bluuebunny/crossref_metadata_2025 huggingface dataset:
THE EFFECT OF ABSCISIC ACID ON GROWTH, PHOTOSYNTHETIC RATE AND CARBOHYDRATE METABOLISM IN LEMNA MINOR L.
Authors: McLAREN JAMES S. , SMITH HARRY
Published: May 2006

Inclusion of 10‐6 M ABA in the growth medium of Lemna minor L. inhibited frond multiplication rate and increased dry weight and relative growth rate per frond. Sugar and starch levels were increased over and above that expected from growth inhibition alone. Transfer of fronds to normal nutrient, after 6 days growth in 10‐6 M ABA, resulted in a higher growth rate than controls and a rapid decrease in accumulated carbohydrates. Net photosynthetic rate was initially increased, but declined after 2 days growth in the presence of ABA. This decrease in photosynthetic rate is discussed in relation to the accumulation of carbohydrates. Respiration rate did not increase with higher carbohydrate levels in the presence of ABA.
WATERLOGGING AND PETIOLE EPINASTY IN TOMATO: THE ROLE OF ETHYLENE AND LOW OXYGEN
Authors: JACKSON MICHAEL B. , CAMPBELL D. JOAN
Published: May 2006

Waterlogging the soil promotes epinastic growth of tomato petioles and increases the concentration of ethylene which can be extracted from various parts of the shoot. These concentrations exceed those normally required to promote epinasty when applied to the shoots of non‐waterlogged plants.

Waterlogging also results in a rapid decline in the concentration of dissolved oxygen in the soil water. Low concentrations of oxygen around the roots of plants growing in nutrient solution promote epinastic growth and also increase ethylene concentration in the leaves. Experiments with detached shoots indicate that the root system is required for the response to low O2concentrations to develop.

Ethylene concentrations in the soil can increase during waterlogging to levels which may allow sufficient movement into the shoot to stimulate epinasty.

Treatment with substances which can inhibit the action of ethylene, such as carbon dioxide or 7‐chloro‐4‐ethoxycarbonylmethoxy‐5‐methyl‐2, 1,3‐benzothiadiazole also inhibit the epinastic response in waterlogged plants, in plants with low O2 concentrations around the roots and in plants treated with ethylene. The internal level of carbon dioxide in the lower leaves is little affected by waterlogging for up to 96 h.
RE‐MOBILIZATION AND REDISTRIBUTION OF RESERVES IN THE TULIP BULB IN RELATION TO NEW GROWTH UNTIL ANTHESIS
Authors: HO L. C. , REES A. R.
Published: May 2006

The organic carbon content and the amount and identity of 14C‐labelled compounds derived from the 14C‐leaf assimilates fixed in the previous season were examined in various organs of tulip bulbs at replanting, on transfer to the glasshouse and at anthesis. Differences in the partition of reserves to various organs were related to the timing of their development and growth, their sink strengths and to their position relative to source organs (initially the bulb scales, later also the leaves). Leaves and roots were the major sinks which received 75% of the 14C‐reserves exported from the scales in the first three months’at low temperature (the first period). After 21 days at 18°C up to anthesis (the second period), the new leaves were a further source of carbon for the continued growth of the flower, stem and daughter bulbs. Daughter bulbs appeared to be the only organs still receiving carbon from the scales during the second period, and this was stored mainly as starch. A high rate of respiratory loss of carbon by the whole tulip plant, and particularly by the scales, was indicated in the second period.
ANALYSES OF AMINO ACIDS IN FLOWER NECTARS OF HYBRIDS AND THEIR PARENTS, WITH PHYLOGENETIC IMPLICATIONS
Authors: BAKER I. , BAKER H. G.
Published: May 2006

A method for the collection and analysis of free amino acids in very small quantities of nectar is described. By dansylation and three‐system polyamide chromatography individual amino acids may be detected at concentrations as low as 10 pmoles per μl. This has been used for the identification of constellations of acids present in floral nectar from species and hybrids of Aloë, Oxalis, Silene, Cercidium and Armeria. Almost without exception, nectars of F1 hybrids contain all of the amino acids found in the nectars of both parents combined. The usefulness of this‘additiveness’in tracing the phylogeny of groups of species in which allopolyploidy and auto‐polyploidy may have played a role is illustrated by analyses of nectars from species of Geranium (section Ruberta). Also the value of nectar amino acid analyses in the investigation of intro‐gressive hybridization is illustrated by studies of Aquilegia and Penstemon in the Sierra Nevada of California. The constancy of the amino acid patterns in parental species contrasts with the recombination patterns in the hybrid swarms. Finally, it is suggested that nectar amino acid patterns are as useful chemotaxonomically as other groups of plant chemicals and should be utilized accordingly.
THE STABILITY OF CHLOROPLASTS FROM SIPHONACEOUS ALGAE IN SYMBIOSIS WITH SACOGLOSSAN MOLLUSCS
Authors: TRENCH ROBERT K. , OHLHORST SHARON
Published: May 2006

Chloroplasts from siphonaceous algae remain photosynthetically active in the digestive epithelial cells of the sacoglossan opistobranchs Elysia viridis and Tridachia crispata for up to 3 months. During this time, chlorophylls and glycolipids are not synthesized, but the synthesis of small molecular weight metabolites such as sugars, amino acids etc. can readily be demonstrated. Analysis of the capacity of symbiotic chloroplasts to synthesize ribulose diphosphate carboxylase and membrane proteins produced negative results in both instances, even though photosynthetic CO2 fixation could always be demonstrated. These findings show that symbiotic chloroplasts are biochemically stable entities, and that they neither grow nor divide while in the animals’cells. It it likely that chloroplasts depend on the plant cell nucleus and cytoplasmic protein synthesizing machinery for the synthesis of many of their structural and enzymatic components.
STUDIES ON THE NUTRITION AND GROWTH OF DROSERA SPECIES WITH REFERENCE TO THE CARNIVOROUS HABIT
Authors: CHANDLER G. E. , ANDERSON J. W.
Published: May 2006

