bluuebunny/crossref_metadata_2025_split huggingface dataset:
THE MATING SYSTEMS OF FUNGI
Authors: BURNETT J. H. , BOULTER M. EILEEN 
Published: May 2006

SummaryIsolations of Mycocaha denudata and M. duriaeana were grown in plate culture and their mating systems studied. The former species is heteromictic and shows both bipolar diaphoromixis and facultative homo‐heteromixis, the latter species is almost certainly homomictic. None of these mating systems have been found before in Nidulariales. It is suggested that the abundance, morphological variation and ecological tolerance of these species may be related to their kinds of mating system. Facultative homo‐heteromixis in M. denudata results in spores being produced in a single peridiolum which are either homocaryotic or heterocaryotic in respect of mating‐type factors. The condition is due to a dominant gene Pd which determines a precocious division of the four nuclei, formed by a normal meiosis, in each basidium. The eight nuclei so formed appear to migrate at random, in respect of the mating‐type factors they carry, into the basidiospores which are each ultimately binucleate. This mechanism is not yet known in other Basidiomycetes.Isolations of M. denudata fell into two groups (I and II) between which there was complete sterility but no other constant distinguishing features could be observed between them. The occurrence of such groups is thought to be of significance in fungi and at present it seems best to regard them as comparable to sibling species. Four mating‐type factors were identified amongst the six isolations of group I, seven amongst the sixteen isolations of group II. Estimates of the total numbers of mating‐type factors in group I and group II are seven to eight and twelve to thirteen respectively. Thus, like other Nidulariales, M. denudata appears to have only a relatively small number of mating‐type factors and the relation of this to inbreeding and dispersal mechanisms is discussed.
MOVEMENT OF GROWTH REGULATORS IN PLANTS
Authors: McCREADY C. C. , JACOBS W. P. 
Published: May 2006

SummaryIndoleacetic acid and 2,4‐dichlorophenoxyacetic acid, labelled with carbon‐14, were applied in agar blocks to one end of sections cut from the petioles of primary leaves of Phaseolus vulgaris at various stages in their development. The movement of 14C by polar transport into agar blocks at the other end of the sections was measured and compared with the elongation of the sections. With both auxins there was a steady decline in the polarity of movement of 14C—due mainly to a steady increase of movement in the acropetal direction—in petioles from successively older plants. This decreasing polarity was closely associated with a progressive decrease in the ability of the sections to grow in length.
EPIDERMAL STRUCTURE AND DEVELOPMENT OF STOMATA IN EPHEDRA FOLIATA BOISS.
Authors: PANT D. D. , MEHRA BHARATI 
Published: May 2006

SummaryThe epidermal structure of the leaf and stem of Ephedra foliata Boiss. is described. The epidermis of internodes and leaves shows longitudinal rows of cells and stomata. In the nodes and the leaf bases the stomata are irregularly orientated. The subsidiary cells are perigene and the development of stomata is typically haplocheilic.
AN ADDITION TO THE BISPORIC EMBRYO SACS—THE DICRAEA TYPE
Authors: MUKKADA A. J. 
Published: May 2006

SummaryThe embryo sac in Dicraea is tetra‐nucleate and follows a bisporic development. It comprises a single synergid, an egg cell and two juxtaposed antipodal cells. This justifies the establishment of a new type under the bisporic embryo sacs which may be designated as the Dicraea type.
ORGANELLE DISTRIBUTION IN THE STATOCYTE CELLS OF THE ROOT‐TIP OF VICIA FABA IN RELATION TO GEOTROPIC STIMULATION
Authors: GRIFFITHS HILARY J. , AUDUS L. J. 
Published: May 2006

