bluuebunny/crossref_metadata_2025 huggingface dataset:
AUXIN AND BORON IN RELATION TO THE ROOTING RESPONSE AND AGEING OF MUNG BEAN CUTTINGS
Authors: JARVIS B. C. , ALI A. H. N. , SHAHEED A. I.
Published: May 2006

Boron is required for development of root primordia on stem cuttings of mung bean seedlings. Although exogenous boron is not required until more than 48 h after stem cuttings are placed in auxin, it may be supplied at any previous time, including during growth of the seedlings. There is a progressive loss of rooting response to auxin and boron when cuttings are aged in water prior to rooting treatment. This ageing effect is not influenced by the presence of boron but is considerably reduced by application of dilute solutions of auxin, which are themselves without effect on rooting. Cuttings prepared from seedlings grown in the presence of boron initiate fewer roots in response to low concentrations of auxin than do cuttings taken from seedlings raised in the absence of boron. Despite being required for development of root primordia, boron is antagonistic to the influence of low concentrations of supplied auxin on rooting. The possibility that boron regulates endogenous auxin levels during root development is discussed.
ALLOCATION OF PHOTOSYNTHETICALLY FIXED CARBON INFESTUCA OVINAL. ANDNARDUS STRICT AL.
Authors: ATKINSON C. J. , FARRAR J. F.
Published: May 2006

The allocation of carbon in two montane grasses was followed using14C labelling and gas exchange measurements. Both grasses showed similar total non‐structural carbohydrate contents and net allocation of carbon. A six‐compartmental model (with root and shoot each composed of soluble, storage and structural material) was used to summarize the data, to provide estimates of carbohydrate turnover rates, and to produce complete carbon budgets. Storage carbohydrate was heavily labelled and turned over rapidly, with half‐times of 25 h inFestuca ovinaand 15 h inNardus stricta.This does not support the idea that storage carbohydrates are deposited only to be mobilized in response to environmental perturbations. It is suggested that the small relative growth rates in these species are not the result of inefficient use of fixed carbon, but of slow rates of photosynthesis; the respiratory costs of growth are similar to those for barley. The large flux of carbon through storage carbohydrate is suggested to ensure a readily available supply of sugars for metabolism, independent of environmental conditions.
PHOTOSYNTHESIS AND RESPIRATION IN THE SUB‐ANTARCTIC TUSSOCK GRASS POA COOKII
Authors: BATE G. C. , SMITH V. R.
Published: May 2006

Poa cookii dominates the tussock grasslands at islands of the Kerguelen Province of the sub‐Antarctic. In common with other sub‐Antarctic Poa species it is highly productive. Infra‐red gas analysis studies at Marion Island (46° S, 37° E) showed that P. cookii is a C3 photosynthetic type plant, possessing a high CO2 compensation concentration (c. 100 p.p.m.) and apparently high rates of photorespiration. However, photosynthetic light saturation was not attained at a photosynthetic photon flux density (PPFD) of 2000μmol m−2s−1, possibly due to leaf anatomical features causing shading of the chlorophyllous mesophyll. Compensating irradiance values were 5 to 11 μmol m−2s−1. Net photosynthesis occurred below 0 °C and increased with temperature up to 10 to 12 °C, remaining constant up to 19 to 23 °C, depending in PPFD. Dark respiration increased exponentially with temperature and at 32 °C the temperature optimum had not been reached. Photorespiration also increased with temperature but rates were lower than those of dark respiration. Increasing the wind velocity over a leaf immediately decreased the net assimilation rate, which then slowly recovered to almost the original level. It appears that the grass is well‐adapted to sub‐Antarctic conditions of low light, low (seldom freezing) temperatures and high wind.
PHOTOSYNTHESIS BY ISOLATED CODIUM FRAGILE CHLOROPLASTS OF VARYING INTERNAL PHOSPHATE STATUS
Authors: RUTTER J. C. , COBB A. H.
Published: May 2006

Photosynthesis by isolated Codium fragile frond‐tip chloroplasts appeared to be inversely related to stromal orthophosphate (Pi) and polyphosphate content. Thus, exogenous 10 mM Pi inhibited photosynthesis by chloroplasts with a relatively high internal phosphate status but stimulated it when internal phosphate status was low. Inhibition of 14CO2 fixation by 5 mM Pi was not accompanied by any significant release of photosynthetically‐reduced 14C and may therefore be mediated by processes other than, or in addition to, stromal depletion of metabolites as a result of translocator action. In chloroplasts where photosynthesis was stimulated by exogenous Pi, phosphoglyceric acid or glucose‐6‐phosphate this effect was reversed by the addition of a second test substrate suggesting translocator involvement in this reversal.
TRANSLOCATION OF ORTHOPHOSPHATE AND GLUCOSE‐6‐phosphate IN CODIUM FRAGILE CHLOROPLASTS
Authors: RUTTER J. C. , COBB A. H.
Published: May 2006

Uptake of 32Pi (orthophosphate) by isolated frond‐tip chloroplasts of Codium fragile (Suringar) Hariot was light‐stimulated, strongly inhibited by 50 μM p‐chloromercuriphenyl sulphonic acid (pCMS) and showed an exponential increase with exogenous Pi concentrations above 1 mM, However, [14C] glucose‐6‐phosphate (G‐6‐P) uptake showed saturation kinetics, was not light‐stimulated, was less sensitive to pCMS and was slower than Pi uptake.

Exogenous Pi stimulated the release of radioactivity from chloroplasts preloaded with [14C]G‐6‐P and vice versa. 3‐Phosphoglycerate (PGA) readily stimulated label release from 32Pi‐preloaded chloroplasts, but only slightly stimulated the release of label from [14C]G‐6‐P‐preloaded chloroplasts. The apparent PGA‐stimulated release of Pi was inhibited by 50μM pCMS but the exchange of Pi with G‐6‐P, as indicated by back‐exchange studies, showed no consistent sensitivity to pCMS.

