bluuebunny/crossref_metadata_2025 huggingface dataset:
THE SIGNIFICANCE OF ACIDIC LICHEN SUBSTANCES IN THE ESTIMATION OF CHLOROPHYLL AND PHAEOPHYTIN IN LICHENS
Authors: BROWN D. H. , HOOKER T. N.
Published: May 2006

Acidic lichen substances are shown to be responsible for degrading extracted chlorophyll to phaeophytins in certain species of lichens and a method is proposed for eliminating this error during pigment extraction. The proposed extraction and measurement method is applied to lichens that have been maintained in either dry or deep frozen conditions.
POLLEN SPECTRA FROM PLIOCENE CRAG AT ORFORD, SUFFOLK
Authors: ANDREW R. , WEST R. G.
Published: May 2006

A pollen diagram from the pre‐Pleistocene marine sediments near Orford, Suffolk, shows the presence of a forest flora, mainly coniferous, with a number of exotic genera of Eastern Asian/North American affinity, including Sequoia‐type, Sciadopitys and Taxodium‐type. It is suggested that this pollen assemblage may be Brunssumian (Lower Pliocene) in age.
THE EFFECT OF COTYLEDONS ON CHLOROPLAST DEVELOPMENT IN PRIMARY LEAVES OF PHASEOLUS VULGARIS
Authors: WHATLEY JEAN M.
Published: May 2006

When seeds of Phaseolus vulgaris are allowed to develop normally in fruits on the mature plant, the plastids in the primary leaves of the embryo within the seed do not develop into mature chloroplasts. However, when the developing seeds are removed from the parent plants, the cotyledons detached, and the embryonic axes grown on agar, primary leaf plastids differentiate into mature chloroplasts within 7 days. In embryos with attached cotyledons, and similarly grown for a week on agar, plastids fail to differentiate.

In primary leaves of dormant seeds allowed to germinate on agar, lamellar development begins earlier in seedlings from which the cotyledons have been removed than in those with attached cotyledons, although there is no significant difference between the two groups of seedlings in the time required for the chloroplasts to become fully mature. Plastid differentiation in primary leaves of developing seeds of Phaseolus therefore appears to be inhibited initially by the presence of the cotyledons. This inhibitory effect apparently declines during seed ripening and dormancy.
COMPARTMENTALIZATION IN THE COTYLEDONARY CELLS OF PHASEOLUS VULGARIS L. SEEDS: A DIFFERENTIAL SEDIMENTATION STUDY
Authors: PUSZTAI A. , CROY R. R. D. , GRANT G. , WATT W. B.
Published: May 2006

The appearance and the yield of sedimentable organelles from the cotyledons of Phaseolus vulgaris L. were measured with respect to the influence of the method of homogenization, the choice of dry or imbibed seeds, and the composition and the concentration of the homogenization medium. Sucrose, (0.2–0.8 M), the addition of Mg2+ (2 × 10−4M) or EDTA (3 × 10−3M) or the replacement of sucrose with mannitol made little difference to the average size distribution or the amount recovered of the 21 000 gav× 10 min pelleted organelles, the main protein body‐containing fraction of the homogenate. Slicing the imbibed seeds with a razor blade or by a mechanical rotary cutter combined with a short extraction was the gentlest and the most efficient method for the production of organelles. Cell homogenates were fractionated on the basis of size by differential sedimentation into several subcellular fractions. These included a residue, starch particles (300 g× 10 min), a main protein body fraction (21 000 gav× 10 min), 38 000 gav× 60 min pellets, 78 000 gav× 240 min pellets and a final supernatant. The activity in these fractions of several catabolic enzymes was measured. Most of the activity of the acidic nucleases, amylases, the BAPA‐ase and a substantial part of the acidic phosphatase and the cathepsin A‐type enzyme(s) were found in the supernatant, while no specific DNA‐ase was found in these seeds. Protein bodies contained some of the trypsin inhibitors and most (if not all) of the lectins and Glycoprotein II. Most of the endopeptidase (azoproteinase) activity of the cotyledons appeared to be tightly bound to the cell walls or to other insoluble structural elements. Protein bodies and other intracellular organelles had very little autolytic activity and, thus, the main storage proteins of the seed were not degraded during the first 4 days of germination.
EXPERIMENTAL ALTERATION OF SOIL MICROBIAL POPULATIONS FOR STUDYING EFFECTS ON HIGHER PLANT INTERACTIONS
Authors: NEWMAN E. I. , CAMPBELL R. , ROVIRA A. D.
Published: May 2006

In order to investigate how soil microorganisms can affect the balance between higher plants growing together, it would be desirable to have soils similar in chemical properties but differing microbially, and to be able to maintain differences for several months without special isolation techniques. Two methods for achieving this were tried. Firstly, soil was fumigated with two different chemicals, chloropicrin and methyl bromide. The second method was to sterilize the soil by γ‐irradiation and then add contrasting inocula, either seed‐washings, soil bacterial suspension or total soil inoculum. After treatment, the soils were placed in pots in a glasshouse. Lolium perenne, Rumex acetosa and Trifolium repens were grown on them, separately and in two‐species mixtures.

The fumigation method proved unsatisfactory since the two treated soils differed significantly in ammonium content but only slightly in microbial abundance. The three inoculum treatments following irradiation resulted in large differences in abundance of various microbial groups, and some of the differences were still present after four months; ammonium contents of the three soils differed only slightly, though all three had much more ammonium than the untreated soil.

