bluuebunny/crossref_metadata_2025_split huggingface dataset:
LIME‐CHLOROSIS AS A FACTOR IN SEEDLING ESTABLISHMENT ON CALCAREOUS SOILS
Authors: HUTCHINSON T. C. 
Published: May 2006

SummaryA comparative study under uniform laboratory conditions has been made of the relative susceptibility to lime‐chlorosis of 135 British species. These species were chosen as being either (a) largely confined to calcareous soils or (b) largely confined to non‐calcareous, especially acidic, soils. A number of species of wider soil tolerance were also grown. It was found that the species of groups (a) and (b) differed markedly from each other in chlorosis susceptibility. More than 90% of the species of calcareous soils were either resistant to lime‐chlorosis or were only mildly affected, whilst more than 60% of the species of acidic soils were susceptible to the condition. Evidence is presented that divergence in chlorosis susceptibility has occurred both within genera and within species. Family differences would also seem to occur. A possible mechanism for the origin of these differences and their ecological significance is discussed.
ABSORPTION OF NITROGEN BY MYCORRHIZAL ROOTS OF BEECH
Authors: CARRODUS B. B. 
Published: May 2006

SummaryThe effects of ammonium chloride, potassium nitrate and potassium chloride on the rate of 14CO2 incorporation into beech mycorrhizas were compared. It was confirmed that the rate of incorporation of 14CO2 was increased by ammonia and that glutamine became heavily labelled in its presence. No such effect was evident in the case of nitrate. Both potassium chloride and potassium nitrate stimulated 14CO2 incorporation as compared with samples kept in water but the extra radioactivity was found primarily in malate. This is the result to be expected if potassium is absorbed more readily than the associated anion. It is concluded that nitrate is not readily utilized by excised beech mycorrhizas. The primary destination of absorbed ammonia appears to be the fungal sheath.
A DISC ELECTROPHORETIC STUDY OF GLOBULIN PROTEINS OF LEGUME SEEDS WITH REFERENCE TO THEIR SYSTEMATICS
Authors: BOULTER D. , THURMAN D. A. , DERBYSHIRE E. 
Published: May 2006

SummaryThe globulins extracted from a number of different species of legume seeds have been subjected to disc electrophoresis. In the limited sample surveyed, the tribes Vicieae, Phaseoleae, Diocleae, Trifolieae and Daibergieae were each characterized by a distinctive protein band pattern. When the globulins of genera from the Loteae, Galacteae and Glycineae were examined, two types of protein band patterns were obtained which were distinctive for each tribe. A wider range of protein band patterns were obtained when genera of the Cajaneae were examined. The one species of Abrus examined possessed a globulin protein band pattern which differed from the patterns found in any other genera of the tribes examined.If the findings reported here can be extended to a much greater range of genera without significant change, then for some tribes within the Leguminosae a distinctive protein band pattern can be obtained when their seed globulins are electrophorized.
FINGERPRINT PATTERNS OF THE GLOBULIN FRACTION OBTAINED FROM SEEDS OF VARIOUS SPECIES OF THE FABACEAE
Authors: JACKSON P. , MILTON J. M. , BOULTER D. 
Published: May 2006

SummaryThe patterns (fingerprints) of the peptides separated from tryptic digests of the globulin fraction of seeds of five genera of the Vicieae have been compared and shown to be very similar. Patterns obtained with Phaseolus vulgaris, and two species of Canavalia (Phaseoleae, sensu lato), were different from those of the Vicieae; the two Canavalia species gave an identical pattern. Fingerprints of the globulin fraction of Abrus precatorius (Abreae) differed from those of Phaseolus vulgaris and also from those of the various members of the Vicieae.The usefulness of this method for supplying data for systematic purposes is discussed.
EXPERIMENTS ON THE ECOLOGICAL SIGNIFICANCE OF PHYCOMYCETOUS MYCORRHIZAS
Authors: BAYLIS G. T. S. 
Published: May 2006