The presence of two separate and distinct phosphate translocators in the envelopes of C. fragile frond‐tip chloroplasts is postulated: (a) one facilitating the exchange of PGA with Pi, which is relatively fast, light‐stimulated and sensitive to inhibition by 50 μM pCMS; (b) another facilitating the relatively slower exchange of Pi with G‐6‐P which is not light‐stimulated and shows little sensitivity to pCMS.
PIGMENT/PROTEIN COMPLEXES OF THE INTERTIDAL ALGACODIUM FRAGILE(SURINGAR) HARIOT
Authors: BENSON ERICA E. , COBB A. H.
Published: May 2006

Six pigment‐containing bands were isolated fromCodium fragilethylakoids using sodium dodecyl sulphate/polyacrylamide gel electrophoresis. Two, designated CPla and CP1, were associated with Photosystem I and enriched in chlorophyllaand a‐carotene, and two light‐harvesting complexes (dimer LHCP1 and monomer LHCP2) were enriched in chlorophyllb, siphonoxanthin, siphonein and neoxanthin. A fifth pigment/protein (CPa) was not successfully characterized. Undissociated free pigment contained almost all the violaxanthin recovered from gel eluates and a high concentration of siphonoxanthin.

Several high (100 ± 3.0 to 62 ± 7.7 kilodaltons) and two low molecular weight proteins (15.2 ± 1.2 to 16.5 plusmn; 1.2 and 18.0 kilodaltons) were thought to be associated with CPla and CP1. LHCP1 contained a protein of molecular weight 56 ± 24 kilodaltons and LHCP, a 29 kilodaltons protein, however the behaviour of these complexes after denaturation was particularly unusual in that on re‐electrophoresis the denatured monomer appeared to reassociate and proteins of 59, 56 and 28 kilodaltons were resolved. The composition of these pigment/protein complexes suggests that a large proportion of the pigments present inC. fragilechloroplasts function in a light‐harvesting capacity and this may be an adaptation to submarine photosynthesis.
A MODULAR APPROACH TO ANALYSIS OF PLANT GROWTH
Authors: PORTER J. R.
Published: May 2006

This paper describes how plants can be studied as developing modular systems, with growth described as a population‐type process defined by the rate of production of modular plant parts.

A simple model of dynamics of meristems is developed and is followed by discussion of such features of growth as meristematic flux and the change from vegetative to a flowering state, the positional distribution of meristems and the probabilities of meristems undergoing transitions that result in architectural differences between plants.
PHYSIOLOGICAL‐ENVIRONMENTAL INTERACTIONS IN LICHENS
Authors: MACFARLANE J. D. , KERSHAW K. A. , WEBBER M. R.
Published: May 2006

Despite the contrasting thermal and light environment of sun and shade ecotypes of Cladonia rangiferina, analysis of the pattern of net photosynthesis throughout the year as well as enzyme polymorphism in each morphotype has found little genotypic difference.

The large disparity between photosynthetic capacity in the sun and shade replicates is shown to be due simply to a difference in chlorophyll content. There is a significant decline in photosynthetic capacity in November and this is found to be reversible uncoupling of photosynthetic units (PU's) during the winter period. The control of coupling and uncoupling of PU's is shown to be mediated by both daylength and thallus temperatures, and a double environmental signal in June and July of short days coupled to low temperature will initiate and finalize the event within 12 h. This response pattern is discussed in relation to identical capacity changes in other lichen species. Apart from a single isoenzyme difference in esterase polymorphism, no differences in the zymograms of leucine aminopeptidase, phosphoglucoisomerase, or acid phosphatase were detected and this overall genetic homogeneity was equally evident in a general protein gel.

This unexpected degree of homogeneity is discussed in terms of the difficulties in assessing enzyme polymorphisms in different plant populations without maximum refinement of protein preparation methods and electrophoretic techniques. It is concluded that the two quite distinct sun and shade morphotypes only reflect phenotypic differences. In contrast however significant differences are reported in the distribution of specific enzymes between the tops and bases of the podetia.
INFLUENCE OF OZONE ON CARBON PARTITIONING IN TOMATO: POTENTIAL ROLE OF CARBON FLOW IN REGULATION OF THE MYCORRHIZAL SYMBIOSIS UNDER CONDITIONS OF STRESS
Authors: McCOOL P. M. , MENGE J. A.
Published: May 2006

Tomato seedlings inoculated with the vesicular‐arbuscular mycorrhizal fungus, Glomus fasciculatus, were exposed for 3 h to 15 parts 10−8 (294 μg m−3) ozone twice weekly or to 30 parts 10−8 (589 μg m−3) ozone once per week, for 9 weeks. Mycorrhizal infection was reduced by 46 and 63 % in the 15 and 30 parts 10−8 ozone treatments, respectively. The total dry weight of mycorrhizal plants was significantly reduced in the 30 parts 10−8 ozone treatment but dry weights of non‐mycorrhizal plants were not affected by any ozone treatment. In a second experiment, 3–week‐old seedlings of tomato inoculated with G. fasciculatus were twice exposed to 30 parts 1O−8 ozone or filtered air for 3 h with a 7‐day interval. Soluble amino acids in root exudates and root extracts were significantly reduced in mycorrhizal plants exposed to ozone. The amino acid content of non‐mycorrhizal exudates was not reduced by ozone but was significantly increased in root extracts. Levels of reducing sugars also declined in root exudates and in root extracts of mycorrhizal and non‐mycorrhizal plants exposed to ozone. A greater amount of photoassimilated 14CO2 was retained in leaves and less translocated to roots 4 h after fumigation with ozone. Labelled leaves exhibited no leaf injury until 8 h after exposure to ozone and showed only 10 to 20% chlorosis after 24 h.
A COMPARISON OF THE RESPONSES OF LOLIUM PERENNE L. *, HOLCUS LANATUS L. AND DESCHAMPSIA FLEXUOSA (L.) TRIN. TO A LOCALIZED SUPPLY OF NITROGEN
Authors: ROBINSON D. , RORISON I. H.
Published: May 2006