SummaryBy means of the electron microscope a study has been made of the changes in organelle distribution in the cells of the root cap of Vicia faba seedlings resulting from a 20 minute geotropic stimulation in the horizontal position. From photographs of whole cells at constant magnification, counts were made of the numbers of amyloplasts, mitochondria and dictyosomes in each of four equal quarters of the cell divided along, and transverse to, the main root axis. The volumes of the characteristic endoplasmic reticulum masses per cell quarter were also measured.The only bodies showing marked sedimentation to the lower side of the cell were the amyloplasts. The dictyosomes showed a small but statistically significant displacement into the quarter not occupied by the amyloplasts but since their concentration per unit of cytoplasm did not change, it was inferred that they moved passively in the cytoplasm displaced by the sedi‐menting amyloplasts. Similar trends were shown by the mitochondria but these did not reach 5% significance levels. There also appeared to be significant displacement of the endoplasmic reticulum masses into the upper halves of the cells.The implications of these findings are discussed in the context of current theories of gravi‐perception in plants.
PRODUCTION OF PECTIC ENZYMES BY PATHOGENIC AND SYMBIOTIC RHIZOCTONIA STRAINS
Authors: PÉROMBELON M. , HADLEY G. 
Published: May 2006

SummaryFive strains of Rhizoctonia, selected for their symbiotic and/or pathogenic characteristics, were investigated with regard to growth and pectic enzyme production in culture. Growth patterns of the strains were similar on glucose and pectin carbon sources, pectin being less efficient than glucose in terms of mycelial dry weight produced. Assays of endopolymethylgalacturonase, endopolygalacturonase and protopectinase in culture filtrates showed that on pectin media all of these enzymes were produced by each of the strains although the relative degree of activity varied. Enzyme production by the orchid endophyte strains used was no less than, and in one case was far greater than, that by the pathogenic strains. The significance of these results is discussed with regard to host/endophyte relationships.
THE RESPIRATION CLIMACTERIC IN APPLE FRUITS
Authors: HULME A. C. , JONES J. D. , WOOLTORTON L. S. C. 
Published: May 2006

SummaryChanges in the activity, in terms of O2 uptake and CO2 output in presence of malate and succinate substrates and of succinic and malic dehydrogenases, diaphorase and cytoehrome‐c reductase, of mitochondrial preparations from the peel and pulp of apple tissue, were followed during the development of the respiration climacteric in fruit on the tree. There was a general increase in activity beginning in peel tissue. Oxidative phosphorylation by the mitochondrial preparations was maintained at a high level throughout the period. At the same time a threefold increase in malic enzyme (M.E.) and carboxylase activity was observed. It is suggested that these observations show that the climacteric rise in apple fruits attached to the tree is initiated by an increase in mitochondrial activity and develops through the joint action of increased activity of M.E. and carboxylase.
CARBOHYDRATE PHYSIOLOGY OF MYCORRHIZAL ROOTS OF BEECH
Authors: LEWIS D. H. , HARLEY J. L. 
Published: May 2006

SummaryIn order to test the relevance of previous results of this series to conditions operative in the intact plant, a technique was devised to simulate translocation of sucrose to mycorrhizal roots and to determine its morphological and biochemical destinations by the use of [14C]sugar. It was shown that the fungus can absorb sugar from the host and that its chemical destination is essentially similar to that of exogenous sucrose, namely a synthesis of mannitol, trehalose and glycogen.In connection with the possibility of reciprocal flow from fungus to host, the ability of uninfected roots to utilize the soluble sugars of the fungus was tested. Whereas mycorrhizas readily absorb and metabolize mannitol and trehalose, uninfected roots have almost no ability to utilize mannitol and are restricted in their utilization of trehalose, throwing considerable doubt on the possibility of sugar absorption by host from fungus.The hypothesis is developed that the fungus absorbs carbohydrates from the host and transforms them into reserve substances peculiar to itself, so maintaining a concentration gradient with respect to the host carbohydrate. The mycorrhizal system has the added advantage to the fungus that its reserve sugars are not readily re‐available to the host. As polyols are abundant in many angiosperm parasites, the Physiology of polyols in general is reviewed with the conclusion that the role postulated for this class of compound in mycorrhizas may be applicable to host‐parasite relations in general.
ON THE FLORAL ELEMENTS OF THE SEMI‐ARID ZONES OF INDIA AND THEIR ECOLOGICAL SIGNIFICANCE
Authors: BHARUCHA F. R. , MEHER‐HOMJI V. M. 
Published: May 2006