Drosera whittakeri was grown in sand cultures supplemented with inorganic salt solutions lacking either nitrogen, sulphur, phosphorus or the microelements. Application of the insect Drosophila melanogaster to the tentacles of plants raised on nitrogen or sulphur deficient medium, enhanced growth, which on nitrogen deficient medium was accompanied by decreased nitrogen content per unit weight although the total nitrogen per plant was unaffected. Application of insects to plants on media deficient in phosphorus or the microelements had no effect on growth but significantly increased the phosphorus content of plants grown on a complete nutrient solution or media deficient in phosphorus or nitrogen. Insects would not serve as a heterotrophic carbon source for the realization of maximum growth of plants grown at very low light intensities.

Optimum growth of Drosera binata (and usually D. whittakeri) was attained by applying insects to plants raised on nitrogen‐free medium; addition of inorganic nitrogen (as nitrate) to the nutrient solution to plants raised under these conditions inhibited growth. Optimum growth was not achieved by growing plants on a complete nutrient solution in the absence of insects.

Up to 50% of the phosphorus in the tubers of D. whittakeri occurred as inositol hexaphos‐phate. Phosphorus was rapidly transferred to the growing parts of the plant on emergence. During the growing season, plants with higher than average phosphorus content developed new rhizomes on which new tubers formed. The indigenous distribution of Drosera species in southeastern Australia is not restricted to soils of very low phosphorus, nitrogen and sulphur status.
BIOCHEMICAL AND CYTOLOGICAL EFFECTS OF SULPHUR DIOXIDE ON PLANT METABOLISM
Authors: MALHOTRA S. S. , HOCKING D.
Published: May 2006

Biochemical effects of sulphur dioxide arise from its unique ability to act as an oxidizing or a reducing agent. Among some of the important metabolic effects are direct interference with photosynthetic CO2fixation (competitive inhibition of ribulose diphosphate carboxylase by SO3−) and with energy metabolism (inhibition of mitochondrial ATP production by SO3=). Many indirect effects result from formation of sulphites and organic sulphonates with other cell constituents. These compounds can cause inhibition of a variety of metabolic enzyme systems. All these factors are probably instrumental in the gross disruption of chloroplast and mitochondrial ultrastructure. Injurious effects result when sulphur dioxide is taken up in excess of the capacity of the tissue to incorporate sulphur into the normal metabolic activities.

The ubiquitous presence of small amounts of SO, and the subtle and varied nature of its biochemical effects suggest that crop losses to SO, pollution may be more widespread and serious than is generally suspected.
THE MECHANISM OF CHILL‐ AND DROUGHT‐HARDENING OF PHASEOLUS VULGARIS LEAVES
Authors: WILSON J. M.
Published: May 2006

Drought‐hardening at 25° C, 40% R.H. by witholding water from the roots for 4 days is as effective in preventing chilling‐injury to the leaves of Phaseolus vulgaris as 4 days chill‐hardening at 12° C, 85% R.H. During chill‐hardening the degree of unsaturation of the fatty acids associated with the phospholipids increased and this was considered to prevent water loss and electrolyte leakage by lowering the temperature at which phase changes occur in the membrane lipids to below 5° C (Wilson and Crawford, 1974b). However, drought‐hardening at 25° C, 40% R.H. resulted in no increase in the degree of unsaturation of the phospholipids or glycolipids suggesting that lipid phase changes are not the primary cause of chilling‐injury. Furthermore, a re‐examination of the conditions under which water and electrolytes leak from the leaves of P. vulgaris indicates that phase changes in the membrane lipids of the plasmalemma and other organelles at 5° C are only of minor importance in determining the extent and speed of chilling‐injury. The primary cause of chilling‐injury to P. vulgaris leaves on transfer from 25° C, 85% R.H. to 5° C, 85% R.H. is leaf dehydration due to the opening of the stomata at a time when the permeability of the roots to water is low. The primary factor inducing hardening against chilling‐injury in P. vulgaris is a water stress and not low temperature per se.
AGEING IN EXCISED ROOTS OF TOMATO
Authors: WESTON GEOFFREY D.
Published: May 2006

Incubation of roots in glucose medium drastically enhanced ageing on subsequent subculture in. sucrose medium. The pretreatment of sector as opposed to tip cultures in 5% glucose reduced the period required to 36 h from the previously lowest figure of 72 h. Excision of root tips caused a reduction in both cell division and enlargement whilst FUDR, hydroxyurea and colchicine reduced the effect of glucose on ageing. The results are discussed in terms of the hypothesis that cell division is required during the glucose treatment for ageing to be enhanced.
ION LOCALIZATION AND SALT SECRETION IN SPOROBOLUS ARENARIUS (GOU.) DUV.‐JOUV.
Authors: RAMATI A. , LIPHSCHITZ NILI , WAISEL Y.
Published: May 2006

The secretion of ions from salt glands and the salt content of Sporobolus arenarius leaves were investigated. The NaCl concentration of the test solution was positively correlated with that of the secreted fluid and of the leaves.

