bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of light and temperature on photosynthesis of the nuisance algaCladophora glomerata(L.) Kutz from Green Bay, Lake Michigan
Authors: LESTER WILLIAM W. , ADAMS MICHAEL S. , FARMER ANDREW M.
Published: April 2006

summary

Seasonal measurements of light‐ and temperature‐dependence of photosynthesis of the nuisance algaCladophora glomerata(L.) Kutz were determined under laboratory conditions with algal samples collected from lower Green Bay, Lake Michigan. Photosynthesis rates were determined using oxygen difference in water circulated around the speciments. Photosynthesis reached light saturation at about 790 μmol photons m−2S−1(PAR) and had a temperature optimum between 28 and 31°c; maximum rates were 25–50 mg O2g dwt−1h‐1. These parameters varied seasonally with water temperatures. There was no evidence for a decline in photosynthetic rate with increasing temperature over the ranges used in this study. It is concluded that, in this instance, such an effect is not responsible for the mid‐season decline of this species. Other effects, such as those of respiration, photorespiration and phenology may, therefore, be important.
Use of carotenoid ratios, ethylene emissions and buffer capacities for the early diagnosis of forest decline
Authors: WOLFENDEN JENNIFER , ROBINSON DEBORAH C. , CAPE J. N. , PATERSON I. S. , FRANCIS B. J. , MEHLHORN H. , WELLBURN A. R.
Published: April 2006

summary

Norway spruce trees were sampled at twelve sites in Western Europe; each site was known to have been exposed to different levels of atmospheric pollutants. Amongst a wide range of other tests, ratios of needle pigments and buffering capacity were measured in needle samples taken from each site and gas samples taken from similar twigs were subsequently analysed for hydrocarbons. Rates of ethylene emissions were low from needles in relatively unpolluted areas and higher at sites experiencing frequent ozone episodes, higher rainfall acidity or elevated levels of primary pollutants. A similar trend was observed for certain pigment ratios, and a strong correlation was found between ethylene emissions and the ratios of violaxanthin to antheraxanthin. The buffering capacities of 2‐year‐old needles did not differ in any consistent way between sites. In current‐year needles, alkaline buffering was significantly reduced at polluted sites but no significant site‐related trend towards acidic buffering was apparent. The relative value of each of the three tests as early diagnostic indicators of pollutant damage is discussed.
Cell‐wall‐bound peroxidase activity in roots of mycorrhizal Allium porrum
Authors: SPANU P. , BONFANTE‐FASOLO P.
Published: April 2006

summary

The activity of cell‐wall‐bound peroxidase in Allium porrum L. roots was measured during root growth and development of vesicular–arbuscular mycorrhiza with Glomus versiforme (Karst.) Berch. The peak of activity in infected plants was higher than in non‐infected ones and occurred during the initial stages of fungal penetration. When the infection was established and the roots highly colonized the activity decreased to the levels in non‐mycorrhizal roots. Ultrastructural localization using diaminobenzidine revealed an increase in the electron‐dense deposits in the middle lamella corresponding with fungal penetration. No activity was seen in the matrix deposited around the intracellular fungal structures. The overall distribution of peroxidase activity was the same in mycorrhizal and non‐mycorrhizal roots.
Fluoride‐induced enhancement and inhibition of photosynthesis in four taxa of Pinus
Authors: DOLEY D.
Published: April 2006

summary

Pinus elliottii Englem. var. elliottii (PEE) and three varities of Pinus caribaea Morelet [var. caribaea Barr, et Golf. (PCC), var. bahamensis Barr. et Golf. (PCB) and var. hondurensis Bafr. et Golf (PCH)] were grown for a total of 125 days under gaseous hydrogen fluoride at 0.0, 1.2, 1.8.and 4.3 μg F m−3. Apparent photosynthesis was measured on 10–12 plants in each taxon and treatment during the last 10 days of the experiment, using needles free from visible injury that had matured before (old) or during the experiment (young). Rates of apparent photosynthesis were significantly greater in young needles of PCB and PCH exposed to 1.2 than to 4.3 μg F m−3, and in old needles of PCH exposed to 1.2 than to 0.0, 1.8 and 4.3 μg F m−3. Chlorophyll concentrations in old needles were consistently lower than those in young needles, but varied less with changes in ambient fluoride concentration, differences in photosynthetic rates of PCB, PCC and PCH corresponded generally with differences in concentrations of chlorophylls a, b and (a+b). Ambient fluoride concentrations less than about 1 μg F m3 appear unlikely to have deleterious short‐term effects on chlorophyll concentrations and photosynthesis in these taxa.
Sensitivity of forest plant reproduction to long‐range transported air pollutants: the effects of wet deposited acidity and copper on reproduction of Populus tremuloides*
Authors: COX R. M.
Published: April 2006

