bluuebunny/crossref_metadata_2025 huggingface dataset:
A NEW METHOD FOR THE COMPARISON OF POPULATIONS THAT CONTAIN HYBRIDS*
Authors: GAY PETER A.
Published: May 2006

Summary

Orthodox statistical methods frequently cannot be employed in the analysis of data obtained from natural populations that contain hybrids. The method outlined, which is based upon Anderson's technique of Hybrid Indices, eliminates some of the subjective element that is inherent in that technique and facilitates the comparison and summary description of complex populations that contain hybrids. The variation of these two statistics in various types of population is illustrated and the value and limitations of the method discussed.
RHOSGOGH COMMON, RADNORSHIRE: STRATIGRAPHY AND POLLEN ANALYSIS
Authors: BARTLEY DAVID D.
Published: May 2006

Summary

A number of stratigraphical sections and four pollen diagrams have been constructed in an attempt to trace the history and development of the area.

Together, the pollen diagrams cover a period starting in zone I of the Late‐glacial period and ending in zone VIII. The diagrams are generally of a western type but correspond more closely with the Somerset diagrams than with the Cardiganshire or Shropshire type.

Correlation between the stratigraphy and the pollen analysis show that the Common and its immediate surroundings began its development towards the end of the last glaci‐ation when the irregular dumping of drift material led to the impounding of a long, shallow lake. By progressive deposition of material, at first mineral but later organic, the lake basin gradually became filled and the vegetation which covered it passed through the stages of a typical hydrosere to Spagnum bog and Callunetum. At about the time of the Boreal‐Alantic transition the course of the succession, which had until then included Phragmites‐Cladmm fen, became altered and the fen and reedswamp stages are now represented by an impoverished swamp dominated by species of Juncus and Carex.

The birchwood‐with‐Phragmites has developed from a lagg vegetation while the birchwood‐with‐Cflmv and the southern birchwood have been formed by the colonization of the bog communities, the former at a comparatively recent date.

The most recent of those deposits which have been investigated are the downwash clays which are correlated in the pollen diagram with zone VIII and were apparently produced as a result of forest clearance and increasing wetness of climate.
STUDIES ON THE GROWTH OF EXCISED ROOTS
Authors: STREET H. E. , HUGHES JOYCE C. , LEWIS J. SYLVIA
Published: May 2006

Summary

Twenty‐one L‐amino acids and the amides L‐glutamine and L‐asparagine have been tested for their effects on the growth of excised tomato roots, by adding them singly to a medium of pH 4.8 containing the standard amount of nitrate. L‐ and D‐cystine were growth‐stimulatory. The amides, L‐aspartic acid and L‐arginine, did not significantly affect growth in concentrations up to 25 mg/1. The other amino acids were, to very differing extents, inhibitory to growth. The inhibitory activity of certain amino acids was greater at pH 6.8 than at 4.8. At this pH low concentrations of L‐arginine enhanced growth. The L‐ and D‐ forms of the amino acids differed in their inhibitory activity.

With the exception of L‐glutamine and, to a lesser extent, of L‐asparagine and the natural forms of the dicarboxylic amino acids, all the amino acids tested as sole nitrogen sources for root growth were completely ineffective at both pH 4.8 and 6.8. This applied also to the ‘balanced’ mixtures of amino acids which had only low inhibitory activity when added to a nitrate‐containing medium.

“Bacto’ casamino acids (an acid‐hydrolysed casein) was more effective than ammonium as a nitrogen source over the range pH 4.8 to 7.0, but was only as effective as nitrate at pH values close to neutrality.

At pH values of 5.3 or above, the growth of excised tomato roots on ammonium was markedly stimulated by the addition of amino‐acid mixtures whose composition was based upon amino‐acid analyses of hydrolysed casein. A mixture of the basic amino acids only was almost as effective as more complex mixtures. At pH 6.8 ammonium plus a suitable amino‐acid mixture supported growth equal to that with the casamino acids. The very poor growth of excised tomato roots supplied with ammonium at pH 4.8 was, however, not significantly enhanced by the amino‐acid additions which were markedly stimulatory at higher pH values, and was inferior to growth with casamino acids at this pH. A high level of root growth cannot yet be achieved at pH 4.8 in the absence of nitrate.
CYTOGENETIG RELATIONSHIPS OF VIOLA LACTEA SM. AND OTHER WEST EUROPEAN AROSULATE VIOLETS
Authors: MOORE D. M. , HARVEY M. J.
Published: May 2006

Summary

1. The interrelationships of five western European violets are determined by examining chromosome pairing in their F1 hybrids. Viola stagnina Kit. (n= 10), V. pumila Chaix. (n= 20), V. canina L. sspp. canina and montana (L.) Fries. (n= 20) and V. lactea Sm (n= 29) belong to the group Arosulatae and Viola riviniana Rchb. (n= 20) is in the group Rosulantes.

2. (a) Seven artificial interspecific hybrids were studied and the most frequent meiotic chromosomal arrangements can be summarized as follows: Viola canina × lactea (2n= 49)—2011+91; V. canina × stagnina (2n= 30)—101 + 101; V. canina (sspp. canina and montana) × riviniana (2n= 40)—1011+201; V. lactea × riviniana (2n= 49)—1011+291; V. pumila × canina (2n= 40)—1011 + 201; V. lactea × pumila (2n= 49)—1011+291.