Electron probe analysis revealed different contents of sodium, potassium and chloride in mesophyll and gland cells. Variations in the relative and absolute content of these ions suggest that an active secretion mechanism is located within the gland cells.
PLANT GROWTH RESPONSES TO VESICULAR‐ARBUSCULAR MYCORRHIZA
Authors: MOSSE B. , POWELL C. LI. , HAYMAN D. S.
Published: May 2006

Interactions between vesicular‐arbuscular (VA) mycorrhiza, utilization of rock phosphate and nodulation were examined in three legumes (clover, Stylosanthes and Centrosema) and in onions, grown in eight P‐deficient soils ranging from pH 8.1 to 5.3. Irrespective of pH, inoculation with VA endophytes increased P uptake in all host plants in all the soils when the indigenous endophytes had been removed by irradiation, but appreciable increases in plant dry weight only occurred when P concentrations of the uninoculated plants were low, generally below 0.15%. In the acid soils adding rock phosphate generally improved growth of the non‐mycorrhizal plants and inoculation with VA endophytes greatly improved its utilization. The effects persisted when the soil was used a second time. In neutral and alkaline soils rock phosphate was unavailable to non‐mycorrhizal plants and remained so after inoculation with VA endophytes.

Legumes inoculated with the appropriate Rhizobium strain only nodulated in the most P‐deficient soils when they were also mycorrhizal, and added rock phosphate greatly improved nodulation and nitrogen fixation of the mycorrhizal plants. Some pilot experiments in unsterile soils are also described and the bearing of these results on field inoculation with VA endophytes is discussed.
‘STALAGMIFORM’ ROOTS IN LIMESTONE CAVES
Authors: LAMONT BYRON B. , LANGE B. J.
Published: May 2006

‘Stalagmiform’ roots are here defined as dense, stalagmite‐like aggregations of roots and rootlets which protrude from the sandy floor of certain limestone caves. Paper chromatography showed these structures were associated with large trees of Eucalyptus gomphocephala growing above the caves. They seem to form in response to localized abundance of water at sites beneath drip‐points in the cave ceiling.

The anatomy of ectomycorrhizal and non‐infected stalagmiform rootlets was similar to that of Eucalypt rootlets. Non‐pathogenic endophytes were also often present, giving many rootlets an endomycorrhizal character. This unusual combination of features places the stalagmiform root in a separate category from other specialized root structures.
SEQUESTRATION OF CYTOPLASMIC ORTHOPHOSPHATE BY MANNOSE AND ITS DIFFERENTIAL EFFECT ON PHOTOSYNTHETIC STARCH SYNTHESIS IN C3 AND C4 SPECIES
Authors: HEROLD A. , LEWIS D. H. , WALKER D. A.
Published: May 2006

Leaf tissues from many C3 species respond to exogenous mannose in the light by a marked stimulation of starch synthesis. This is attributed to a decreased movement of triose phosphate from the chloroplast following sequestration of cytoplasmic orthophosphate as mannose phosphate and interference with the phosphate translocator. By contrast, in most C4 species, feeding of mannose inhibits starch synthesis. It is concluded that, in these plants, the principal effect of sequestration of orthophosphate is interference with the regeneration of the CO2‐acceptor.
HORMONES IN PLANTS BEARING NITROGEN‐FIXING ROOT NODULES: THE DISTRIBUTION OF CYTOKININS IN VICIA FABA L.
Authors: HENSON I. E. , WHEELER C. T.
Published: May 2006

Cytokinin activity in extracts of nodules, roots, stems and leaves of Vicia faba L. was estimated using the soybean callus bioassay. High levels of cytokinins were present in nodules and leaves while the amounts detected in roots and stems were much lower. Cytokinin levels in the root nodules were as much as twelve to thirteen times those detected in the roots.

At least three kinds of cytokinins were present in the plant, two of which had similar chromatographic properties to the cytokinin zeatin and its riboside. The third cytokinin had properties which distinguished it from any of the known cytokinins. This peak was predominant in the leaves while the zeatin riboside‐like peak was the main cytokinin detected in the root nodules and roots.
DAILY PATTERNS OF SHOOT ELONGATION IN PINUS RADIATA AND EUCALYPTUS REGNANS
Authors: CREMER K. W.
Published: May 2006

Diurnal patterns of shoot elongation, obtained by mechanical growth recorders, were compared with those of leaf elongation and stem radius; the relationships of these to environmental factors were studied in the field and in growth chambers.

In sunny weather, minimal elongation (or shrinkage) occurred during the mornings, and maximal elongation rates during late afternoons. On rainy days, elongation patterns tended to be undefined.

The observed patterns appeared related to diurnal changes in water balance, air temperature and light. There was no evidence of an endogenous rhythm. Rising evaporative demand during sunny mornings resulted in contractions in shoot and leaf lengths and in the thickness of the stem live bark. Re‐expansion occurred in the evening and at night, or during the day when evaporative demand was reduced by cloud cover and rain. Shoots also contracted on frosty nights, but expanded rapidly following thawing early in the mornings. Temperature also positively influenced growth (i.e. irreversible increase in size). Light appeared to inhibit shoot growth in the mornings, but this effect was confounded with the tendency of shoots to shrink in length due to dehydration.

