Barbiturate-induced Disorientation of Root and Shoot Geotropism in Germinating Cruciferous Seedlings

Cruciferous seedlings germinated on glass-distilled water andon barbital manifested normal root and shoot geotropisms whereastwisted roots and shoots were evident in seedlings germinatedon amobarbital and secobarbital, the roots often being completelysuspended in the air. The marked difference in germination anddevelopment behaviour of cress and white mustard seedlings germinatedon barbital compared with that on amobarbital and secobarbitalindicate that the Meyer-Overton principle of drug potency andlipid solubility was operative in both species of germinatingseedlings. Lepidium sativum L., Sinapsis alba L., seed germination, geotropism, barbiturates     

Eco-physiological studies on desert plants

Summary The O₂ uptake and RQ of germinating negatively photoblastic Zygophyllum coccineum seeds were studied during the first fourty hours after soaking in water under dark or light conditions. Five phases could be distinguished in the course of O₂ uptake in water in dark. The respiration course in light did not differ from that in dark till the 12th hour after soaking, then it deviated showing a low level, The RQ values in dark and light are nearly identical; both had sharp decline between the 8th and the 16th hour after soaking. Light, by blocking germination, affected the O₂ uptake.Moisture stress simulated by mannitol solutions caused a decrease in the O₂ uptake of seeds and seedlings. Na₂SO₄ caused a reduction and a lag in the time of maximum O₂ uptake. NaCl showed a particular effect on respiration of germinating seeds causing earlier rise and decrease in O₂ uptake than in water. NaCl was effective in rising the O₂ uptake of seedlings specially those supplied with glucose. Its effect was not pronounced on starved seedlings. O₂ uptake of seedlings germinated in NaCl was considerably high when compared with that of seeds germinating in the same medium 40 hours after soaking.The decreasing effect of moisture stress caused by mannitol on O₂ uptake was reversed by diluting the medium or replacing it with water. Values of O₂ uptake on number of seedlings basis are different from those calculated on fresh weight basis due to the difference in water content of seedlings germinated under various conditions.     

Effect of Barbiturates on Rice Seedling Germination and Developmental Behaviour

Rice seedling germination and developmental behaviour were examinedin the presence of six different barbituric acid derivatives.The relationship between liquid/aqueous partition coefficientsof barbiturates and their interference with, but not completeinhibition of, normal mitochondria1 oxidative metabolism observedin animal mitochondria in vitro also appear to be factors influencingthe effects of these compounds on the germination and developmentalbehaviour of the rice seedlings described in this investigation.Evidence is presented here which points to normal oxidativemetabolism as being a necessary requisite for normal light responseand normal morphogenetic development in germinating rice seedlings.     

A new method to detect cadmium uptake in protoplasts

The mechanism for cadmium (Cd²⁺) uptake into the cytosol of protoplasts from 5- to 7-day-old wheat seedlings (Triticum aestivum L. cv. Kadett) was investigated by a new method, using fluorescence microscopy and the heavy metal-specific fluorescent dye, 5-nitrobenzothiazole coumarin, BTC-5N. Cadmium fluorescence gradually increased in the cytosol of shoot and root protoplasts upon repeated additions of CdCl₂ to the external medium, reflecting an uptake of Cd²⁺. The uptake was inhibited by calcium and potassium chloride, as well as by Verapamil and tetraethylammonium (TEA), inhibitors of calcium and potassium channels, respectively. Calcium competitively inhibited the cadmium uptake. The metabolic inhibitors vanadate and dinitrophenol partly inhibited the uptake, suggesting it was dependent on membrane potential. The results indicate that cadmium is taken up by channels permeable to both calcium and potassium. The total uptake of cadmium into the protoplasts was also detected by unidirectional flux analyses using ¹⁰⁹Cd²⁺, and showed approximately the same maximal concentration of Cd²⁺ as the fluorescence measurements. By combining the two methods it is possible to detect both uptake into the cytosol and into the vacuole.Abbreviations BTC-5N, AM Acetoxymethyl ester of 5-nitrobenzothiazole coumarin - DNP 2,4-Dinitrophenol - TEA Tetraethylammonium     

d- rice seedling development in periodically stirred water in sealed environments

Summary

Large numbers of germinating seedlings of two rice cultivars exhibited d^- type development consisting solely of completely white coleoptile growth after 15 days in the light in both static and periodically stirred water environments in completely sealed jars. Thus, whether germinated in static or agitated water in the sealed environments, coleoptile greening and subsequent normal seedling development were inhibited by hypoxic stress caused by the large numbers of germinating rice seedlings competing for the limited environmental oxygen supply. Consequently, the evidence presented points away from the formation of unfavourable oxygen diffusion gradients in static water environments in the sealed jars as having been responsible for d type seedling development observed in previous investigations. Continuous aeration of the 15-day-old static and periodically stirred aquatic environments, respectively, resulted in complete reversal of all d seedlings into normal green plants.     

