bluuebunny/crossref_metadata_2025 huggingface dataset:
EFFECTS OF GROWTH REGULATING SUBSTANCES AND WATER POTENTIAL ON THE DEVELOPMENT OF SECONDARY XYLEM IN FRAXINUS
Authors: DOLEY D. , LEYTON L.
Published: May 2006

Summary

Marked variations in secondary vascular growth of detached Fraximis excelsior L. stems were obtained with changes in water potential and in IAA and GA concentrations in the culture medium. The width of new tissue, the number of fibres and the mean fibre diameter increased with IAA concentration up to 10 mg.1−1 and generally with GA concentration up to 100 mg.1−1, but by far the greatest influence was that of water potential wbich, especially between zero and −0.1 J.g−1, significantly depressed cell division and expansion. Expansion of cambial initials to a diameter of about 6 μ appeared to be necessary before active cell division commenced.

Vessel development was particularly sensitive to IAA supply and the amount of IAA required for the formation of groups of vessels increased as the number of constituent vessels increased and as the water potential was reduced. Gibberellin bad no significant effect on the number of vessel groups formed, but appeared to increase the number of vessels formed in any group. Vessel formation may occur without cell division in an initially dormant cambium. Increasing the IAA supply led to increasing vessel cross sectional areas, but progressively less effectively as the water potential was reduced; the marked reduction in vessel lumen area between zero and −0.1 J.g−1 potential suggests that vessels formed at reduced water potentials may have different metabolic patterns than those formed at zero potential from an active cambium.

The significance of the depressing effect on cell division and expansion of even a slight reduction in water potential is discussed in relation to wood development in trees growing under conditions of moisture stress.
THE EFFECT OF TRANSPIRATION RATE ON THE LEAF WATER POTENTIAL OF SAND AND SOIL ROOTED PLANTS
Authors: TINKLIN R. , WEATHERLEY P. E.
Published: May 2006

Summary

Twelve‐week‐old Ricimis comiminis plants were transplanted to boxes of sand or soil in which the water table was maintained at various levels below the root system. The boxes were placed in a climatological wind tunnel and transpiration varied by altering the humidity of the air stream. Responses in the water potential depression (= suction force or D.P.D.) of the leaves (ΔW1) and stomatal conductance were followed.

With a fine sand it was found that when the water table was high (15 cm below the roots) ΔW1, was 6 atm. irrespective of the rate of transpiration and behaved therefore as if the roots were surrounded by free water as previously shown. When the water table was 25 cm below the roots, ΔW1 was also 6 atm. provided the transpiration rate was low (0.4 g/dm2 leaf/hour) but when the transpiration rate was raised threefold, ΔW1, rose steeply to a value of 12 atm., a steady state value being approached in about 8 hours (see Fig. 3). On reducing the transpiration rate, ΔW1, returned to 6 atm. This rise in ΔW1, is interpreted as due to a rise in the ΔW of the water in the sand at the root surface, this in turn resulting from the low water conductivity of the sand at this height above the water table. Varying the humidity continuously between saturation and about 40% relative humidity through a 24‐hour cycle produced a regular 24‐hour cycle of transpiration (see Figs.4, 5 and 6). Responses in ΔW1, in plants rooted in fine sand, clay soil and moorland soil were explicable in terms of the above hypothesis of the development of perirhizal zones of soil water tension.

These results suggest that much of the ecologically significant water stress in plants is a manifestation of the dynamic gradients of water potential developing in the perirhizal zones and that these can be considerable even when the water stress in the bulk of the soil is virtually zero.
THE DNA CONTENT OF THE CELLS OF THE QUIESCENT CENTRE AND ROOT CAP OF ZEA MAYS
Authors: CLOWES F. A. L.
Published: May 2006

Summary

The light absorption of Feulgen‐stained nuclei in regions of the root apical meristems of Zea has been measured in sections by an integrating microdensitometer. Most of the cells of the quiescent centre are at the 2C level of DNA and most of the cap initials are at or near the 4C level as predicted from pulse labelling data. But, in the quiescent centre, there are more cells between 2C and 4C and fewer cells at 4C than are predicted from pulse labelling. Possible reasons discussed for these discrepancies include stopping the mitotic cycle in S, nuclei entering mitosis before the 4C level is attained and stimulation of the quiescent centre by radiation damage to the meristem from labelling methods.

The cap initials include some cells with more than the 4C amount of DNA, but, when the cap cells stop dividing, they remain at 2C for some time. Some of them then attain higher DNA contents, but there is no evidence to support the common view that the root cap is highly polyploid.
A STUDY OF THE ROOT SYSTEM OF BARLEY
Authors: HACKETT C.
Published: May 2006

Summary

A quantitative study has been made of the root systems of two varieties of barley (Hordeum vulgare L. vars. Maris Badger and Proctor) grown in water culture under three nutrient regimes—complete nutrient supply and deficiencies of potassium and phosphorus. The weight of the root systems, and the number, length and diameter of the seminal and nodal axes and laterals were measured. From these measurements, surface area and volume were calculated, and to show changes in the relationships between these quantities an expression of the fineness of the root systems, termed the average diameter, was derived. This paper describes the root systems after 4 weeks growth.

Maris Badger was more affected than Proctor by nutrient deficiency, but in both varieties the main effect was on the size of the nodal, as opposed to the seminal, root system. The number of axes and the length of the primary laterals were greatly reduced by both potassium and phosphorus deficiency but, by comparison, the mean length of the axes, the number of primary laterals per axis and the diameter of all types of root member were little affected.