Since growth and reversible changes in shoot length often occurred simultaneously in different portions of the same shoot and since the zones of reversible change and growth overlapped, the measurement and analysis of hourly growth responses can be complicated; a distinction must therefore be made between growth (which is irreversible) and elongation (which may include both growth and reversible changes in shoot length).
SCANNING ELECTRON MICROSCOPIC OBSERVATIONS ON THE GAMETOPHYTE AND SPERM OF THE BRACKEN FERN, PTERIDIUM AQUILINUM (L.) KUHN
Authors: ELMORE H. W. , ADAMS R. J.
Published: May 2006

The three‐dimensional structure of the gametophyte and sperm of the bracken fern is described. The sperm consists of a body with approximately three gyres and approximately forty cilia. The cilia are attached to the anterior end and oriented in a latero‐posterior fashion.
THE ORIGINS OF ASPLENIUM CRETICUM AND A. HAUSSKNECHTII
Authors: BROWNSEY P. J.
Published: May 2006

Cytogenetic evidence from experimental hybrids is presented to show that Asplenium haussknechtii, a widespread fern of Asia Minor, is an allotetraploid species which has originated from hybridization between the two diploid species, A. aegaeum and A. ruta‐muraria subsp. dolomiticum. The morphology of the three species is consistent with this hypothesis. Cytogenetic evidence from other experimental hybrids indicates that A. creticum, a fern endemic to Crete, is also allotetraploid, sharing one parent with A. haussknechtii and having A. viride as its second parent. Morphological evidence confirms that A. creticum is most likely to have arisen from hybridization between A. viride and A. aegaeum. Elucidation of the parentage of these two species means that the evolutionary origins of all the tetraploid species of Asplenium known from continental Europe have now been determined. The origins of these species and the development of the Asplenium flora of Crete are discussed in relation to the Pleistocene glaciations.
A NOTE ON THE EVOLUTIONARY STATUS OF ALUMINIUM‐ACCUMULATORS AMONG DICOTYLEDONS
Authors: CHENERY ERNEST M. , SPORNE KENNETH R.
Published: May 2006

Among dicotyledons, the ability to accumulate large quantities of aluminium is statistically corre;ated with seven primitive characters. It is especially common among those families that were present in the early fossil history of the group and among tropical rain‐forest families. it is concluded, therefore, that aluminium‐accumulation is itself a primitive character.
UNCOUPLING OF ELECTRON TRANSPORT BY ANIONIC QUINONOID REDOX INDICATOR DYES
Authors: HILL R. , CROFTS A. R. , PRINCE R. C. , EVANS E. HILARY , GOOD N. E. , WALKER D. A.
Published: May 2006

A considerable range of oxidation‐reduction dyes has been studied with reference to reactions with illuminated chloroplast preparations. Experimental methods included dye‐mediated H+‐and H‐transfer across liposome membranes, comparison of increase in the uncoupling properties with increase of substituting halogen atoms and effect of halogen substitution on distribution of anion between water and octanol. In the absence of halogen substitution a relatively high concentration of a dye is needed for significant uncoupling. Introduction of the sulphonic group ‐SO3Na abolishes the uncoupling effect even in presence of halogen substitution.
ION UPTAKE IN RELATION TO THE DEVELOPMENT OF A ROOT HYPODERMIS
Authors: FERGUSON I. B. , CLARKSON D. T.
Published: May 2006

The suberization of the outer cortical cells in the basal zones of maize roots to form a hypodermis reduced the radial movement of phosphate towards the stele. Suberization of these cells appeared to place a far greater restriction on the translocation of phosphate to the shoot than the suberization of the endodermis. Under the same conditions as were used for growing maize, barley roots did not develop a hypodermis, and phosphate movement from the basal zones of the root axes was not restricted.
THE DISTRIBUTION OF THE PROTEIN PHASEOLIN IN THE INTACT PLANT AND CULTURED TISSUES OF PHASEOLUS VULGARIS L.
Authors: FRAME R. , WHEELER C. T. , BOWES B. G. , STEWART‐TULL† D. E. S.
Published: May 2006

Analysis of the salt‐soluble protein extracts of leaves, stems, roots, cultured roots and callus tissue derived from the cotyledons of the developing seed show that only the intact plant roots synthesize a protein immunologically similar to the seed storage protein, phaseolin.
ECOLOGICAL PHYSIOLOGY OF THE LICHEN HYPOGYMNIA PHYSODES
Authors: FARRAR J. F. , SMITH D. C.
Published: May 2006

When air‐dry thalli of Hypogymnia physodes are immersed in water, four main features characterize the rewetting phase. (1) There is an immediate and substantial release of gas, the‘wetting burst’. Although the released gas appears to be mostly CO2, it is non‐metabolic in origin and probably the result of a previous adsorption of gas onto polysaccharide sheaths surrounding fungal hyphae. (2) There is a period of 1‐2 h increased respiration,‘resaturation respiration’, which, unlike basal respiration, is cyanide‐sensitive. The cause of resaturation respiration remains obscure, but could result from exposure of respiratory substrate to enzymes from which they are normally separated. (3) There is a brief period (1–2 min) in which there is a rapid loss of organic and inorganic solutes from the thallus. Since water is a structural component of membranes, removal of some of this water during drying probably caused increased permeability so accounting for the losses observed. (4) There is a very rapid recovery of processes including photosynthesis and nutrient uptake. Even 10 s after rewetting, incorporation of 32P was 60% inhibited by DNP.

The ecological significance of these features is discussed, particularly in relation to the apparent need of many lichens for periodic drying.
CONTROL BY THE EMBRYOSAC OVER POLLEN TUBE GROWTH IN THE STYLE OF THE AVOCADO (PERSEA AMERICANA MILL.)
Authors: SEDGLEY M.
Published: May 2006

In experiments studying pollination of avocado it was observed that an average of sixty‐six pollen grains germinated on the stigma. The tubes penetrated the stigma but about half developed swollen tips and proceeded no further than the base of the stigma. Reduction in tube number continued until between approximately half and three‐quarters of the way down the style (1.75–2.5 mm) a single tube remained to reach the ovary containing a single embryosac. In 50% of the ovaries observed two embryosacs were present in the one ovule and 18% of these attracted two pollen tubes. Control by the embryosac over pollen tube growth is suggested.
GENECOLOGICAL STUDIES OF LEAD TOLERANCE IN GROUNDSEL (SENECIO VULGARIS L.)
Authors: BRIGGS D.
Published: May 2006