summary

Few, if any, studies have been carried out that examine and relate in vivo pollen germination following stimulated wet deposition of acidity and copper with various fruit and seed set parameters of trees. The methods used with inflorescences of a wind‐pollinated tree, Populus tremuloides Michx., are reported here. The responses of components of the reproductive system to rain simulants indicated significant (P < 005) overall response of in vivo pollen germination to pH. The combined data demonstrated a significant (P < 005) negative correlation between germination and pH. However, the response in the absence of copper showed no linear correlation because of a recovery at the lowest pH used (26). The effect of simulated rain at the time of pollination was shown to increase fruit abortion significantly. In addition, an overall significant negative correlation was found between fruit abortion and pH, but again in the absence of copper, fruit abortion recovered at the lowest pH (2–6). Seeds per fruit and percentage of placenta with full seeds were significantly reduced at pH 2–6 in the presence of 0–05 mg 1−1 Cu compared with the control. These two seed set parameters were also significantly intercorrelated (P < 0.01) with fruit abortion suggesting that lack of seed set may be the cause of the abortion. The significant correlation of both in vivo pollen germination and fruit abortion with pH, especially in the presence of copper, supports the view that inhibition of the pollen on the stigma by the simulated rain is responsible for the lack of seed set above the required threshold that prevents fruit abortion.
Fungal colonization of attached beech branches
Authors: CHAPELA I. H. , BODDY LYNNE
Published: April 2006

summary

Early colonizing fungal communities in beech branches exhibit a distinct spatial organization. Decay often begins in distal regions with stain‐associated fungi, which derive from latent propagules in the wood and bark, effecting the first stages of colonization. This characteristic assemblage is followed by a more combative group of wood‐rotting fungi, particularly Basidiomycotina. The resource at the front of colonization is partitioned between individuals of different species intermixed without clear delimitation. By contrast, the more combative Basidiomycotina which arrive later and displace the fungi in the colonization front usually occupy much larger spatial domains clearly delimited by interaction zone‐lines.
Fungal colonization of attached beech branches
Authors: CHAPELA I. H. , BODDY LYNNE
Published: April 2006

summary

Fungal colonization of healthy beech (Fogus sylvatica L.) branches was studied by sectioning branch lengths and drying the sections under controlled regimes. Maintaining water saturation prevented any fungal development in the wood, while active mycelium was isolated as soon as 14 days after the start of the drying period. Fungi developing in these sections were naturally established in healthy branches in the field and formed a floristically denned group, dominated by Hypoxylon fragiforme (Scop.) Kickx., H. nummularium Buill.: Fr., Nectria coccinea (Pers.: Fr.) Fr., and Coniophora putaena (Fr.) P. Karst., and also included coelomycete species. This group was obtained independently of position of the branch in the canopy, season of sampling over an 11 ‐month period, and site, sampling including four sites in south‐west Britain and one in the French Pyrenees. Several species in this group are specific or show a preference for beech as a host.

Direct observations and isolation from sections with time indicated that whereas most species developed inwards from the bark, H. fragiforme and H. nummularium grew out from pockets within the wood. Each pocket contained a genetically different individual, as revealed by colony morphology and vegetative incompatibility tests.

It was established that water content of the wood is the major determinant for the initial development of fungi in the xylem of beech, and that these early colonizers derive from inoculum latent in the healthy, living branches.
Vesicular–arbuscular mycorrhizas and the soil‐disturbance‐induced reduction of nutrient absorption in maize
Authors: FAIRCHILD G. L. , MILLER M. H.
Published: April 2006

summary

In previously reported studies, maize seedlings absorbed more phosphorus (P) from soil in a long‐term zero‐till system than from the same soil after disturbance. This partly resulted from greater vesicular‐arbuscular (VA) mycorrhizal infection in the undisturbed soil. In the study reported herein, a growth room experiment was conducted to determine how long a soil must remain undisturbed before subsequent disturbance will reduce P absorption. Starting with disturbed soil, maize was grown for 3‐week cycles. At the conclusion of each growth cycle, half of the pots were disturbed and replanted whereas the other half was replanted without disturbing. Over the three growth cycles, major increases in mycorrhizal infection in the plants in the undisturbed soil were observed concurrently with the increases in nutrient absorption.