(b) V. canina ssp. canina × riviniana and V. lactea × riviniana also had supernumerary chromosomes, derived from their riviniana parent. These varied in number, even between the p.m.c. of a single hybrid plant, which suggests somatic chromosomal irregularity, possibly during premeiotic mitosis.

(c) The two hybrids involving V. pumila frequently showed a high proportion of multivalents, as well as ‘clumping’ of the bivalents; the univalents were generally distinct but some tended to show secondary association at M1.

3. The genomic constitutions of the species were deduced from the chromosome pairing in the hybrids. The species are seen to be related in a reticulate pattern which is based on the combination of genomes by allopolyploidy. Within this pattern the groups, Arosulatae and Rosulantes, merge into one another, at least one genome being shared by species in each group.

4. The affinities and origin of Viola lactea are discussed. It is an allohexaploid deriving two genomes from V. canina. The species carrying the third genome cannot be found in western Europe and it is suggested that, if it still exists, it may be among the diploid Arosulatae in eastern Asia.
AN EFFECT OF GIBBERELLIC ACID ON GIRGUMNUTATION
Authors: McCOMB A. J.
Published: May 2006

Summary

Gibberellic acid causes a marked increase in the amplitude of circumnutation in dwarf pea seedlings. The effect may be detected within 12 hours from the time of treatment. The relation was investigated between the time at which this effect occurred and the time at which increased growth of the shoot was detected.
FLORAL PIGMENTS IN PAPAVER AND THEIR SIGNIFICANCE IN THE SYSTEMATICS OF THE GENUS
Authors: ACHESON R. M. , JENKINS C. L. , HARPER JOHN L. , McNAUGHTON I. H.
Published: May 2006

Summary

Chromatographic analysis of the floral pigments of species of the genus Papaver revealed the presence of cyanidin and pelargonidin derivatives and in addition yellow compounds which were not anthocyanins. The distribution of these pigments among the poppy species supports Fedde's division of the genus into sections, and suggests an affinity between the sections Pilosa and Scapiflora. The pigments of three interspecific hybrids showed the biochemical versatility of the less versatile parent.

The anthocyanins of petals and stamens frequently differed and the bases of petals normally contained petal and stamen pigments in mixture. High concentrations of cyanidin pigments were not found in the same floral parts as either yellow pigments or high concentrations of pelargonidin derivatives.
PHYSIOLOGICAL STUDIES OF GERMINATION IN THE GENUS AVENA
Authors: DRENNAN DONALD S. H.
Published: May 2006

Summary

Changes in fats, sugars and starch have been followed in grains of A. sativa during the first few days in germination conditions.

A decrease in fats and some of the sugars present in the dry grain was evident during the first day; the utilization of starch did not commence until between the first and second days.

It is concluded that the metabolism of the germinating grain is not initially dependent on starch‐derived materials. Fats and some of the sugars are suggested as likely alternatives for respiratory substrates.

The relevance of this to previous studies on the development of starch‐degrading enzymes in germinating and dormant grains of Avena spp. is discussed.
THE EFFECTS OF DAY‐LENGTH ON THE DEVELOPMENT OF THE SPOROPHYTE OF POLYTRICHUM ALOIDES HEDW. AND P. PILIFERUM HEDW.
Authors: HUGHES J. G.
Published: May 2006

Summary

The apical meristem of the sporophyte of Polytrichum spp. has been described briefly. The meristem is described as vegetative so long as it continues to contribute cells to the seta: in this vegetative phase the endothecium is a distinct histogen. In the reproductive phase all the cells in the meristem are used in the construction of the sporangium and the onset of this phase is marked by the segmentation of the endothecium from below upwards.

Experiments with P. aloides Hedw. and P. piliferum Hedw. indicate that the development of the sporangium, once initiated, is conditioned by seasonal factors, but the transition from the vegetative to the reproductive phase is conditioned by some other factor(s) not identified. When the growth of a sporangium is inhibited by experimental conditions, vegetative growth is not prolonged.
STUDIES ON THE PROTEINS, PEPTIDES AND FREE AMINO ACIDS IN GYSTOGARPIG AND TETRASPORIG PLANTS OF AGARDHIELLA ROBUSTA FROM BOMBAY
Authors: LEWIS E. J. , GONZALVES ELLA A.
Published: May 2006

Summary

Cystocarpic and tetrasporic plants of Agardhiella robusta (Grev.) Boergs., collected from Bombay, were analysed separately for the constituent amino acids in the proteins, peptides and in free state, by using a quantitative paper chromatographic technique. A total of twenty‐four amino acids were detected in them. Qualitative variations occurred between cystocarpic and tetrasporic specimens only in the peptide hydrolysates, and quantitative differences were observed in some individual amino acids in the proteins, peptides and in the free state.
THE ANEMIA ADIANTIFOLIA COMPLEX IN JAMAICA
Authors: WALKER TREVOR G.
Published: May 2006

Summary

It has been shown that Anemia adiantifolia, which has customarily been regarded as a uniform species, forms a polyploid series in Jamaica, with diploid, triploid and tetraploid cytotypes. The tetraploid backcrosses to the diploid in the wild to give rise to sterile triploid hybrids. The latter form thirty‐eight bivalents and thirty‐eight univalents at meiosis and this, coupled with the morphological and cytological evidence, indicates that the diploid is one of the parents of the allotetraploid. Distributional studies of the forms in Jamaica from a sample of eighty‐seven plants show that the diploid is the more common form, both numerically and distributionally. Little evidence can be adduced from the morphology of the tetraploid as to its other diploid parent.
SUGAR ABSORPTION BY CHAETOMIUM GLOBOSUM
Authors: WALSH J. H. , HARLEY J. L.
Published: May 2006

Summary

The absorption of the sugars, glucose and fructose, by Chaetomium globosum does not involve an accumulation against an internal concentration but is associated with immediate assimilation. The process is sensitive to the presence of inhibitors, anaerobiosis, and to the concentration supplied. The relationship to concentration is hyperbolic and the half maximum rates occur at about 6–8 × 10‐3 M for fructose and 9 × 10‐5 M for glucose. Glucose and fructose compete for the uptake mechanism so that in mixed solutions when the glucose concentration is at about 13% of that of fructose the uptake of the latter is abolished.