Fumigation increased the growth of all three species in monoculture to about an equal extent but, in the two‐species mixtures, it altered the balance in favour of Lolium against Rumex and Trifolium, and in favour of Rumex against Trifolium. Irradiation increased the growth of Lolium but reduced the growth of Trifolium. Among the three inoculum treatments, all three species in monoculture showed faster growth with total soil inoculum than with seed inoculum in the early stages but the difference disappeared later. Following irradiation, the balance between species in mixtures was much as expected from monoculture growth; the one exception was Lolium v. Rumex, where bacterial inoculum gave a balance more in favour of Lolium than would be expected.
POLLEN TRANSFER AND POLLINATION IN THE COMMON FIG (FICUS CARICA L.)
Authors: GALIL J. , NEEMAN G.
Published: May 2006

The traditional ideas, as to how pollination is achieved in the common fig (Ficus carica L.), are untenable because the very narrow entrance slits of the ostiole render it very difficult for the pollen vector (the agaonid wasp Blastophaga psenes L.) to introduce pollen on its body surface into the female receptive fig. The process is now shown to entail: (a) loading of pollen in the polleniferous fig into intersegmental and pleural invaginations which form in the shrunken body of the wasp following water loss; (b) unloading of pollen in the receptive fig, as a result of partial swelling and contortion of the wasp's body during oviposition attempts. Conditions in the cavities of polleniferous and receptive figs are discussed in connection with the pollination process.
THE POLLINATION ECOLOGY OFEPIPACTIS CONSIMILISDON (ORCHIDACEAE) IN ISRAEL
Authors: IVRI YARIV , DAFNI AMOTS
Published: May 2006

Observations on the pollination ecology ofEpipactis consimilisDon (Orchidaceae) in Israel are described. The pollinators were found to be eight species of five genera of hover files (Syrphidae), especiallySphaerophoria scriptaandS. rueppellii.

Different behaviour patterns of the insect species and the sexes thereof are given and discussed. It is suggested that the flower mimics the shape and colour of aphids and this attracts aphidophagous hover flies.
INCORPORATING CHECKS AGAINST OBSERVER ERROR INTO IDENTIFICATION KEYS
Authors: PAYNE R. W. , PREECE D. A.
Published: May 2006

A method is suggested for checking for errors that may be made when an identification (or diagnostic) key is used. Such errors may arise either from tests being incorrectly used or observed, or because the specimen examined is aberrant or incomplete. The method involves constructing a check key for each endpoint of the main key. Use of the appropriate check key confirms or corrects the initial identification.
CHANGES IN THE LEVELS OF ENDOGENOUS CYTOKININS AND INDOLE‐3‐ACETIC ACID DURING EPIPHYLLOUS BUD FORMATION IN BRYOPHYLLUM DAIGREMONTIANUM
Authors: HENSON I. E. , WAREING P. F.
Published: May 2006

Levels of endogenous cytokinins and indole‐3‐acetic acid (IAA) in mature leaves and shoot tips of Bryophyllum daigremontianum (R. Hamet and Perr.) Berg, were determined at various times following transfer of the plants from short to long photoperiods, a treatment which results in release of the epiphyllous buds from correlative inhibition. There were transient increases in levels of both cytokinins and IAA following transfer to long days. The increase in IAA levels occurred prior to the increase in cytokinins. Maximum IAA levels were present in shoot tips 5 to 10 days after transfer, while maximum cytokinin activity was not detected until after 20 long days in the case of shoot tips, and 10 to 20 long days with mature leaves. Growth of epiphyllous buds, which was restricted to the shoot tips, became apparent only after 20 long days. Levels of both cytokinins and IAA were higher in shoot tips of plants grown throughout in short days than in plants raised entirely in long days. The types of cytokinins present in the two sets of plants did not, however, appear to differ.
RATES OF TRANSLOCATION AND PHOTOSYNTHESIS IN MIMOSA PUDICA L.
Authors: HODDINOTT JOHN
Published: May 2006

Following mechanical stimulation, the leaves of Mimosa close and their photosynthetic rate declines by 40%. The translocation rate remains constant during leaf closure suggesting that blockage of transport by rapid sieve plate callose formation is not occurring. The rates of photosynthesis and translocation do not appear to be closely coupled.
A HISTOCHEMICAL INVESTIGATION OF LEAD UPTAKE IN RAPHANUS SATIVUS
Authors: LANE S. D. , MARTIN E. S.
Published: May 2006

A histochemical method was used to investigate the distribution of applied lead in the seed and seedling stage of Raphanus sativus. Lead contamination of the embryo was inhibited by the testa until it ruptured during imbibition. In seedlings, lead moved into the root cortex predominantly along the cell walls as far as the endodermis. Beyond the endodermis lead was localized extensively in the vascular tissues. There was little movement of lead from the vascular tissue into the surrounding tissue of the stem and cotyledons.
THE UPTAKE OF THIOUREA BY CHLORELLA
Authors: SYRETT P. J. , BEKHEET I. A.
Published: May 2006

Cells of Chlorella fusca grown with urea as nitrogen source take up and accumulate thiourea; ammonium‐grown cells take up thiourea more slowly. Uptake results from a metabolic process superimposed on passive diffusion. The uptake system has a high affinity for thiourea and urea. Fifty μM thiourea allows half the maximum rate of uptake. Urea inhibits competitively uptake of thiourea and, from the kinetics of inhibition, it can be concluded that the half‐saturation constant for urea is about 5 μM. Uptake of thiourea by urea‐grown organisms is not inhibited by low concentrations of nitrate or of ammonium. There is evidence that the cells metabolize thiourea to a limited extent.
THE FINE STRUCTURE OF PROCHLORON
Authors: WHATLEY JEAN M.
Published: May 2006