Deficiency of potassium reduced the length of the primary laterals to a greater extent than that of phosphorus; in addition, it completely inhibited the formation of secondary laterals. Consequently, the average diameter of the root systems of the potassium‐deficient plants was greater than that of the phosphorus‐deficient plants.

Interactions between variety and nutrition were highly significant statistically, especially with respect to the development of laterals.
A NOTE ON THE OCCURRENCE OF VITIS AND OTHER NEW PLANT RECORDS FROM THE PLEISTOCENE DEPOSITS AT HOXNE, SUFFOLK
Authors: TURNER C.
Published: May 2006

Summary

A number of new plant records are described from the Pleistocene deposits at Hoxne, Suffolk. These include a seed of Vitis. The significance of Vitis records from Holstein interglacial deposits across north‐west Europe is discussed in the light of its present ecology and distribution.
THE EFFECT OF CERTAIN GROWTH SUBSTANCES ON ASYMBIOTIC GERMINATION AND DEVELOPMENT OF ORCHIS PURPURELLA
Authors: HADLEY G. , HARVAIS G.
Published: May 2006

Summary

The effect of some growth substances on gernnination and development of Orchis (Dactylorchis) purpurella seeds was studied in an attempt to simulate the developmental pattern observed in symbiotic cultures.

Gibberellic acid enhanced protocorm survival and caused abnormal elongation of the emergent shoot but did not influence the growth and overall size of the protocorms. Indoleacetic acid impeded germination and caused some elongation of the protocorms. Kinetin, both alone and in conjunction with indoleacetic acid, had a pronounced effect on growth and development and the results suggested that the auxin/cytokinin ratio is important in controlling root and shoot initiation. Adenine appeared to have little effect.

The growth factor mixtures used did not have as beneficial an effect on protocorm development as did the presence of either symbiotic fungi or undefined fractions such as potato extract and coconut milk, suggesting that symbiotic fungi also provide other growth substances.
TAPETAL ORIGIN OF POLLEN‐COAT SUBSTANCES IN LILIUM
Authors: HESLOP‐HARRISON J.
Published: May 2006

Summary

At maturity, the pollen of Lilium spp. is coated with an adhesive, pigmented material, the Pollenkitt of German authors. This material contains a lipid component and carotenoid pigments; in L. longiflorum the principal pigment is α‐carotene 5,6‐epoxide. Synthesis of the coat materials takes place in the tapetum. The pigments accumulate in osmiophilic globuli from the time of release of the spores from the tetrad until the dissolution of the tapetum as a tissue. The lipids and associated pigments are then discharged into the loculi, where they migrate between the spores, filling the recesses in the surface of the exine.
NITROGEN METABOLISM IN DEVELOPING SEEDS OF VICIA FABA
Authors: BOULTER D. , DAVIS O. J.
Published: May 2006

Summary

Fruits of Vicia faba L. were harvested from plants grown outdoors to provide a developmental series trom flower opening to maturity. Pod and seed were separated, extracted, and the changes in distribution of protein and non‐protein nitrogen determined. Amino acid content of pod and seed was determined and changes in albumin protein were characterized by acrylamide gel electrophoresis.

The bulk of nitrogenous material accumulated by the seed was found to be globulin protein, and accumulation was found to coincide with the appearance of protein granules in the developing cotyledons. Similar protein bodies were observed in the maternal tissues of the young ovule, but not in pod tissues, and possible sources of nitrogenous material destined for globulin synthesis are discussed.
A COMPARISON OF SOME PROPERTIES OF VICILIN AND LEGUMIN ISOLATED FROM SEEDS OF PISUM SATIVUM, VICIA FABA AND CICER ARIETINUM
Authors: JACKSON P. , BOULTER D. , THURMAN D. A.
Published: May 2006

Summary

A comparison has been made of the globulins, vicilin and legumin, prepared by isoelectric precipitation, of the seeds of three species of the Vicieae, namely Pisum sativum, Vicia faba and Cicer arietinum. Their amino acid composition, band patterns after electrophoresis upon polacrylamide‐urea gels, fingerprint patterns of their tryptic digests and N‐terminal amino acids were compared. Considerable portions of the amino acid sequences of vicilin and legumin of Pisum sativum are probably the same or very similar and both proteins consist of a number of sub‐units. Vicia faba and Cicer arietinum also contain two proteins homologous with the vicilin and legumin of Pisum sativum. The homologous proteins of the three species resemble each other more closely than do the vicilin and legumin of any one species.
THE ECTOTROPHIC MYCORRHIZAS OF ALNUS VIRIDIS (CHAIX) D.C. AND THEIR SIGNIFICANCE IN RESPECT TO PHOSPHORUS UPTAKE
Authors: MEJSTRIK V. , BENECKE U.
Published: May 2006

Summary

Three subtypes of mycorrhizas, sensu Dominik (1955), were found on roots of Alnus viridis growing in New Zealand. Roots with 60% of their rootlets mycorrhizal absorbed phosphate five times as rapidly as non‐mycorrhizal roots. Root nodules appear unable to absorb labelled phosphorus actively from externally supplied solution.
CYTOTAXONOMIC VARIATION IN POTENTILLA FRUTICOSA L.
Authors: ELKINGTON T. T.
Published: May 2006

Summary

Potentilla fruticosa is a widespread species for which chromosome numbers of 2n = 14 (diploid), 2n= 28 (tetraploid) and 2n = 42 (hexaploid) have been published from wild populations. These are listed together with a number of new counts. A morphological study of North American and European plants shows that the diploids are hermaphrodite and the tetraploids dioecious, and that the diploids have smaller pollen and stomata than the tetraploids. These distinguishing characters are used to show that the populations of P. fruticosa from northern Europe are tetraploid and those from southern Europe, western Asia and North America are diploid. Subspecific status is given to the tetraploids and diploids; the tetraploid cytotype is the type subspecies and the diploid is named ssp. floribunda (Pursh) Elkington.