The uptake of carbohydrate from sucrose solutions is mainly an uptake of the hexose moeities released from sucrose. The amount of sucrose absorbed intact is very small. Sucrose is split by an enzyme system which appears to be located at or near the hyphal surface. It is relatively resistant to temperature and metabolic inhibitors and appears to be stimulated by alkali metal ions in solution.
PLANT GROWTH AND THE AERIAL ENVIRONMENT
Authors: EVANS G. C. , HUGHES A. P.
Published: May 2006

Summary

If it cannot be assumed that the rate of increase of dry weight of a plant per unit leaf area (unit leaf rate or net assimilation rate) is constant, the computation of a mean value for this rate over a period between two harvests requires information or assumptions as to the relationship between dry weight (W) and leaf area (1). With sufficient information the problem can be solved graphically, but it is usual to assume either that W = a+bL or that W = a+bL2, where a and b are constants, leading to two well‐known formulae which suffice for many purposes. For more precise work, it is here shown that the solutions of a general case, W = a+bLn, where n is a third constant, are related to these formulae in a manner depending only upon n and upon p, the ratio of leaf areas at the first and second harvest. Various methods of computing the constants are described, their significance is discussed, and it is shown that for the young stages of certain plants n is close to I and the constant a is negligibly small. Later n increases, and the constant a becomes significant. Finally these methods are used to recompute the estimates of unit leaf rate given in Paper II of this series.
MOVEMENT OF GROWTH REGULATORS IN PLANTS
Authors: McCREADY C. C.
Published: May 2006

Summary

The synthetic auxin 2,4‐dichlorophenoxyacetic acid (2,4‐D), labelled with carbon‐14 in the carboxyl group, was applied in blocks of agar gel to either the apical or the basal ends of segments cut from the petioles of young primary leaves of Phaseolus vulgaris, and the carbon‐14 appearing in receiving blocks at the other end was measured. When application was made to the apical ends, all the carbon‐14 accumulating in the receiving blocks appeared to be still in the form of 2,4‐D. This basipetal transport had a velocity of 0.6–1.0 mm/hour, and continued even when the concentration of 2,4‐D in the receiving blocks had become higher than that remaining in the donor blocks. Acropetal movement was much smaller. The ratio of acropetal to basipetal movement was approximately constant with time at low concentrations of 2,4‐D. At a high concentration, the ratio was increased; with longer segments it was decreased. More 2,4‐D entered the segments from blocks applied to the apical than to the basal ends. It is concluded that 2,4‐D is moved through these petiole segments by active polar transport.
A NUMERICAL REPRESENTATION FOR TAXONOMIC KEYS
Authors: OSBORNE D. V.
Published: May 2006

Summary

Some of the limitations of the usual type of dichotomous taxonomic key are pointed out. It is suggested that a particular method of representing the characteristic features of a species in numerical form can overcome some of these limitations. Identification by this method is rapid, can often be made correctly in spite of minor errois of observation, and requires no computation or computing equipment. The method may therefore be of particular use in the field.
THE DEVELOPMENT OF HALIDRYS SILIOUOSA (L.) LYNGB.
Authors: MOSS BETTY , LACEY ALAN
Published: May 2006

Summary

From culture experiments it has been shown that the early stages in the development of Halidrys siliquosa are more similar to those of Cystoseira and Sargassum than to those of Fucus. The young plant has cryptoblasts along the primary frond and these are absent from the adult thallus. These hair pits are associated with the development of apical cells and the definitive axis of the adult thallus. The first year's growth is entirely vegetative and results in a pinnately branched thallus of ‘leafy laterals’only.

Air vesicles are differentiated during the second year's growth and fertile receptacles are formed later. The receptacles are initiated from the end of August and new ones continue to be formed until December. Gametes are differentiated shortly before their discharge from December till March. After gamete discharge the receptacles disintegrate.

The adult thallus shows a seasonal periodicity in growth and reproduction. There is a period of rapid vegetative growth during the spring and early summer which is followed by receptacle differentiation and‐then gamete discharge from December to March.
WOOD FIBRES WITH LIVING PROTOPLASTS
Authors: FAHN A. , LESHEM B.
Published: May 2006

Summary

It has been observed that in many woody plants the libriform fibres, and in some the fibre tracheids, retain living protoplasts in the entire sapwood. It is suggested, therefore, that the definition of fibres usually given in botanical textbooks, should be changed. From the preliminary study it appears that living protoplasts persist mainly in shrubs and subshrubs. As these life‐forms generally represent the woody vegetation of unfavourable habitats, it may be possible that living fibres are adaptive characters.
SOME ASPECTS OF THE THEORY OF DICHOTOMOUS KEYS
Authors: OSBORNE DONALD V.
Published: May 2006

Summary

The structure of dichotomous keys is discussed, and some general theorems are proved concerning the number and arrangement of the taxa in any given key. The possibility is considered that the various questions in a key may occasionally be answered wrongly, the key then leading to a wrong determination. It is shown that if this possibility exists, then the probability of a right determination is almost always improved by changing the structure of the key to make it as ‘short’as possible.