Impaired Anthocyanin Production in Barbiturate treated Zea mays Seedlings

Anthocyanin production was impaired in both roots and shootsof Zea mays seedlings germinated on 1 and 2 mM concentrationsof four barbiturates having different lipid/aqueous partitioncoefficients. The severity of impaired anthocyanin productionwas greater in those seedlings treated with the higher lipidsoluble barbiturates irrespective of the concentrations used.Indirect evidence is presented which indicates that barbituratesinterfere with normal membrane physiology responsible for anthocyaninproduction. Anthocyanin, barbiturate, seedlings, Zea mays     

The Effect of pH and Bicarbonate Ions on the Uptake of Salts by Disks of Red Beet

1. The uptake of potassium chloride by disks of beetroot in solutionsat different pH values has been followed over periods of severaldays.
2. It was found that, as the pH was raised from approximately6to 9 the rate of uptake of potassium from 0.0024 M. potassiumchloride increased, and there was a corresponding increase inthe amount of potassium held by the disks at satura tion. Boththe rate of uptake and the final content of potassium in diskskept in solutions at pH 8.5 were frequently double those atpH 6.
3. The rate of uptake of chloride ions was only slightlyaffectedby the pH value of the medium. The final chloride contentwasapproximately the same in disks kept at different pH values.
4. The above ‘pH effect’ on potassium uptake hasbeenshown to be related to the uptake of bicarbonate ions presentin the alkaline solution; the additional potassium ions accumulatedaccompanying the bicarbonate anions taken up.
5. The bicarbonateions accumulated are converted primarily tomalic acid.

     

Active chloride transport in rabbit thick ascending limb of Henle's loop and elasmobranch rectal gland: chloride fluxes in isolated plasma membranes

Summary To investigate directly whether a sodium-potassium-chloride cotransport system is operating in the mammalian thick ascending limb of Henle's loop (TALH) and in the elasmobranch rectal gland, plasma membrane vesicles were prepared from TALH cells isolated from rabbit kidney outer medulla and from rectal glands ofSqualus acanthias, and chloride uptake was measured by a rapid filtration technique. Chloride uptake into TALH vesicles in the presence of a 25 mM Na₂SO₄, 25 mM K₂SO₄ gradient reached 70% of equilibrium at 2.5 min. In the presence of both sodium and potassium, the 15 s chloride uptake was inhibited 35% by 1 mM bumetanide. When either sodium or potassium was removed from the incubation medium, chloride uptake decreased to the level observed in the presence of 1 mM bumetanide. 0.5 mM SITS had no effect on chloride uptake by the plasma membrane vesicles. This sodium and potassium dependent, bumetanide sensitive chloride uptake was also observed under tracer exchange conditions. Chloride uptake into rectal gland plasma membrane vesicles in the presence of a 50 mM Na₂SO₄, 50 mM K₂SO₄ gradient reached 80% of equilibrium at 2.5 min. 1 mM bumetanide inhibited the 15 s uptake of chloride by 34% and removal of either sodium or potassium from the incubation medium reduced chloride uptake to the level observed in the presence of bumetanide under both gradient and tracer exchange conditions. These studies provide additional support for the hypothesis that a sodium-potassium-chloride cotransport system is operating in these epithelia.Abbreviations SITS 4-acetamido-4-isothiocyanato-stilbene-2,2-disulfonic acid - TALH thick ascending limb of Henle's loop     