SummaryThe mixed rain forest of New Zealand is dominated by conifers and dicotylous trees all of which form phycomycetous mycorrhizas. They may be present only intermittently in the field, but they become conspicuous in seedlings potted in forest soil. The time required to establish infection is variable, and may exceed 1 year. Growth is limited meanwhile by the reserve of phosphorus in the seed.Heating forest soils to temperatures above 55°C had two contrasted effects on the growth of tree seedlings—a small favourable effect associated with a rise in available phosphate measured hy the Truog test, and a larger deleterious effect associated with destruction of potential endophytes. Coprosma robusta (Rubiaceae) was the species principally used for experiments. By adding sufficient soluble phosphate to either heated or unheated soil vigorous non‐mycorrhizal plants were obtained. In the unheated soil there were also mycorrhizal plants which were, if anything, smaller. With less phosphate plants with numerous mycorrhizas were always larger than those with little or no infection; with no added phosphate there was virtually no growth unless mycorrhizas were formed. The relatively slow‐growing Griselinia littoralis differed in that when mycorrhizal it was insensitive to added phosphate. In steamed soil the growth of non‐mycorrhizal plants of both species was directly proportional to the amount of phosphate added.In Coprosma robusta shading to about one‐third of full daylight did not reduce mycorrhizal infection.Chemical analyses are given which demonstrate the low availability of phosphorus in the soils employed, and the greater uptake by mycorrhizal plants.These observ'ations suggest that mycorrhizas are normally essential for the uptake of phosphorus from forest soils, the phycomycetous type being particularly important in the Tropics and Southern Hemisphere, where the ectotrophic type has been little recorded.
ANALYSIS OF A CORE FROM SLAPTON LEY
Authors: CRABTREE K. , ROUND E. E. 
Published: May 2006

SummaryDetailed analyses of pollen, chemistry and diatoms have been carried out on material taken with a Livingstone corer from the Lower Ley, near Slapton, South Devon, The stratigraphy and the three approaches to reconstructing past events all point to a series of marked changes within the short section sampled, and all within pollen zone VIII. The degree of correlation between the different analyses is stressed and used to suggest ecological changes within tbe Ley and on the surrounding land surface, The permanence of the shingle ridge separating the Ley from the sea is verified, at least for the period under consideration, by the lack of any evidence of a period of marked marine incursion into the Ley.
STUDIES IN THE PHYSIOLOGY OF LICHENS
Authors: DREW E. A. , SMITH D. C. 
Published: May 2006

SummaryA method for directly isolating cells of the algal symbiont (Nostoc) in quantity from the thallus of Peltigera polydactyla is described. Such directly isolated algae excrete much of the photosynthetically fixed carbon into the medium as glucose, but they lose this property after only 48 hours in culture, at which time the cells begin to release only small amounts of a compound which may be a polysaccharide. These results are discussed in the context of the transfer of fixed carbon from alga to fungus in the lichen thallus during photosynthesis. After the lichen algae had been in pure culture for some time, they showed a carbohydrate metabolism intermediate in a number of respects between the directly isolated Nostoc and a strain of free‐living N. muscorum. All three kinds of algae were able to utilize externally supplied glucose. The Nostoc from lichens could not utilize mannitol.
STUDIES IN THE PHYSIOLOGY OF LICHENS
Authors: DREW E. A. , SMITH D. C. 
Published: May 2006

SummarySeveral lines of evidence confirm that glucose moves from alga to fungus in the thallus of Peltigera polydactyla during photosynthesis. When thallus discs are incubated in NaH14CO3 solutions in the light, [14C]glucose is detectable after i minute but [14C]mannitol—the principal product of photosynthesis—is not apparent until after 2 minutes. If high concentrations (2% w/v) of [12C]glucose are included in the media, then [14C]glucose diffuses out of the tissues, no [14C]mannitol is formed, and no translocation of 14C from algal layer to medulla occurs. These effects are explained on the basis that the [14C]glucose released by the algal cells is prevented from entering the fungus because of competitive inhibition by the non‐radioactive glucose in the medium. The concentration of glucose in the medium required to achieve a 50% inhibition was approximately 0.004 M. It was found that 2‐deoxy‐glucose and 3‐methylglucose had similar effects to glucose, but fructose, galactose, mannose and mannitol had no effect on the movement of 14C between the symbionts and they were unable to prevent discs taking up glucose from very dilute (approximately 10−6m) solutions. The rate of movement of glucose between the symbionts was rapid. No penetration of algal cells by fungal haustoria could be detected.
LEAF CHLOROSIS AND STOMATAL APERTURE *
Authors: SHIMSHI D. 
Published: May 2006

