Osmoregulation in halophytic higher plants: a comparative study of soluble carbohydrates, polyols, betaines and free proline

Abstract. The levels of soluble carbohydrates, polyols, betaines and free proline have been determined in different organs of sixteen plants collected on coastal salt marshes. Among the carbohydrates, sucrose, fructose and glucose accumulated at quite high levels. Sucrose is particularly abundant in the monocots Juncus maritima, Phragmites communis and Scirpus maritimus. Maltose is quite abundant in Atriplex hastata and rhamnose in Plantago maritima roots. High levels of polyols were detected in Aster tripolium, Juncus maritimus, Plantago maritima and Phragmites communis. According to their capacity to accumulate carbohydrates and (or) nitrogenous solutes, halophytic higher plants can be divided into three main groups: (1) species producing high levels of soluble carbohydrates only, (2) species accumulating both carbohydrates and nitrogenous compounds, (3) species producing more nitrogenous solutes than soluble carbohydrates. The possible functions of these various organic solutes, including a role in equalizing the relative water potentials of cytoplasm and vacuole and to lower the internal potential, are discussed.     

A comparative study of the tolerance of salt marsh plants to manganese

Summary Salicornia europaea, Puccinellia maritima, Triglochin maritima, Aster tripolium, Plantago maritima, Armeria maritima, Juncus gerardii andFestuca rubra, collected as seed from a salt marsh at Portaferry, County Down, were grown on saline (340 mM NaCl) and non saline nutrient solutions at five concentrations of manganese sulphate (0.025–10.0 mM). After an eight week growing period, shoot and root yields and the concentrations of sodium, potassium, calcium and manganese in the shoots were determined.Except forS. europaea the saline treatments had a strongly limiting effect on plant growth. Each of the species investigated showed a degree of tolerance to high concentrations of manganese which was similar to that of calcifuge species and plants characteristic of waterlogged sand dune slack communities, but which was very much greater than that ofArrhenatherum elatius a species usually excluded from acidic soils. There was little evidence to support the hypothesis that tolerance of high manganese concentrations was correlated with the position of the experimental plants in the salt marsh ecotone or that the manganese nutrition of halophytic and glycophytic marsh species differs. Whilst manganese uptake increased proportionally with solution manganese concentration, there were few other major effects of manganese on the balance of shoot cation concentrations in the plants investigated. Both antagonistic and synergistic effects of sodium on manganese uptake were recorded for different species.     

Avoidance of sodium accumulation by the stomatal guard cells of the halophyte Aster tripolium

X-ray microanalysis has revealed that the sodium content ofthe stomatal guard cells of Aster tripolium remains much lowerthan that of other leaf cells when the plants are grown at highsalinity. Large amounts of sodium did, in contrast, accumulatein epidermal and subsidiary cells, and particularly in the mesophylltissue, suggesting that a mechanism exists to limit the extentof its entry into guard cells. Even in plants grown at highsalinity, the content of potassium was much higher than thatof sodium in the guard cells, consistent with the view thatthis is a major ion involved in determining stomatal movementsin this halophyte. Determinations were also made for the nonhalophyte Commelinacommunis, and it was found that the guard cells accumulatedlarge amounts of sodium when it was presented to them as analternative to potassium. It is suggested that the acquisition by the guard cells of someability to restrict the intake of sodium ions may be an importantcomponent of sodium-driven regulation of transpiration, andhence of salinity tolerance, in A. tripolium. Key words: Salinity tolerance, sodium, potassium, stomata, Aster tripolium     

High occurrence of rare inland halophytes on post‐mining sites in western Ukraine

Rare inland halophytic vegetation including the associations Salicornietum prostratae, Spergulario marginatae‐Suaedetum prostratae, Puccinellietum limosae, com. Puccinellietum limosae – a variant of Aster tripolium subsp. pannonicus and Astero pannonici‐Bolboschoenetum compacti have been found on 3 localities in the Drohobych region of western Ukraine. These are isolated (‘island’) localities, almost unknown until today. Halophytes grew there on salted sites in the vicinity of the old salt industry. Species of halophytes previously not known from this region were discovered: Aster tripolium subsp. pannonicus, Bolboschoenus maritimus, Gypsophila paniculata, Limonium gmelinii, Lotus tenuis, Puccinellia distans, Sonchus palustris, Suaeda prostrata, Trifolium fragiferum var. bonannii, Triglochin maritima, Typha laxmannii and Zannichellia palustris subsp. pedicellata. The occurence of these plants strictly depends on the presence of salt in the soil and they are endangered by shrinkage of salted sites following the termination of the salt industry in Drohobych region.     