It is suggested that the centre of evolution of shrubby Potentillas is in eastern Asia and that westwards migration took place separately to the north and south by tetraploids and diploids respectively. The North American populations are most likely to have immigrated across the Bering Straits from north‐east Asia.
THE ASSESSMENT OF A METHOD FOR THE DETERMINATION OF ABSOLUTE POLLEN FREQUENCIES
Authors: MATTHEWS J.
Published: May 2006

Summary

One method for the estimation of absolute pollen frequencies involves the addition of a known amount of an exotic pollen to a known quantity of sediment. From the observed ratio of indigenous to exotic pollen, the absolute quantity of indigenous per unit volume of sediment can be calculated.

The pollen of Nyssa sylvatica was considered to be a suitable exotic for addition to northwestern European Post‐glacial sediments to be measured by this method. A series of experiments was made to estimate the settling rate of fresh N. sylvatica pollen in pure glycerine, to determine the period of agitation required to produce an even suspension of N. sylvatica pollen in pure glycerine, to observe the effects of KOH treatment and acetolysis on a mixture of fresh N. sylvatica and Ailanthus eligantissima pollen and to estimate the experimental error of the method by using it to determine the quantity of pollen in a series of homogenized samples of gyttja.

The value of the method for the estimation of absolute pollen frequencies is assessed.
STUDIES IN THE VEGETATIONAL HISTORY OF MID‐WALES
Authors: MOORE P. D. , CHATER E. H.
Published: May 2006

Summary

Pollen diagrams are presented from two sites in the uplands of mid‐Wales. One of these, the Elan Valley Bog, provides a continuous record of vegetational history during the Post‐glacial period. Many of the conclusions drawn from this pollen diagram are confirmed by reference to the other site at Llyn Gynon.
TWO POLLEN DIAGRAMS FROM THE MAINLAND, ORKNEY ISLANDS
Authors: MOAR N. T.
Published: May 2006

Summary

Two pollen diagrams, one through Late‐Weichselian and early Flandrian sediments and the other through Flandrian sediments from sites on the western side of the Mainland, Orkney Islands are discussed. The results provide an outline of vegetation development from Late‐Weichselian time and imply that at its best the dominant vegetation has a birch and hazel shrubland. On the basis of present evidence the Late‐Weichselian and Flandrian floras were impoverished and the presence of pollen derived from trees of mixed‐oak‐forest does not necessarily imply that these trees grew locally.
CHANGES IN ABSCISSION‐ACCELERATING SUBSTANCES WITH DEVELOPMENT OF COTTON FRUIT
Authors: SMITH O. E.
Published: May 2006

Summary

Cotton bolls of known ages from 2 to 50 days after anthesis were extracted with acetone. The chromatographed extracts were examined for abscission activity on the cotton explant test and gibberellin activity on the dwarf maize test. The abscission‐accelerating substances (ABA and gibberellins) were very high in young fruit, showing a peak at about 6 days, then declined to nil at 20 days. An unidentified abscission accelerator showed a marked peak at 15 days. Abscisic acid, GA3, another gibberellin which acts biologically like GA5 and GA9, and an abscission‐retarding substance were all extracted from 5‐day‐old bolls.
COMPARISONS OF FRUITING AND DEBLOSSOMED MAIDEN APPLE TREES, AND OF NON‐FRUITING TREES ON A DWARFING AND AN INVIGORATING ROOTSTOCK
Authors: AVERY D. J.
Published: May 2006

Summary

The dry weight increment of all parts, especially the rootstock, was less in fruiting than in non‐fruiting maiden Worcester Pearmain apple trees; the fruit accounted for one‐third of the total increment on M.IX. Fewer shoots grew out, and they had decreased rates of extension from the end of June, especially the later‐formed shoots. The leaves were smaller and this was the earliest observed difference between fruiting and deblossomed trees. The rate of leaf production was lower after late July. While fruiting affected the shoots on the tree as a whole, the proximity of fruit affected individual shoots. The influence of fruit was less in August and growth of the trees increased relative to deblossomed trees.

Growth rates of leaves and shoots were similar until late June on deblossomed trees on dwarfing M.IX and on non‐fruiting trees on invigorating M.XVI, but many more shoots extended on M.XVI in June. Shoots on M.IX extended at a much decreased rate in July and early August and the internodes were shorter but thicker than on M.XVI. In trees on M.IX a smaller proportion of the dry weight increment was in the rootstoek. The efficiency of leaves on M.XVI was greater than of leaves of deblossomed trees on M.IX, but less than on fruiting trees. These data, and additional facts published by other workers, have been integrated in an attempt to explain the dwarfing mechanism of M.IX.