The fine structure is described of Prochloron, a unicellular prokaryotic alga which contains both chlorophyll a and chlorophyll b. The cell wall resembles that of a blue‐green alga. The thylakoids and cytoplasm together occupy a wide peripheral band. However, the thylakoids are present not as single lamellae, as in blue‐green algae, but in pairs or, sometimes, in thicker stacks. Both thylakoids and cytoplasm are absent from a large central zone which is generally electron‐transparent, but may contain electron‐dense granules and fibrils. The function of the central zone is not known.
AMINO ACID MOVEMENT FROM LEAVES OF TUSSILAGO FARFARA L. TO THE RUST, PUCCINIA POARUM NEILS.
Authors: BURRELL M. M. , LEWIS D. H.
Published: May 2006

The amino acids, alanine, aspartic acid, glutamic acid, glutamine and serine, were labelled when 14CO2 was supplied to leaves of Tussilago farfara. Exogenously supplied [14C] glycine, serine, cysteine and methionine are rapidly metabolized by host tissue. An isotope dilution technique was used to investigate the movement of amino acids into the rust pustule. The results indicate that serine and alanine are absorbed more readily from the host than aspartic acid, glutamic acid or glutamine.
EFFECTS OF LIGHT INTENSITY ON THE FORMATION OF VESICULAR‐ARBUSCULAR ENDOMYCORRHIZAS ON ALLIUM CEPA BY GIGASPORA CALOSPORA
Authors: FURLAN V. , FORTIN J.‐A.
Published: May 2006

Four different light intensities exerted distinctly different effects on the formation, reproduction and influence of vesicular‐arbuscular mycorrhiza on onion plants. Over a growth period of 100 days, the rate of infection under low light intensities (5 and 10 klux) was more rapid and the percentage of infection higher than on mycorrhizal plants cultivated under a light of 15 and 20 klux. The production of spores increased with light intensity. A plant growth enhancement occurred at all light levels but was most pronounced under a 10 klux light regime.
PHYSIOLOGICAL‐ENVIRONMENTAL INTERACTIONS IN LICHENS
Authors: KERSHAW K. A.
Published: May 2006

The control of the net photosynthetic rate in Peltigera canina var. praetextata and P. polydactyla by temperature, light and moisture has been examined on a seasonal basis. Mean optimum values of 6 mg CO2 g−1·h−1 are achieved by young lobes of either species during late spring, summer and early winter. However, under full winter conditions optimum net photo‐synthetic rates fall to 3 mg CO2 g−1·h−1. Light saturation is approximately 500 μE m−2 s−1 at all times of the year, but the temperature at which maximum rates of net photosynthesis are achieved changes markedly throughout the year in both species. In winter, maximum rates occur at an experimental thallus temperature of 5°C but by mid‐summer, the optimum temperature for net photosynthesis is c. 30°C, which corresponds to equivalent ambient temperature levels in the field. This temperature acclimation of net photosynthetic optima is achieved without any significant change in respiration rate and shows a remarkable degree of homeostasis during spring, summer and early winter. The results strongly emphasize the unsatisfactory nature of the univariate experimental design which has often been used in lichen physiological ecology. The extreme importance of a controlled storage temperature for experimental lichen material is also clearly evident. The low net photosynthetic rates in winter show the same pattern in both Peltigera species during these low temperature and short day conditions.
H+ AND Ca2+ IN PHLOEM AND SYMPLAST: RELATION OF RELATIVE IMMOBILITY OF THE IONS TO THE CYTOPLASMIC NATURE OF THE TRANSPORT PATHS
Authors: RAVEN J. A.
Published: May 2006

The capacity of the symplast and the phloem to transport Ca2+ and H* (OH−) is discussed in relation to the concentrations of free and bound Ca2+ and H* in these transport systems, and the general restrictions on the concentrations of free Ca2+ and H* in cytoplasm. It is concluded that the low Ca2+ and H+ transport capacity of symplast and phloem are consequences of the cytoplasmic nature of these transport systems. The significance of the low transport capacity for these two ions relative to the rate at which the plant produces or consumes H+ or can take up Ca2+ and transport it in the xylem is discussed. Other transport characteristics of the phloem can also be related to the cytoplasmic nature of the transport conduit: the nature of the transported organic C and N compounds is partly dependent on the requirement that high concentrations of these solutes can be tolerated by cytoplasmic enzymes, i.e. sucrose, mannitol and amino‐acids are ‘compatible solutes'. The properties of the intracellular transport systems (symplast and phloem) are contrasted with those of extracellular transport systems such as plant xylem and animal blood.
ASPARTATE‐DEPENDENT ALANINE PRODUCTION BY LEAF DISCS OF AMARANTHUS PANICULATUS, AN ASPARTATE UTILIZING NAD‐MALIC ENZYME TYPE C4 PLANT
Authors: RAGHAVENDRA A. S. , DAS V. S. R.
Published: May 2006

Illuminated leaf discs of Amaranthus paniculatus formed alanine rapidly after infiltration with aspartate. a‐oxoglutarate and glutamate accelerated aspartate‐dependent alanine production. Alanine was also formed by A. paniculatus leaf discs infiltrated with oxalacetate; this production was stimulated only by glutamate. Our results confirm that alanine can be formed rapidly from aspartate in C4 plants. Aspartate‐dependent alanine production was stimulated greatly by light. The stimulatory effect of light could almost be replaced by ATP in presence of sodium ions. These findings are discussed in relation to a possible light‐dependent active transport of amino acids into the bundle sheath, mediated by Na+‐dependent ATPase activity.
TOLERANCE OF ANOXIA AND ETHANOL METABOLISM IN GERMINATING SEEDS
Authors: CRAWFORD R. M. M.
Published: May 2006

