bluuebunny/crossref_metadata_2025_split huggingface dataset:
AMINO ACIDS AS NITROGEN SOURCES FOR THE GROWTH OF EXCISED ROOTS OF RED CLOVER
Authors: HARRIS G. P. 
Published: May 2006

SummaryTwo clones of excised roots of red clover have been established and maintained in culture. One of these (Clone A) was selected as showing a satisfactory level of growth in the standard medium and the other (Clone Z) as being relatively resistant to growth inhibition by L‐aspartic acid.L‐aspartic acid, L‐asparagine, L‐glutamic acid and L‐α‐alanine were each effective as sole sources of nitrogen for the growth of excised roots of Clone Z but not for roots of Clone A.L‐aspartic acid, L‐glutamic acid and L‐α‐alanine each depressed the growth of the roots when supplied in the presence of nitrate. Roots of Clone Z were more resistant to growth inhibition by these amino acids than roots of Clone A.L‐valine and glycine were ineffective as sole sources of nitrogen for growth of roots of either clone and were inhibitory to growth when supplied in the presence of nitrate.L‐arginine was effective as a sole source of nitrogen for the growth of roots of both Clone A and Clone Z. With increasing concentrations of the amino acid supplied in the presence of nitrate, growth of roots of both clones was first stimulated and then depressed.In experiments with Clone A, it was shown that D‐arginine was similar to L‐arginine in its effects on growth, but that DL‐alanine was more inhibitory than L‐alanine.When amino acids were supplied as sole sources of nitrogen, growth was always inferior to that obtained with nitrate. Urea, however, supported a level of growth similar to that supported by nitrate.The technique of excised root culture is suited to the study of the utilization of amino acids as nitrogen sources for plant growth. Nitrogen deficiency can be developed rapidly in excised root‐tips and the technique permits work with clonal material under sterile, controlled conditions. A number of investigations of the nutrient requirements of excised roots have included an examination of effects of amino acids on growth (White, 1937, 1939; Baylor and Rappaport, 1950; Boll, 1954; Skinner and Street, 1954; Roberts and Street, 1955). In these cases the primary objective has been to test amino acids as potential growth factors rather than as nitrogen sources for the roots. However, Skinner and Street (1954), working with excised roots of groundsel, established that L‐arginine, L‐ornithine, L‐citrulline and L‐lysine, which were stimulatory to growth in the presence of nitrate, were also effective in supporting growth in the absence of other nitrogen sources.
THE COMPARATIVE BIOLOGY OF CLOSELY RELATED SPECIES LIVING IN THE SAME AREA
Authors: MCNAUGHTON I. H. , HARPER JOHN L. 
Published: May 2006

SummaryIt has been demonstrated that in Britain five species of Papaver (a) frequently occur together, (b) flower over the same general period, (c) are normally insect‐pollinated and possess insect visitors in common. Hybrids are rare under natural conditions although some can easily be produced artificially.The external barriers reducing the chances of natural hybridization are the facts that (a) some of the species have mechanisms facilitating self‐pollination, and (b) specific selection by the principal insect visitor, the honey‐bee, tends to reduce the chances of cross‐pollination between the species.
THE MATHEMATICAL RELATIONSHIP BETWEEN THE LENGTHS OF LATERAL NERVES AND THEIR POSITIONS ON A LEAF
Authors: BURTON R. F. 
Published: May 2006

SummaryAn equation is proposed which has been successfully applied to the leaves or leaflets of fifteen species, relating the lengths of the main lateral nerves to their positions on the midrib. Certain constants arising from the equation are shown to be interrelated or correlated with the position of the leaf on the shoot.The validity of the equation and the possibility of more general application among Dicotyledons is discussed. No explanation in terms of the growth processes of the leaf has been found.
THE INFLUENCE OF ENVIRONMENTAL CONDITIONS ON INFLORESCENCE DEVELOPMENT IN SOME LONG‐DAY GRASSES
Authors: EVANS L. T. 
Published: May 2006

