marsh resident Pardosa purbeckensis and its sister species the inland‐living Pardosa agrestis are exposed to experimental conditions with different levels of salinity. Individuals (45 males and 20–45 females per treatment) are placed in individual air‐tight boxes filled with water‐saturated sand. Three levels of salinity are tested: nonsaline (0‰), medium saline (33–35‰) and highly saline (66–70‰). Contents of carbon, hydrogen and nitrogen and the molar ration carbon/nitrogen remain constant over time and do not differ among salinity treatments, indicating that starvation effects on survival, if any, are similar for all treatments. Conversely, body water significantly decreases over time and differs among salinity treatments, in accordance with patterns of survival. Conforming to their habitat preference, the survival of P. saltans and P. agrestis decreases quickly under highly saline conditions. Pardosa purbeckensis, however, has a high survival under both saline and nonsaline conditions. The duration of survival of females is significantly lower than that of males of P. saltans and P. purbeckensis. Durations of survival of ground‐living wolf spiders exposed to salinity partly match their habitat distribution but do not explain the restriction of salt‐marsh species to saline habitats.     

Growth performance of an inland population of Plantago maritima in response to nitrogen and salinity

The inland distribution of Plantago maritima in Ireland and Britain is strongly western and generally associated with base-rich soils or with flushes in more acidic upland soils. Plants from an eastern Irish salt marsh and from an inland population growing on shallow calcareous soils in east County Clare, Ireland, were grown in culture solutions with a range of seawater dilutions (10–100%) and nitrogen (2.8–140 ppm N) concentrations added as ammonium nitrate. A low nitrogen supply (2.8 ppm N) resulted in very low dry matter production but with increased nitrogen, plant growth increased, even of inland population plants in 50% seawater. Some inland plants survived 100% seawater, but growth was much reduced. The relatively high salinity tolerance of this inland population is discussed.Nomenclature follows Flora Europaea (Tutin et al., 1964–80) for angiosperms, Watson (1968) for bryophytes and Hawksworth et al. (1980) for lichens.Thanks are due to the Central Marine Services Unit and Michael Coughlan, Microbiology Department at University College Galway for Mullaghmore soil nitrogen analyses.     

The effects of the interaction between salinity and nitrogen limitation in Agrostis stolonifera L.

Salt-tolerant Agrostis stolonifera ecotypes commonly grow on upper salt marshes, environments regarded as having a limited nitrogen supply. The interaction between salinity and nitrate supply limitation was studied in two ecotypes of A. stolonifera, one isolated from an upper salt marsh and one from an inland habitat. The ion, amino acid, glycine betaine and sugar contents of the two ecotypes were determined over a range of external salt concentrations and levels of nitrate supply. In vivo nitrate reductase activity was also measured. Several low molecular weight nitrogenous compounds accumulated in the salt-stressed plants. Nitrogen supply limitation had a great effect on the way in which the plants responded to salt stress. In particular, the concentrations of the soluble organic nitrogenous compounds were reduced. The results are discussed with respect to the salt marsh environment, and possible models for cytoplasmic osmoregulation are presented.Acknowledgements: One of us (MJH) gratefully acknowledges the receipt of a research studentship from the Science Research Council, U.K. We would also like to thank Mrs E. E. Griffiths for skilled technical assistance, and Dr I. Ahmad for help with the amino acid analysis.     

不同生态型芦苇种群对盐胁迫的生长和光合特性

土壤盐渍化是影响我国土壤利用效率的主要因素之一,芦苇是改良土壤盐渍化的良好实验材料,但芦苇有着多种的生态型,比较各生态型芦苇的耐盐差异成为亟待解决的问题。通过设置淡水(0.00%)与加盐(质量浓度2.00%)处理控制实验,测量芦苇的生长指标和光合指标,比较河口型芦苇与内陆型芦苇耐盐性,寻找合适生态型的芦苇作为改良土壤盐渍化的生物材料。在实验中,与淡水条件相比,加盐(2.00%)处理条件下,河口型芦苇和内陆型芦苇的株高(height)、蒸腾速率(E)均显著性下降,但是两种生态型的芦苇的水分利用效率(WUE)明显提高;河口型的芦苇相对生长速率(RGR)和气孔导度(Gs)都明显高于内陆型芦苇。在淡水环境中,河口型芦苇的相对生长速率(RGR)和净光合速率(A)都显著性地高于内陆型芦苇。结果表明两种生态型的芦苇在进化过程中存在一定程度上的分化,盐胁迫会抑制两种芦苇的生长,两种生态型芦苇的相对生长速率和气孔导度在盐胁迫下出现明显地差异,表明两种生态型的芦苇对盐度的响应机制有所差异。相比于内陆型芦苇,河口型芦苇有着更强的耐盐性,内陆型及河口型芦苇的表型性状差异主要是由于其原生境的差异所决定的。     