Soils from a range of native British habitats for Senecio vulgaris L. have been found to contain significantly different amounts of lead ranging from several hundred parts per million along roadsides and on rubbish dumps to minute quantities in coastal sandy soils. Root growth of seedlings in simple water culture revealed different degrees of tolerance between topodemes to soluble lead, apparently related to the lead content of the soil. Studies of root growth in a range of native soils suggest a more complex relationship between growth and lead content. The genecological implications of these findings are discussed, including the possibility that lead‐tolerant roadside variants may be of recent origin.
STUDIES IN THE VEGETATIONAL HISTORY OF MID WALES
Authors: HANDA S. , MOORE P. D.
Published: May 2006

The basal sediments of three pingo basins from the valleys of the Cledlyn and Cletwr in west Wales have been analysed palynologically. The basal pollen‐bearing deposits indicate that sedimentation began in all three basins at a time prior to the invasion of trees and before the initial expansion of Juniperus at the opening of the Flandrian. Radiocarbon dating confirms that the subsequent Juniperus peak is early Flandrian in age rather than belonging to the Allerød interstadial. The vegetational succession documented at the three sites allows a reconstruction of both regional and local developments during the transition from late‐Devensian to Flandrian times. These events broadly resemble those described for other parts of mid Wales, but with certain, notable differences. These sites in the Teifi Valley system have very low proportions of montane and arctic‐alpine types represented in their pollen records; this contrasts markedly with the site previously described from the uplands at Elan Valley. Also they do not give indication of the early Corylus rise which occurred just 20 km north at Gwarllyn. The likely explanation for this is that invasion and spread of Corylus was localized in what is now the Cardigan Bay area and pollen derived from this early expansion was carried to the exposed Mynnedd Bach area, but did not penetrate south‐eastwards into the Teifi Valley region. Evidence from these sites suggests that Pinus sylvestris and Alnus glutinosa were established locally in the area soon after the demise of Juniperus.

In addition to providing data on vegetational history in this area, these studies also supply information concerning the origin and decay of pingos during late‐Devensian times. The fact that the basal sediments predate the Juniperus rise demonstrates that the melting of the pingo ice cores and the collapse of their domes occurred before temperatures were high enough to allow Juniperus to attain its maximum flowering potential. This in turn would indicate that pingo ice melt has a lower temperature threshold than Juniperus flowering and that the threshold was therefore crossed first. This being so, it is reasonable to deduce that the pingos could not have survived the late‐Devensian interstadial (Allerød), for during it, even in the uplands, the Juniperus flowering threshold was crossed. All of the pingos examined, therefore, appear to have formed and decayed during the post‐interstadial cold phase (Godwin's zone III).
THE DISTRIBUTION OF EUROPEAN PTERIDOPHYTES: A NUMERICAL ANALYSIS
Authors: BIRKS H. J. B.
Published: May 2006

The distribution of 144 species of pteridophyte in sixty‐five areas within Europe was analysed by minimum‐variance cluster analysis and principal co‐ordinates analysis. Fifteen floristic regions and twenty‐one floristic elements were delimited, and the distribution and composition of these are described. Inter‐relationships between the elements and regions are demonstrated, and the major floristic divisions revealed within Europe are discussed. Possible ecological and historical causes for these patterns are considered.
FACTORS AFFECTING THE REDUCTION OF ACETYLENE BY ROOT NODULES OF LUPINUS SPECIES
Authors: TRINICK M. J. , DILWORTH M. J. , GROUNDS M.
Published: May 2006

A number of parameters affecting acetylene reduction by root nodules of Lupinus angustifolius, L. cosentinii and L. luteus have been studied.

Acetylene reduction could be satisfactorily measured in air provided a sufficiently high pC2H2 was used. However, evacuation of air from containers was not harmful to the nodule system. The maximal rate of acetylene reduction occurred at 23°C but the rate was hardly less at 33°C. Plant age had a marked effect upon the rate of acetylene reduction in its nodules. Rates of acetylene reduction in nodules were maintained at high levels after the onset of flowering but rapid reduction in nodule activity occurred after pods were filled. Decapitation of plants had little or no effect on acetylene reduction by the nodules, but removal of the nodules reduced their activity by 70–85%. Brief rinsing of the nodules and rapid drying with blotting paper had little effect on their acetylene reducing activity, but prolonged wetting markedly decreased it.

Nodulated roots and whole plants responded similarly to pO2. Acetylene reduction was zero in the absence of oxygen, increased to a maximum rate by 0.2–0.25 atm O2, remained constant up to 0.4–0.5 atm O2, and then declined sharply to nearly zero at 0.9 atm.

We detected no diurnal rhythm, attributable to effects of light on supply of photosynthate, with any of the three species.
THE INVOLVEMENT OF FLAVOUR VOLATILES IN THE RESISTANCE TO DOWNY MILDEW OF WILD AND CULTIVATED FORMS OF BRASSICA OLERACEA
Authors: GREENHALGH J. R. , MITCHELL N. D.
Published: May 2006

The possible involvement of flavour volatiles in the resistance of Brassica oleracea L. seedlings to cabbage downy mildew (Peronospora parasitica (Pers. ex Fr.) Fr.) was investigated using seedlings of a number of commercial Brassica oleracea cultivars. Flavour volatiles are primarily released as a result of tissue damage in brassicas. Only one cultivar tested was resistant to the disease and its tissue macerates yielded the greatest concentration of volatiles. One of these compounds, allyl isothiocyanate, proved to be highly toxic to the pathogen and was produced in much greater concentrations in macerates of cotyledon than first leaf tissue. The ability of seedlings to produce allyl isothiocyanate in large amounts following tissue damage may inhibit the growth of Peronospora parasitica in resistant seedlings. Wild populations of Brassva oleracea L. subsp. oleracea (wild cabbage) were also tested for disease resistance, and the highest proportions of resistant seedlings were found in those populations containing high levels of flavour volatiles. The longest established wild populations possessed the highest average concentrations of flavour volatiles, and it is suggested that selective breeding has resulted in a reduction in the amounts of these compounds in cultivated forms. This change may be a contributory factor towards the lack of resistance shown by modern cultivars.
CELL PRODUCTION BY ROOT CAPS
Authors: CLOWES F. A. L.
Published: May 2006