HIGH AFFINITY CHOLINE UPTAKE: IONIC AND ENERGY REQUIREMENTS

Abstract— High affinity choline uptake into rat hippocampal synaptosomes was examined at 37°C when various ions were deleted from normal Kreb's-Ringer media. When sodium chloride was replaced by sucrose, lithium chloride, cesium chloride or rubidium chloride, choline uptake was markedly reduced. When the sodium concentrations of the Kreb's media were gradually reduced to zero, the uptake was gradually reduced in parallel. A kinetic analysis performed at low and normal sodium concentrations revealed changes in K_m and V^max values. When several non-chloride sodium salts were utilized, the uptake was reduced in all cases suggesting also a chloride-dependence in addition to the sodium-dependence. Omission of calcium chloride or magnesium sulfate from the media did not alter uptake. Sodium-dependent choline uptake was examined over a range of potassium concentrations (0–35 DIM). It was found that uptake was maximal between potassium concentrations of 0.35–4.8 mm but was reduced at both lower and higher potassium concentrations. The kinetics of uptake were examined under varying potassium concentrations, and at low potassium, only a change in V_max was observed while at high potassium concentrations, there were changes in both K^m and V^max values. Preincubation and incubation of synaptosomes with 0.1 m -ouabain, 0.1 mm -2,4-dinitrophenol and 1 mm -KCN caused a reduction in sodium-dependent uptake. When dextrose was omitted from the preincubation and incubation media there was also a reduction in sodium-dependent uptake. By contrast, the sodium-independent uptake was unaffected by the metabolic inhibitors or omission of dextrose, and had a very low Q₁₀. When various incubation temperatures were utilized in uptake experiments, the Q¹⁰ for the interval 37-27°C was 2.7 and the activation energy was 22.7 kcal/mol. Slightly different ionic dependences were observed when animals pretreated with pentobarbital of oentylenetetrazol were utilized as the source of synaptosomes.     

Role of potassium channels in chlorogenic acid-induced apoptotic volume decrease and cell cycle arrest in Candida albicans

BackgroundChlorogenic acid (CRA) is an abundant phenolic compound in the human diet. CRA has a potent antifungal effect, inducing cell death in Candida albicans. However, there are no further studies to investigate the antifungal mechanism of CRA, associated with ion channels.MethodsTo evaluate the inhibitory effects on CRA-induced cell death, C. albicans cells were pretreated with potassium and chloride channel blockers, separately. Flow cytometry was carried out to detect several hallmarks of apoptosis, such as cell cycle arrest, caspase activation, and DNA fragmentation, after staining of the cells with SYTOX green, FITC-VAD-FMK, and TUNEL.ResultsCRA caused excessive potassium efflux, and an apoptotic volume decrease (AVD) was observed. This change, in turn, induced cytosolic calcium uptake and cell cycle arrest in C. albicans. Moreover, CRA induced caspase activation and DNA fragmentation, which are considered apoptotic markers. In contrast, the potassium efflux and proapoptotic changes were inhibited when potassium channels were blocked, whereas there was no inhibitory effect when chloride channels were blocked.ConclusionsCRA induces potassium efflux, leading to AVD and G2/M cell cycle arrest in C. albicans. Therefore, potassium efflux via potassium channels regulates the CRA-induced apoptosis, stimulating several apoptotic processes.General significanceThis study improves the understanding of the antifungal mechanism of CRA and its association with ion homeostasis, thereby pointing to a role of potassium channels in CRA-induced apoptosis.     

Effects of barbiturates on human platelet aggregation differ depending on their chemical structures

The effects of barbiturates on human platelet function are not fully understood. Since we have already revealed the effects and mechanisms of thiopental, thiamylal, and pentobarbital in platelets, the present study attempted to elucidate (i) the effects of other barbiturates on human platelet aggregation, (ii) the underlying mechanisms, and (iii) the structure-function relationship of barbiturates in platelets. Barbiturates, including amobarbital, butalbital, secobarbital, barbital, phenobarbital, metharbital, and primidone, were examined. Human platelet aggregation induced by adenosine diphosphate (ADP), epinephrine, and (+)-9,11-epithia-11,12-methano-thromboxane A2 (STA2), a thromboxane A2 analog, was measured using an 8-channel light-transmission aggregometer. The cytosolic free calcium concentration ([Ca2+]i) was measured by fluorometer using fura-2 loaded platelets. Inositol 1,4,5-trisphosphate (IP3) formation induced by STA2 was determined by a commercially available IP3 assay kit. Amobarbital, butalbital, and secobarbital suppressed ADP-, epinephrine- and STA2-induced platelet aggregation and the STA2-induced [Ca2+]i increase, even when Ca2+ influx was blocked by Ni2+. However, they did not affect STA2-induced IP3 formation. Barbital, phenobarbital, metharbital, and primidone (up to 1 mM) had no effect on ADP- and epinephrine-induced platelet aggregation. Thus, we conclude that amobarbital, butalbital, and secobarbital inhibit platelet aggregation by suppressing [Ca2+]i increase without affecting IP3 formation. However, these antiaggregatory effects may not have clinical importance, since the barbiturate concentrations used were higher than clinically relevant ones. The other tested barbiturates had no effects on platelet aggregation. The data indicate that the effects of barbiturates on platelet aggregation differ depending on their chemical structures.     