SummaryTwo zones of semi‐arid climate are recognized in India, one in the north contiguous with the desert of Thar, extending into Rajasthan, the Punjab and North Gujarat and the other in parts of the Deccan and Madras State in the south.Analysis of the flora of these regions reveals that seventeen types of floral elements are represented in these semi‐arid zones. The Southern zone has higher percentages of the Indian element and, to some extent, of the Indo‐Malayan. On the other hand, the northern zone is richer in the North African‐Indian Desert (Saharo‐Sindian) element. North African Steppe element and in the Mediterranean‐Oriental element. The elements of tropical and warm countries as well as the cosmopolitan element are equally frequent in both the zones. The percentage of the endemic element is very low in these regions, not exceeding 2.5%.The pattern of distribution of these floral elements is explained on the basis of the bioclimatic conditions prevailing in the Afro‐Asian continents.Finally, it is shown that contrasting seasonal aspects in the annual cycle of the climate—the alternation of a very long dry period with a short rainy season and of a cool and short‐day winter with a hot long‐day summer—permit the development of several floral elements.
THE EFFECTS OF ENVIRONMENT ON WOOD FORMATION AND CAMBIAL ACTIVITY IN ROBINIA PSEUDACACIA L.
Authors: WAISEL YOAV , FAHN A. 
Published: May 2006

SUMMARYAn investigation into the factors controlling cambial activity and wood production in Robinia pseudacacia is reported.The effects of temperature on the activity of the cambium are of prime importance. At relatively high temperatures the cambium is active, while at low temperatures dormancy is induced.Changes in photoperiod seem to affect the type of wood produced more than the activity of the cambium. Under long day conditions, xylem elements of the early wood type are formed, while under short day conditions the xylem produced is of the late wood type.Photoperiod affects cambial activity and the type of its derivatives through its control of the buds. Under high temperature and short day conditions, axillary buds have been found to sprout occasionally. Below these buds the wood produced is of the early type.Inhibitors produced by the leaves and retained in the stems seem to participate in the control of the cambial activity of R. pseudacacia.
DIFFERENTIAL RESPONSE OF THE EDAPHIC ECOTYPES IN CYNODON DACTYLON (L) PERS. TO SOIL CALCIUM
Authors: RAMAKRISHNAN P. S. , SINGH VIJAY K. 
Published: May 2006

SummaryThis paper describes the differential response to calcium of the three edaphic ecotypes of Cynodon dactylon (L) Pers. growing, respectively, on non‐calcareous, moderately calcareous, and highly calcareous soils. A close correlation was discernible for the three populations with the habitats they occupy in nature. The population from a highly calcareous soil showed a better yield in calcareous soils than in non‐calcareous soils, though in highly calcareous soils it tended to decrease. The reverse was found to be the case for the population from non‐calcareous soils; the population from moderately calcareous soil showed an intermediate behaviour. Significantly different responses were found between the three populations with regard to mineral uptake in both calcareous and non‐calcareous soils. Although calcium uptake was higher in the case of plants from non‐calcareous soils compared to those from calcareous soils in experiments using calcareous and non‐calcareous soils, in extremely calcareous soil the reverse was found to be the case. The ash content and the uptake of calcium, potassium and magnesium, in general, increased with increase in soil calcium level. However, the calcium uptake of the populations from moderately calcareous or non‐calcareous soils and the magnesium uptake of the latter decreased in highly calcareous soils. It is concluded from the present studies that there are at least three ‘edaphic ecotypes’ within this species, each markedly different from the other in its physiologic‐ecological attributes and that the basis for the differentiation is chiefly due to their response to soil calcium.
TWO QUATERNARY DEPOSITS IN THE LOWER TEES BASIN
Authors: BELLAMY D. J. , BRADSHAW M. E. , MILLINGTON G. R. , SIMMONS L G. 
Published: May 2006

SummaryTwo deposits from the Tees basin are investigated for their stratigraphical and pollen‐analytical content. A series of marls and lake muds from Romaldkirk includes material from zones I‐VIc of the Post‐glacial sequence and contained Bos bones. The deposit at Burtree Lane was revealed temporarily during motorway construction and covers zones IV‐VI. Its chief feature of interest is the thick layers of bryophyte peat which constitute the organic material, especially Paludella squarrosa which occurs in profusion. Other mosses include Acrocladium giganteum, A. cuspidatum, Camptothecium nitens, and the first British Post‐glacial record of Helodium blandowii. The possible developmental history of the deposits is discussed in the light of contemporary floating mat vegetation around some Polish lakes.
CYTOTAXONOMIC RELATIONSHIPS BETWEEN THE EUROPEAN AND NORTH AMERICAN ROSTRATE VIOLETS
Authors: HARVEY M. J. 
Published: May 2006