Three grasses were grown in a split‐root solution culture experiment in which only a fraction of the root system of each plant was supplied with 4.0 mol m−3 N as NH4NO3. The solutions were labelled with 15NO3 or 15rNH4 during the final 24 h of the experiment. Deschampsia flexuosa, unlike Holcus lanatus and Lolium perenne, showed no reduction in total dry weight production relative to the controls. Proportionately greater increases in specific N‐absorption rate were measured in D. flexuosa compared with H. lanatus and L. perenne. All three species exhibited large changes in root morphology (length : dry weight). In D. flexuosa such changes were confined only to those roots having direct access to N (+ N roots); in H. lanatus and L. perenne this response occurred also in the rest of the root system (‐N roots). The proportion of 15N transported to the ‐ N roots was greater in H. lanatus and L. perenne. Increased transport of ammonium‐N to the shoot was found in D. flexuosa and, it is suggested, this stabilized the root: shoot ratio and maintained maximum relative growth rate. The smaller absolute N demand of D. flexuosa was such that responses to maximize N uptake, to confine to a greater extent the utilization of N to +N roots, and to maintain N supply to the shoot, ensured full compensation for the restricted N supply. The inherently higher N demands of H. lanatus and L. perenne could not be met by increases in specific absorption rates. In addition, the transport of relatively greater amounts of 15N to – N roots rather than to the shoot, and the consequent increase in root: shoot ratios prevented compensation from being achieved to the same extent.

Thus, the efficient utilization of dry matter and nutrient resources appear to be important factors enabling D. flexuosa to grow effectively under restricted conditions of nutrient supply.
GENECOLOGICAL STUDIES OF RUMEX CRISPUS L.
Authors: AKEROYD J. R. , BRIGGS D.
Published: May 2006

Samples from 23 British populations of Rumex crispus L., including material of three principal variants described in this species, were transplanted into two garden trials. It was discovered that some characteristics, which distinguished the variants in the field, were less evident or less clear‐cut in cultivation. However, plants from different habitat types did remain distinct in certain features, in particular, the time of first flowering and pattern of tubercles on the fruits. Some variation between populations within habitat types was detected by the transplant experiments.
GENECOLOGICAL STUDIES OF RUMEX CRISPUSL.
Authors: AKEROYD J. R. , BRIGGS D.
Published: May 2006

Open‐pollinated seed was collected from several seed parents in each of 16 British populations of Rumex crispus L., representing the three principal variants of this species. Progeny of these seed parents (family lines) were grown in a garden trial, which revealed statistically significant differences between and within the populations sampled.

(1) Coastal plants had denser inflorescences, fewer flowering stems, later anthesis and a greater development of corky perianth tubercles than inland plants.

(2) Plants from riverine tidal mud at Tintern were distinct in their exceptional height, more or less uncrisped leaves, lax inflorescences, very early flowering and tubercle pattern intermediate to coastal and inland plants.

(3) There was considerable variation between populations within coastal and inland habitats and within family lines. This spectrum of variation suggested that both outbreeding and inbreeding might occur in R. crispus.

(4) Many plants from inland populations, with the exception of those from Tintern, flowered in their first year of growth, whereas populations from coastal areas and Tintern flowered in their second (or a later) year of growth.

(5) There was evidence of gene flow between coastal and inland variants of R. crispus at ‘points of contact’, especially where coastal habitats had been disturbed. Plants from a few inland sites appeared to be hybrids between R. crispus and R. obtusifolius.

(6) In cultivation, inland populations flowered consistently earlier than coastal plants. A similar difference in flowering time was recorded in a field study of a coastal area of Suffolk.
GROWTH CURVE OF THE LICHEN RHIZOCARPON GEOGRAPHICUM
Authors: ARMSTRONG R. A.
Published: May 2006

Summary

Data on the growth curve of the lichen Rhizocarpon geographicum were obtained by measuring the radial growth rates (mm per 1.5 years) of 39 thalli from 2 to 65 mm in diameter growing in the same environment. An Aplin and Hill plot (ri–r1 against In r2– In r1) of the data and regression analyses suggested an initial phase of growth (up to a diameter of about 7 mm) in which the relative growth rate increased rapidly. This was followed by a phase in which the relative growth rate fell but the radial growth, rate continued to rise (7 to 20 mm in diameter). Radial growth was then relatively constant until about 45 mm diameter and then declined. The Aplin and Hill model did not fit the data as a whole but may apply for a transient period in thalli between about 7 and 16 mm in diameter. This curve shows some similarities to that suggested by lichenometric studies but differs in showing a less steep decline in growth rate after the ‘great’ period.
CYCLIC VEGETATIONAL AND EDAPHIC CHANGES IN AN ARTHRO CNEMUM COMMUNITY IN SRI LANKA
Authors: de SILVA P. H. A. U. , PEMADASA M. A. , HERATH R. M.
Published: May 2006