Four independent methods show that the cell‐doubling time of the first tier of cap initials is about 10 h in roots of Zea growing at 23°C. By the fourth tier the cell‐doubling time lengthens to about 90 h due to cells going out of cycle though these can go on synthesizing DNA. The first four tiers produce enough cells to renew the cap in from 22 to 33 h. This high rate of cell production is confirmed by observing the transit of cells marked by caffeine along the length of the cap. Although some cells reach the tip of the cap quickly, others remain within the meristem for 24 h without dividing. The results are discussed in relation to work on other plants and to the anomalous cell cycles of the cap meristem of Zea.
AN ANALYSIS OF COMPETITIVE ABILITY IN THREE PERENNIAL GRASSES
Authors: MAHMOUD A. , GRIME J. P.
Published: May 2006

Competitive interactions between three perennial grasses of contrasted ecology were investigated using an experimental design which permitted measurement of the effects of paired species upon each other. Under productive conditions, each pairing resulted in the total elimination of one species and the order of competitive ability was Arrhenatherum elatius > Agrostis tenuis > Festuca ovina. Under conditions of severe nitrogen stress, the impact of competition upon yield was reduced but the order of competitive ability was unaffected. The results suggest (1) that competitive abilities above and below ground are interdependent and covariable and (2) that the ability to compete for mineral nutrients may be of relatively minor importance in the adaptive physiology of species colonizing very infertile soils.
SOME EFFECTS OF THREE HERBICIDAL AUXINS ON STOMATAL MOVEMENTS
Authors: PEMADASA M. A. , JEYASEELAN K.
Published: May 2006

Summary

The effects of 2, 4‐dichlorophenoxyacetic acid (2,4‐D), 2, 4,5‐trichlorophenoxyacetic acid (2,4,5‐T) and 2‐methyl‐4‐chlorophenoxyacetic acid (MCPA) on stomatal opening on illumination of excised, turgid leaves of Stachytarpheta indica were studied by microscopic examination of epidermal strips fixed in absolute ethanol. All three herbicides prevented wide opening of stomata and accumulation of potassium in the guard cells; hydrolysis of stomatal starch was hindered by 2, 4,5‐T and MCPA and hastened by 2, 4‐D. Carbon dioxide‐free air was effective in compensating substantially the effects of 2, 4,5‐T and MCPA but not of 2, 4‐D. It is concluded that 2, 4,5‐T and MCPA arrest light‐induced stomatal opening partly by disturbing the carbon dioxide balance in the leaf and partly by hindering starch hydrolysis and potassium accumulation in the guard cells, whereas 2, 4‐D appears to exert a more direct effect, probably by affecting the membrane permeability, on guard cells although inhibition of potassium accumulation may also be partly involved in its action.
SUCCULENCE, CATIONS AND ORGANIC ACIDS IN LEAVES OF KALANCHOE DAIGREMONTIANA GROWN IN LONG AND SHORT DAYS IN SOIL AND WATER CULTURE
Authors: PHILLIPS R. D. , JENNINGS D. H.
Published: May 2006

Summary

Leaves of Kalanchoe daigremontiana grown in short days in John Innes compost possessed a higher water content per unit dry weight than leaves of similar age from long‐day plants. For both treatments, the older the leaf the greater the water content. The effect of short days was to reduce dry weight production. When plants were grown in water culture, the differences were less marked and there was no significant difference in water content between leaves on the same plant. It is believed that, in water culture, the plants were not subjected to so large a water stress. Calcium was the major cation in the leaf, with a concentration some three to seven times that of potassium. The concentration of sodium was low but, under certain conditions, dry weight production was reduced when this cation was not added to the medium. The total concentration of organic acids never exceeded 210–230 μquiv. cm−3, if the total concentration of calcium, potassium and sodium did not also reach this value. Above this concentration an increase in total acid was accompanied by an equivalent increase in the total concentration of the three cations. Such an increase was only observed in long‐day plants. The results are discussed in relation to the control of dark fixation in CAM plants.
UPTAKE AND METABOLISM OF INSECT METABOLITES BY LEAVES AND TENTACLES OF DROSERA SPECIES
Authors: CHANDLER G. E. , ANDERSON J. W.
Published: May 2006

Summary

When insects (Drosophila melanogaster) were supplied with [35S]sulphate, methionine sulphoxide, cysteine, cysteic acid and taurine became labelled. When the insects were applied to the leaves of Drosera hinata, label in the plant was associated with methionine sulphoxide, cysteine, cysteic acid and sulphate but not taurine. Application of [35S]sulphate to the leaves of D. binata produced a similar labelling pattern except that cysteic acid was not labelled. There were some differences in sulphur metabolism between axenic cultures and field grown plants; axenic cultures, for example, did not incorporate 35S‐label into methionine sulphoxide.
VESICULAR‐ARBUSCULAR MYCORRHIZA IN SOME NIGERIAN SOILS AND THEIR EFFECT ON THE GROWTH OF COWPEA (VIGNA UNGUICULATA), TOMATO (LYCOPERSICON ESCULENTUM) AND MAIZE (ZEA MAYS)
Authors: SANNI SHERIFF O.
Published: May 2006