The possibility is also considered of adding alternative identification paths through the key (‘reticulations’), starting at points where a particularly difficult question is asked. It is shown that this practice usually improves the key in respect of the determination of certain taxa, but may often diminish the overall probability of correct determination averaged over all taxa.
OBSERVATIONS ON NATURAL CLONES OF TRIFOLIUM REPENS L.
Authors: HARBERD D. J.
Published: May 2006

Summary

An attempt was made to map the distributions of some of the individual clones of Trifolium repens in an area of about 600 sq. yd of fixed dune vegetation. The field observations were checked in culture by morphological examination and by cross‐pollination. Most of the clones were limited to small patches of land (up to 6 yd across) and in relation to the vigorous vegetative spread of the species this might indicate a maximum age of genotype of about 20 years. However, one clone was found to be distributed in five discrete patches, each of small size but collectively giving a discontinuous spread of more than 20 yd. The five patches were limited to a narrow ecological zone suggesting specialization in ecological tolerance. The presence of a second genotype which occurred in two patches ecologically similar to one another but contrasting strongly with those of the first genotype indicated differentiation of ecological tolerance between genotypes within the population. These results are contrasted with those published earlier for Festuca. It is pointed out that if vegetative spread is limited by ecological factors the size of the area occupied by a clone cannot be regarded as a function of age, and that consequently the Trifolium genotypes observed might be just as ancient as those of Festuca.
THE PARASITISM OF CUSCUTA
Authors: MACLEOD D. G.
Published: May 2006

Summary

The presence of several transaminase enzymes has been demonstrated in Cuscuta reflexa and C. campestris. The activity of glutamate–aspartate transaminase in Cuscuta and host plants was measured. At least part of the transaminase activity of C, campestris and C. reflexa is located on the mitochondria. The presence of glutamic dehydrogenase in C. reflexa was demonstrated. An evolutionary scheme is postulated for the parasitism of Cuscuta.
THE GROWTH OF THE CHERRY OF ROBUSTA COFFEE
Authors: DANCER J.
Published: May 2006

Summary

After a period of initial growth the water content of the cherry increases considerably although that of the bean is not high during early development. Leaf reduction early in the growth period or water deficit, early or late, reduces growth. The later increase in weight of the bean is due to an increase in dry matter.
EQUATIONAL RELATIONS BETWEEN NUTRIENT QUANTITIES AND CELLULAR GROWTH
Authors: BOSS M. L.
Published: May 2006

Summary

The quantities of five nutrients (N, P, K, Mg, Ca) were estimated in enlarging maize root tip cells. When consecutive cell fresh weights were plotted against the total quantity of any one nutrient per cell a parabolic curve resulted which fits the expression: W = kXn, where W is the fresh weight per cell, X the nutrient quantity and n and k are constants. The inference that may be drawn is that, under a defined environment, cell weight and nutrient quantity are related to each other by a constant quantitative factor. Two equations are derived to support the above hypothesis and also to support a related hypothesis that there might exist a quantitative relationship between any one nutrient and all other nutrients in a given cell at any one time.
OBSERVATIONS ON THE FLORAL BIOLOGY OF DIGITALIS SPECIES
Authors: PERCIVAL MARY , MORGAN PATRICIA
Published: May 2006

Summary

Observations were made on the floral biology of Digitalis amandiana, D. ambigua, D. lanata, D. lutea and D. purpurea. The rhythms of flowering, pollen presentation, stigma opening and nectar secretion were investigated and the amount and concentration of the nectar measured. The flower sizes and insect sizes were compared, and proved that Bombus lucorum workers and queens, and B. agrorum workers and queens, were unable to reach the bottom of the corolla tube of Digitalis lutea. Bombus lucorum chiefly chose this species as nectar seeped along the lower side of the corolla to heights which it could reach (see addendum). The other species had no mechanical barrier to full exploitation of the nectar by B. lucorum and B. agrorum. B. agrorum preferentially worked Digitalis ambigua in early summer and D. lanata later.

This paper describes observations made over two seasons, in both natural and glasshouse conditions. The full significance of much of the data cannot yet be evaluated but a tentative assessment of the significance of bee visits for pollination and hybridization is given.
SURFACE ASSOCIATIONS BETWEEN PARTICLES AND THE ENDOPLASMIC RETICULUM IN PROTOPLASMIC STREAMING
Authors: THAINE R.
Published: May 2006

Summary

Protoplasmic streaming was observed in Tradescantia virginiana staminal hair cells using a bright field oil immersion obective and particle movements were followed in the cytoplasm. By recording and plotting particle positions in every fourth frame of a cine film, different velocities were measured for particles which appeared to follow a common pathway in a transvacuolar strand. From the same kind of analysis, various patterns of particle movement were revealed on the surface of the nucleus.