SummaryUnder conditions which encourage stomatal opening, nitrogen deficiency (induced in wheat, sugar beets, maize and groundnuts) and iron deficiency (induced in groundnuts) markedly reduce stomatal aperture, as evaluated by means of a porometer. The effect of these deficiencies on stomatal behaviour seems to be mediated through their effect on leaf chlorophyll content. Foliar applications of urea to chlorotic leaves of nitrogen‐deficient maize restore both normal chlorophyll content and normal stomatal behaviour to the treated leaves, indicating that both variables are related on a localized, rather than a systemic level. In groundnuts the relation between chlorophyll content and stomatal aperture is the same, regardless of whether chlorosis was caused by nitrogen or iron deficiency. Chlorotic leaves had a lower apparent water saturation deficit than green leaves.
INTERACTIONS OF CARBON DIOXIDE CONCENTRATION, LIGHT INTENSITY AND TEMPERATURE ON PLANT RESISTANCES TO WATER VAPOUR AND CARBON DIOXIDE DIFFUSION
Authors: WHITEMAN P. C. , KOLLER D. 
Published: May 2006

SummaryExchange of water vapour and carbon dioxide, between whole sunflower plants and an atmosphere controlled to required CO2 and water vapour concentrations, was measured in a polythene chamber. Plant resistances to diffusion of CO2 and H2O were calculated. From the combined data of net flux of CO2(“P”), resistances to CO2 uptake, and atmospheric CO2 concentration [CO2]atm, the intercellular space CO2 concentration [CO2]int could be calculated.[CO2]int was linearly related to [CO2]atm and this relationship was modified by light intensity. Plant age, between 3 and 6 weeks, did not alter the relationship. The ratio of [CO2]int to [CO2]atm was shown to be equivalent to the ratio of mesophyll resistance to CO2 diffusion (rm) to total resistance to CO2 diffusion (RCO2).At a given [CO2]atm, [CO2]int decreased with increasing light intensity between 500 and 5500 ft‐candles but was little affected by leaf temperatures between 18 and 34° C. On the other hand, the minimum internal CO2 concentration Γ, measured as the equilibrium CO2 compensation point, increased linearly over the same temperature range but was little affected by light intensity above 500 ft‐candles. The effects of temperature and light on [CO2]int are in contrast to their effects on the Γ value. Therefore, it is less likely that temperature effects on [CO2]in, measured in the normal photosynthetic [CO2]atm range, are responsible for‘midday stomatal closure’as inferred from observations of temperature effects on Γ alone.By comparing the effects of temperature and light intensities on stomatal resistance over the same range of [CO2]int values, direct effects of light and temperature, not mediated through changes in [CO2]int were demonstrated. The interactions of the factors involved are discussed.
THE ORIGIN AND DEVELOPMENT OF THE PHELLOGEN IN ROBINIA PSEUDACACIA L.
Authors: ARZEE TOVA , LIPHSCHITZ NILI , WAISEL Y. 
Published: May 2006

SummaryThe ontogenetic development of the phellogen in Robinia pseudacacia plants was studied. The first phellogen differentiates in the seedling stage from collenchyma cells in the second or third layer beneath the epidermis. The subsequent phellogen is periodically derived from phloem parenchyma cells.The site of phellogen initiation was shown to be affected by climatic conditions as well as by various growth substances. Under long‐day and high‐temperature conditions the phellogen was initiated in a lower internode, as compared with plants grown under the other three combinations of photoperiod and thermoperiod, Gibberellic acid and naphthalene acetic acid had distinct retarding effects on initiation Kinetin and tri‐iodo‐benzoic acid treatments showed no effect.
SUGAR ABSORPTION AND COMPARTMENTATION IN POTATO TUBER SLICES*
Authors: HARDY P. J. , NORTON G. 
Published: May 2006