Summary

The perennial shrub Arthrocnemum indicum dominates in certain saline habitats in Sri Lanka. Its growth‐vigour declines with ageing. As the plant grows into a clump with its radiating prostrate shoots and upright aerial shoots bearing clusters of branches, it traps wind‐borne sand, so developing a hummock. Each clump on its hummock follows a cycle of pioneer, building, mature, degenerate and eroded phases with concomitant vegetational and edaphic changes. This cycle was elucidated in a community on the north‐west coast of Sri Lanka. During upgrade phases of the cycle, fine sand, organic debris and humus continue to accumulate in and around the thickly‐branched, vigorously‐growing Arthrocnemum clump, and this improves the moisture status of the developing hummock; the concentrations of nutrients also increase, as a result of accretion of wind‐borne particles and through reduction (by the closed Arthrocnemum canopy) of nutrient‐loss by wind‐erosion, surface run‐off and leaching. These trends are reversed during the downgrade phases. As the growth‐vigour of ageing shoots declines, the clump becomes increasingly open and the exposed hammock suffers wind‐induced erosion; the moisture status deteriorates as fine sand and organic matter are lost by wind‐erosion, which, together with enhanced leaching, also causes nutrient‐loss leading to soil impoverishment. The eventual death of the Arthrocnemum clump and continued hummock‐erosion complete the cycle. The subordinate Cynodon dactylon occurs more abundantly on degenerating than on developing hummocks; thus, the Arthrocnemum cycle appears to impose an inverse cyclic succession of its abundance. Accordingly, cyclic vegetational and edaphic changes in this community are closely correlated with the phasic development of the dominant A. indicum.
A GROWTH CABINET PROVIDING VARIABLE SPECTRAL PHOTON DISTRIBUTIONS AT HIGH FLUENCE RATES
Authors: HUGHES J. E. , HEATHCOTE L. , BAMBRIDGE K. , BLACK C. R.
Published: May 2006

Summary

A plant growth cabinet providing a flexible facility for photomorphogenic and photoperiodic research is described. The growth chamber is divided into quarters which are optically isolated, and has a recirculating air‐conditioning system. The various light sources and filters available are discussed in relation to their desirable features. The chosen sources of white light (metal halide discharge lamps) are capable of generating approximately 800 μmol m−2 s−1 (400 to 700 nm). Tungsten‐halogen filament lamps are used to provide longer wavelengths. Infra‐red filters (acrylic sheet and water) reduced heat loading to a negligible level. Data are presented for internode length in plants of Chenopodium album L. grown under different fluence rates of supplementary far‐red light in the new cabinet.
FORMATION OF METACHROMATIC GRANULES FOLLOWING PHOSPHATE UPTAKE BY MYCELIAL HYPHAE OF AN ECTOMYCORRHIZAL FUNGUS
Authors: LAPEYRIE F. F. , CHILVERS G. A. , DOUGLASS P. A.
Published: May 2006

Summary

Abundant metachromatic granules, presumed to contain polyphosphate, were present in mycelial hyphae of Paxillus involutus (Batsch. ex Fr.) Fr. grown in phosphate‐rich medium, but were absent when the medium lacked phosphate. Phosphorus‐starved hyphae placed into phosphate‐containing solutions developed granules within 3 to 4 h. Most of this period was required for synthesis of granule materials, since phosphate uptake occurred within minutes. Both phosphate uptake and granule formation are active processes, affected by low temperature and respiratory inhibitiors. No special importance seemed to attach to the presence of any of the following cations: Ca2+; Mg2+; K+; or Na+; and two different isolates of P. involutus, one calcifuge and one calcicole, showed no differential effects regarding granule formation in the presence and absence of Ca2+ and Mg2+.
ECTOMYCORRHIZA FORMATION IN EUCALYPTUS
Authors: MALAJCZUK N. , MOLINA R. , TRAPPE J. M.
Published: May 2006

Summary

Ultrastmcture of Eucalyptus ectomycorrhizas initiated by compatible, host‐specific fungi and by broad‐host range fungi was compared with that of roots inoculated with incompatible, conifer‐specific ectomycorrhizal fungi. The results indicate little difference in morphology between ectomycorrhizas formed by compatible, host‐specific fungi and those formed by broad‐host‐range fungi. However, interaction between eucalypt roots and incompatible fungus species known to be conifer‐specific induced either deposition of tannins in root tissue or, in the case of the Pseudotsuga‐speciiic Suillus lakei, a characteristic hypersensitive reaction which resulted in lysis of hyphae and of epidermal and outer cortical cells of roots.
CANOPY STRUCTURE AND MICROCLIMATE OF TWO WET GRASSLAND COMMUNITIES
Authors: FLIERVOET L. M. , WERGER M. J. A.
Published: May 2006

Summary

In two adjacent wet grasslands, a Cirsio‐Molinietum and a Senecioni‐Brometum, in the Netherlands, above‐ground phytomass, leaf area index (LAI), and canopy structure were measured at peak flowering season, during three consecutive years. Microclimate profiles in the canopies were measured. The Cirsio‐Molinietum produced a smaller phytomass with a larger LAI than the Senecioni‐Brometum, and the stem/leaf ratios were different too. Relative distribution of phytomass and leaf area in the canopies were remarkably constant during the three years and independent of total values. Differences in canopy structure including differences in vertical arrangement of phytomass and leaf area, leaf angles and leaf sizes result in differences in light interception patterns, air temperatures and saturation deficits within the canopies, and in soil temperatures. These differences are interpreted in terms of relative growth rates of the constituent species and photosynthetic performances of the vegetation types.
INDUCTION OF CYTOCHROME P‐450 IN INTACT MUNG BEANS
Authors: HENDRY G. A. F. , JONES O. T. G.
Published: May 2006

Summary

Induction of cytochrome P‐450 in intact plants is described for the first time. Geraniol and from‐cinnamate, substrates for plant cytochrome P‐450 reactions, induce the formation of cytochrome P‐450 when fed to seedlings of mung bean [Vigna radiata (L.) Wilczek. cv. Berken, syn Phasealus aureus Roxbl, The carbon monoxide difference spectra of the induced forms of cytochrome P‐450 have absorbance maxima of 449 nm (with geraniol) and 451 nm (with cinnamate) compared with the endogenous form at 452 nm and indicate the presence of multiple forms of cytochrome P‐450. The induction of cytochrome P‐450 was suppressed by feeding laevulinic acid or cyctoheximide, inhibitors respectively of haem and protein synthesis. The use of solvents for the dilution and uptake of water‐insoluble inducing compounds is described, together with the effect of such solvents on plant microsomal cytochromes.
OXYGEN DIFFUSION IN PEA
Authors: ARMSTRONG W. , HEALY M. T.
Published: May 2006

Summary

The apical oxygen concentrations in the primary roots of agar‐grown pea plants were assayed polarographically with the roots immersed in anaerobic media, their laterals present or excised, and with or without the sub‐apical regions jacketed in a solid agar.