Phase contrast observations of leaf hair cells of Primula obconica and Perilla frutescens showed that the endoplasmic reticulum was particularly well developed in regions of active protoplasmic streaming. Tubules of the endoplasmic reticulum were mainly in parallel orientation, with occasional lateral connections and anastomoses. Groups of parallel, endoplasmic reticulum tubules also appeared to be in continuity with the nucleus and, although these elements approached the nucleus at different angles from the parietal cytoplasm, they were more usually orientated with the long axis of the cell. Particles moved along the endoplasmic reticulum surfaces, sometimes in opposite directions on adjacent tubules, and a dynamic association was observed between the endoplasmic reticulum and mobile particles. This association was well illustrated when endoplasmic reticulum developed in a microscopically undifferentiated region of parietal cytoplasm. As the endoplasmic reticulum developed, the undifferentiated region was apparently transformed and became part of the endoplasmic reticulum. Occasionally, a centre of endoplasmic reticulum development was observed as a compact, complex pattern of tubules which gradually became orientated in a more linear manner as it expanded. This differentiation occurred in association with unusual, concentric, particle movement at the development centre. Finally the endoplasmic reticulum elements formed parallel pathways as commonly seen in actively streaming cytoplasm. These observations are incompatible with current theories of protoplasmic streaming which propose that particles are carried along by the fluid endoplasm or the endoplasmic reticulum. An extension of earlier theories has been made to explain the movement of particles in relation to the activities of the endoplasmic reticulum.

Associations of particles and membranes were also observed in cytoplasm of cells involved in the synthesis and transport of organic nutrients. This structural association may be part of a common transport mechanism within parenchyma cells and over long distances in the vascular system.
APICAL DOMINANCE IN FUCUS VESICULOSUS
Authors: MOSS BETTY
Published: May 2006

Apical tips of Fucus vesiculosus L. were grown in sterile sea water. The apical cell region was excised surgically and this resulted in a decreased rate of growth of the segment and the regeneration of new branches. Treatment of cultured tips, whose apical cell region had been excised, with four auxins and two anti‐auxins revealed a striking effect. The latter treatment induced up to three or four times the number of branches regenerated in control experiments. Extraction and chromatographic procedures carried out on apical tips from November to January showed that a mixture of stimulatory and inhibitor)’growth substances was present. It is concluded that growth regulators play a part in determining apical dominance in Fucus.
INCREASES IN THE CAPACITY OF PEA TISSUE TO FORM ACYL‐ASPARTIC ACIDS SPECIFICALLY INDUCED BY AUXINS
Authors: SUDI J.
Published: May 2006

Summary

A study has been made of the factors which influence the rate of formation of 3‐indoIeacetyl‐L‐aspartate and i‐naphthaleneacetyl‐L‐aspartate when segments of etiolated pea stems are treated with 3‐indolylacetic acid (IAA) and i‐naphthaleneacetic acid (NAA). When the tissue is placed in the auxin solution there is an initial lag in the formation of each conjugate and the maximal capacity is not reached until 6 hours. If the tissue is pretreated with non‐radioactive IAA or NAA for 8–14 hours before transference to radioactive IAA or NAA, the amount of conjugate formed in the next 2 hours is up to six times greater than that formed in tissues receiving no pretreatment. Apparent substrate saturation of the system is reached when the external concentration of IAA and NAA is about 50 and 15 mg/1 respectively.

Induction of the formation of IAA aspartate is not a consequence of auxin‐induced extension growth since it also takes place in fully extended segments.

The capacities of other auxins to induce the formation of both IAA and NAA aspartateswere assessed. It was established that both conjugates are also induced when the segments are pretreated with 2,4‐dichlorophenoxyacetic acid, 2,3,6‐trichlorobenzoic acid and S‐carboxymethyl‐N, N‐dimethyldithiocarbamate. In contrast, pretreatment with other carboxylic acids such as benzoic acid (which itself can form an aspartate) or transcinnamic acid, 3, 5‐dichlorophenoxy‐acetic acid and α‐2, 4‐dichlorophenoxy‐iso‐butyric acid does not affect the rate of formation of either IAA or NAA aspartate.

These findings are interpreted in terms of induced enzyme formation in a system where the capacity for induction is specifically restricted to compounds which have a high auxinic activity. It is also clear that compounds showing a high inductive capacity are not necessarily suitable substrates nor are substrates necessarily capable of induction.
COMPARATIVE PHYSIOLOGICAL STUDIES ON DESCHAMPSIA FLEXUOSA, HOLCUS MOLLIS, ARRHENATHERUM ELATIUS AND KOELERIA GRACILIS IN RELATION TO GROWTH ON CALCAREOUS SOILS
Authors: WOOLHOUSE H. W.
Published: May 2006

Summary

The four grasses Deschampsia flexuosa, Holcus mollis, Arrhenatherum elatius and Koeleria gracilis grow on a wide range of soil types under natural conditions. Little is known of the physiological mechanisms by which the different species are adapted to particular soils. In glasshouse experiments all four species grew well on a fertile garden soil but showed varying diminution of growth on a calcareous soil, amounting in the extreme case of Deschampsia flexuosa to near failure, accompanied by chlorosis and severe inhibition of root development. The involvement of bicarbonate is suggested by the severe inhibition of growth of roots of D. flexuosa grown in water culture. Bicarbonate is without effect on the respiration of roots of the four species in short‐term experiments but roots of D. flexuosa showed a much greater rate of 14C‐bicarbonate fixation than the other species.