Trees on M.IX are smaller because they are restricted to fewer growing points which continue extension for a shorter period. It is believed that the even smaller rate of growth of the root system limits the trees so that they are unable fully to utilize the products of photosynthesis in growth.
VESICULAR INVOLVEMENT IN DIFFERENTIATING PLANT VASCULAR CELLS
Authors: ROBARDS A. W. , KIDWAI PARVEEN
Published: May 2006

Summary

In differentiating xylem cells a prima facie case is made for the following cytoplasmic events to occur:

Production of vesicles from dictyosomes and endoplasmic reticulum, and probable guidance of these vesicles to the wall by microtubules.

Secondary formation of multivesicular bodies from dictyosome‐derived vesicles, which also move to the plasmalemma and fuse with it.

Passage of single vesicles across the plasmalemma to form lomasomes.

Evagination of the plasmalemma to form plasmalemmasomes.

Formation of myelin‐like bodies by the endoplasmic reticulum.

The fusion of vesicles and vacuoles with each other.

These processes are thought to be associated in general with the formation and separate transport of different wall precursors and enzymes to their appropriate sites and, possibly, with the management of synthetic by‐products.
THE MAINTENANCE OF STRUCTURE AND SHAPE IN THREE MALLEE EUCALYPTS
Authors: HOLLAND P. G.
Published: May 2006

Summary

To estimate the tissue production of stands of large woody plants a simple morphological analysis on a sample of the plants must be attempted if a rational clipping routine is to be established. It is shown that such an analysis reveals much about the maintenance of stem structure and shape by three species of mallee Eucalyptus. The species have a branching system which can be described by the geomorphologist's law of stream numbers and their shape is explicable in terms of this system and the effects of apical dominance on new twig growth.
GENECOLOGICAL DIFFERENTIATION OF LEAF MORPHOLOGY IN GERANIUM SANGUINEUM L.
Authors: LEWIS MARTIN C.
Published: May 2006

Summary

Genecological differentiation of leaf dissection and size in European samples of Geranium sanguineum L. is considered against a background of the ecological behaviour of this species. The differentiation is analysed using Variance Analysis and shown to be closely correlated with a community classification based on eco‐geographical indicator species; leaf dissection is correlated with the ‘continentality’ and leaf size with the ‘openness’ of the original community. The variation in both cases is ecoclinal. The importance of morphological differentiation to studies of adaptation is discussed in the light of current knowledge.
AN INTERGLACIAL PEAT AT FUGLA NESS, SHETLAND
Authors: BIRKS H. J. B. , RANSOM MAREE E.
Published: May 2006

Summary

The stratigraphy of a peat bed about 1.5 m thick lying between boulder clays at Fugla Ness on North Roe of Shetland Mainland is described, and the results of analyses of pollen, spores, seeds, leaves and wood remains are presented. These analyses indicate wooded conditions, and the assemblage is considered to be of interglacial character. On the basis of floristic affinities it is equated with the closing phases of the Gortian Interglacial stage of Ireland. The most notable taxa represented include Abies, Chamaepericlymenum suecicuni, Daboecia canlabrica. Erica mackaiana, E. scoparia var. macrosperma and Picea. The phytogeographical significance of the fossil flora is briefly considered.
CONTRIBUTIONS TO THE ECOLOGY OF BRACKEN (PTERIDIUM AQUILINUM)
Authors: WATT A. S.
Published: May 2006

Summary

The crown forms of bracken in the marginal belts of areas D and E are examined in relation to the changing age‐structure of the frond population and damage by frost.

In both areas there is a rise in height to a maximum followed in area D by a slight fall and then a levelling off in the distal part. In area E there is a uniform fall from the maximum to about half that height.

The rise in the proximal part in both is regarded as an expression of inherent potentialities, and the fall in the distal of the influence chiefly of the ecological factors of frost and drought.

Data of frost mortality from permanent transects (1936–40) show similar and parallel values in the proximal parts hut in the distal the values in area D are low, in area E high. These not only differentiate area D from area E hut the distal from the proximal in each.

Frost mortality is related to the date of emergence, this in turn to the amount and continuity of the litter and this to the density, height and distribution of the fronds. As the thickness of the litter is about the same at maximum height and mortality only slightly greater in area E at this point, it is argued that some other factor is primarily beginning to operate just behind the region of maximum height. Frost, though important, does not initiate the fall although it contributes largely to it.

Various observations (including the high correlation between the length of the petiole, which is fed exclusively from reserves, and the length of the lamina of the previous year, as a rough measure of the capacity to add to reserves) suggest the limited movement of reserves within the plant; and a hypothesis is formulated based on a hypothetical breakdown of food transport in the main and lateral axes at an age (approximately 30–35 years) in consequence of which the physical unitary system is differentiated into a large apical (proximal) physiological unit, and a distal part bearing lateral branch systems which are physiologically independent of the parent plant and of each other. As in the parent plant, so in the lateral branch systems, transport in the axes fails on attaining the appropriate age. Thus while the branch systems increase in size distally (though at a diminishing rate, because of competition from neighbours), the physiological units decrease. Smaller plants carry smaller fronds and the reduced litter‐cover means less protection from winter frost, earlier emergence and a higher spring frost mortality.

The hypothesis applies to area D, but the physiological units there are on deeper soil and provide enough litter to delay emergence, reduce spring frost mortality and winter frost damage to zero.

Because of the deeper soil and ahundant litter in area D the frond population is much more self‐protective and self‐regulatory and much less under the direct influence of the hahitat factors drought and frost.
AN APPLICATION OF ORDINATION TO GENECOLOGY
Authors: WILKINS D. A. , LEWIS M. C.
Published: May 2006

Summary

Genecological differences in leaf size and dissection were known in Geranium sanguineum from uniform garden trials. Floristic data from the original habitats were used to construct a principal components ordination of the sites, and the first four axes were examined for correlations with the genecological data.