Seeds resistant to soaking injury and the associated condition of anoxia regulate glycolysis so that there is minimal production of ethanol. This regulation is achieved by low anaerobic respiration rates, the minimization of the Pasteur effect, and by the production of lactate as an alternative to ethanol during the early stages of anaerobiosis. Resistant seeds differ from those intolerant of soaking where anoxia causes an acceleration of glycolysis, an induction of alcohol dehydrogenase activity and the production of large quantities of ethanol as the exclusive end‐product of glycolysis. Seeds tolerant of soaking are therefore similar to the roots of flood‐tolerant plants where ethanol production is also limited during periods cf anoxia.
TOLERANCE OF ANOXIA AND THE METABOLISM OF ETHANOL IN TREE ROOTS
Authors: CRAWFORD R. M. M. , BAINES MARGARET A.
Published: May 2006

Ethanol can always be detected in the trunks and roots of forest trees and in the roots of pot‐grown tree‐seedlings under both flooded and unflooded conditions. The constant presence of this anaerobic product indicates that tree‐roots and trunks exist continually in a state of total or partial anoxia. In forest trees the ethanol content at the base of the tree trunk was correlated significantly with that found in the roots and fluctuated throughout the year, reaching a maximum in winter and early spring. The highest values were noted in trees exposed to the greatest amount of flooding. Pot‐grown trees of Pinus contorta and Picea sitchensis showed an immediate reaction to anoxia with a simultaneous increase in root ethanol content when placed in unaerated water culture. In the flood‐intolerant P. sitchensis anoxia induced a twelve‐fold increase in ethanol and this attained 5 μmoles g−1 fresh weight, while over the same period the ethanol in the roots of the flood‐tolerant Pinus contorta increased only three‐fold to 0.7 μmoles g−1 fresh weight. These species provide another example of flooding tolerance being found in association with the ability to limit ethanol production.
LONG TERM CULTURE METHODS FOR THE PRODUCTION OF ISOTOPICALLY LABELLED PLANT MATERIAL
Authors: KNIGHT A. H.
Published: May 2006

The culture of isotopically labelled plant material for subsequent experimental use is described. The isotopes used were 65Zn in ryegrass for chemical composition analysis related to animal nutrition, 22Na and 36Cl in beetroot for plant physiological ionic studies, 59Fe in wheat grain for human metabolic studies, 45Ca in wheat for subsequent germination and the study of calcium distribution in seedling roots, and 14C in plant material for production of labelled humic substances. Consideration is given to the various factors involved, such as methods of incoporation of label into the plant, radiation damage, levels of specific activity and double labelling.
NITRATE REDUCTION BY WHOLE CELLS OF ANKISTRODESMUS BRA UNII AND CHLAMYDOMONAS REINHARDI
Authors: HIPKIN C. R. , SYRETT P. J.
Published: May 2006

Methods are described for the assay of nitrate reductase in frozen/thawed cells of Ankistrodesmus braunii and Chlamy domonas reinhardi. Because Ankistrodesmus nitrate reductase can use NADPH as an electron‐donor and because the cells of Ankistrodesmus contain a high concentration of glucose‐6‐phosphate, it is suggested that, in frozen‐thawed cells, nitrate reduction is coupled, through NADPH, to the oxidation of glucose‐6‐phosphate. With Chla‐mydomonas cells either exogenous NADH or reduced FMN can act as reductant. The permeability of Chlamy domonas cells can also be increased by glycerol treatment and this makes assay of nitrate reductase possible without freezing and thawing.
THE GROWTH CURVE OF THE CRUSTOSE LICHEN BUELLIA CANESCENS (DICKS.) DE NOT.
Authors: PROCTOR M. C. F.
Published: May 2006

Growth curves for Buellia canescens have been constructed using photographic measurements of thalli in situ over yearly intervals. The curves approximate to a simple model based on the assumption that relative growth rate is proportional to the area of thallus in an annulus of constant width within the growing margin.
THE CYTOLOGY OF PLANTLETS DERIVED FROM CULTURED ANTHERS OF NICOTIANA SYLVESTRIS
Authors: McCOMB J. A. , McCOMB A. J.
Published: May 2006

Cultured anthers of Nicotiana sylvestris produced 70% haploid, 14% diploid, 8% triploid, 2% tetraploid and 6% mixaploid plantlets. Immediately pre‐mitotic anthers produced no plantlets; mitotic and immediately post‐mitotic ones did so. Stage of anther development at initiation of culture was not related to production of non‐haploids. Embryoids arose from divisions of the vegetative nucleus. In microspores containing globular embryoids 0, 1 or 2 nuclei derived from the generative nucleus could be recognised; these, however, contributed few if any viable cells to the developing plantlets. Metaphase plates with higher than the haploid number of chromosomes were seen and probably arose through nuclear fusion at an early stage.
A LONG SUB‐FOSSIL OAK TREE‐RING CHRONOLOGY FROM THE NORTH OF IRELAND
Authors: PILCHER J. R. , HILLAM J. , BAILLIE M. G. L. , PEARSON G. W.
Published: May 2006

A 2990 year floating tree‐ring chronology has been constructed using bog oaks from low altitudes in the north east of Ireland. The basic building blocks of this chronology are site chronologies made from the ring patterns of trees from individual sites. The construction of site chronologies and of the 2990 year master chronology are described. Applications of this chronology and its extensions include radiocarbon calibration which is already under way, stable isotope measurements for palaeotemperature estimation, and climatic interpretations based on the ring widths.
THE DEVELOPMENT OF ENDOMYCORRHIZAL ROOT SYSTEMS: I. SPREAD OF INFECTION AND GROWTH‐PROMOTING EFFECTS WITH FOUR SPECIES OF VESICULAR‐ARBUSCULAR ENDOPHYTE
Authors: SANDERS F. E. , TINKER P. B. , BLACK R. L. B. , PALMERLEY S. M.
Published: May 2006

Four vesicular‐arbuscular endophytes were inoculated into onions cultured in soil in a growth chamber. Dry weight, root length, infected root length, phosphorus content and quantity of external mycelium were measured at intervals. Three endophytes produced similar hyphal inflows, growth increments and external mycelium. One endophyte produced no growth increase in the host, and had little external mycelium and slow increase in percentage infection.
PLANT GROWTH RESPONSES TO VESICULAR‐ARBUSCULAR MYCORRHIZA
Authors: MOSSE BARBARA
Published: May 2006

This paper reports results of inoculation with vesicular‐arbuscular (VA) endophytes in twelve unsterile soils with and without added rock phosphate or Hyperphosphat. Stylosanthes guyanensis, and in two soils also maize, were grown in pots and plant weight, P uptake, nodule weight and nitrogenase activity were measured at harvest.