Low-molecular-weight carbohydrates in some salt-stressed plants

A study was made of the effects of salinity on the concentrations of free sugars, glycinebetaine, proline and other chemical components of Aster tripolium L., Daucus carota L., Honkenya peploides (L.) Ehr. and Plantago coronopus L. (Dicotyledones); and Carex extensa Good., Eleocharis uniglumis (Link) Schutt., Juncus maritima Lam. and Schoenoplectus tabernaemontani (C. C. Gmel.) Palla (Monocotyledones) grown in the laboratory. In Plantago coronopus the level of the polyol sorbitol increased when the plants were subjected to NaCl stress, while in Honkenya peploides the cyclitol pinitol accumulated. No consistent pattern emerged with respect to the changes in free sugar contents in either the monocotyledonous or dicotyledonous plants, though the monocotyledonous plants generally had higher sugar contents.     

Utilization, diet and diet selection by brent geese Branta bernicla bernicla on salt-marshes in Norfolk

The diet and utilization by brent geese of two plant communities ( Limonium/Armeria marsh—a short sward community in the upper mid salt-marsh and composed of several species, and Salicornia marsh—a community of the lower salt-marsh dominated by Salicornia europuea agg. and Aster tripolium ) were studied on the north Norfolk coast. The biomass on these communities was highest in autumn and declined markedly in November owing to the senescence and die-off of the succulent species. This decline was not significantly precipitated by the grazing of the geese but coincided with their switch to inland habitats where the biomass m^-2 and total food available on fields of winter wheat and grassland within the population's home range was 20–30 times greater. Brent geese continued to graze salt-marsh at a low intensity through the winter, feeding largely on Puccinellia maritima. In spring they returned largely to Limonium/Armeria marsh where they significantly reduced the regrowth of Puccinellia maritima.
The main plant species ealen was Puccinellia maritima , especially in mid winter. Salicornia maritima agg. leaves and seeds formed much of the diet in autumn, whereas Triglochin maritima, Plantago maritima and Aster tripolium were important foods on Limonium/Armeria marsh in spring. All these species were selected at some part of the year. Selection was related to the proline (an imino acid used by salt-marsh plants as an osmoregulator) and chloride content and avoidance related to tannins. Two species which contained condensed tannins. Limonium vulgare and Armeria maritima , were rarely eaten. As well as being a nutrient, proline may help to neutralize the effects of tannins in the diet if incorporated into proline-rich proteins.     

Directional and non‐directional vegetation changes in a temperate salt marsh in relation to biotic and abiotic factors

Abstract. The effects of reduction and cessation of sheep grazing on salt‐marsh vegetation were studied on a formerly intensively grazed salt marsh in northern Germany. Plant species cover was recorded in 45 permanent plots from 1992 to 2000. In 1995, physical and chemical soil parameters were analysed. Results of Redundancy Analysis (RDA) indicated that salinity and the depth of anoxic conditions below the surface were the most important soil factors related to the spatial vegetation pattern. Furthermore, plant species distribution was influenced by present and past grazing intensity, by soil grain size and nitrogen content. Vegetation changes over 9 yr were analysed by non‐linear regression. The cover of Aster tripolium, Atriplex portulacoides, and, to a lesser extent, Artemisia maritima and Elymus athericus increased due to reduced grazing pressure, whereas the cover of Salicornia europaea decreased. After a strong increase in the first years Aster decreased 2 to 6 yr after abandonment. In the mid salt‐marsh zone Puccinellia maritima was replaced by Festuca rubra. The cover of Puccinellia, Festuca, Suaeda maritima, Glaux maritima and Salicornia fluctuated strongly, probably due to differences in weather conditions and inundation frequency. Species richness per 4 m² generally increased while vegetation evenness decreased during the study period. Only in the high salt marsh abandoned for 9 yr did the number of species decrease slightly. Thus far, cessation of grazing did not lead to large‐scale dominance of single plant species.     