The first axis was found to be associated with leaf size and the second and third with leaf dissection. An ecological interpretation of the axes was attempted from the occurrence of indicator species of known ecological tolerance. This showed that position along the second and third axes was highly correlated with the representation of steppe perennial species. No such interpretation was found for the first axis.

The value of this approach for the identification of ecological gradients in genecology is discussed.
EFFECT OF ENDOGONE MYCORRHIZA ON PLANT GROWTH
Authors: DAFT M. J. , NICOLSON T. H.
Published: May 2006

Summary

Varying amounts of soluble phosphate were applied over different periods during the growth of mycorrhizal maize. The amount of the endophyte produced within the root system and the growth of the host were related inversely. Repeated small doses of soluble phosphate over long periods depressed the production of the fungus more than when given over shorter periods. Large single applications of soluble phosphate applied early in the growth of the host also reduced the amount of the endophyte more than when given later. The role of mycorrhiza in relation to phosphate nutrition is discussed.
EFFECT OF ENDOGONE MYCORRHIZA ON PLANT GROWTH
Authors: DAFT M. J. , NICOLSON T. H.
Published: May 2006

Summary

The effects of concentration of the inoculum on growth of the host and level of infection were investigated in mycorrhizal tomatoes. All concentrations of the endophyte, ranging between 225 and three chlamydospores per plant, led to significant stimulation of growth. Measurements of height of plants and length of leaves during growth indicated that inocula containing low numbers of spores stimulated the host less than more concentrated inocula. Plants inoculated with high numbers of spores produced more upper and retained more lower leaves whereas plants inoculated with low numbers retained more lower leaves than uninfected control plants. Dry weight determinations of the foliage made at the end of the experiment showed that all inoculated treatments were larger than the control treatments. The concentration of spores in the inoculum did not appear to influence the final level of infection.
EFFECTS OF INHIBITORS ON PHOTOSYNTHESIS AND THE ACTIVE INFLUXES OF K AND CL IN HYDRODICTYON AFRICANUM
Authors: RAVEN J. A.
Published: May 2006

Summary

The effects of the inhibitors HOQNO, salicylaldoxime, DSPD, NaCN, DNP, desaspidin, antimycin A and CCCP on photosynthesis and active K and Cl influxes in the light and the dark in Hydrodictyon africanum are reported. It is concluded (1) that active K influx in the dark is powered by oxidative phosphorylation; (2) that ATP produced by oxidative phosphorylation is not required for the full light‐stimulation of K influx; (3) that either cyclic or pseudocyclic photophosphorylation can power K influx in the light; (4) that Cl influx in the dark requires the operation of the mitochondrial electron transport chain; (5) that Cl influx in the light requires both photosystem one and photosystem two; (6) that cyclic photophosphorylation is not required for steady‐state photosynthesis in aerobic conditions at high light intensity.
SOME EFFECTS OF TEMPERATURE AND PHOTOPERIOD ON GROWTH AND FLORAL DEVELOPMENT IN THREE WINTER ANNUALS
Authors: CLARK S. C.
Published: May 2006

Summary

An experiment on the effects of temperature and day length on the vegetative and reproductive growth of populations of the winter annuals, Catapodium rigidum, Erophila verna and Saxifraga tridactylites from the west of Ireland, is described. The results are used to show the potentialities of subjecting plants at different stages of development to the same treatments, as a method of assessing the role of environmental factors under natural conditions. Catapodium rigidum was found to have an absolute vernalization requirement and long days were required for suhsequent development of inflorescences up to the flowering stage. Short days given after inflorescences had begun to develop resulted in the formation of secondary tillers at the extremities of primary tillers (‘mops’) and proliferations. Any vernalization requirement of Erophila verna and Saxifraga tridactylites was satisfied by mid‐November. The development of flower buds in winter was more rapid in Erophila verna than in Saxifraga tridactylites. Day length did not effect the number of flower buds produced by either species but they differed in their ability to mature fruits in short days.
SOME ASPECTS OF THE MORPHOLOGY, EMBRYOLOGY AND BIOLOGY OF TERNIOLA ZEYLANICA (GARDNER) TULASNE
Authors: MUKKADA ANTONY J.
Published: May 2006

Summary

The plant body in Terniola zeylanica (Gardner) Tulasne, a member of the Podostemaceae, consists of a creeping thallus. The flowers are bisexual, hypogynous and trimerous. The anthers are dithecous and all the microsporangia are arranged on the inner side of the anther and parallel to each other. The anther wall consists of four layers. The tapetum is of the secretory type. Quadripartition of the mother cells is simultaneous and the tetrads are isobilateral or tetrahedral. The microspore nucleus divides by an asymmetric spindle and the pollen grains are shed at the two‐celled stage. The ovules are anatropous, tenuinucellar and bitegminal with the micropyle formed solely by the outer integument. Both the integuments differentiate simultaneously. The embryo sac is bisporic, five‐nucleate and follows the reduced Allium type. A pseudo‐embryo sac is formed during early embryogeny. Both entomophily and anemophily are prevalent. Syngamy takes place normally. Previous reports of double fertilization are not confirmed. A primary endosperm nucleus is not formed and there is no endosperm. The development of the embryo follows the Solanad type and the embryo possesses a large, coeno‐cytic, haustorial cell. The development and maturation of the seed coat and pericarp have been studied. The cells of the inner epidermis of the ovary wall become binucleate and at times even multinucleate.
THE UPTAKE OF 32P BY DIFFERENT KINDS OF ECTOTROPHIC MYCORRHIZA OF PINUS
Authors: MEJSTŘIK V.
Published: May 2006