Oxygen concentrations declined for several days following emergence as a function of accumulated demands of primary and lateral Touts for oxygen, internal diffusive resistance, and radial oxygen leakage from both primary root and laterals. Under the combined influence of all these factors (unjacketed roots with laterals), primary root apices could become totally anoxic when only 4 to 6 d old. Total apical anoxia did not occur however if lateral roots were excised, Or if sub‐apical regions of the roots remained encased in the solid agar. In these roots the decline in apical oxygen concentration continued for about 7 d of growth, after which the trend was reversed, and at 40 d apical concentrations as high as 7% were recorded. The anoxic state, which after 4d had characterized unjacketed roots with laterals, was also alleviated m approx. 10 d; at 40 d apical oxygen concentrations had risen to 3.5 to 4.5%.

Respiratory rates in the primary root declined both with distance from the apex and with time. IT was concluded that it was chiefly these effects which accounted for the subsequent elevation of the oxygen concentrations in the primary‐ apex.

It is pointed out that the oxygen demands of flooded soil might even lead to apical anoxia m the roots of 2‐d‐old plants. However, it is also tentatively suggested that, since respiratory decline can restore a better balance between oxygen demand and internal supply in pea roots, the ageing pea plant may become eventually somewhat less sensitive to soil waterlogging.
RESPONSES OF ADAXIAL AND ABAXIAL STOMATA TO LIGHT AND WATER DEFICITS IN SUNFLOWER AND SORGHUM
Authors: TURNER N. C. , SINGH D. P.
Published: May 2006

Summary

The responses of adaxial and abaxial stomata to light and water deficits were followed in normally‐oriented and inverted leaves of sunflower (Helianthus annuus L. cv. Hysun 30) and sorghum (Sorghum bicolor (L.) Moench cv. RS 610) In both species, but especially in sunflower, the adaxial and abaxial stomata closed at the same leaf water potential. However, as a water deficit was imposed, the stomata facing away from the light source, i.e. abaxial stomata in the normal leaf and the adaxial stomata in the inverted leaf, closed more rapidly than the stomata facing the light source. In both sorghum and sunflower the resistance of the adaxial epidermis was higher than that of that abaxial at the same photon flux densities; in sunflower, but not in sorghum this was correlated with the stomatal frequency. The sorghum stomata acclimated to High light, i.e. the adaxial stomata in a normal leaf and the abaxial stomata in an inverted leaf had high resistances on inversion, but the resistance decreased slowly over a per tad of days. Acclimation was not the sole factor involved in the difference in response to light of adaxial and abaxial sorghum stomata. Short‐term leaf inversion reduced the rate of net photosynthesis by 20 to 30% at all photon flux densities.

We conclude that adaxial stomata in sorghum, hut not in sunflower, differ inherently from stomata in their response to light. However, in both species there was no inherent between adaxial and abaxial stomata to rapidly‐imposed water deficits.
EFFECTS OF SIMULATED ACTDIC RAIN ON YIELDS OF FIELD‐GROWN SOYBEANS
Authors: EVANS L. S. , LEWIN K. F. , PATTI M. J.
Published: May 2006

Summary

An experiment was performed during the summer of 1982 to determine the effects of simulated acidic rain on seed yields on two commercial cultivars of soybeans grown according to standard agronomic practices. Plants were shielded from all ambient rainfalls automatically by two amount exclusion covers and exposed to simulated rainfalls m quantities equal to the average amount of rainfall that occurs at the site. Seed yields of cv. Amsoy exposed twice weekly to simulated rain of pH 4.1, 3.3 and 2.7 were, respectively, 3.0, 9.0, and 12.8% below yields of plants exposed to simulated rain of pH 5.6. A treatment‐response function of seed yield vs rainfall pH for Amsoy was y= 10.20+0.587 x and had a correlation coefficient of 0.96 (y is seed mass per plant and x is the pH of the simulated rain). For cv, Williams, seed yields of plants exposed to simulated rainfalls of pH 5.6, 4.1, 3 3 and 2.7 were 11.5, 10.5, 11.4 and 11.4 g, respectively. A treatment‐response function of seed yield vs rainfall pH for Williams was y= 11.13 + 0.016x which had a correlation coefficient of 0.038. Plants of Amsoy and Williams grown in plots adjacent to the exclusion shelters had mean seed yields of 11.4 and 9.8 g per plant, respectively. Seed yield per plant was dependent upon number of pods per plant because the number of seeds per pod did not vary among treatments for each cultivar.
DIFFERENTIAL EFFECTS OF OZONE AND SULPHUR DIOXIDE ON THE FINE STRUCTURE OF SPINACH LEAF CELLS
Authors: MIYAKE HIROSHI , FURUKAWA AKIO , TOTOSUKA TSUMUGU , MAEDA EIZO
Published: May 2006