SummaryThere is a reasonably close relation between the length and the stage of morphological development of the inflorescences of Lolium temulentum and L. perenne over a wide range of environmental conditions. Since inflorescence length increases exponentially under constant conditions the relative growth rate of the inflorescence provides a suitable index of the rate of inflorescence development.The rate of inflorescence development in various grasses has been found to be unaffected by the extent of vernalization, and to be increased by increasing temperature, photoperiod length and number of long days given.Under standardized temperature and photoperiod conditions during inflorescence development there is a hyperbolic relation between the rate of inflorescence development and the number of inductive long days given to plants of L. temulentum, and to fully vernalized plants of Cynosurus cristatus. Lolium temulentum plants require exposure to only I long day for induction to occur.The rate of inflorescence development is only slightly affected by the interpolation of short days between the inductive long days given to plants of L. temulentum. Cynosurus cristatus plants exposed to only 4 to 8 long days bore inflorescences with proliferous fertile spikelets, while in those given 9 to 11 long days, vegetative proliferation was restricted to the sterile spikelets. With Lolium perenne plants teratological features of the inflorescence were associated with the interpolation of a period in short days at moderately high temperatures between vernalization and exposure to long‐day conditions.It is concluded that the rate of inflorescence development may, under standardized conditions, provide an index of the intensity of photoperiodic induction, although the way in which the inductive stimulus influences this rate is not clear.
THE DIATOM FLORA OF A SALT MARSH ON THE RIVER DEE
Authors: ROUND F. E. 
Published: May 2006

SummaryThe diatom flora of a salt marsh at Neston, Cheshire, and its seasonal cycle has been investigated. The flora on the surface of sand, silted sand, a stream and in pans has been recorded. The differences in the flora of the habitats on the salt marsh and the variation in the flora from the upper to the lower marsh have been examined and the data as a whole compared with that of earlier workers.
CULTURE STUDIES OF BANGIA ATROPURPUREA (ROTH) AG.
Authors: BELCHER J. H. 
Published: May 2006

SummaryThe freshwater Bangia atropurpurea (Roth) Ag. and the marine B. fuscopurpurea (Dillw.) Lyngb. have both been studied in unialgal culture. They are morphologically similar and have been united by some authors under the former name, but a comparison of salinity ranges in cultures has shown that they differ, only showing optimum growth in freshwater and marine media respectively.B. atropurpiirea has also been kept under observation in the field for three years and little seasonal periodicity has been noticed. In cultures of this species branched filaments and Conchocelis‐stages have been obtained, both bearing monospores. These stages are described in detail.
STUDIES OF THE LICHEN SYMBIOSIS
Authors: SCOTT G. D. 
Published: May 2006

SummaryCulture studies and field observations on Peltigera praetextata (Flk.) Vain, provide evidence of the existence of a delicate state of balance between the co‐symbionts of this lichen.Excessive supply of nutrients to discs of the lichen results in the outgrowth of the phycobiont and consequent destruction of the symbiotic relationship.The conjoint effect of excessive moisture and light is shown to bring about similar symbiotic breakdown.It is suggested that these three factors acting together as a growth‐regulating system are chiefly responsible for the success of the lichen symbiosis.
THE POSITION OF REGENERATING GAMBIA A NEW HYPOTHESIS
Authors: JOHN  , WARREN WILSON PAMELA M. 
Published: May 2006

SummaryWhen young stems are wounded or grafted so that the cambium is interrupted, new vascular cambia tend to regenerate in the callus proliferating from the wounded surfaces. The position in which such cambia arise varies according to the type of wound, but usually is such as to restore locally the normal condition of a closed cambial cylinder. Two theories have hitherto been proposed to define how the positions of these regenerating cambia are controlled. This paper presents evidence that neither of these theories is valid in all situations, and proposes a new working hypothesis. This ‘gradient induction’ hypothesis is stated at the end of the paper. It is in agreement with all types of wound and graft so far studied, and seems also to extend to cambium formation in tissue culture and perhaps to procambium formation in normal apices.
MERICLINAL CHIMERAS IN THE POTATO VARIETY GLADSTONE
Authors: HOWARD H. W. 
Published: May 2006

Summary

The potato variety Gladstone, which has white‐splashed‐pink tubers, produces very rarely tubers which have a nearly full red periderm. These tubers are periclinal chimeras, only layer I at the growing point having changed.
A study of mericlinal tubers suggested a minimum number of six initial cells for layer I at the stem apex of axillary buds.
The rarity of mericlinal tubers is due to tubers being formed by axillary meristems which originate as only a small part of the main stem.
STUDIES IN SYSTEMATIC BARK MORPHOLOGY
Authors: WHITMORE T. C. 
Published: May 2006