p-Fluorophenylalanine-Induced Restriction of Ion Uptake and Assimilation by Maize Roots

Roots of decapitated maize seedlings (Zea mays L.) were exposed for 12 hours to 1.0 millimolar KNO₃ (98.5 atom per cent ¹⁵N) in the presence and absence (control) of 0.1 millimolar p-fluorophenylalanine (FPA), an analog of the amino acid phenylalanine. FPA decreased nitrate uptake but had little effect on potassium uptake. In contrast, accumulation of both ions in the xylem exudate was greatly restricted. The proportion of reduced ¹⁵N-nitrogen that was translocated at each time was also restricted by FPA. These observations are interpreted as indicating that synthesis of functional protein(s) is required for nitrate uptake and for transport of potassium, nitrate, and reduced-¹⁵N from xylem parenchyma cells into xylem elements. The effect of FPA on nitrate reduction is less clear. Initially, FPA limited nitrate reduction more than nitrate uptake, but by 8 hours the cumulative reduction of entering nitrate was similar (~35%) in both control and FPA-treated roots. A relationship between nitrate uptake and nitrate reduction is implied. It is suggested that nitrate influx regulates the proportion of nitrate reductase in the active state, and thereby regulates concurrent nitrate reduction in decapitated maize seedlings.     

The relationship of sodium uptake,potassium rejection,and skin potential in isolated frog skin

1. Isolated surviving frog skin, when bathed with the same kind of diluted Ringer's solution on both sides, shows a negative correlation between net active salt uptake by the epithelium and spontaneous skin potential. Average values of 0.15 to 0.86 µeq. x hr.^–1 x cm.^–2 were measured and correlated with average skin potentials ranging from 107 to 25 mv. 2. Sodium uptake exceeded chloride uptake by about the same amount, irrespective of the height of the skin potential. 3. The same skins which exhibited a negative correlation between net uptake of sodium chloride and skin potential showed a positive correlation between net potassium rejection from the epithelium and skin potential, for voltages above 30 to 40 mv. In skins of voltages lower than this, potassium ions were taken up rather than rejected. Average values for rejection of +11.8 to –0.8 centi-µeq. x hr.^–1 x cm.^–2 were measured. 4. Net fluid uptake, associated with active uptake of sodium chloride, was small and occurred in the direction of the salt uptake. No dependence of net fluid uptake upon skin potential was observed. 5. Skins of winter frogs, pretreated with a commercial purified ACTH preparation, were less active than their respective controls with regard to uptake of sodium chloride. Rejection of potassium was the same in treated and untreated skins. Posterior pituitary factors, as possible contaminants, did not account for the effect of the ACTH preparation. 6. DOCA, DOC, and cortisone did not alter the normal correlation referred to under (1) and (3). 7. In interpreting the experimental results on theoretical grounds, it is suggested (a) that in normal skin, it is the variation in the electric conductance in skin of chloride ions which essentially, although not exclusively, determines the rate of net uptake of sodium chloride, (b) that a factor in the ACTH preparation used, possibly ACTH itself, may have lowered the electric conductance in skin of sodium ions either truly or apparently, (c) that potassium ions are treated by the skin primarily as passive ions. There is some indication that potassium ions are also actively taken up by the epithelium of skin.     

Committee for the study of the Scottish Flora

Summary

Three different oxygen-containing germination environments demonstrate the profound influence exerted by environmental oxygen (0₂) on growth and plastogenesis in coleoptiles of light-germinated rice seedlings. Coleoptile greening is extensive in low numbers of seedlings germinated in a sealed, initially air-saturated, static water environment and in large numbers of seedlings germinated under unagitated water underambient gaseous exchange conditions. In seedlings germinated in air (?21% 0₂), coleoptile greening is sparse and extension growth is much reduced compared with coleoptile extension growth of the submerged seedlings. Coleoptile greening and shoot and root growth are completely inhibited under hypoxia resulting from large numbers of germinating seedlings competing for the limited 0₂ supply in the sealed, initially air-saturated, static water environment. Coleoptile extension growth is highest under hypoxia and lowest under ?21% 0₂. The observations presented here demonstrate that 0₂ stress and non- stress conditions serve as environmental signals which influence growth behaviour and plastogenesis in coleoptiles of light-germinated rice seedlings.     