Summary

The rates of uptake of phosphate by two different kinds of mycorrhiza of Pinus radiata (Fa and Ca) were both greater than that of uninfected roots at all temperatures studied. Over periods of 160 minutes the optimum temperature for both mycorrhizal and uninfected roots was about 25° C, but the uptake rate of type Fa fell off more steeply above this optimum than that of Ca over the same time‐period. Uninfected roots showed, at all temperatures, a more rapid rate of absorption over the first 60 minutes of the experimental period than later.
THE MODE OF ACTION OF KINETIN IN MAINTAINING THE PROTEIN CONTENT OF DETACHED TROPAEOLUM MAJUS LEAVES
Authors: MIZRAHI YOSEF , AMIR JACOB , RICHMOND AMOS E.
Published: May 2006

Summary

Kinetin maintains the protein content of detached leaves, but the reason is not clear. This work attempted to find out whether the effect arises from maintenance of protein synthesis or retardation of protein breakdown. Protein synthesis and degradation in detached Tropaeolum majus leaves were estimated by measuring the incorporation into amino acids and protein of photo‐synthetically fixed 14C, and by determining the total amounts of amino acids and protein present in ageing leaves. Protein synthesis in kinetin‐treated leaves kept in darkness was higher than in the control. Rough calculation showed, however, that enhancement of protein synthesis by kinetin cannot directly account for the higher protein level found after this treatment. It seems to result from decreased degradation rather than from the maintenance of protein synthesis.
A TAXONOMIC STUDY OF LABIATAE AND RELATED GENERA
Authors: EL‐GAZZAR A. , WATSON L.
Published: May 2006

Summary

Extensive comparative anatomical and morphological observations have been made on 400 species (138 genera) of Labiatae and Verbenaceae sensu lato. Two computational analyses, very different and calling for different coded interpretations of the data, gave essentially similar classifications. These analyses and subsequent taxonomic consideration result in an arrangement which does not reflect the present family boundary. Four of Bentham's eight tribes of Labiatae (Ocimoideae, Satureieae p.p., Monardeae, Nepeteae) seem distinctly different from the rest which come closer to Verbenaceae. Of ten subfamilies and tribes sampled, only Ajugoideae and Verbenoideae emerge intact. In terms of this sample, forty‐seven genera gain support but twenty‐five are heterogeneous in that species form groups not conforming with present generic boundaries.
RESPONSE OF ADAXIAL AND ABAXIAL STOMATA TO LIGHT
Authors: TURNER NEIL C.
Published: May 2006

Summary

The response to light by adaxial and abaxial stomata was measured with an aspirated diffusion porometer in normal and inverted leaves of sorghum (Sorghum bicolor (L.) Moench) and tobacco (Nicotiana tabacum L.). The adaxial stomata, normally exposed to bright light, closed at 2000 ft‐candles in both sorghum and tobacco whereas the abaxial stomata, normally in dim light, closed at approximately 1000 ft‐candles in sorghum and 200 ft‐candles in tobacco. The greater sensitivity of the abaxial stomata to light in both the monocotyledon, sorghum and the dicotyledon, tobacco, indicates that the phenomenon is widely distributed and occurs irrespective of differences in stomatal density. Further, the narrowing of the adaxial stomata which occurred upon leaf inversion suggests that the level of carbon dioxide within the intercellular spaces of the leaf does not control stomatal apertures.
REGULATION OF THE GROWTH POTENTIAL OF DOUGLAS FIR SEEDLINGS DURING DORMANCY
Authors: LAVENDER D. P. , HERMANN R. K.
Published: May 2006

Summary

The three experiments indicated that individual buds were the receptors for the growth stimulus produced by extended photoperiods during the autumn and winter. No evidence of transport of growth stimulatory materials from active to dormant bud was noted. Buds whose chilling requirements were fully satisfied initiated growth in response to favourable temperatures rather than to long photoperiods.

Initiation of activity by lateral cambia required material exported from both expanding buds and mature foliage.

No significant correlation between shoot and root growth was found. Although neither active buds nor applications of exogenous IAA or GA stimulated roots growth, both root elongation and initiation were found to be dependent upon some substance or substances, presumably hormones or carbohydrates, exported from mature foliage.

Findings indicated that seedling physiology during the dormant period may be controlled by a changing balance in growth inhibitors and promoters.
A VIRESCENS MUTANT OF PHASEOLUS VULGARIS; GROWTH, PIGMENT AND PLASTID CHARACTERS
Authors: DALE J. E. , HEYES J. K.
Published: May 2006

Summary

A slow‐greening mutant growing at a slower rate than control plants is described. Mutant plants produce less chlorophyll than control plants, and their rate of production of pigment is lower. There is some evidence that chlorophyll is broken down in the mutant under high light conditions. Plastid numbers per leaf cell are similar in control and mutant, but a reduction in leaf cell number in the mutant results in their containing fewer plastids per leaf. The slow accumulation of chlorophyll by plastids of the mutant is correlated with a slow development of plastid fine structure, in particular in stacking of grana, as seen by electron microscopy.
TRISTYLY IN LYTHRUM JUNCEUM *
Authors: DULBERGER RIVKA
Published: May 2006