SummaryFour European and three North American species of Viola belonging to subsection Rostratae were investigated cytotaxonomically to determine the likelihood of a past trans‐Atlantic migration of genomes. By analysis of meiotic pairing in hybrids it was concluded that two species, V. rupestris and V. adunca, were closely related, but from geographical evidence it seemed more likely that some ancestral species had migrated from Asia to North America via Beringia and not across the north Atlantic region.In most hybrids there was considerable failure of chromosome pairing at meiosis and it was concluded that there are no close trans‐Atlantic relationships between the remaining species despite their interesting geographical distributions which had partly suggested the investigation in the first place.The chromosome numbers and distributions of the plants investigated are reported.
PHYSIOLOGY AND ECOLOGY OF ORCHID MYCORRHIZAL FUNGI WITH REFERENCE TO SEEDLING NUTRITION
Authors: SMITH SARAH E. 
Published: May 2006

SummaryOrchid mycorrhizal fungi have been assumed to supply carbohydrates to the orchid seedlings with which they are associated. To do this they must be able to utilize a regular source of carbohydrate in the soil, and also to translocate soluble compounds to the orchids. Mycorrhizal Rhizoctonia spp. were shown to decompose filter paper cellulose in pure culture. Secondly, R. repens and R. solani, isolated from Dactylorchis purpurella, were able to compete with other soil micro‐organisms in the exploitation of cellulose buried in unsterilized soil. Rhizoctonia repens was found capable of translocating 32P and‘14C labelled compounds in an already established mycelium. Radioactivity could also be detected in infected seedlings if tracers were fed to the infecting hyphae some distance from the seedlings. This translocation from fungus to seedlings resulted in greater growth of the seedlings if cellulose was available to the infecting fungus than if no carbohydrates were supplied to either fungus or seedlings.
CHANGES WITH AGE IN THE PHOTOSYNTHETIC AND RESPIRATORY COMPONENTS OF THE NET ASSIMILATION RATES OF SUGAR BEET AND WHEAT
Authors: WATSON D. J. , WILSON J. H. , FORD MARGARET A. , FRENCH S. A. W. 
Published: May 2006

SummaryThe net assimilation rates (E) of sugar beet and wheat growing in a controlled environment, and their components, the rates of photosynthesis (P) and respiration (R) of the whole plant per unit leaf area, were determined at intervals by a method described previously that depends on measuring the decrease in E when photosynthesis is prevented on some days during an experimental period by keeping plants in darkness. An alternative method of changing the duration of photosynthesis, by shortening the daily photoperiod, gave estimates of P and R almost identical with those obtained by shading plants throughout some days.In a period of 50 days from sowing for wheat and 90 days for sugar beet, E decreased by about a half. The value of P was always much greater than R; the smallest ratio of P to R was 5. Most of the decrease in E with age was caused by decrease in P, and the change in R with age was relatively small. At 30 days after sowing, E of sugar beet was twice that of wheat, wholly because of difference in P. These experiments confirm that, except perhaps in extreme conditions, change in E can safely be attributed to change in photosynthetic rate.
THE GROWTH OF TOMATO SEEDLINGS IN RELATION TO THE FORM OF THE NITROGEN SUPPLY
Authors: WOOLHOUSE H. W. , HARDWICK K. 
Published: May 2006

SummaryYoung tomato plants grown in nutrient solution cultures in which all of the nitrogen supply was in the form of nitrate had a higher relative growth rate than plants grown with ammonium nitrogen. Total phosphorus content expressed on a unit dry weight basis was not significantly different in the two treatments, but inorganic phosphorus content was high and organic phosphorus correspondingly low in ammonium‐grown as compared to nitrate‐grown plants. After 13 days this difference was found only in the shoots, but after 17 days the composition of the roots was similarly affected. Nitrate fed to ammonia‐grown plants resulted in a rapid increase in the dry matter and in organic phosphorus content in the young, incompletely expanded leaves. Total potassium content expressed on a dry weight basis did not differ in the two treatments for the first 10 days but thereafter the concentration in the ammonia‐grown plants fell whilst that in the nitrate grown plants remained approximately constant. The lowered potassium content in ammonia‐grown plants was first apparent in the leaves after 10 days, in the stems later and finally in the roots after 21 days. The causes of this reduced potassium content and its relationship to the lowered phosphate esterification and declining unit leaf rate are discussed.
THE EFFECTS OF FREQUENCY AND SEASON OF CLIPPING ON THE MORPHOLOGY, PRODUCTIVITY AND CHEMICAL COMPOSITION OF CALLUNA VULGARIS (L) HULL
Authors: GRANT SHEILA A. , HUNTER R. F. 
Published: May 2006