SummaryThe production of xylem and phloem sets up tangential stretching forces through the bark. In the living inner bark the resulting strains are mainly accommodated in Dipterocarpaceae by the formation of expansion tissue. The strain set up by a given annual girth increment decreases with increasing girth to a low steady amount at about 90 cm (3 ft) girth. Phloem formation in a mature tree only sets up small strains. These increase from zero at the cambium to a maximum at the surface. Many barks have more expansion tissue than this accounts for; the rest accommodates the strains set up by xylem formation. The tangential extent of the expansion tissue at a given distance from the cambium in any bark is in fact a measure of the ratio of the xylem and phloem growth rates. The three groups of Bark Types in Dipterocarpaceae with different amounts of expansion tissue (Whitmore, 1962a) are therefore groups with different xylem/ phloem ratios.Phloem growth rate determines periderm pattern and sometimes sloughing rate too. Fissure shape is controlled by periderm pattern and sloughing rate. The xylem growth rate is similar in different groups of dipterocarps. Thus the xylem/phloem ratio is an inverse measure of the phloem growth rate which cannot be measured directly. There is therefore a correlation between the xylem/phloem ratio and periderm pattern, sloughing and fissure shape.Similarities within the three groups of Bark Types in Dipterocarpaceae arise, therefore, from the dependence of periderm pattern, sloughing and fissure shape on the xylem/phloem ratio. Differences within the three groups arise from features, which are independent of the ratio: inter alia the phloem proliferation tissue, which probably varies phenotypically, and the sloughing mechanism.It follows that the xylem/phloem ratio is an important factor in the interpretation of diptero‐carp bark construction.There is no evidence of growth periodicity in the barks examined. Calculations show that the phloem is often conducting for more than 1 year to an observed maximum of 11.4 years; this is in marked contrast with most reports for temperate phloems.
UPTAKE OF SULPHUR BY EXCISED BEECH MYCORRHIZAS
Authors: MORRISON T. M. 
Published: May 2006

SummaryExcised mycorrhizas of Fagus were immersed in 35S solution for varying periods after which fungal mantles were dissected from host roots and both components were assayed separately for activity. In general 50% of the sulphur absorbed by mycorrhizas was found in the fungal mantle after 2 hours but this percentage was higher after shorter periods of immersion. Separation of mantle and cores before immersion in the active solution made little difference to absorption by either component.A comparison was made between absorption of 32P and 35S in both excised and intact mycorrhizas. This showed that the two elements had different absorption patterns and it is concluded that the benefit due to possession of mycorrhizas lies in the large reservoir of phosphorus in the fungal component and in the increased rate of absorption of phosphorus even after this reservoir has been established.
STUDIES IN BRITISH PRIMULAS
Authors: VALENTINE D. H. , WOODELL S. R. J. 
Published: May 2006

SummaryCrosses between three diploid species Primula veris, P. vulgaris and P. elatior show marked seed incompatibility. Crosses between the corresponding three autotetraploids give results which are closely comparable with those for the diploids. In both, reciprocal interspecific crosses always produce different and characteristic syndromes of seed development.Crosses between a diploid and its autotetraploid also show marked seed incompatibility of a similar kind. The data can be interpreted in terms of a hypothesis which assigns different genetic values to the genomes of the species and in which it is assumed that the genetic value of an autotetraploid is twice that of its diploid. The degree of seed failure can then be shown to be related to the difference in the genetic values of the paternal and maternal contributions to the tissues of the seed (embryo and endosperm).The hypothesis has been tested by making crosses between a diploid species and the autotetraploid of a different species (P. veris 2n—P. elatior 4n), in which there are both qualitative and quantitative differences in the genetic contributions of the parents. The results agree fairly well with expectation, but not exactly.The results are discussed in the light of current theories of seed incompatibility, and suggestions for further work, both in Primula and other genera, are made.
STUDIES IN SYSTEMATIC BARK MORPHOLOGY
Authors: WHITMORE T. C. 
Published: May 2006