Summary

Lythrum junceum was found to be tristylic in Israel. The three floral forms differ in style length, stamen length, pollen size, presence or absence of starch in the pollen and in stigma size. In the majority of natural populations examined, the three forms were represented in roughly equivalent numbers. The results of an artificial pollination programme demonstrate that the trimorphism is accompanied by physiological incompatibility, typical to tristylic plants. Self‐pollinations were sterile. Intra‐form and inter‐form pollinations between anthers and stigmas at different levels were also sterile. The inhibition of pollen tubes occurs in the style. Inter‐form pollinations between anthers and stigmas at equivalent level resulted in seed production, the most fertile form being the mid‐styled one; these differences were lost in open‐pollinated plots. Tristyly in L. salicaria with 2n= 30 is recorded. A comparison is made between tristyly in L. junceum and L. salicaria and it is suggested that tristyly in the latter has evolved later than in the former.
EUTRIPLOID FACULTATIVE AGAMOSPERMY IN TARAXACUM
Authors: RICHARDS A. J.
Published: May 2006

Summary

Diploidy is reported in the species Taraxacum brachyglossum, T. subcyanolepis and in the T. punctatum/austriacum complex. In each case, diploids are found in company with triploids of the same species, which are shown in the case of T. brachyglossum to be facultative agamosperms. These have regular pollen and show incomplete seed‐set in the absence of cross‐pollination. Triploids in T. subcyanolepis and T. punctatum/austriacum are similar and are also thought to be facultative agamosperms. This is the first report of eutriploid, facultative agamospermy in Taraxacum.

Diploid sexuals may be recognized by regular pollen and no seed‐set in insect‐free conditions. Obligate agomosperms have highly irregular pollen, large regular pollen or no pollen and set good seed.

It is shown that sexual diploids can give rise to triploids apparently as a result of fertilization by incompletely reduced pollen in triploids. Some triploids can give rise to diploids, perhaps through reduction in the female meiosis, which is synaptic, followed by fertilization with haploid pollen.

Suggestions are made as to the mechanism controlling facultative agamospermy in disomic triploid and eutriploid individuals. Critical phases seem to be the course of the female meiosis and the timing of autonomous embryony.
THE BREAKDOWN OF PAINT SURFACES BY ENTEROMORPHA SP.
Authors: MOSS BETTY , WOODHEAD P.
Published: May 2006

Summary

Enteromorpha is the dominant alga associated with the fouling of large ships. Using the electron scanning microscope on germinating zoospores and on young plants which had been raised in culture it has been shown that the primary and subsequent rhizoids which are produced by the plant penetrate the substrate and so cause physical breakdown of a paint surface.

Among the algae causing severe fouling of large ocean‐going ships, Enteromorpha is the most common. It sometimes occurs in such extensive growths as to slow a tanker down to about one‐third of its normal speed. Anti‐fouling paints have been designed mainly to resist or to repel the settling larvae of barnacles and other animals and since they do not prevent the growth of algae attention is now being focused to this problem. While studying the settlement of Enteromorpha swarmers on paint surfaces we looked at the method of attachment and the damage to the paint which resulted from their germination and growth. Observations were made with an electron scanning microscope so that the germinating zoospores could be seen in situ growing on a painted surface.
A VIRUS OF BLUE‐GREEN ALGAE FROM FRESHWATER HABITATS IN SCOTLAND
Authors: DAFT M. J. , BEGG J. , STEWART W. D. P.
Published: May 2006

Summary

A virus which is pathogenic to certain blue‐green algae belonging to the genera Plectonema, Phormidium and Lyngbya has been isolated from a variety of freshwater habitats in Scotland and has been detected over a 12‐month period in one of these habitats. The virus (D‐1) is a cyanophage, has an isohedral head and a short tail and is morphologically and serologically related to the LPP‐1 virus isolated from the United States and the GIII virus isolated from Israel by other workers. The partially purified virus has an absorption spectrum characteristic of a nucleoprotein with a maximum at 260 nm and a minimum at 243 nm. D‐1 is temperature sensitive being inactivated on heating at 60°C for 6 minutes. Its multiplication rate is fast, increasing from an initial titre of 103 to 1012PFU/ml within 40 hours. The lysis of the host cell results in a rapid loss of the phycobilin and chlorophyll pigments.
THE MORPHOLOGY AND COMPOSITION OF ISOLATED PLANT CUTICLES
Authors: BAKER E. A.
Published: May 2006

Summary

The morphology of the inner and outer surfaces of cuticular membranes of mono‐ and dicotyledonous leaves and fruits was studied with the scanning electron microscope. Variations in surface structure are related to differences in thickness and composition of the membranes. Delicate leaf membranes have fine ridges and simple stomata, well‐developed membranes, thick V‐shaped ridges and heavily cutinized stomata. Fruit membranes show deep ridges and extensive secondary cutinization. The most heavily cutinized structures occur in membranes which yield high proportions of 10,16‐dihydroxyhexadecanoic or 9,10,18‐trihydroxyoctadecanoic acid which suggests that the membrane thickness and the complexity of the structural features are associated with the degree of hydroxylation of the constituent cutin acids. The relationship between the structure and composition of the cuticular membrane and the type and growth habit of the plant is discussed.
EFFECTS OF ENVIRONMENT ON RELATIONS BETWEEN EXTENSION AND CAMBIAL GROWTH OF POPULUS EUPHRATICA OLIV.
Authors: LIPHSCHITZ NILI , WAISEL YOAV
Published: May 2006