It is suggested that the reduced growth of plants on calcareous soils may often be attributed to effects of bicarbonate on the physiology and growth of the root system leading only in extreme cases to chlorosis of the leaves. The data are discussed in relation to relevant physiological and ecological work. An appendix is added providing calculation of probable bicarbonate concentrations in calcareous soil solutions to provide a basis for the concentrations employed in laboratory studies.
THE PREPARATION AND PROPERTIES OF o‐DIPHENOL: OXYGEN OXIDOREDUCTASE FROM POTATO TUBERS
Authors: ABUKHARMA D. A. , WOOLHOUSE H. W.
Published: May 2006

Summary

An o‐diphenol: oxygen oxidoreductase (E.C. 1.10.3.1) has been purified from potato tubers. The enzyme shows a similar affinity for a range of substrates although the affinity is highest for chlorogenic acid, which occurs naturally in potato tubers. The affinity for oxygen is relatively low (Km= 2.23 × 10−4 m).

The pattern of activity over a range of pH values varied considerably with different substrates. Ultracentrifuge studies and agar gel electrophoresis suggest the preparation is relatively pure although throughout purification the preparation showed an increasing cresolase as well as o‐diphenoloxidase activity.

It is suggested that the cresolase activity is a normal component of the enzyme activity which may well be of importance in vivo. The high potency of a number of inhibitors including the copper‐specific 3:4 dichlorophenyl serine suggests that this metal is an integral part of the prosthetic group.
THE BASIC ACTION OF GIBBERELLIC ACID IN ELONGATION OF ‘METEOR’ PEA STEMS
Authors: ARNEY S. E. , MANCINELLI P.
Published: May 2006

Summary

The published evidence on the histological action of gibberellins does not favour the widespread belief that the primary action of gibberellic acid (GA) in stem growth is on cell elongation. Histological evidence from Meteor pea internodes shows that the main effect of GA is to stimulate cell division; and even when applied to internodes which have passed into the vacuolation phase of growth GA often re‐activates cell division. Mitotic activity in the apical meristem of Meteor pea stems is also stimulated by GA. The experimental results suggest that the primary effect of GA on caulescent plants, as on rosette plants, is to increase mitotic activity in apical and sub‐apical meristems; the cell elongation effect of GA may well be a derivative of the increased mitotic activity, possibly through an increased production of auxin in the meristematic region.
RELATIONSHIP BETWEEN ROOT GROWTH OF FLAX (LINUM USITATISSIMUM) AND SOIL WATER POTENTIAL
Authors: NEWMAN E. I.
Published: May 2006

Summary

Flax plants were grown in vertical cylinders of soil contained in polyethylene tubing. Root growth was estimated from the number of roots crossing vertical and horizontal lines on the tube surface. After the plants were 29 days old, some of the soil cylinders received no more water, and root growth and soil water content in each 10 cm layer of soil were determined at 2‐day intervals. When a graph of root growth against soil water potential is plotted, points from each 10 cm layer fall approximately on the same concave curve. A marked reduction in root growth first occurred at — 7 bars total water potential. At — 15 bars, root growth was 20% or less of the rate before drying, but some root growth occurred in soil drier than — 20 bars. The results suggest that root growth in each layer was not influenced by water potential elsewhere in the plant.
A POROMETER FOR USE IN THE FIELD
Authors: WEATHERLEY P. E.
Published: May 2006

Summary

A falling mercury plug draws air through a leaf cup in series with a standard capillary resistance bridged by a mercury manometer. Readings on the manometer correspond to leaf conductances. Thus no timing is necessary. The cup is a short length of latex rubber tubing (mternal diameter 2·5 mm) held in position by a light clip. The apparatus can be held and operated in one hand leaving the other free to manipulate the porometer chp. No levelling is necessary. The poro‐meter is contained in a case 24 × 6 × 3 cm and is easily portable. Using the apparatus itself, capillaries are readily standardized in units of conductance expressed in terms of rate of flow of air through the capillary per unit pressure difference (mm3/min/rnm Hg). Using a 2·5 mm cup the highest stomatal conductances measured were around 200 units. Three standard capillaries are incorporated in the porometer allowing approximately a 500‐fold change in leaf conductances to be covered.

The performance of the instrument on Sambucus nigra, Vaccinium vitis‐idaea and Poa annua is demonstrated and some of its advantages and weaknesses discussed.
STUDIES ON OXYGEN TRANSPORT THROUGH MUSTARD SEEDLINGS (SINAPIS ALBA L.)
Authors: GREENWOOD D. J.
Published: May 2006

Summary

The entry of oxygen into various organs and the transport of oxygen through plant tissues was studied. Seedlings had their roots embedded in agar‐gel to exclude oxygen. The gas atmosphere around a part of the plant was changed from nitrogen to oxygen and the subsequent increase in oxygen concentration at a point on the root surface was measured. Changing the atmosphere around the stems and leaves induced rises in oxygen concentrations throughout the length of the roots to the root tips. An equation derived by assuming that transport was by gaseous diffusion and was large in comparison with metabolic uptake, fitted the increases in oxygen concentration at points on the roots within 3 cm of the stems, but not at the root tips. The discrepancy was accounted for by the greater value of metabolic uptake relative to oxygen transport at the root tips than near the stems. Thus all the results were consistent with oxygen diffusing through gas spaces within the plants.

Removing all the leaves restricted the entry of oxygen into the aerial portions of the plants, but the extent to which it did so was reduced by subjecting the seedlings to water stress and was less with old than with young seedlings. Excising the leaves was considered to release cell sap which blocked the gas channels.

Exposure of either the stem or a segment of root to oxygen resulted in a small amount of oxygen being transported along the roots.