Quantification and fatty acid profiles of sulfolipids in two halophytes and a glycophyte grown under different salt concentrations

This study was aimed at understanding the role of sulfolipids in salt tolerance mechanisms of the halophytes Aster tripolium L., Compositae, and Sesuvium portulacastrum L., Aizoaceae, and of the glycophyte Arabidopsis thaliana (L.) Heynh., Brassicaceae. In Aster and Sesuvium the sulfolipid contents increased significantly under salt stress conditions (517 mM or 864 mM). In Arabidopsis, changes in sulfolipid contents were not observed (NaCl up to 100 mM). The fatty acid profile of sulfoquinovosyldiacylglycerol (SQDG) in Aster was modified with increasing NaCl concentrations. LC-MS analyses of sulfolipids from Aster and Sesuvium revealed the presence of 18:3/18:3 and 16:0/18:3 molecules. Obviously, the function of sulfolipids during salt stress differs between halophytic species and between halophytes and glycophytes where sulfolipid accumulation was not observed.     

Nitrogen Effects on Leaf Anatomy within the Intercalary Meristems of Tall Fescue Leaf Blades

Longitudinal elongation contributes most to leaf area expansionof grasses and its rate is known to be strongly affected byN. Our objective was to determine the effect of two N regimes(N₀and N+) on the gradient of leaf tissue formation in meristemsof two contrasting tall fescue (Festuca arundinacea Schreb.)genotypes. Proportions of epidermal, mesophyll and vasculartissue as well as intercellular air space were determined throughoutthe base of actively elongating leaves. The area of leaf transversesections nearly doubled between the ligule and the distal endof the growth zone (about 30 mm), and was mainly associatedwith lateral epidermal and mesophyll cell division in the proximal5.0–7.5 mm. Further increase in transverse area was dueto the formation of intercellular airspace and transverse expansionof epidermal cells. Depending on genotype and N treatment themesophyll, epidermis, vascular bundles and air space comprised45–54%, 20–28%, 6–9%, and 17–21%, respectively,of transverse leaf area in the distal part of the growth zone.After a slight increase close to the leaf base, the area ofvascular tissue remained constant throughout the growth zone.The proportion of air space to mesophyll space was higher atN₀than at N+ because mesophyll area was enhanced by N+ to agreater degree than by N₀. In the genotype with slow leaf elongation,the increase in cross-sectional leaf area was due to an increasein both leaf width and leaf thickness. In the genotype whichhad faster leaf elongation and wider leaves, only leaf thicknesswas enhanced by N+. Copyright 2001 Annals of Botany Company Festuca arundinacea(Schreb.), tall fescue, leaf anatomy, growth zone, nitrogen     

The Late-Weichselian Flora of the Isle of Man

The last glacial deposits of the Ballaugh-Kirkmichael area in the north-east of the Isle of Man have been investigated by analysis of pollen and macroscopic fossils and by radiocarbon dating. Assemblages totalling over 160 taxa of vascular plants and mosses have been recorded from strata referred to Late-Weichselian zones I, II and III. Among the most noteworthy species are 46 not now living on the island; these include Dianthus deltoides, Juncus balticus, Lychnis viscaria, Ranunculus hyperboreus, Sibbaldia procumbens, Meesia tristicha, Helodium blandowii and Polytrichum norvegicum. The vegetation comprised a great diversity of communities of open, largely calcareous grassland, snow beds, mires both base-rich and base-poor, flushes, freshwater, inundated flats and calcareous dunes. Saline conditions are indicated by Glaux maritima and Triglochin maritima. Trees were represented only by Betula and the taller shrubs by Juniperus and Salix.     

Aster tripolium L. and Sesuvium portulacastrum L.: two halophytes, two strategies to survive in saline habitats.