The introduced endophyte established well in all but one of the soils and inoculated plants with added phosphate grew best in eleven soils. Utilization of added rock phosphate was often considerably increased by inoculation but there was no evidence of increased availability. Inoculum density in the soil, rather than its phosphate status seemed to determine responses to VA inoculation, which were greatest in soils containing few indigenous endophytes. VA inoculation often stimulated nodulation by rhizobia but, in contrast to irradiated soils, there was no clear relationship between percentage plant P and nodulation. The results are discussed in relation to the possibility of field inoculation with VA endophytes.
COLORIMETRIC QUANTIFICATION OF VESICULAR‐ARBUSCULAR MYCORRHIZAL INFECTION IN ONION
Authors: BECKER W. N. , GERDEMANN J. W.
Published: May 2006

A colorimetric method of estimating vesicular‐arbuscular mycorrhizal infection was developed and tested using onions inoculated with Glomus fasciculatus. Absorbances at 400 nanometers of water extracts from a series of mixtures of yellow (mycorrhizal) and white (nonmycorrhizal) roots had significant correlation with the percent yellow roots by weight in the mixtures. The percentage of mycorrhizal infection determined by a chitin assay or by a staining method was significantly correlated with the percentage of yellow roots by weight. The percentage of mycorrhizal infection determined by the colorimetric method was also significantly correlated with root/shoot ratios. The colorimetric method is offered as an alternative to the more time consuming quantitative methods of estimating the extent of vesicular‐arbuscular mycorrhizal infection now in use.
TRANSLOCATION INTO MATURE LEAVES–THE EFFECT OF GROWTH PATTERN
Authors: THROWER STELLA L.
Published: May 2006

In rosette plants, import of labelled assimilate by mature leaves is a normal part of the trans‐location pattern. Following elongation and loss of the rosette habit with the onset of flowering, the translocation pattern becomes that typical of elongate plants, characterised by lack of movement into mature leaves.
DIURNAL STOMATAL AND ACIDITY RHYTHMS IN ORCHID LEAVES
Authors: GOH C. J. , AVADHANI P. N. , LOH C. S. , HANEGRAAF C. , ARDITTI J.
Published: May 2006

The stomata of Arachnis cv. Maggie Oei, Aranda cv. Deborah, Arundina graminifolia, Bromheadia finlaysoniana, Cattleya bowringiana×C. forbesii and Spathoglottis plicata (Orchidaceae) occur only on the lower epidermis of the leaves and are located within hyperstomatic chambers formed by cuticular ledges extending from the guard cells. Arachnis, Aranda and Cattleya have thick leaves which exhibit Crassulacean acid metabolism, and their stomata open when acidity levels are lowest, or shortly thereafter. Aranda and Arachnis require higher light intensities for sufficient deacidification to permit stomatal opening than Cattleya. Stomata of the thin‐leaved Arundina, Bromheadia and Spathoglottis open during the day. The stomatal rhythms, morphology and distribution, as well as the pathways of carbon fixation and light requirements for deacidification, reflect the natural habitat of each species or the parents of the three hybrids.
HORMONES IN PLANTS BEARING NITROGEN‐FIXING ROOT NODULES:
Authors: HENSON I. E. , WHEELER C. T.
Published: May 2006

The content of gibberellin‐like (GA‐like) substances in various parts of young alder (Alnus glutinosa (L.) Gaertn.) plants was estimated by means of the lettuce hypocotyl bioassay. The highest levels of GA‐like activity were found in the root nodules, of dormant plants, plants emerging from dormancy, and plants in full leaf.

No major differences were found in the roots and leaves of nodulated as opposed to non‐nodulated plants, although the stems of nodulated plants did contain lower levels of GA‐like activity.

The detection of seasonal changes in GA‐like activity in root nodules from mature trees was dependent upon the method of chromatography employed. One major peak of biological activity was detected following paper chromatography and no large changes were detected in the level of this component. In contrast, three zones of GA‐like activity could be detected after thin layer chromatography (TLC) and there were marked seasonal changes in activity in these three zones. This can be attributed either to changes in levels of the GA‐like substances themselves and/or to variations in the amounts of impurities interfering with the response of the bioassay.