Oxygen transport from the aerial portions of the plant to a point on the roots, 1–2 cm from the hase of the stems, was almost independent of (a) the aeration conditions of the growth media; (b) the mechanical impedence to root growth offered by the media; (c) root length; (d) shoot length; (e) age of plant.
SHADE TOLERANCE IN TREE SEEDLINGS
Authors: LOACH K.
Published: May 2006

Summary

Seedlings of five tree species of different shade tolerance were raised in full daylight and in three degrees of shade. Leaf chlorophyll content, the rate of respiration in darkness at 30°C and photosynthesis rates at 30°C over a range of light intensities, were measured in each case. The initial slope of the curve, relating photosynthesis rate and light intensity, provides a measure of the capacity of the photochemical system of the leaves and was usually steeper in shade grown leaves than in sun leaves. Thus all species showed a degree of adaptation to shade conditions, but, surprisingly, leaves of the shade tolerant species had slightly less steep slopes than the intolerant species. This was offset by a considerably lower rate of leaf respiration and a lower light compensation point in the tolerant species, so that considered over a range of varying low light intensities, the net photosynthesis would probably be similar in both groups. Moreover, whilst leaves of the tolerant species tended to show reduced respiratory activity when grown in shade, this was less evident in the intolerant species. The differences in rates of respiration may he the most important determinants of success or failure in woodland shade, where the plant may spend many more hours below than above the light compensation point.
THE RELATION BETWEEN HOST AND ENDOPHYTE IN ORCHID MYCORRHIZA
Authors: HARVAIS G. , HADLEY G.
Published: May 2006

Summary

Extensive isolation of root endophytes from Orchis (Daciylorchis) purpurella and other British orchids yielded a variety of strains of Rhizoctonia and of other fungi. R. repens, a common orchid endophyte, occurred in several host species and habitats. R. solani was uncommon, being obtained only from Orchis purpurella and Coeloglossum viride in certain situations. Most Rhizoctonia strains were obtained from only one plant and one habitat and the evidence indicated that there was no specificity between host and endophyte.

In symbiosis tests isolates from roots generally infected the protocorms but did not always stimulate the growth of the species from which they originated. Four strains of R. solani isolated from soil were stimulatory to Orchis purpurella protocorms. Of four Rhizoctonia solani strains pathogenic on crop hosts, two stimulated protocorm growth and one was parasitic. It is suggested that the occurrence of a strain as a root endophyte may largely be a reflection of its distribution and of the factors affecting its growth in the soil.
HEMIPARASITIC NUTRITION IN ANGIOSPERMS
Authors: GOVIER R. N. , NELSON M. DENISE , PATE J. S.
Published: May 2006

Summary

Plants of the hemiparasite Odontites verna (red bartsia) benefited markedly through association with barley (Hordeum vulgare L.) or white clover (Trifolium repens L.). Benefit commenced after the establishment of haustorial connections on the roots of a host.

Compounds containing labelled carbon moved through haustoria into the hemiparasite following feeding of [14C]urea or 14C‐labelled carbon dioxide to shoots of a range of host species. The reverse movement from hemiparasite to host was of a very small proportion although the hemiparasite was clearly capable of transferring assimilates from its leaves to all parts of its root system.

A bleeding sap technique was used to study the common metabolites released from the roots of Odontites, barley and white clover and to determine those organic compounds involved in transfer from each host to the hemiparasite. After a short exposure of the host shoot to 14CO2, it was possible to recover labelled amides, amino acids, organic acids and sugars in sap exuding from the cut root stumps of host and hemiparasite, and in the ethanol‐soluble fractions of host roots and hemiparasite tissues. Labelled sucrose was not detected in the bleeding sap or tissues of the hemiparasite although it was the main labelled compound to be translocated to the host root. The hemiparasite root appeared to metabolize a proportion of the assimilates that it received from a host plant.

Odontites grown alone was capable of a limited rate of synthesis of amino acids in its own roots. When grown in association with a suitable host, assimilation of nitrate by roots of the hemiparasite was supplemented by absorption of amides, amino acids and other metabolites elaborated in the host. The spectra of compounds entering the hemiparasite varied greatly with the host species, these differences being reflected in the composition of the pool of soluble compounds in the mature hemiparasite.
PHELLOGEN ACTIVITY IN ROBINIA PSEUDACACIA L.
Authors: WAISEL Y. , LIPHSCHITZ NILI , ARZEE TOVA
Published: May 2006

Summary

Phellogen activity in Robinia pseudacacia and some of the factors controlling it were investigated. A highly active phellogen is characterized by the production of large thin‐walled phellem cells. A layer of flat, thick‐walled phellem cells next to the phellogen characterizes an inactive meristem. The annual rhythm of phellogen activity of Robinia trees grown outdoors reveals that the phellogen is active twice a year, while under the same conditions the cambium is active once a year only. Under controlled conditions of temperature and day‐length the phellogen was found to be active mainly under combinations of short day and high temperature or long day and low temperature.
STUDIES ON THE TRANSPORT OF OXYGEN THROUGH THE STEMS AND ROOTS OF VEGETABLE SEEDLINGS
Authors: GREENWOOD D. J.
Published: May 2006

Summary

Experiments were carried out to determine whether oxygen could enter the leaves of vegetable seedlings and be transported through the tissues to the roots. The technique involved embedding seedlings in agar/potassium phosphate gel to exclude oxygen; the atmosphere around the leaves was varied and oxygen concentrations were measured at points on the root surface 0.5–2.0 cm from the junction of stem and root system. When the gas around the leaves was changed from nitrogen to oxygen, the oxygen concentration at the root surfaces increased rapidly. The rates of increase agreed approximately with those calculated by assuming that the plants contained continuous non‐tortuous gas‐filled channels, the view that diffusion through these channels was the means by which oxygen was transported through the plant, and that the gas channels were within about 12 μ of the root surfaces.