Aster tripolium L. (Dollart, Germany) and Sesuvium portulacastrum L. (Dakhla, Morocco) are potential halophytic vegetables, fodder plants, and ornamentals for re-vegetating saline land. To compare their strategies involved in salt tolerance both plants were grown with 0%, 1.5%, and 3% (Aster) or 0%, 2.5%, and 5% (Sesuvium) NaCl in the watering solution. The growth rate was reduced in both species with increasing NaCl concentrations. The quotient of Na(+)/K(+) indicates that Aster accumulates more K(+) in comparison to Na(+) while the reverse is true for Sesuvium. Osmolality of the leaf sap increased with increasing NaCl concentration in both Aster and Sesuvium. Transpiration rate was severely reduced in both Aster (3%) and Sesuvium (5%) plants after 10 d of NaCl watering. The CO(2) assimilation rate decreased in Aster (3%) and Sesuvium (5%) NaCl-treated plants from day 5 to day 10. The most important results from chlorophyll fluorescence measurements were derived from the non-photochemical quenching analysis (NPQ). First, both plants had linearly increasing levels of NPQ with increasing NaCl concentrations. Second, Sesuvium had almost half the NPQ value when compared to Aster under increased soil salinity. In Aster P-ATPase activities were decreased in plants treated with 3% NaCl after three days of treatment, F-ATPase activities increased with increasing NaCl concentrations and no clear changes were measured in V-ATPase activities. In Sesuvium any changes could be observed in the three ATPase activities determined. To conclude, Aster and Sesuvium use different strategies in adaptation to soil salinity.     

The Effect of Temperature on Leaf Appearance in Rice

Temperature is the principal environmental determinant of cropleaf appearance. The objective of this study is to analyse whetherthere are different effects of day temperature (T_D) and nighttemperature (T_N) on main-stem leaf appearance in rice (OryzasativaL.). Plants of 12 rice cultivars were grown at five constant temperatures(22, 24, 26, 28 and 32 °C) and four diurnally fluctuatingtemperatures (T_D/T_N: 26 /22, 30 /22, 22 /26 and 22 /30 °C)with a constant photoperiod of 12hd^-1. The leaf appearance onthe main stem was measured. A constant change in leaf appearance rate was observed duringontogeny. The relation between the number of emerged leavesand days from seedling emergence was described by a power-lawequation with only one cultivar-specific parameter. Values forthis parameter were estimated for the five constant temperaturetreatments, and the relation between this parameter and temperaturewas quantified by a nonlinear model. Leaf appearance for thefour fluctuating temperature treatments could be accuratelypredicted on the basis of these relations in each cultivar.This indicated that there were no specific effects ofT_DandT_Nonleaf appearance in rice, in contrast with phenological developmentto flowering. The optimum temperature for leaf development wasfound to be substantially higher than for development to flowering. The final main-stem leaf number differed with diurnal temperatureconditions. When a diurnal temperature delayed flowering, itincreased the leaf number as well. This might explain whyT_DandT_Nhada different effect on development to flowering but not on leafdevelopment. Oryza sativa; rice; leaf appearance; leaf number; day and night temperature     

Epidermal Cell Division and the Coordination of Leaf and Tiller Development

Initiation and development of grass leaves and tillers are oftendescribed individually with little attention to possible interrelationshipsamong organs. In order to better understand these interrelationships,this research examined epidermal cell division during developmentaltransitions at the apical meristem of tall fescue (Festuca arundinaceaSchreb.). Ten seedlings were harvested each day for a 9-d period,and lengths of main shoot leaves and primary tillers were measured.In addition, numbers and lengths of epidermal cells were determinedfor 0·5 mm segments along the basal 3 mm of each leafand tiller. Primordia development and onset of rapid leaf elongationwere characterized by an increase in the number of cells perepidermal file with mean cell length remaining near 20 µmper cell. After the leaf had lengthened to 1-1·5 mm,cells near the leaf tip ceased dividing and increased in length,at which time leaf elongation rate increased rapidly. Liguleformation, marking the boundary between blade and sheath cells,occurred prior to leaf tip emergence above the whorl of oldersheaths, while the earliest differentiation between blade andsheath cells probably began when leaves were < 1 mm long.Major transitions in leaf and tiller development appeared tobe synchronized among at least three adjacent nodes. At theoldest node, cessation of cell division in the leaf sheath wasaccompanied by initiation of cell division and elongation inthe associated tiller bud. At the next younger node the ligulewas being initiated, while at the youngest node cell divisioncommenced in the leaf primordium, as elongation of a new leafblade began. This synchronization of events suggests a key rolefor the cell division process in regulating leaf and tillerdevelopment.Copyright 1994, 1999 Academic Press Festuca arundinacea Schreb., tall fescue, cell division, leaf initiation, tillering, ligule development     