SummaryThe bark structure and surface pattern of mature trees of Fagus sylvatica L., Quercus robur L. and Castanea sativa Mill, are described in detail and the rate of phloem growth calculated. Differences between Fagus and the other two species are ascribed largely to its slower phloem growth rate. Similarities between the bark of these Fagaceae and certain Dipterocarpaceae are described, and the significance of differences is explored. Comparison with other Fagaceae shows variation in bark in the family to be as wide as in Dipterocarpaceae. It is suggested that phloem growth rate is an important factor controlling bark surface pattern and has been important in bark evolution.
STUDIES IN POTENTILLAL.
Authors: SMITH GORDON L. 
Published: May 2006

SummaryThe mechanism of reproduction by seed in five British topodemes of Potentilla tabernaemontani has been investigated by means of crossing experiments and embryologically. With a variety of Potentilla species as pollen plants, crossing experiments yield progenies, which, except for the occasional aberrant, are uniform and resemble the female parent in morphology. Embryological preparations show meiosis to be suppressed in all topodemes. In all except one topodeme, the majority of unreduced embryo sacs are diplosporous in origin, in the other they are predominantly aposporous. Although the egg cell is capable of autonomous parthenogenetic development, functional seed is never formed without previous pollination. The conclusion to be drawn from embryology and crossing experiments is therefore that the seed produced is almost completely pseudogamous, thereby reproducing faithfully the genotype of the parent. The topodeme from Fleam Dyke, Cambridge, differed from the others investigated in a number of important respects. These included chromosome number, male sterility, the origin of unreduced embryo sacs and the precocious development of parthenogenetic embryos.
CONSEQUENCES OF ULTRAVIOLET RADIATION ON THE DIFFERENTIATION AND GROWTH OF FERN GAMETOPHYTES
Authors: KATO YUKIO 
Published: May 2006

SummaryThe effects of ultraviolet light (u.v.), principally at 2537 Å, on the differentiation and growth of gametophytes in Pteris vittata, Osmunda japonica and Dryopteris varia were investigated. It was ascertained that a single cell may be isolated by u.v.‐irradiation and that a normal gametophyte can be regenerated from such a cell.When gametophytes grown under low intensity (150 lux) white light before u.v.‐irradiation were irradiated with a high dose, an apico‐basal gradient of ability to survive was clearly shown. The survival of each of the cells composing a protonema seems to be related to two different factors; a marked ability for cell division or rapid recovery from the damage of u.v. at the apical region and a high resistance to u.v. at the basal region.Under both culture conditions, cells of a definite length alone survive. General effects induced by the u.v.‐irradiation include reversal of the polarity in a protonema and modification of the developmental axis. In addition, swelling of the rhizoid and protonema cells, and occurrence of ‘rhizoidal protonema’ were also described.
THE METABOLISM OF [1,3‐14C] ACETONE BY HIGHER PLANT TISSUES
Authors: COSSINS E. A. 
Published: May 2006

SummaryThe metabolism of [1,3‐14C] acetone by plant tissues has been examined. Under the experimental conditions used, 14C of methyl labelled acetone was rapidly incorporated into CO2, organic acids, amino acids, lipids and into the insoluble residue. In pea cotyledons and beet leaves, acetate and formate together contained the bulk of the radioactivity of the organic acid fraction. The possibility is discussed that acetone, accumulating during the early stages of germination in peas may be subsequently metabolized as seedling development takes place.
CHANGES IN THE SIZE OF ORTHOPHOSPHATE POOLS IN MYCORRHIZAL ROOTS OF BEECH WITH REFERENCE TO ABSORPTION OF THE ION FROM THE EXTERNAL MEDIUM
Authors: JENNINGS D. H. 
Published: May 2006

SummaryAt concentrations of potassium dihydrogen phosphate in the external medium below 10−3 M, the greater proportion of phosphate which enters beech mycorrhizal roots is incorporated into bound form. Above 10−3 M, an increasing proportion is accumulated unchanged as orthophos‐phate. Studies using 32P confirm, in greater detail, the observation of Harley and Loughman (1963) that phosphate in the external medium rapidly equilibrates with a small pool of ortho‐phosphate within the fungal sheath, from which the ion is incorporated into bound form or transferred either to the host core or to a larger pool in the sheath itself. Ammonium chloride at 10−2 M increases the total uptake of phosphate through an increase in the rate of both the incorporation into bound form and the primary absorption process. Ammonium chloride over the range 10−4 to 10−1 M brings about an increase in the size of the small pool. However, ammonium chloride has no detectable effect on phosphate fractions in the absence of phosphate in the external medium. Sodium azide, on the other hand, causes a breakdown of bound phosphate, although it is only at high concentration that this inhibitor has any detectable effect on the level of orthophosphate within the roots. The results suggest that the size of the small pool may be an important determinant of phosphate uptake at low concentration and that the role of potassium in the primary absorption process must not be overlooked.
INCORPORATION OF CARBON DIOXIDE INTO EXCISED BEECH MYCORRHIZAS IN THE PRESENCE AND ABSENCE OF AMMONIA
Authors: HARLEY J. L. 
Published: May 2006