Experiments were also carried out to determine whether the roots of seedlings could grow in oxygen‐free media. Seedlings were grown in an atmosphere of air with their roots in columns of agar‐gel containing yeast and glucose. Depending on the amount of yeast and glucose in the gel, the oxygen concentration fell to zero at depths of between 0.5 and 2.0 cm from the gel surface. Seedling roots rapidly penetrated oxygen‐free zones in the gel but the extent of penetration appeared to be unrelated to the depth of zero oxygen concentration.

A similar pattern of results was obtained with seedlings of twelve different species and it was concluded that the stems and roots of most seedlings contain continuous, non‐tortuous gas channels through which oxygen diffused. When the plants were grown under anaerobic conditions such diffusion could satisfy all the roots’requirements for oxygen.
MICROFIBRILS IN THE LORICA OF THE FRESHWATER ALGA DINOBRYON
Authors: KARIM A. G. A. , ROUND F. E.
Published: May 2006

Summary

The presence of very fine microfibrils in the lorica of species of Dinobryon has been revealed by electron‐microscope examination of shadowed material. No indication of scales or annular components in the lorica, such as have been recorded by earlier workers using the light microscope, can be detected.
CUTICLE STRUCTURE AND WATER RELATIONS OF THE NEEDLES OF PINUS RADIATA (D. DON)
Authors: LEYTON L. , ARMITAGE I. P.
Published: May 2006

Summary

The fine structure of the cuticle of mature needles of Pinus radiata has been studied from electron micrographs of carbon replicas of the needle surface. The whole of the needle surface appears to be covered by a layer of wax from which, with the exception of the inner surface normally enclosed by the sheath, arise numerous tubular waxy outgrowths similar to those previously observed in P. sylvestris. Unlike P. sylvestris, these outgrowths cover only a portion of the exposed needle surface and the underlying wax layer ranges in appearance from smooth to slightly granular, with no indication of a plate‐like structure.

When the needles were immersed in water, very little was taken up into the basal region of the needles normally enclosed by the sheath compared with the exposed surfaces; the tips of the needles showed the highest permeability to water. The inner surfaces of the needles were consistently more wettable than the outer surfaces, and the surfaces normally enclosed by the basal sheath, corresponding to the youngest regions of the needle, were much less wettable than the exposed surfaces. The inner enclosed surface was the least wettable of all; this may be due to differences in the chemical composition of the wax, besides the absence of weathering.

When young needles were prematurely exposed by removing the basal sheath, tubular, waxy outgrowths appeared, similar to those found on the exposed surfaces of the mature needles; when young needles were bound together to prevent them from parting, an entirely different structure developed consisting of minute granules forming a reticulum over the surface.

The significance of the above findings is discussed in relation to the reputed relatively high cuticular transpiration of P. radiata and its ability to absorb water directly into the foliage from precipitation; it appears that this species is well adapted to the moist atmospheric conditions characteristic of its native habitat in the Californian ‘fog belt’ region.
INTROGRESSIVE HYBRIDIZATION BETWEEN BETULA NANA L. AND B. PUBESCENS EHRH. IN NORTH‐WEST ICELAND
Authors: ELKINGTON T. T.
Published: May 2006

Summary

In Iceland the genus Betula is represented by B. nana L., which has little morphological variation, and a variable series of shrub and tree birches. A comparison of these variable populations in the Skjaldfannardalur area, Isafjardardjup, north‐west Iceland with British populations of B. pubescens Ehrh. (2n= 56) and B. nana (2n= 28) using histograms of hybrid indices has been made and it is concluded that the variation is due to introgressive hybridization between B. pubescens and B. nana. The introgressed B. pubescens populations have a lower fertility than those of B. nana.

The mechanism of gene flow is discussed and it is suggested that it is more likely to be either direct from diploid to tetraploid levels or via intermediate triploids rather than through the formation of aneuploid complexes.
AN ULTRASTRUCTURAL STUDY OF SEXUAL REPRODUCTION IN PYTHIUM ULTIMUM
Authors: MARCHANT R.
Published: May 2006

Summary

The original observations of sexual reproduction in Pythium ultimum have been re‐interpreted in the light of electron microscope observations. The antheridium of P. ultimum penetrates the oogonium with only a slight constriction of the antheridium and not through a tube as described previously. During the development of the oospore the amount of storage material increases and the wall thickens. In the mature oospore there is a single centrally placed nucleus and most of the rest of the oospore is filled with storage material. The few remaining organelles are found in small pockets between the storage organelles. The lenticular body, originally described as the nucleus, appears to be an artifact produced from the periplasm.
STUDIES IN DACTYLIS
Authors: PARKER P. F. , BORRILL M.
Published: May 2006

Summary

Hybridizations were carried out between samples of ten diploid Dactylis subspecies. Both pollen fertility and ‘fertility index’ of hybrids decreased from initial cross to F2. There was no correlation of fertility with geographical distribution of the parents, and despite the fall in hybrid fertility it was considered that gene exchange would not be completely prevented.