Summary

Spinach (Spinacia oleraceaL. cv, New Asia) plants were continuously fumigated with 0.5 μ11−2O3and 1.0 μ11−1SO2singly or in combination. The leaf tissues were examined by electron microscopy at various intervals until they were necrosed. The first indication of O3injury was swelling of thylakoids in the chloroplasts, which was followed by swelling of Golgi bodies, endoplasmic reticulum and nuclear envelopes. The internal space of the mitochondrial cristae was reduced. Later the chloroplasts were deformed. Sulphur dioxide injury first appeared as swelling of the stroma and deformation of the chloroplasts. Swelling of thylakoids appeared later. After both treatments the ceils ultimately collapsed and their contents were aggregated. When O3and SO2were supplied simultaneously, the appearance and development of injury were markedly accelerated compared with either of the single fumigations. The cells mainly showed the features of SO2injury following simultaneous fumigation.
UPTAKE OF [14C]GLUCOSE BY ASYMBIOTIC AND MYCORRHIZAL ORCHID PROTOCORMS
Authors: HADLEY G.
Published: May 2006

Summary

In cultures of Goodyera repens Br. infected with its natural mycorrhizal endophyte, Ceratobasidium Cornigerum (Bourdot) Rogers, 14C supplied as glucose reached a peak in the external mycelium within 48 h but accumulated in protocorms over several days. Uptake directly from the substrate into non‐infected protocorms was much slower with less incorporation of 14C into insoluble material than occurred in infected protocorms. There was a similar pattern of uptake from two Ceratobasidium spp. into Dactylorhiza purpurella (T. & T. A. Steph) Soó but the amount of glucose accumulated was less using a natural endophyte than with an isolate originally obtained from rice plants. Using an un‐named Cymbidium hybrid in symbiosis with Ceratobasidium sp. from D. purpurella, there were low rates of uptake into both non‐infected and infected protocorms.

14C from glucose appeared in mannitol and trehalose in mycelium but mainly in glucose, fructose and sucrose in the orchid, with traces of trehalose in infected tissue. In freshly‐infected protocorms, only trehalose became labelled in the pre‐digestive phase of infection and there was no evidence of transfer of 14C from fungus to host before digestion of hyphae occurred.
POLLEN GERMINATION INHIBITORS IN EXTRACTS OFBRASSICA OLERACEAL. STIGMAS
Authors: HODGKIN T. , LYON G. D.
Published: May 2006

Summary

Pollen germination inhibitors were shown to be present in extracts of stigmas from twoBrassica oleraceaL. lines by thin‐layer chromatographic bioassay. Some inhibitors were common to extracts of unpollinated, self‐pollinated and cross‐pollinated stigmas whilst others were only detected m stigma extracts following self‐incompatible self‐pollinations. With sampling times of 2, 4 and 24 h after pollination, inhibitors from self‐pollinated stigmas were at their highest concentration approximately 2 h after pollination but were declining by 4 h, and were virtually absent by 24 h. A possible role for these pollen germination inhibitors in inhibiting pollen growthin vivois noted.
THE BREAKING OF DORMANCY IN HAZEL SEED BY PRETREATMENT WITH ETHANOL AND MERCURIC CHLORIDE
Authors: JEAVONS R. A. , JARVIS B. C.
Published: May 2006

Summary

Pretreatment of intact hazel (Corylus avellana L.) seed with either ethanol or mercuric chloride alone is without effect in stimulating subsequent germination of seeds in the light. However, when treated with ethanol then soaked in mercuric chloride solution, intact seeds germinate when subsequently sown in light. Treatment with ethanol and mercuric chloride does not replace the light‐requirement of intact seeds. The effect of such treatment is similar to that of removal of the testa. Ethanol may be replaced by diethylether, chloroform or n‐propanol.
RHIZOSPHERE BACTERIAL POPULATION RESPONSES TO ROOT COLONIZATION BY A VESICULAR‐ARBUSCULAR MYCORRH1ZAL FUNGUS *†
Authors: Ames R. N. , Reid C. P. P. , Ingham E. R.
Published: May 2006

Summary

A mixture of bacteria and a vesicular‐arbuscular mycorrhizal fungus isolated from field‐collected sods of blue grama (Bouteloua gracilis (H.B.K.) Griffiths) were tested for their interaction in the rhizosphere of pot‐grown blue grama plants. Populations of the inoculated bacterial species and actinomycete populations, as influenced by the presence or absence of Glomus mosseae (Nicol. and Gerd.) Gerdemann and Trappe, were enumerated by dilution plate counts from rhizosphere and non‐rhizosphere soil samples. Total bacterial counts and the population of one bacterial species in the non‐rhizosphere soil of pots containing plants were significantly greater than in soil of pots without plants. The population of two bacterial species and actinomycetes were not significantly different in the non‐rhizosphere soil of both mycorrhizal and non‐mycorrhizal plant treatments when compared to the soil of pots without plants. In the rhizosphere of mycorrhizal plants, the total bacterial population and colony counts of one of the four bacterial isolates, when expressed as colony‐forming units (CFU) per gram of root dry weight, were significantly reduced compared with controls. The numbers of CFU per gram of rhizosphere soil of one bacterial species were significantly increased by the presence of the mycorrhizal fungus. Although no significant negative correlation was observed between populations of bacterial species in the rhizosphere soils, significant positive correlations between specific bacterial populations depended on whether or not the roots were mycorrhizal.
THE DEVELOPMENT AND ULTRASTRUCTURE OF ECTOMYCORRHIZAS
Authors: DUDDRIDGE J. A. , READ D. J.
Published: May 2006

Summary

The ultrastructure of representative types of ectomycorrhizal root of pine was analysed after collection at different times of year from March to June, using scanning and transmission electron microscopy. In the Pre‐Hartig net zone (PHZ) near the root apex, a well‐developed sheath is present in which are incorporated sloughed root cap cells. There is evidence of dissolution of the host cell wall adjacent to fungal elements in some cells. Sheath structure in the Hartig net zone (HZ) is similar to that in the PHZ, but the residual cells here are collapsed root hairs. Glycogen and polyphosphate granules are abundant in the sheath in March but their number declines in later months. The Hartig net is made up of a pseudoparenchyma of infolded fungal elements and the cortical cells adjacent to it are generally living. No basic difference between niycorrhizal and non‐mycorrhizal cortical cells was observed, thus indicating that, in contrast to pathogenic attack, no adverse reaction to the fungal presence occurs. Reasons for seasonal changes of storage compounds are discussed.
THE DEVELOPMENT AND ULTRASTRUCTURE OF ECTOMYCORRHIZAS
Authors: DUDDRIDGE J. A. , READ D. J.
Published: May 2006