Influence of Xylem Water Potential on Leaf Elongation and Osmotic Adjustment of Wheat and Lupin

The leaf elongation rate and osmotic pressure at full turgorof wheat (Triticum aestivum L.) and lupin (Lupinus cosentiniiGuss.) were measured in well watered plants, in plants thatwere allowed to dry the soil slowly over 7 d, and in plantsin which the water potential of the leaf xylem was maintainedhigh by applying pressure to the roots during the drying cycle.Maintenance of high xylem water potentials failed to preventa reduction in the rate of leaf elongation as the soil dried,while the osmotic pressure at full turgor and the degree ofosmotic adjustment increased as the soil water content decreased.The rate of leaf elongation was reduced more and the degreeof osmotic adjustment was higher in leaves with high xylem waterpotentials than in those in which leaf xylem potentials wereallowed to decrease as soil water content decreased. Osmoticadjustment was linearly correlated with the reduction in leafelongation rate in both wheat and lupin. Key words: Osmotic adjustment, leaf elongation, turgor regulation     

Kinetics of Leaf Growth in Lolium temulentum at Optimal and Chilling Temperatures

Lolium temulentum plants were grown at 20 °C, under an 8-hdaylength, in a controlled-environment chamber, and the kineticsof leaf expansion were observed by measuring the movement ofan optical grid attached to the fourth leaf. The leaf emerged23–24 d after sowing and was fully expanded 9–10d later. Extension rate was maximal between the second and fifthdays after emergence and declined markedly thereafter. Duringthe rapid growth phase the rate of elongation exhibited a distinctdiurnal rhythm, fluctuating between 1.9 to 2.3 mm h^–1in the light period, and 1.3 to 1.7 mm h^–1 in the dark.A circadian oscillation with a period of about 27 h was observedin leaves elongating in continuous darkness. When plants weretransferred to 5 °C soon after emergence of the fourth leafthere was an immediate reduction in rate of growth to about22 per cent of the rate at 20 °C: the Q₁₀ for the mean elongationrate in the range 20–5 °C was 3.7. When plants weretransferred from 20 to 2 °C at fourth leaf emergence, meanextension rate declined to less than 5 per cent, correspondingto a Q₁₀ in the range 5–2 °C of more than 300. Furthermore,growth at 2 °C was confined almost entirely to the darkphase of the photoperiod cycle. The responsive tissue was shownto be a small area of expanding leafless than 1.5 cm above theshoot apex and the possible mechanisms underlying low temperatureeffects in this region are discussed. Lolium temulentum L., leaf growth, auxanometer, low temperature, diurnal rhythm     

The Initiation, Growth, and Emergence of Leaf Primordia in Fragaria

The leaf initiation rate in Fragaria vesca (var. ‘RoyalSovereign’) has been compared with the elongation rateof the leaf primordia at different seasons. Certain conceptionsof growth correlation within the bud are presented. Experimentson the nature of elongation and emergence of primordia are described,and the causes of emergence are discussed.     

Effect of Leaf Age on Potassium Efflux and Net Flux in Tomato Leaf Slices

The effects on leaf age on K (⁸⁶Rb) efflux, influx and net fluxinto lamina slices from leaf 7 on a tomato plant (Lycopersiconesculentum Mill.) were determined. The ontogenetic trend inK efflux was dependent on the external K concentration. At externalKCI concentrations between 0.5 and 10.0 mM, K efflux rates increasedduring leaf elongation. Only a small increase in efflux occurredin mature leaves with increasing age. It is suggested that thetonoplast retains its structural integrity through the initialstages of leaf senescence. In fully expanded leaves, a zeronet K flux (a balance between influx and efflux) was achievedat external KCI concentrations between 1.0 and 3.5 mM. The Kcontent of lamina slices from leaves 5 and 13 remained constantwhen bathed in a solution containing 2 to 3 mM K. It is suggestedthat the decline in K concentration in mature tomato leaf tissueis due to a decline in leaf free space K concentrations below1 to 3 mM which would result in a net efflux out of leaf cells. Lycopersicon esculentum Mill., tor ato, free space, ion fluxes, leaf age, leaf ontogeny, potassium     

Mechanisms of Developmental Integration of Aster novae-angliae L. and Hieracium murorum L.