Ammonium and Potassium Uptake by Citrus Roots

Multiphasic kinetics were indicated for uptake of ammonium and potassium by intact cirtrus seedlings as measured by a continuous flow technique. Uptake at low concentration, below 10^?3M, was biphasis. The patterns for ammonium uptake by 60-day-old and 180-day-old seedlings were similar, but the rates of uptake per g dry weight of root were greater for the younger plants.     

Further photophysical and photochemical characterization of flavins associated with single-shelled vesicles

Summary In order to investigate whether the loop diuretic sensitive, sodium-chloride cotransport system described previously in shark rectal gland is in fact a sodium-potassium chloride cotransport system, plasma membrane vesicles were isolated from rectal glands ofSqualus acanthias and sodium and rubidium uptake were measured by a rapid filtration technique. In addition, the binding of N-methylfurosemide to the membranes was investigated. Sodium uptake into the vesicles in the presence of a 170mm KCl gradient was initially about five-fold higher than in the presence of a 170mm KNO₃ gradient. In the presence of chloride, sodium uptake was inhibited 56% by 0.4mm bumetanide and 40% by 0.8mm N-methylfurosemide. When potassium chloride was replaced by choline chloride or lithium chloride, sodium uptake decreased to the values observed in the presence of potassium nitrate. Replacement of potassium chloride by rubidium chloride, however, did not change sodium uptake. Initial rubidium uptake into the membrane vesicles was about 2.5-fold higher in the presence of a 170mm NaCl gradient than in the presence of a 170mm NaNO₃ gradient. The effect of chloride was completely abolished by 0.4mm bumetanide. Replacement of the sodium chloride gradient by a lithium chloride gradient decreased rubidium uptake by about 40%; replacement by a choline chloride gradient reduced the uptake even further. Rubidium uptake was also strongly inhibited by potassium. Sodium chloride dependence and bumetanide inhibition of rubidium flux were also found in tracer exchange experiments in the absence of salt gradients. The isolated plasma membranes bound³[H]-N-methylfurosemide in a dose-dependent manner. In Scatchard plots, one saturable component could be detected with an apparentK _D of 3.5×10^–6 m and a number of sitesn of 104 pmol/mg protein. At 0.8 m, N-methylfurosemide binding decreased 51% when sodium-free or low-potassium media were used. The same decrease was observed when the chloride concentration was increased from 200 to 600mm or when 1mm bumetanide or furosemide were added to the incubation medium. These studies indicate that the sodium-chloride cotransport system described previously in the rectal gland is in fact a sodium-potassium chloride cotransport system. It is postulated that this transport system plays an essential role in the secondary active chloride secretion of the rectal gland.     

The Circadian Rhythm of Stomatal Opening: Evidence for the Involvement of Potassium and Chloride Fluxes

Epidermal strips were taken from plants of Commelina communisat opposite phases of an entrained circadian rhythm, at timeswhich corresponded to the middle of the day phase and the middleof the night phase. Earlier observations of much reduced openingin response to external stimuli in the night phase were confirmed. Evidence is now presented that uptake or retention of specificions by the guard cells is affected by the phase of the rhythm.The overt expression of the rhythm was reduced if the epidermiswas presented with potassium iminodiacetate instead of potassiumchloride. Iminodiacetate is a non-absorbable anion, and thisresult suggested that chloride uptake is important for the fullexpression of the rhythm. The use of an anion channel inhibitor(DIDS) gave strong support for this conclusion. Reduced uptakeof chloride would explain an earlier observation that formationof malate is greater during the night phase. When the guard cells were presented with sodium chloride insteadof potassium chloride there was still an overt expression ofthe rhythm, but this was of reduced magnitude. This suggeststhat potassium movements might contribute to the rhythm, andstudies of ionic fluxes using ⁸⁶Rb as a tracer showed greatereffluxes during the night phase. It is concluded that the circadian rhythm in stomatal openingmay be the result of a varying ability of the guard cells toaccumulate or retain both chloride and potassium ions. Key words: Circadian rhythm, stomatal opening, Commelina communis, potassium and chloride fluxes     