Summary

Spores of fungi forming vesicular‐arbuscular mycorrhiza were collected from Ibadan, Iwo and Egbeda series at the experimental plots of Federal Department of Agricultural Research, Moor Plantation, Ibadan. These were used to inoculate cowpea, maize and tomato. The presence of vesicular‐arbuscular mycorrhiza was detected in the roots of these plants after a few weeks of growth. Dry weights of roots and shoots, and total P and N were determined. There was a positive correlation between the presence of vesicular‐arbuscular mycorrhiza and the amounts of P and N in the tissues.
VESICULAR‐ARCUSCULAR MYCORRHIZA IN SOME NIGERIAN SOILS: THE EFFECT OF GIGASPORA GIGANTEA ON THE GROWTH OF RICE
Authors: SANNI SHERIFF O.
Published: May 2006

Summary

Azygospores of Gigaspora gigantea isolated from soil in Moor Plantation area were used to inoculate rice in a glasshouse experiment. There was a positive correlation between the presence of vesicular‐arbuscular mycorrhiza, the numbers of spores in individual root system and the growth of rice. Better growth was observed in mycorrhizal plants than either control or treatment with strengite alone.
FUNGAL POLYOL METABOLITES IN THE CONTROL OF CARBOHYDRATE METABOLISM OF MYCORRHIZAL ROOTS OF BEECH
Authors: WEDDING RANDOLPH T. , HARLEY JOHN L.
Published: May 2006

Summary

Eight enzymes concerned with carbohydrate metabolism, extracted and partially purified from mycorrhizal roots of beech, were studied to determine the possible role of a number of sugar alcohols (polyols) as effectors for the carbohydrate metabolism of the roots.

Various patterns of inhibition of these enzymes by different polyols were found. Mannitol and threitol were the most effective of the polyols studied in terms of the number of enzymes affected and the apparent inhibition constants for the affected reactions. None produced an activation of the enzyme reactions.

The possible significance of these enzyme inhibitions as indicating ways in which the presence of the sheath of fungal mycelium may alter the utilization of carbohydrate in the tree and result in translocation to the symbiotic fungus, and the relation of these findings to the known characteristics of mycorrhizas are discussed.
THE PHYSIOLOGY OF SYMBIOSIS IN GOODYERA REPENS
Authors: PURVES S. , HADLEY G.
Published: May 2006

Summary

In asymbiotic culture, Goodyera repens germinated and grew well in the presence of 1% glucose and potato extract. Growth on trehalose, a fungal sugar, was comparable with that on glucose. Infected protocorms which grew best on a cellulose carbon source were larger than asymbiotic ones on all media tested.

Asymbiotic protocorms grew slowly and acquired high levels of starch while infected material grew rapidly without accumulating starch. When starch‐rich protocorms were infected, their starch became depleted while their growth rate increased, indicating that the fungus suppressed starch synthesis by its host.

When green plantlets were fed with 14CO2, infected plantlets showed greater incorporation into insoluble substances than did asymbiotic ones.
SEASONAL VARIATION IN THE SECONDARY PHLOEM FROM THE MAIN TRUNKS OF WILLOW AND SYCAMORE TREES
Authors: LAWTON JUNE R.
Published: May 2006

Summary

The structure of the phloem near to the cambium is described for mature trees of Salix fragilis L. and Acer pseudoplatanus L. Changes in the structure of the phloem were investigated by light and electron microscopy. Measurements of the dimensions of the sieve tube elements show that those formed during the winter months are small in diameter and that the area of phloem formed from June to September is greater and the diameter of the individual sieve tubes larger. In both species there are some sieve tubes close to the cambium with open pores in the sieve plates throughout the year. The extent of callose deposition of the sieve plates, as shown by u.v. fluorescence microscopy, can be correlated with the age of the sieve tubes. The sieve plates in Acer are simple and those in Salix, compound and very oblique. The depth of phloem showing callose fluorescence changes during the year. There is an increase in the depth of phloem with open pores on the sieve plates through to September in both Willow and Sycamore, which can be correlated with a natural increase in temperature and day length.
RADIOCARBON DATING OF FLANDRIAN POLLEN ZONES IN WALES AND NORTHERN ENGLAND
Authors: HIBBERT F. A. , SWITSUR V. R.
Published: May 2006

Summary

The boundaries of Flandrian pollen assemblage zones at three sites within the British Isles have been dated by the radiocarbon method and corresponding zones have been found to exhibit a broad synchroneity. The mean sedimentation rates for the deposits fall within the range for other British and north European sites.
CYTOKININS IN XANTHIUM STRUMARIUM L.: SOME ASPECTS OF THE PHOTOPERIODIC CONTROL OF ENDOGENOUS LEVELS
Authors: HENSON I. E. , WAREING P. F.
Published: May 2006

The effects of photoperiod on cytokinin levels in Xanthium strumarium L. were examined using a single photoperiodic cycle. Increasing the night length from 6 to 16 h resulted in a progressive decline in cytokinin levels in leaf laminae and buds. Interruption of a 16‐h dark period midway by either a 5‐ or 60‐min light‐break at least partially negated the depressive effect of the dark period on cytokinin levels. All peaks of cytokinin activity were similarly affected by short day treatment. The reduction of cytokinin levels in response to a long dark period was dependent upon the presence of leaves greater than 1.0 cm in length but not upon the presence of buds. While exposure of the entire plant to a single long dark period led to a marked reduction in cytokinin levels in the leaf laminae, no such reduction was apparent in leaves which were exposed individually to a long night (with the rest of the plant, including the majority of the leaves, left in long day). The latter treatment did, however, lead to a partial reduction in the cytokinin flux from the detopped root system. Bark ringing of the stem between roots and leaves prior to photoperiodic treatment largely prevented the short day‐induced decline in cytokinin levels in both leaf laminae and root exudate. These results are taken to indicate the existence of a shoot‐to‐root signal capable of moderating cytokinin production in the root system.
THE CONTRIBUTION OF CURRENT PHOTOSYNTHESIS TO GROWTH AND DEVELOPMENT IN THE TULIP DURING FLOWERING
Authors: HO L. C. , REES A. R.
Published: May 2006

Leaves of tulip plants were treated with 14CO2 on three occasions during flowering, one week apart–at the bud stage, at early flowering and when flowers were fully opened. The amount of 14C fixation was examined 5 min after a pulse application of 14CO2 and the organic carbon and 14C contents of various organs were examined 24 h later.