This paper is an inquiry into the regulatory features of developmentof Aster novae-angliae and Hieracium murorum. Computer-generatedplant models are compared with real plants to analyze branching,conver sion from vegetative to flowering development, stem elongation,and flowering.     

The Relationship between the Growth of the Primary Leaf and of the Coleoptile in Seedlings of Avena and Triticum

Partial inhibition of extension growth of the primary leaf occurswhen whole Triticum seedlings are immersed in aerated solutionsof IAA but is replaced by growth promotion when sucrose is addedto the external solution. In seedlings in which the coleoptilehas been excised, IAA increases the growth of the leaf bothwith and without additional sucrose. Inhibition of the leaf by moderate concentrations of IAA nolonger occurs when the seedling is detached from the endosperm.Sucrose added to the external solution raised the percentageelongation of the coleoptile almost to the level of that attainedin intact seedlings without additional carbohydrate. It alsoenabled the leaf to show a positive growth response with IAA. The results indicate that in intact seedlings treated with IAAthe growth of the primary leaf is markedly diminished owingto diversion of carbohydrate to the coleoptile if the growthof the latter is promoted as a result of the treatment. Whenthe competition of the coleoptile for carbohydrate is diminishedor eliminated, acceleration of the growth of the primary leafby IAA becomes apparent. In addition to the endogenous rhythm, with a period close to24 hours, induced in the growth-rate of the coleoptile whenseedlings of Avena are transferred from red light to darkness,a similar rhythm, with a slightly longer period, is inducedin the growth-rate of the primary leaf. This rhythm persistsin elongating leaves so long as they remain within the coleoptile.It can be recorded for at least 100 hours in deseeded seedlings. When intact seedlings of Avena are immersed for one hour inrelatively high concentrations of IAA and then transferred todistilled water for 18 hours, the elongation of the coleoptileis greater and the inhibition of the leaf is less than whenthey are transferred to humid air. Sections of the leaf of Triticum showed a slight increase inelongation in concentrations of IAA up to 5 mg./l., but no evidencewas obtained that sections of leaf and coleoptile exert any.influenceon each other's elongation when floated together on solutionsof IAA.     

Kinetics of Maize Leaf Elongation: I. INCREASED YIELD THRESHOLD LIMITS SHORT-TERM, STEADY-STATE ELONGATION RATES AFTER EXPOSURE TO SALINITY

The short-term responses of leaf elongation to salinity areinvestigated in this study. The kinetics of maize (Zea maysL.) leaf elongation were measured with Linear Variable DifferentialTransformers (LVDTs). After exposure to salinity (0 to 120 molm^–3 NaCl), leaf elongation rates (LER) declined rapidly.Within 4 h, LER had recovered and reached a new steady-statefor all salinity treatments. These rates were reduced by 10,20, and 60% of control rates by 40, 80 and 120 mol m^–3NaCl, respectively. Osmotic adjustment in the growing zone ofleaves was correlated with the recovery of LER after plant exposureto salinity. However, after 4 h of exposure, the osmolalityof the cell sap continued to increase without effect on steady-stateLER. Estimates of the apparent turgor in the growing zone indicatedthat turgor was no longer limiting LER of salt-stressed plantsafter 4 h. An in vivo technique was developed to apply a unidirectionalforce to intact growing leaves of maize to mimic increases inelongation force. Relative elongation rate (RER) were increasedby adding weights to the LVDT core to increase elongation force.Plots of RER as a function of elongation force gave estimatesof two growth coefficients: the yield threshold and the yieldingcoefficient, mL/(m + L), where m is the cell wall extensibilityand L is the hydraulic conductivity. RER as a function of elongationforce was determined immediately, 05, 4, and 21 h after plantswere salinized. Estimates of the growth coefficients indicatedthat the apparent yield threshold decreased immediately aftersalinization. However, when LER reached steady-state, the yieldthreshold of salt-stressed plants had increased above controlvalues and was the only limiting growth coefficient. There wereno significant effects of salinity on the yielding coefficients,cell wall extensibility or hydraulic conductivity. One of theadvantages of this in vivo technique over other methods is thatyield threshold, yielding coefficient, and cell wall extensibilitycan be determined without the confounding effects of woundingor osmotic stress. This technique may prove widely applicableto the study of other growth regulating factors. Key words: Salinity, leaf growth, Zea mays L