Summary

The development of ectomycorrhizas of pine was followed experimentally using either sterile peat–vermiculite with nutrient solution or natural non‐sterile field soil. Roots were harvested sequentially and comparative analyses of their ultrastructure were obtained. Hartig net formation is initiated before the formation of a compact sheath in both types of synthesis but, while the net formed after 3 weeks in sterile culture and was complete after 6 and 8 weeks, in non‐sterile soil its initiation was delayed until 11 weeks and it had reached a depth of only one cortical cell after 19 weeks. While differences in gross morphology of mycorrhizas can be recognized, the structure of the host–fungus interface in the Hartig net region is comparable in mycorrhizas formed with different soils or different isolates. In the young Hartig net, separate host and fungal cell walls are distinguishable, while in the mature net they lose their integrity. No marked change of structure is observed within the cortical cells adjacent to the Hartig net and their organization is similar to that of cortical cells of non‐mycorrhizal lateral roots. The development and structure of the host–fungus interface is discussed in relation to its possible function.
MODIFICATION OF THE HOST‐FUNGUS INTERFACE IN MYCORRHIZAS SYNTHESIZED BETWEEN SUILLUS BOVJNUS (FR.) O. KUNTZ AND PINUS SYLVESTRIS L.
Authors: DUDDRIDGE J. A. , READ D. J.
Published: May 2006

Summary

Ultrastructural analysis of the host–fungus interface of mycorrhizas synthesized between Sutilus bovinus and Pinus sylvestris in media containing high concentrations of glucose reveals abnormalities of behaviour in both fungus and host. Vigorous fungal growth leads in some cases to isolation and death of host cortical cells. In other host cells, the wall adjacent to the fungus produces irregular ingrowths closely followed by the host plasmalernma. The cytology of these host cells is indicative of high physiological activity. Histochemical analysis shows the protuberances to be of a material similar to that of primary cell walls but with deposition of callose occurring late in their development. It is suggested that these structures may either represent a defence reaction on the part of the host to the presence of the fungus or that they may be similar to those wall ingrowths produced in transfer cells. Analogies between these structures and the latter are drawn and their possible function is discussed in relation to host and fungus nutrition and other types of transfer cell systems.
CHLORIDE TRANSPORT INENTEROMORPHA INTESTINALIS(L.) LINK
Authors: RITCHIE R. J. , LARKUM A. W. D.
Published: May 2006

Summary

Rates of36Cl−labelling, efflux and uptake were measured onEnteromorphaplants grown in sea‐water (547 mM Cl−), and also in brackish water medium [Artificial Cape Banks Spring Water (ACBSW), 25.5 mM Cl−, 20.4 mM Na+ and 0.5 mM K+]. Efflux experiments showed that, inEnteromorphaplants grown in seawater, light did not affect Cl−fluxes at the plasmalemma and tonoplast. Typical experiments exhibited two exchanged phases but a significant number (8/32) exhibited a single exchange phase; this was more likely to occur in darkness. Influx experiments also showed no effect of light on the tonoplast flux. Transfer of plants grown and labelled in seawater to low salinity medium caused a rapid loss of36C1−label; however, this was related to the change in osmotic potential of the medium rather than to changes in [Cl−o] or [K+0]. Exchange of36Cl−did not depend on [K+o] in seawater. Cyanide decreased36Cl−uptake in the dark but not in the light. In low salinity medium (ACBSW),36Cl−labelling and the plasmalemma flux inEnteromorphaplants were independent of light; however, the intracellular compartmentation of Cl−differed between light and dark. The tonoplast flux was also greater in the light. Intracellular Cl−was about 300 mmol kg−1in seawater plants and about 159 mmolkg−1in ACBSW plants. The cytoplasmic Cl−concentration ([CI−0]) based on compartmental analysis was about 200 mM inEnteromorphaplants in seawater and ACBSW medium. Use of this [Cl−0] value and the Nernst equation suggests active Cl−uptake in plants in both seawater and ACBSW. However it is unlikely that the cytoplasmic [Cl−] is above about 70 to 100 mM since many cytoplasmic enzymes are inhibited by high [Cl−0]. Taking this lower estimate of [C1−0], the Nernst criterion suggests passive accumulation of Cl−across the plasmalemma in seawater but active transport would be likely in plants in ACBSW medium. Where separate plasmalemma and tonoplast fluxes were detectable, plasmalemma fluxes were higher in low salinity medium than in seawater (about 500vs300 nmol m−2s−1); the tonoplast flux was about 30 nmol m−2s−1in seawater plants and about 20 and 10 nmol m−2s−1in light and dark, respectively, in ACBSW‐grown plants. In experiments where only a single exchange phase could be detected the apparent plasmalemma flux was only about 30 nmol−2s−1. Apparently the plasmalemma can exist in two permeability states to Cl−(0.2 to 1.0vs0.03 nm s−1).
STRUCTURE, ENVIRONMENTAL EFFECTS ON THEIR FORMATION, AND FUNCTION OF PROTEOID ROOTS INLEUCADENDRON LAUREOLUM(PROTEACEAE)
Authors: LAMONT B. B. , BROWN G. , MITCHELL D. T.
Published: May 2006