SummaryAn experiment is described in which heather plants growing in boxes were clipped either in summer or in winter at different yearly frequencies. The effects of the treatments on morphology, productivity and chemical composition are described.The view is put forward that the vigour of growth is dependent on the physiological age of the plant and that this is determined by the distribution of the dry matter among the leaf and current seasons shoots, the older stems and wood, and roots.It is suggested that a grazing intensity where approximately 60% of the current season's shoot length is removed should be the best form of moor management.
PHOSPHOHEXOISOMERASE IN BEECH MYCORRHIZA
Authors: HARLEY J. L. , LOUGHMAN B. C. 
Published: May 2006

SummaryPhosphohexoisomerase is shown to be present in beech mycorrhizas and to be distributed between host and fungal tissues approximately in proportion to dry weight. These results show that the different destinations of glucose and fructose absorbed by mycorrhizas is not explicable in terms of the absence of this enzyme from mycorrhizas or from their fungal tissues.
THE MEASUREMENT OF SOIL WATER TENSION IN THE FIELD
Authors: WEBSTER R. 
Published: May 2006

SummaryThe water in soil under growing plants is not in equilibrium and knowledge of the soil water tension must be based on direct measurements from several tensiometers. A cheap, reliable and easily maintained tensiometer for field use is described. The instruments are constructed mainly from nylon, with mercury manometers, and have been assembled in sets of six with a single support and mercury reservoir for the manometers. The nature and extent of the variation of the water tension from point to point in the soil have been measured at a number of sites in the Oxford district. On arithmetic scales frequency distributions are very skew but may be normalized by logarithmic transformation (to pF). The degree of variation is in general moderate: coefficients of variation range from 4 % to 25 % depending on kind of soil and time of year. Since the cost of the tensiometers described is low there is no reason why comparative studies on soil water tension should not be carried out with adequate replication.
CAMBIAL ACTIVITY IN EUCALYPTUS CAMALDULENSIS DEHN.
Authors: WAISEL Y. , ILANA NOAH  , FAHN A. 
Published: May 2006

SummaryThe production of xylem and phloem elements by the cambium of Eucalyptus camaldudensis was investigated. Plants grown under various climatic treatments were exposed to 14CO2 for short periods. This treatment left a marker in the xylem and in the phloem cells derived from the cambium during the exposure. Thus, the newly formed cell layers could be counted. Results reveal that the ratio of the number of xylem layers produced to the number of phloem layers produced (4: 1) is practically independent of many environmental factors. The ratio was also found to he independent of the rate of cell production as well as of the width of the undifferentiated cambial zone.Changes in the ratio of xylem to phloem were not found in plants treated with naphthalene acetic acid, kinetin or triiodobenzoic acid, nor in plants which were defoliated or disbudded. However, a higher ratio was found for plants treated with gibberellic acid.
A RE‐APPRAISAL OF THE ELECTROMETRIC METHOD FOR THE DETERMINATION OF THE CONCENTRATION OF CARBON DIOXIDE IN SOIL ATMOSPHERES
Authors: LEE J. A. , WOOLHOUSE H. W. 
Published: May 2006

SummaryThe electrometric method for the measurement of Pco2 in soil atmospheres is considered from the pomt of view of accuracy and equilibration time. Departures from the expected relationship between the equilibrium pH of 0.01 M sodium bicarbonate solution and Pco2 emphasize the need for calibrations with each experimental procedure. A particular weakness of the method is the long equilibration time which is shown to be susceptible to both temperature and Pco2 gradient and to be particularly long in the range of the most frequently encountered CO2 concentrations in the soil.