Summary

Variations in the xylem increment and vessel diameter were found among Populus euphratica Oliv. trees from habitats of different water regimes. Vigorous shoot growth under conditions of ample water supply was associated with wide annual xylem rings and diffuse porous wood. Restricted shoot elongation of trees on dry sites was associated with narrow annual rings and ring porous wood. The influence of environmental factors on xylem production appeared to be indirect and to be largely mediated through physiological activity of the shoot system.
CALLUNA, CASSIOPE AND HARRIMANELLA: A TAXONOMIC AND EVOLUTIONARY PROBLEM
Authors: STEVENS P. F.
Published: May 2006

Summary

Leaf types in Calluna, Cassiope and Harrimanella are described; the so‐called needle leaf of Cassiope lycopodioides and C. mertensiana is shown to be derived from the channelled leaves found in the majority of species of Cassiope, possibly via an intermediate stage such as C. redowskii, which has leaves like the finger of a glove. The needle leaves of C. palpebrata are superficially different from the other leaf types of the genus, as are those of Harrimanella. A considerable number of differences justifying the maintenance of Cassiope and Harrimanella as separate genera are listed. The relationship of Cassiope and Harrimanella to the Rhododen‐droideae and Vaccinioideae are discussed, and although these two genera are very isolated in the Ericaceae they are closer to the Andromedeae than to any other group. With Calluna they have little in common apart from characters occurring sporadically throughout the family; although Cassiope and Calluna are similar in a number of points Harrimanella and Cassiope differ in these characters. The evidence suggests that Calluna is a member of the Ericoideae, although separable as a monotypic tribe; Cassiope and Harrimanella are not at all close to the Ericoideae. It is concluded that leaf type is a character which must be used with caution in establishing relationships within the Ericaceae; the evolutionary significance of the rather frequent conflict between relationships suggested by leaf type and those suggested by floral characters is briefly discussed.
THE ADVANCEMENT INDEX AND TROPICAL RAIN‐FOREST
Authors: SPORNE KENNETH R.
Published: May 2006

Summary

This is a reply to a suggestion that the characters used for assessing the relative primitiveness of dicotyledon families are merely adaptations to life in tropical rain‐forest and are not, therefore, reliable indicators of primitiveness. Arguments are put forward that rain‐forest plants should be expected to be primitive, regardless of the place of origin of angiosperms. Recent findings of palynologists are shown to give strong support to advancement index calculations.
NITROGEN METABOLISM IN LICHENS
Authors: KERSHAW K. A. , MILLBANK J. W.
Published: May 2006

Nitrogen fixed by, and secreted from, the blue‐green algal component of Peltigera aphthosa to the thallus has been shown to be utilized almost exclusively by the fungal component. After allowance for the proportions of fungal and green algal components, only approximately 3 % of the expected proportion of secreted nitrogen is accumulated by the green algal cells.

The implications of this on the possible theories describing the relationships existing in the lichen symbiosis are discussed.
NUTRITIONAL REQUIREMENTS OF THE EDAPHIC ECOTYPES IN MELILOTUS ALBA MEDIC.
Authors: RAMAKRISHNAN P. S.
Published: May 2006

The acidic and calcareous populations of Melilotus alba behave differently when grown in competition than when grown in isolation from each other. Thus, the acidic population which did well in both calcareous and acidic media in competition‐free cultures, showed good growth yield in acidic soils only when in competition with the calcareous population. Further, the differences observed between the two populations in competition‐free experiments became more pronounced when grown mixed. The time of introduction of either of the two populations into the mixture affects the final dry weight yield of the shoot, depending upon the soil type. In mixed cultures of the two populations, the calcareous population grown in an acidic soil and the acidic population grown in a calcareous soil responded by mortality of individuals, especially when the second population in each case was introduced earlier into the mixture.
EFFECTS OF GROWTH REGULATING SUBSTANCES AND WATER POTENTIAL ON THE DEVELOPMENT OF WOUND CALLUS IN FRAXINUS
Authors: DOLEY D. , LEYTON L.
Published: May 2006

The rate of growth of wound callus from the cut ends of Fraxinus excelsior L. stems was reduced by lowering the water potential of the culture medium using sucrose and/or polyethylene glycol; the first decrement in potential, from 0 to – 1 bar, had a particularly depressing effect. Gibberellic acid up to 100 mg 1‐1 had no significant influence, whilst indol‐3‐yl‐acetic (IAA) appeared to exert an effect only through its interaction with the water potential. The importance of water potential in tissue development appears to have been frequently overlooked in the use of relatively high sucrose concentrations in tissue culture media, and may account in part for the frequent observation of an optimum sugar concentration for growth. Calluses produced at zero water potential were characterized by active surface growth, relatively little internal differentiation, and a semicircular section. At reduced potentials (–1 bar and lower), the calluses had suberized surfaces and were circular in section; increase in size occurred mainly through the activity of the vascular cambium and a subsurface meristem. More lignified xylem and sclercids were produced in calluses grown at –1 and –2 bars than at zero water potential; at each water potential there appeared to be an optimum IAA concentration for xylem differentiation and this optimum tended to increase as the water potential was increased. Xylem was always associated with a cambium which extended from the subtending twig. Differentiation of vascular tissues, in particular lignified xylem, appears to require physical pressure in addition to a certain concentration of auxin; at zero water potential, sufficient pressure appears to be developed when the callus reaches a certain size, whilst at lower potentials it is induced by suberization of the superficial cells of the callus restraining the expansion of the underlying tissues.