A number of peaks of GA‐like activity were detected by lettuce and rice bioassays following analysis of a large‐scale extract on a preparative high performance liquid chromatograph (HPLC). However, both the total number and the identity of the substances responsible for this activity, remain to be determined.
CARBOHYDRATE OXIDATION IN DEVELOPING BARLEY ENDOSPERM
Authors: DUFFUS C. M. , ROSIE R.
Published: May 2006

The presence of a number of pentose phosphate pathway (PPP) enzymes in developing barley endosperm is reported. The relative importance of the Embden‐Meyerhof‐Parnas pathway (EMPP) and the PPP throughout endosperm development was assessed by following the changes in activity of five EMPP and four PPP enzymes. The patterns of activity of the EMPP enzymes were very similar with pronounced peaks of activity at 35 days after anthesis thereafter falling to low or zero levels at the onset of maturity. The PPP enzymes, on the other hand, rose to maximum levels around 30–35 days falling only slightly thereafter.
VARIATIONS IN THE BASIC PATHWAY OF CHLOROPLAST DEVELOPMENT
Authors: WHATLEY JEAN M.
Published: May 2006

The sequence of ultrastructural changes which take place during chloroplast development in leaves of plants of Phaseolus vulgaris grown in the light is compared with that of plants grown in the dark. Further comparisons are made with the developmental sequence found in the hypocotyls of Phaseolus and in the leaves of Zea mays. It is concluded that there is a single basic pathway of chloroplast development. Variations in this pathway are related to blocks in the sequence resulting in the accumulation of storage materials such as phytoferritin and prolamellar bodies, characteristic of the species or tissue concerned. An attempt has been made to assess the ubiquity and duration of an association between plastids and the E.R. in lower plant species compared with the angiosperms. A plastid‐E.R. association is common and persistent in lower plant species whereas in angiosperms it is apparently transitory and confined to immature or specialized cells.
THE EFFECTS OF LIGHT INTENSITY ON ACETYLENE REDUCTION BY BLUE‐GREEN ALGAL MATS IN SUB‐TROPICAL GRASSLAND
Authors: JONES K.
Published: May 2006

High light intensities such as those found during the middle of the day in southern Africa are not responsible for inhibition of acetylene reduction by mats of blue‐green algae in kikuyu lawns. Similar results were obtained with uni‐algal cultures of Nostoc isolated from the algal mats. Short term experiments (3 h) with both cultures and algal mats showed a direct relationship between acetylene reduction and light intensities of up to 323 lux but no significant increase in acetylene reduction for light intensities above this. The amount of acetylene reduction by algae in the dark is determined by the light intensity received prior to darkness.
THE EFFECTS OF TEMPERATURE ON ACETYLENE REDUCTION BY MATS OF BLUE‐GREEN ALGAE IN SUB‐TROPICAL GRASSLAND
Authors: JONES K.
Published: May 2006

Temperature is the main factor governing the rate of acetylene reduction by mats of blue‐green algae in sub‐tropical kikuyu lawns. High midday temperatures (40°C at soil surface) inhibit acetylene reduction and low temperatures prior to dawn reduce the rate of nocturnal acetylene reduction. Data obtained from laboratory studies on algal mats and on Nostoc isolated from the mats are in agreement with those from in situ measurements confirming an acetylene reduction of 30–35°C with inhibition above 40°C.
A TEST OF BURCK'S HYPOTHESIS RELATING ANTHER DEHISCENCE TO NECTAR SECRETION
Authors: SCHMID RUDOLF , ALPERT PETER H.
Published: May 2006

William Burck in 1906/07 suggested that anther dehiscence in many flowers results from loss of considerable amounts of water not by transpiration, as commonly believed, but rather by withdrawal of the water internally to other tissues, particularly nectaries. Tests on flowers of eight dicotyledons failed to provide confirmatory evidence for Burck's conclusions. A number of additional, largely theoretical objections to Burck's hypothesis are also presented. Experimental evidence also suggests that anther dehiscence may not be exclusively the simple desiccatory process generally envisioned by botanists.
POLYAMINES AS SOLE NITROGEN SOURCES FOR HELIANTHUS TUBEROSUS EXPLANTS IN VITRO
Authors: BAGNI N. , CALZONI G. L. , SPERANZA A.
Published: May 2006

Putrescine, spermidine, spermine have been tested for their ability to substitute for inorganic nitrogen for the growth of explants from dormant tubers of Helianthus tuberosus. Explants grew as well on putrescine + indole acetic acid (IAA) as on nitrate + IAA or gluta‐mine + IAA but no growth occurred with spermine + IAA and an intermediate growth effect was observed in explants grown on spermidine + IAA, although this last result was not confirmed in tubers of different years. Growth increments have been related to pH variation in culture medium. Radioactive polyamines were transformed by the tuber explants to arginine and glutamine.

The presence of radioactive putrescine after [1,4‐14C] spermidine feeding to explants grown on spermidine + IAA, as well as the presence of large amounts of spermidine in explants grown on spermine + IAA, indicate a reversal of the pathways of spermidine and spermine biosynthesis. We suggest that putrescine arises by such reversal. This hypothesis does not exclude processes of direct transamination from polyamines to α‐ketoacids.
MYCORRHIZAL FUNGI STIMULATE UPTAKE OF SOLUBLE AND INSOLUBLE PHOSPHATE FERTILIZER FROM A PHOSPHATE‐DEFICIENT SOIL
Authors: POWELL C. LL. , DANIEL JEANNETTE
Published: May 2006

One crop of clover followed by three crops of ryegrass were infected with several mycorrhizal fungi and grown in sterilized soil which had received soluble phosphate or Nauru rock phosphate. Plant growth responses to mycorrhizal infection were larger in later crops. Glomus tenuis was successfully introduced into soil already infested with the indigenous mycorrhizal fungi, and was the most efficient fungus used at stimulating phosphate uptake. In all four crops, Nauru rock phosphate was available to mycorrhizal plants but unavailable to non‐mycorrhizal plants. Plants infected with G. tenuis and the indigenous mycorrhizal fungi recovered 10‐27% of the phosphate fertilizer applied to the soil while non‐mycorrhizal plants recovered only 0.4‐13%.
EFFECT OF ARBUSCULAR MYCORRHIZA ON PLANT GROWTH
Authors: DAFT M. J. , EL‐GIAHMI A. A.
Published: May 2006

Defoliation of maize and tomatoes reduced the mycorrhizal growth response and development of the endophyte, estimated as percentage infection, root pigmentation and spore production. More fresh and dry matter was produced in mycorrhizal grasses harvested on three separate occasions than from a single final harvest. The total yields from two harvests and the yield from a single harvest of alfalfa were similar although nodulated and mycorrhizal plants were larger at each harvest. In both grasses and alfalfa, periodic harvesting reduced the mycorrhizal infection by approximately 50%.