Summary

Proteoid roots are abundant on field and potted plants ofLeucadendron laureolum(Lam.) Fourcade, accounting for up to 40% of the root mass (in 9‐month‐old plants in sand), and up to 400 g−1of new season's roots (in 18‐month‐old plants in humus‐amended sand). There may be over 250 hairy rootlets per 10 mm of parent axis, giving a total surface area almost 15 times that of an equivalent mass of parent roots. Microsymbionts are absent, but chlorornycetin suppressed proteoid root formation, providing limited evidence of the need for a bacterial cofactor. Proteoid roots formed preferentially in humus‐amended sand but were elminated, with little effect on non‐proteoid roots, when organic fertilizer high in P was added. In the field, proteoid roots were confined to a 50 mm wide root mat just beneath the leaf litter around the parent plant. The greater soil volume explored directly by proteoid roots, despite lower soil P availability, may largely explain the greater rate of P uptake by plants in Clovelly sand than that m Hutton clay‐loam, although differential rates of solubilization and root respiration also appeared to be involved.
THE EFFECT OF MYCORRHIZAL INFECTION OF GOODYERA REPENS AND ITS CONTROL BY FUNGICIDE
Authors: ALEXANDER CLARE , HADLEY G.
Published: May 2006

Summary

Studies of the orchid Goodyera repens Br. growing on agar media in association with its natural endophyte Rkizoctonia goodyerae‐repentis Constantin and Dufour showed that mycorrhizal plants of different developmental stages had significantly higher growth rates and level of P and N than did uninfected ones. Treatment of mycorrhizal plants with the fungicide thiabendazole stopped growth of external mycelium and caused a significant decrease in growth rate, P and N content, percentage infection and net assimilation rate. These results suggest that the mycorrhizal fungus enhances nutrient uptake and allows greater growth rates, a situation similar to that found in non‐orchid mycorrhizas.
INTERACTIONS BETWEEN ENDOMYCORRHIZAS AND SOIL NITROGEN AND PHOSPHORUS ON THE GROWTH OF RYEGRASS
Authors: HALL I. R. , JOHNSTONE P. D. , DOLBY R.
Published: May 2006

Summary

In two pot experiments with a soil deficient in P and N, vesicular‐arbuscular mycorrhizas stimulated the shoot growth of Lolium perenne L. greatest (24%) with the highest levels of applied P and/or N, and where the shoot N and P concentrations approached the normal agronomic range. It is suggested that applied N, and possibly P, resulted in mycorrhizas making a more important contribution to the plant's P or Cu status. Previous experiments purporting to show the mycorrhizal dependency of species are criticized if the levels of nutrients in the soil (other than P) which might have been limiting were not considered.

Mycorrhizas reduced root/shoot ratios even in those treatments where a growth response was not detected.

There was a negative relationship within treatments between responsiveness to mycorrhizas and the size of the non‐mycorrhizal plant. This may have relevance in plant breeding.
GENECOLOGICAL STUDIES OFURTICA DIOICAL.
Authors: POLLARD A. J. , BRIGGS D.
Published: May 2006

Summary

The stinging hairs ofUrtica dioica(stinging nettle) have often been described as defences against grazing; however, no experimental studies have tested this proposition. Variability in the number of stinging hairs borne by plants has been described, and is known to have a genetic basis. This variability extends to plants which are virtually stingless. Comparison of grazing preferences of two species of herbivores (rabbits and sheep) on plants of known stinging hair density revealed that: (1) Both herbivores preferentially grazed plants with lower stinging hair densities under controlled conditions; (2) In a field experiment in an area with intense rabbit grazing, higher grazing damage was observed on plants with lower stinging hair densities; (3) Patterns of grazing damage, and observations of herbivore behaviour, suggested that stinging hairs act to deter consumption of significant amounts of plant matter, even by herbivores which had not developed learned avoidance.

It is likely that grazing by large mammals could act as a strong selective force for higher stinging hair densities in nettles. Theoretical treatments of plant‐herbivore interactions based on invertebrate grazing patterns may be too simplistic to apply to mammalian herbivores that are large, mobile, behaviorally complex, and yet dietarily generalist.
FREQUENCY AND GROUPING OF VESSEL ENDINGS IN ALFALFA (MEDICAGO SATIVA) SHOOTS *
Authors: WIEBE H. H. , GREER R. L. , VAN ALFEN N. K.
Published: May 2006

Summary

Vessel endings in various parts of the alfalfa (Medicago sativa L.) shoot were mapped by an India ink movement method. Stems were excised at various locations between the fifth and sixth nodes below the apex and placed in vials of India ink. Vessel endings were determined by examining the distance to which ink penetrated in the transpiration stream; the particles of India ink are too large to pass from vessel to vessel through pit membranes. The highest frequencies of vessel endings were found (1) in the petiolules and blades of the leaflets, (2) in the pulvinus of the petiole where the leaf traces emerge from the stem and anastomose while traversing the abscission zone, and (3) in the stem nodes where leaf traces arise and vascular bundles anastomose. The frequency of vessel endings was low and uniformly distributed throughout both internodes and petioles. Vessels were longest in the internodes and shortest in the leaflets. The regions where vessel endings were grouped coincided with those determined in other studies to be particularly susceptible to vascular blocking by macromolecules such as those produced by vascular wilt pathogens.
MICROPROPAGATION OF BIRCH AND MYCORRHIZAL FORMATION IN VITRO
Authors: GRELLIER B. , LETOUZE R. , STRULLU D. G.
Published: May 2006

Summary

Ectomycorrhizal syntheses between Paxillus involutus (Batsch.) Fr. and Betula pendula Roth, were carried out in controlled conditions. The fungal symbiont forms mycorrhizas with axenic seedlings and microcuttings derived from a clone produced in vitro of birch. The symbiosis stimulates the growth of the whole of the mycorrhizal plants. From a histological study of synthesized material, various stages of the mycorrhizal formation were described.