Effects of NaCl stress on seed germination and seedling development of Brassica insularis Moris (Brassicaceae)

• Brassica insularis is a protected plant that grows on both coastal and inland cliffs in the western Mediterranean Basin. The objective of this study was to test if any variability exists in the salt stress response during seed germination and seedling development in this species relative to its provenance habitat.
• Variability among three populations in the salt stress effects on seed germination and recovery under different temperatures was evaluated. The effect of nebulisation of a salt solution on seedling development was evaluated between populations growing at different distances from the sea.
• Seeds of B. insularis could germinate at NaCl concentrations up to 200 mm . Seed viability was negatively affected by salt, and recovery ability decreased with increasing temperature or salinity. Inter‐population variability was detected in salt response during the seed germination phase, as well as in seedling salt spray tolerance. The inland population seedlings had drastically decreased survival and life span and failed to survive to the end of the experiment. In contrast, at least 90% of the coastal seedlings survived, even when sprayed at the highest frequency with salt solution.
• This study allowed investigation of two natural factors, soil salinity and marine aerosols, widely present in the B. insularis habitat, and provided the first insights into ecology of this protected species and its distribution in the Mediterranean. These results might be useful in understanding the actual distributions of other species with the same ecology that experience these same abiotic parameters.

     

International study on Artemia XLIX. Salinity effects on survival,maturity, growth,biometrics, reproductive and lifespan characteristics of a bisexual and a parthenogenetic population of Artemia

Two Artemia populations, a bisexual from San Francisco Bay (California, USA) and a parthenogenetic from Tanggu area (Tianjin province, People's Republic of China) are assayed for their tolerance and fitness in various salinity levels. This study was carried out under laboratory conditions where salinity effects upon special characteristics of the two Artemia populations, such as survival, growth rate, maturation, morphology, fecundity and life duration, were recorded. This evaluation revealed that the two populations examined exhibits significant differences in their response against elevated salinity levels. Furthermore, specific biometric parameters can be a useful tool for the discrimination and/or determination of their distribution in a mixed population, which, in fact, is the case in Tanggu salt works. Artemia franciscana seems to be a more effective colonizer at higher salinities. The data presented in this study may generate useful suggestions for proper management of the solar saltworks at Tanggu although further experimentation is needed.International interdisciplinary study on Artemia populations coordinated by the Laboratory of Aquaculture & Artemia Reference Center, University of Ghent, Belgium.     

Germination ecology of coastal plants in relation to salt environment

Responses of seed germination to salinity were examined using 37 species collected from salt marshes, cliffs, and fore (unstable) and hind (stable) sand dunes along Japanese coasts. For comparison, seed germination of nine inland species was also examined. The soil salinities in salt marshes ranged from 150 to 300 mmol/L NaCl, whereas those in fore and hind dunes ranged from 0 to 150 mmol/L NaCl, with a few exceptions. Cliff soils showed relatively high salinities up to 300 mmol/L NaCl. Ciff and foredune soils that encountered a typhoon and storm showed high salinities >300 mmol/L NaCl. Salt tolerance in seed germination of coastal plants was ordered by comparing the responses of percentage and rate of germination to salinity conditions up to 200 mmol/L NaCl, being in the order of salt marsh>cliff>foredune≅hind dune≅inland. Thse results indicate that salt tolerance in seed germination of coastal plants is closely related to the salinity conditions of their habitats. Germination experiments under favorable conditions showed that a high percentage of the seeds of salt marsh species germinate rapidly, those of diff species germinate slowly and those of foredune species exhibit a low percentage and low rate of germination. It seems that these germination characteristics contribute to the success of germination at the ‘safe site’ and the subsequent survivorship of emerged plants in their natural habitats.     

Adaptation to salinity inHordeum jubatum L. populations studied using reciprocal transplants

Tillers and seedlings ofHordeum jubatum L. from three sites with contrasting salinity regimes in central Saskatchewan, Canada were reciprocally transplanted in order to examine the tolerance of populations of this species to salinity and related habitat factors. Survival, growth and fecundity of the three populations were controlled more by transplant site characteristics than by genetic differences, i.e. differences among populations at a site tended to be smaller than differences among sites. Survival, growth and reproduction of all three populations were best at the non-saline site. The population originating at the non-saline site showed the poorest growth in the two saline habitats, but still had substantial salt tolerance. Fecundity was greatest when the populations were grow at their site of origin.     