Reduction in daylength and irradiance depressed the growth more in mycorrhizal than in uninfected maize plants. In Rhizobium‐ and Glomus‐infected alfalfa plants, a daylength of 16 h produced the highest carbon contents and C/N ratios. Plants exposed to short days produced more, smaller nodules and had higher nitrogen contents than plants given long days. Long days favoured the development of the mycorrhizal infection and these dually infected plants produced more dry matter, reduced acetylene faster and contained more nitrogen than nodulated only plants. The supply of photosynthate is probably an important factor controlling the development of the mycorrhiza.
NUMERICAL ANALYSIS OF SURFACE POLLEN SPECTRA FROM BANKHEAD MOSS, FIFE
Authors: CASELDINE C. J. , GORDON A. D.
Published: May 2006

An investigation is described which examined the extent to which surface pollen spectra from three transects across a small raised bog reflected the vegetation communities on the bog. Three classification studies of the spectra are described: (i) a principal components analysis; (ii) two hierarchical partitioning methods; (iii) a constrained classification, in which groups of spectra must be formed from neighbouring samples along the transects. Advantages and limitations of these classificatory procedures are discussed, and a synthesis of the results is advocated. The groups of spectra suggested by this approach are found to correspond closely to a grouping of spectra according to the vegetation community from which they were drawn, indicating the existence of characteristic pollen assemblages which are closely related to vegetation communities.
A SUGGESTED CYCLE OF PLASTID DEVELOPMENTAL INTERRELATIONSHIPS
Authors: WHATLEY JEAN M.
Published: May 2006

It is suggested that developmental changes in plastid structure follow a cyclic pathway which may involve the dedifferentiation of mature chloroplasts to proplastids and the subsequent redifferentiation of proplastids to mature chloroplasts. The proposal of a cyclic plastid relationship revives the earlier concept of Schimper. This has generally been discarded in favour of a unidirectional concept which discounts dedifferentiation as a normal process. Justification of the cyclic concept depends largely on the verification that plastid dedifferentiation and re differentiation do indeed take place. Evidence for this comes not only from the literature, but also from personal observations.
CELL DIFFERENTIATION IN EMBRYOIDS AND PLANTLETS OF CELERY TISSUE CULTURES
Authors: AL‐ABTA SAHERA , COLLIN H. A.
Published: May 2006

The formation of globular, heart‐shaped and torpedo‐shaped embryoids was initiated in a cell suspension culture of differentiating celery callus. Sections of these embryoids were examined for cell differentiation. Sections were also taken from plantlets, seedlings and mature plants. No cell differentiation was seen in the globular and heart‐shaped stages but cell differentiation and tissue organization were present at the torpedo stage. The structure of the plantlet was simpler than that of the seedling but this may have been due to the conditions in the culture flask. Both plantlet and seedling leaf showed comparable levels of organization. It is concluded that biochemical development in the embryoid may be related to the onset of cell differentiation.
RESPONSE TO SOIL MOISTURE SUPPLY IN THREE LEGUMINOUS SPECIES
Authors: FOULDS W.
Published: May 2006

Soil moisture is an important factor in the distribution of Trifolium repens, Lotus corniculatus and Medicago lupulina. The first proved to be the most successful on moist soil, growing vigorously and forming numerous seeds. However, the plant was unable to avoid desiccation in droughted conditions where physiological processes such as root and shoot growth, and seed production were inhibited.

In moist and dry soil, the seed production and vegetative yield of Lotus corniculatus were consistent. However, the slow‐growing seedlings and adult plants were relatively intolerant of severe drought.

The annual, Medicago lupulina, displayed the greatest plasticity. On moist soils it formed substantial vegetative parts and prodigious numbers of seeds. In doughted conditions this species was the most tolerant of the three legumes at all stages of the life history, forming many seeds even when the vegetative yield was relatively low.
PHOSPHORUS CONCENTRATIONS IN PLANTS RESPONSIBLE FOR INHIBITION OF MYCORRHIZAL INFECTION
Authors: MENGE J. A. , STEIRLE D. , BAGYARAJ D. J. , JOHNSON E. L. V. , LEONARD R. T.
Published: May 2006

Using a ‘split root’ technique, it was found that phosphorus fertilization of half of the root system of sudangrass could significantly reduce the number of chlamydospores of the mycorrhizal fungus Glomus fasciculatus in the unfertilized half of the root system. In a second experiment, vials of soil containing different concentrations of phosphorus were inserted into pots of sudangrass which were fertilized with different amounts of phosphorus and inoculated with G. fasciculatus. The numbers of chlamydospores, vesicles and arbuscles and the amount of hyphae produced by G. fasciculatus on roots within the vials were not influenced by the soil P in the vials but were inversely correlated with the concentration of P in roots outside the vial. All evidence indicates that it is the concentration of P within the plant and not the soil P which leads to a reduction in colonization, infection, and spore production of G. fasciculatus.
ROOT EXUDATION IN COWPEA AND SORGHUM AND THE EFFECT ON SPORE GERMINATION AND GROWTH OF SOME SOIL FUSARIA
Authors: AYOODUNFA V. S.
Published: May 2006