Total carbon in the mother‐bulb scales fell over 14 days to only 40% of the initial value, whilst that of all new organs increased by 71%. A negligible amount of 14C was recovered from scales or from roots. The 14C recovered from the flower and stem accounted for 83% of 14C exported from leaves at the early flowering stage. The total carbon content of the daughter bulbs increased uniformly with time but the 14C recovered from the daughter bulbs was initially smail but increased to 59% of the exported 14C when the flower was fully opened.

The imported 14C in flower and stem was mainly recovered from the soluble and residual (non‐starch, insoluble) fractions, whilst that in daughter bulbs was from the soluble and starch fractions. The amount of 14C lost by respiration fell from 20% to 10% of initial 14C uptake over the 3‐week period.
FURTHER OBSERVATIONS ON STOMATAL RESPONSES TO SODIUM AZIDE
Authors: PEMADASA M. A. , JEYASEELAN K.
Published: May 2006

Stomatal responses to different concentrations and durations of azide treatment were investigated by microscopic examination of epidermal strips of Stachytarpheta indica fixed in absolute ethanol. Both opening on illumination and closure on darkening of turgid leaves were suppressed by azide, which also arrested starch hydrolysis and accumulation of potassium in the guard cells in light, and starch synthesis and disappearance of stomatal potassium in the dark. The magnitude of the azide effect is a function of concentration and duration of the treatment. Carbon dioxide‐free air was effective in partly reversing the azide effect. It is concluded that azide suppresses stomatal movement partly by disturbing the carbon dioxide balance in the leaf and partly by hindering starch metabolism and transfer of potassium ions across the guard cell membranes.
AN INVESTIGATION OF THE FUNCTIONAL PHLOEM IN WILLOW
Authors: LAWTON JUNE R.
Published: May 2006

Distribution of dyes, 14C, and the position of aphid stylets in the phloem of rooted 2 year cuttings and a standing tree of Salix fragilis correlate with callose formation on the sieve plates. It is suggested that the region concerned with translocation is that portion of the phloem near the cambium, where callose is formed on the sieve plates. During July this region is within the first lignified fibre band where there are sieve tubes in all stages of development, from recently differentiated to those in which definitive callose covers the sieve plate. The majority of sieve tubes in the area have open sieve pores with callose between the pores, and with sparse fibrillar or vesicular cytoplasm.
THE ECOLOGICAL SIGNIFICANCE OF ‘HALOPHYTES’ IN THE DEVENSIAN FLORA
Authors: ADAM PAUL
Published: May 2006

The botanical evidence for the presence of inland saline areas during the Devensian (last glacial) stage is considered. It is suggested that this evidence need not be interpreted as demonstrating the existence of saline conditions. Aspects of the present day ecology of some of the species regarded as halophytic are discussed and alternative hypotheses to explain their occurrence under full glacial conditions are advanced.
STOMATAL RESPONSES TO 2,4‐DINITROPHENOL
Authors: PEMADASA M. A. , KORALEGE S.
Published: May 2006

The effect of 2,4‐dinitrophenol (DNP) on stomatal movement in excised, turgid leaves of Stachytarpheta indica was investigated by microscopic examination of the abaxial epidermis. DNP prevented wide opening on illumination and closure in the dark, and affected concurrent changes in stomatal starch and potassium concentration in the guard cells. Carbon dioxide‐free air failed to reverse the DNP effect. The effect of DNP is attributed largely to its inhibition of hydrolysis of stomatal starch and of active transport of potassium ions to and from the guard cells. The possibility that DNP affects the energy supply for stomatal movements through its inhibition of oxidative phosphorylation is briefly discussed.
ULTRASTRUCTURE OF TACTILE PAPILLAE ON TENDRILS OF ECCREMOCARPUS SCABER R. ET P.
Authors: JUNKER STEFFEN
Published: May 2006

The ultrastructure of the tactile papillae on tendrils of Eccremocarpus scaber was studied. The protoplast is highly vacuolated. Ovoid osmiophilic bodies are regularly scattered between cell wall and plasmalemma. The cytoplasm is rich in organelles, especially endoplasmic reticulum, dictyosomes, golgi vesicles and mitochondria. Chloroplasts contain poorly developed grana. Abundant plasmodesmata were observed in the walls between tactile papillae and epidermal cells and in the anticlinal epidermal cell walls. The possible functional significance of these structures is discussed.
THE ROLE OF ANABAENA IN THE AZOLLA‐ANABAENA SYMBIOSIS
Authors: HILL D. J.
Published: May 2006

The Anabaena cells in Azolla undergo a developmental pattern of differentiation parallel to that of the fern. At the apex, the algal cells are small and rapidly dividing, and do not fix atmospheric nitrogen. After the leaf cavities are colonized, the algal cells form heterocysts, fix nitrogen and the vegetative cells enlarge considerably. The synchrony between the two partners appears to break down under certain environmental conditions leading to alga‐free fern fronds.