Effects of some Cyclic 'Crown' Polyethers on Potassium Uptake, Efflux and Transport in Excised Root Segments and Whole Seedlings

The ionophores benzo-18-crown-6 (18-C-6), t-butylbenzo-18-crown-6(TBB) and di-t-butyldibenzo-30-crown-10 (30-C-10) were testedfor their effects on potassium ion absorption in onion rootsegments, and in wheat and mung bean seedlings. Potassium uptake,efflux and transport were progressively reduced in onion rootsegments and seedlings by 18-C-6 over the range 0.1–1.0mM. The effects of TBB (up to 0.3 mM) were more severe but otherwisegenerally similar to those of 18-C-6 in seedlings. Both ionophoresreduced growth, and at the highest concentrations, resultedin root potassium ion content falling below initial values after48 h treatment. The effects of 30-C-10 were evident at muchlower concentrations, inhibition of net potassium uptake occurringabove 10^–4 M. Between 10^–4 and 10^–4 M 30-C-10,however, a modest but significant stimulation of potassium uptakewas observed in onion roots and seedlings; growth of seedlingswas largely unaffected. The reductions in potassium absorptionwere attributed to the promotion, by the ionophores, of facilitateddiffusion down the electrochemical diffusion gradient, counteringthe efficiency of the potassium ion influx pump. Stimulationof uptake at certain concentrations of 30-C-10 was consideredmore likely to be due to an inhibition of passive potassiumefflux, rather than a stimulation of active influx. The importanceof stability constants, bonding and lipophilicity, in determiningthe relative effectiveness of the ionophores, is discussed. Allium cepa L, onion, Triticum aestivum L, wheat, Phaseolus aureus L, mung bean, cyclic ‘crown’ polyethers, potassium fluxes, ion transport     

Nonosmotic Effects of Polyethylene Glycols upon Sodium Transport and Sodium-Potassium Selectivity by Rice Roots

Addition of polyethylene glycol (PEG) as an osmotic agent (at −230 kilopascals) dramatically lessened the toxicity of NaCl (at 50 moles per cubic meter) to rice (Oryza sativa L.) seedlings. This was explained by a reduction in the uptake of NaCl. This reduction was much greater than could be accounted for by the lowered transpiration rate resulting from the solute potential changes due to the PEG.

Low concentrations of PEG (−33 kilopascals and less) had no effect upon transpiration rate but reduced sodium uptake (from 10-50 moles per cubic meter NaCl) by up to 80%. PEG (at −33 kilopascals) also reduced chloride uptake but had no effect upon the uptake of potassium from low (0.5-2.0 moles per cubic meter) external concentrations. However, the increased uptake of potassium occurring between 2 and 10 moles per cubic meter external concentration was abolished by PEG. Similar concentrations of mannitol had no effect upon sodium uptake in rice. PEG, in similar conditions, had much less effect upon sodium uptake by the more salt-resistant species, barley.

²²Na studies showed that PEG reduced the transport of sodium from root to shoot, but had a long half time for maximal effect (several days).

¹⁴C-labeled PEG was shown to bind to microsomal membranes isolated from rice roots; it is suggested that this is due to multipoint attachment of the complex ions of PEG which exist in aqueous solutions. It is argued that this reduces passive membrane permeability, which accounts for the large effect of PEG on sodium influx in rice and the different effects on sodium influx and (carrier-dependent) potassium influx.

     

Role of the soil Seed Bank in the restoration of a native pinewood at Glen Garry,Inverness-shire

Summary

The potential recovery of ground vegetation in a pinewood at Glen Garry, from which introduced tree species had been removed, was studied by sampling the upper soil seed bank and comparing the species composition of germinating seedlings with extant vegetation. Mean numbers and species of seedlings emerging differed between a control site (not under-planted) and two formerly under-planted sites cleared at different times. Germinating seedling numbers also differed with depth (0–10 cm). Calluna vulgaris and Juncus spp. dominated fifteen species germinating from the seed bank, while some other pinewood species were not found. Although seedling pine occurred, their survival will be affected by competition from Betula spp. and Deschampsia flexuosa. Other elements of the vegetation will recover from the seed bank or by migration, their distribution being influenced by topographic variations and the nature of the developing tree stand. Timing of clearance of exotics in relation to pine seed production and soil scarification might accelerate recovery of the pinewood flora generally.