Exudation patterns in cowpea and sorghum seed and seedlings were studied using a filter paper technique. Profuse exudation was observed from cowpea seeds but this decreased considerably 2 days after germination. Root tips of primary, lateral, and adventitious roots were found to be the major sites of exudation but the older parts of seedling roots also exuded significant quantities of amino acids. Exudates from the roots of both species enhanced the germination of conidia of four Fusarium species previously isolated from the rhizosphere and rhizoplane. The germ tubes and some conidia were lysed by cowpea exudate in 48 h. Mycelial growth in liquid culture was enhanced in cowpea root exudate medium but was scanty in sorghum exudate; the presence of antifungal substance was suspected in the latter. The significance of the results obtained in relation to microbial root colonization and pathogenesis is discussed.
THE MEASUREMENT OF TOLERANCE TO EDAPHIC FACTORS BY MEANS OF ROOT GROWTH
Authors: WILKINS D. A.
Published: May 2006

The tolerance of plants to toxic metals is frequently measured by comparing rates of root growth in culture solutions with and without the addition of the metal, but many variants of the technique are available. Toxicity is often reduced by the presence of other ions, particularly calcium. Control growth rates may be measured beforehand on the same roots or in parallel on a duplicate set. With a single toxic concentration tolerance is defined as the ratio of the two growth rates; with a range of concentrations the slope of the regression of growth on concentration may be used, but there are some complications with stimulation at low concentrations. Probit analysis may be valuable. There is good evidence that tolerance differences are largely of genetical origin.
ECOLOGICAL PHYSIOLOGY OF THE LICHEN HYPOGYMNIA PHYSODES IV. CARBON ALLOCATION AT LOW TEMPERATURES
Authors: FARRAR J.F.
Published: May 2006

A simple three‐compartment model is used to test the assertion that lichens show low incorporation of assimilate into structural material. Changing specific activities of three fractions equated with the compartments of the model are followed using carbon‐14. It is concluded that lichens show tight control over the synthesis of structural material.
SEASONAL VARIATION IN THE CAPACITY FOR NITROGENASE ACTIVITY IN THE LICHEN STEREOCAULON PASCHALE
Authors: HUSS‐DANELL KERSTIN
Published: May 2006

Thalli of Stereocaulon paschale (L.) Fr. were collected at approximately monthly intervals during a 13‐month period from a pine forest in northern Sweden. The capacity for nitrogenase activity (C2H2‐reduction) was studied on each collection under standardized, favourable laboratory conditions. Significantly higher capacities were found in thalli collected from bare ground than in thalli collected under snow, but the capacity decreased in autumn close to the snow covering. At snow melt the increase in capacity was rapid.

To investigate the decrease in capacity during the autumn, S. paschale was exposed to simulated autumn conditions in the laboratory during 2‐week periods. These simulation experiments indicated that the light regime was of importance for nitrogenase activity. Low irradiance during short days caused a marked decrease in the nitrogenase activity, especially in combination with night temperatures above freezing. Night temperatures below zero, per se, did not reduce nitrogenase activity; instead a tendency to stimulate it was found.
ROOT FORMATION IN CUTTINGS OF APPLE (cv. BRAMLEY'S SEEDLING) IN RELATION TO RINGBARKING AND TO ETIOLATION
Authors: DELARGY J. A. , WRIGHT C. E.
Published: May 2006

The effect of excising a cylinder of bark from the base of growing shoots on subsequent root formation in the cuttings was examined in the difficult‐to‐root apple scion variety ‘Bramley's Seedling’. Ringbarking was found to enhance root formation only in etiolated segments of stem and when it was made proximal to the etiolated segment, since root formation took place preferentially distal to the ringbark. A second distal ringbark nullified the promotory influence of a proximal excision. Etiolation, together with proximal ring‐barking, induced root formation in up to 98% of the cuttings.
TOLERANCE OF HOLCUS LANATUS TO LEAD, ZINC AND CADMIUM IN FACTORIAL COMBINATION
Authors: COUGHTREY P. J. , MARTIN M. H.
Published: May 2006

The tolerance of Holcus lanatus to lead, zinc and cadmium alone and in combination was studied in a factorial experiment. Cadmium/zinc, lead/cadmium and lead/cadmium/zinc interactions, as measured by their effect on root growth, occurred but were not consistent between the two populations. The population from a contaminated site showed a distinct tolerance to lead, zinc and cadmium in combination, compared to the non‐tolerant population. These results are discussed in relation to the literature of heavy metal tolerance and metal effects on plants.
THE ADDITIVITY OF THE TOXIC EFFECTS OF Cu, Ni AND Zn IN YOUNG BARLEY
Authors: BECKETT P. H. T. , DAVIS R. D.
Published: May 2006

As part of a study on the use of young barley plants to monitor accumulations of toxic elements arising from sludge or waste disposal, we have examined the interactions between Cu, Ni and Zn in young barley.

We find that Cu has little effect on the amount of Ni or Zn that reaches the shoots or vice versa: Ni uptake is raised by critical levels of Zn; Zn uptake is raised by sub‐critical and critical levels of Ni. These effects are small and may be ignored when monitoring sub‐toxic accumulations. At higher concentrations the interactions are larger and more complex.

A significant part of the quantity of any one of these elements that has been translocated to the photosynthesising tissues of the barley test plant, up to a threshold concentration [T]x, is not toxic, alone or in combination with the other two elements. Toxic effects become apparent from a critical tissue concentration [T]c, above which yield decreases in proportion to increases in log [T]. [T]x/[T]c∼ 1/2 – 2/3. Values of [T]x and [T]c are presented.

The toxic effects of Cu and Zn appear to be antagonistic (effect less than expected) when the tissue concentrations of both are above their critical levels. Apart from this the toxic effects of the elements above their threshold concentrations are directly additive or slightly less than additive.
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Values are presented for K, k, M and m and the critical values of Ia and Ib.

In their general form these results are very similar to those of similar studies on the toxicity of mixed solutions to fish.