SummaryThe uptake and utilization of [14C]sucrose, [14C]glucose and [14C]fructose by mature and immature potato tuber slices was studied. Both tissues absorbed [14C]glucose faster than [l4C]fructose but once absorbed, the hexoses were utilized similarly. In contrast, the greater part of the labelled sugars formed on administration of [14C]sucrose was sequestered at sites separate from the metabolic centres. Sucrose was taken up from the medium against a concentration gradient and transferred to metabolically inactive storage compartments without being hydrolysed either at the cell surface or at any stage during transit.
POLLEN TUBE GROWTH AND SEED SET IN SELF‐INCOMPATIBLE AND SELF‐COMPATIBLE LEAVENWORTHIA (CRUCIFERAE) POPULATIONS
Authors: LLOYD D. G. 
Published: May 2006

SummaryFour geographic races of Leavenworthia crassa and one race of L. alabamica are described as self‐incompatible, since the average frequencies of fruit set and of pollen tube growth into the style are significantly lower after self‐pollination than after cross‐pollination. The frequency of successful self‐pollination in individual plants of these races varies from zero to 100%, and is positively correlated with the average number of seeds in self‐pollinated siliquas. Eleven races of L. crassa and three races of L. alabaimca are adapted to self‐pollination and are described as self‐compatible, although self‐pollinations succeed 2% less frequently than cross‐pollinations. Self‐pollinated siliquas of these races contain an average of 12% fewer seeds than cross‐pollinated siliquas; this is probably an expression of cryptic self‐incompatibility and not the result of the exposure of seed lethals on inbreeding. There is, therefore, no absolute distinction between self‐incompatibility and self‐compatibility in Leavemcorthia.The growth of pollen tubes is compared in successful and unsuccessful pollinations of the same type, in self‐ and cross‐pollinations of the same individuals, and in self‐incompatible and self‐compatible races. Pollen grains react with the stigma even in unsuccessful pollinations and some pollen grains are inhibited in successful pollinations. In both self‐incompatible and self‐compatible races, the average number of emptied pollen grains on the stigmata of successful pollinations (an estimate of the number of pollen tubes in the styles) is similar after self‐ and cross‐pollinations. But the average number of emptied pollen grains is lower in self‐incompatible races than in self‐compatible races. The results are interpreted in terms of the response of pollen grains to an essential growth substance supplied by the stigma.
LICHEN PHYSIOLOGY
Authors: RICHARDSON D. H. S. , HILL D. JACKSON , SMITH D. C. 
Published: May 2006

SummaryThe identity of the carbohydrate moving between the symbionts of a lichen depends on the genus of alga present. Twenty‐seven lichen species, involving eight different genera of algae, have been examined. In lichens containing five genera of Chlorophyceae, carbohydrates move to the fungus as polyols (ribitol in Trebouxia, Myrmecia and Coccomyxa; erythritol in Trentepohlia; and sorbitol in Hyalococcus). In lichens containing three genera of Cyanophyceae (Nostoc, Calothrix and Scytonema) glucose was the carbohydrate moving, although there is a possibility that in the one lichen with Calothrix which was investigated, it may have been a glucan.
STUDIES IN THE RESPIRATORY AND CARBOHYDRATE METABOLISM OF PLANT TISSUES
Authors: BARKER J. 
Published: May 2006

SummaryThe changes of various phosphate compounds were determined during the increase in rate of CO2 output and of sugar content which occurred in low‐sugar potatoes at 1° C. The contents of phosphate compounds were also estimated in high‐ and low‐sugar potatoes at 10° C. The increase in rate of CO2 output associated with higher sugar content could not be attributed wholly to an increase in the amounts of the hexose mono‐ and di‐phosphates; possible explanations are given.The changes observed in glucose‐1‐phosphate do not afford any explanation of the mechanism of sweetening and de‐sweetening in potatoes. In different metabolic data the quotient, glucose‐1‐phosphate/glucose‐6‐phosphate, remained close to that for phosphoglucomutase in vitro.
EFFECTS OF GROWTH REGULATING SUBSTANCES AND WATER POTENTIAL ON THE DEVELOPMENT OF SECONDARY XYLEM IN FRAXINUS
Authors: DOLEY D. , LEYTON L. 
Published: May 2006

SummaryMarked 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

SummaryTwelve‐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

SummaryThe 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

SummaryA 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.