Flood tolerance and the distribution of Iva frutescens across New England salt marshes

Summary Tidal flooding is widely believed to be an important determinant of marsh plant distributions but has rarely been tested in the field. In New England the marsh elder Iva frutescens often dominates the terrestrial border of salt marshes and we examined its flood tolerance and distribution patterns. Marsh elders only occur at elevations where their roots are not subject to prolonged water table flooding. Consequently they are found on the terrestrial border of marshes and at lower elevations associated with drainage ditches and locally elevated surfaces. Marsh elders transplanted to elevations lower than they normally occur died within a year with or without neighbors and greenhouse tests revealed that I. frutescens is much less tolerant of flooded soil conditions than plants found at lower marsh elevations. We also manipulated the water table level of field plots and found that increasing or decreasing water table drainage led to enhanced and diminished I. frutescens performance, respectively. Our results demonstrate the importance of water table dynamics in generating spatial patterns in marsh plant communities and provide further evidence that supports the hypothesis that the seaward distributional limits of marsh plant populations are generally dictated by physical processes.     

Vegetative salt tolerance of barnyard grass mutants selected for salt tolerant germination

Improving salt tolerance of economically important plants is imperative to cope with the increasing soil salinity in many parts of the world. Mutation breeding has been widely used to improve plant performance under salinity stress. In this study, we have mutagenized Echinochloa crusgalli L. with sodium azide and three selected mutants (designated fows A) with salt tolerant germination. Their vegetative growth was compared to that of the wild type after short-term and long-term salt stress. The germination of the three fows A mutants in the presence of inhibitory concentrations of NaCl, KCL, and mannitol was better than that of the wild type. Early growth of the mutants in the presence of 200 mM NaCl was also better than that of the wild type perhaps due to improved K⁺ uptake and enhanced accumulation of sugars particularly sucrose at least in two mutants. But the three mutants and the wild type responded similarly to long-term salt stress. The tolerance mechanisms during short-term and long-term salt stress are discussed.     

GERMINATION AND SEEDLING RESPONSE OF ATLANTIC AND GULF COASTS POPULATIONS OF UNIOLA PANICULATA

Germination response following various periods of cold treatment and seedling response to temperature, daylength, and salinity were studied for several Atlantic and Gulf coasts populations of Uniola paniculata L. Results indicated that Atlantic coast Florida populations did not require cold treatment prior to germination at 95–65 F, but that populations from Virginia and North Carolina did. Gulf coast populations exhibited a germination response intermediate between those just mentioned. Seedling studies revealed that alternating diurnal thermoperiods with daytime temperatures of 80 F and above produced good vegetative growth in all populations with little preference for either short- or long-day conditions. Gulf coast populations produced the most biomass under all treatment conditions. Seedlings from a North Carolina and a Florida population indicated no difference in substrate salt tolerance. Salt tolerance was reduced in the higher temperature thermoperiod for both populations. Seedlings from these two populations produced more biomass in a salt spray treatment than in substrate salinity treatments.     

Plasticity in salt tolerance traits allows for invasion of novel habitat by Japanese knotweed s. l. (Fallopia japonica and F.xbohemica, Polygonaceae)

Japanese knotweeds are among the most invasive organisms in the world. Their recent expansion into salt marsh habitat provides a unique opportunity to investigate how invasives establish in new environments. We used morphology, cytology, and AFLP genotyping to identify taxa and clonal diversity in roadside and salt marsh populations. We conducted a greenhouse study to determine the ability to tolerate salt and whether salt marsh populations are more salt tolerant than roadside populations as measured by the efficiency of PSII, leaf area, succulence, height, root-to-shoot ratio, and total biomass. Clonal diversity was extremely low with one F. japonica clone and five F. ×bohemica genotypes. The two taxa were significantly different in several traits, but did not vary in biomass or plasticity of any trait. All traits were highly plastic in response to salinity, but differed significantly among genets. Despite this variation, plants from the salt marsh habitats did not perform better in the salt treatment, suggesting that they are not better adapted to tolerate salt. Instead, our data support the hypothesis that plasticity in salt tolerance traits may allow these taxa to live in saline habitats without specific adaptation to tolerate salt.