SummaryExcised beech mycorrhizas incorporate 14C into their tissues from dilute bicarbonate solution. The rate is doubled if the mycorrhizas are shaken in ammonium phosphate rather than potassium phosphate. The main distribution is into malic, glutamic and aspartic acids in the presence of potassium. In the presence of ammonium ions glutamine becomes the most strongly labelled compound.
THE MOVEMENT OF TOMATO AUCUBA MOSAIC VIRUS IN TOMATO
Authors: ROBB SHEILA M. 
Published: May 2006

SummaryThe interval which elapses between inoculation of tomato leaves with tomato aucuba mosaic virus and movement of virus into the stem varies considerably. Movement out of young apical leaves appears to be more rapid than that out of mature basal leaves, but the major source of variation is inherent in the individual plant and is not eliminated by standardizing the temperature and light of the environment. Since the time when virus enters the stem cannot be estimated accurately on any one plant, no precise estimate can be formed as to the rate of movement in the stem. Movement may be upwards or downwards. Discontinuity of virus distribution in the stem has been observed and this could be adduced as evidence against autocatalytic spread of virus; on the other hand, in other experiments virus appears to have been intercepted in its passage through the stem, which might make rapid transport through the phloem seem unlikely. This approach to the problem is insufficiently precise either for estimating the rate of movement of tomato aucuba mosaic virus through the plant or for determining its path.
A CYTOGENETIC INVESTIGATION IN A PHYLLITIS‐ASPLENIUM COMPLEX
Authors: EMMOTT JANET I. 
Published: May 2006

SummaryA hybridization programme between diploid and tetraploid representatives of the genus Phyllitis has been carried out and two cases of intergeneric hybrids between Phyllitis and species of Asplenium have been synthesized and are described. Chromosome pairing involving tetraploid forms of Phyllitis scolopendrium from both North America and Japan suggests the occurrence of autosyndesis within the tetraploid genomes. This is not encountered in hybrids involving the tetraploid species P. hybrida. An allopolyploid origin for the latter and an autopolyploid origin for the former is probable although the exact parentage is not certainly known in either case. A working hypothesis concerning the possible course of evolution within the group Phyllitis is put forward in conformity with all the evidence, including that from morphology and geographical distribution, and the steps necessary to confirm or refute it are enumerated.
A NEW DESIGN FOR A PEAT SAMPLER
Authors: THOMAS K. W. 
Published: May 2006

SummaryA new design for a peat sampler is described. This sampler, in the view of the author, has a number of features which are considered to be of advantage both for field work and for the subsequent laboratory investigations of peat deposits. These advantages are listed, the most important being that intact cores covering the whole depth of deposits can be recovered and brought back to the laboratory for detailed investigation.
THE EFFECT OF ALUMINIUM ON THE UPTAKE AND INCORPORATION OF PHOSPHATE BY EXCISED SAINFOIN ROOTS
Authors: RORISON I. H. 
Published: May 2006

SummaryMovement of aluminium into excised root tips of sainfoin follows a normal curve which suggests little or no uptake into non‐free space. Washing in water removes very little aluminium from the roots but washing in dilute buffer solution removes a considerable exchangeable fraction. The pattern of phosphate incorporation in roots pretreated with aluminium is different from that obtained with untreated roots in several respects. Both percentage esterification and the proportions of the esterified fractions differ suggesting both a Donnan free space and a metabolic interference. The small amount of aluminium removed by aqueous washing suggests a minimum of precipitation with aluminium either external to the root, or in the water‐free space of the cortex. The importance of this aluminium‐phosphate effect as a component of aluminium toxicity, its specific sites and rates of reaction, require further experimental assessment.