A significant increase in P absorption occurred in the first growth cycle on undisturbed soil and greater increases occurred after the second and third. At 21 d in the third growth cycle, plants grown in the undisturbed soil had almost twice the dry weight of plants grown in the disturbed and had higher concentrations of N, P, Mg, Cu and Zn in the shoots. Absorption of P between 14 and 21 d of the third growth cycle in the undisturbed soil was 10 times larger than that in the disturbed soil. Absorption of N, Mg, Cu and Zn was more than three times larger. In the third growth cycle, concentrations of N, P, Mg and Zn in the shoot and intensity of VA mycorrhizal infection were greater in the undisturbed soil as early as 14 d after planting. There was a concurrent and rapid increase in VA mycorrhizal infection and P absorption by maize over three growth cycles when an initially disturbed soil was left undisturbed. This rapid concurrent development, particularly starting from an initially disturbed soil, provides good evidence that soil disturbance reduces VA mycorrhizal infection and hence P absorption by maize.
Metabolic characteristics of akinetes of the cyanobacterium Fischerella muscicola
Authors: SINGH SURENDRA , KASHYAP A. K.
Published: April 2006

summary

Mature akinetes of Fischerella muscicola (Thuret) Gom. are shown to have a low rate of respiration and to lack photosynthetic pigments, photosynthetic O2‐evolving activity and the activities of the primary enzymes of inorganic nitrogen assimilation. The C/N ratio steadily increased during akinete differentiation and it is suggested that this increase results because, during akinete development, the loss of the activities of nitrogenase and glutamine synthetase precedes the loss of CO2 fixation.
The enhancement of anther culture efficiency in Brassica napus ssp. oleifera Metzg. (Sinsk.) using low doses of gamma irradiation
Authors: MACDONALD M. V. , HADWIGER M. A. , ASLAM F. N. , INGRAM D. S.
Published: April 2006

summary

Selected buds of Brassica napus ssp. oleifera Metzg. (Sinsk) cvs Ariana and Primor were treated with various doses of γ‐irradiation. When the anthers were removed and cultured, it was shown that low doses of γ‐irradiation greatly enhanced anther culture efficiency in both cultivars. When microspore culture techniques were used, however, embryogenesis was reduced by irradiation in all treatments. Some of the resulting embryoids developed directly into plantlets, whereas others developed abnormally and produced secondary embryoids. Plants were regenerated from both anther embryoids and secondary embryoids and, following diploidization, seed was obtained from these plants.
An in vitro bioassay for the stigmatic product of the self‐incompatibility gene in Papaver rhoeas L.
Authors: FRANKLIN‐TONG V. E. , LAWRENCE M. J. , FRANKLIN F. C. H.
Published: April 2006

summary

This paper reports the development of an in vitro bioassay for the somatic product of the self‐incompatibility gene in Papaver rhoeas L. As with in vivo pollinations, inhibition of pollen tube growth occurs only when the S‐alleles carried by the pollen are matched by those contained in the stigma used to make a print or from which the extract was obtained. Furthermore, these in vitro reactions appear to be quantitatively indistinguishable from those obtained with in vivo pollinations, so that the resolution of the assay allows the distinction between incompatible, half‐compatible and fully compatible reactions to be made on sight rather than by measurement and statistical analysis of pollen tube length.
Influence of ambient ammonium on net potassium uptake by decapitated maize seedlings
Authors: TOPA M. A. , JACKSON W. A.
Published: April 2006

The effects of ambient ammonium on potassium uptake and accumulation in xylem exudate were examined in 6‐d‐old decapitated maize (Zea mays L., ev. Pioneer 3369a) seedlings, Net uptake of both K+ and NH+4 was measured by solution depletion during a 5 h treatment period. [86Rb]K+ influx during a 10 min uptake period was also measured for some treatment combinations over the 5 h period. The presence of ambient 0.2 mM NH+4initially resulted in net efflux of K+ to solution containing 0.2 mM K+, as well as to K+‐free solutions. A transition from net K+ efflux to net K+ uptake occurred after 1.25–1.5 h in solutions containing 0.2 mM K+ and 0–2 mM NH+4. After the transition, the rate of K+ uptake was ∼ 50% of that found in the absence of ambient NH+4 [86Rb]K+ influx from 0.2 mM K+ was inhibited by 50% in the presence of 0.2 mM NH+4. Increasing ambient NH+4 to 2.0 mM increased the initial net efflux of K+ and delayed the time at which transition to net uptake occurred. The combined data indicate that the inhibitory effect of ambient NH+4 on net K+ uptake resulted from an initial but temporary enhancement of K+ efflux, and a constant inhibition of K+ influx. A reciprocal inhibition of net NH+4 uptake by K+ was not observed. Net NH+4 uptake initially was associated with K+ efflux, after which a transition to net H+ occurred. In the presence of NH+4, the transition from net K+ efflux to net K+ uptake, and the associated onset of net H+ efflux took place without measurable alterations in the rate of K+ accumulation in the xylem fluid. These results suggest spatially separate compartments for K+ efflux and xylem deposition.
The effects of removal of the root tip on lateral root distribution in adventitious roots of anion
Authors: LLORET P. G. , CASERO P. J. , NAVASCUÉS J. , PULGARÍN A.
Published: April 2006

Distribution patterns of lateral roots (LRs) were analysed in intact (control) and decapitated adventitious roots (ARs) of Allium cepa L. Removal of the root tip caused: (1) The cessation of elongation of the AR. (2) An increase in the number of LRs per cm which developed on the AR. (3) Changes in the distribution of LRs along the mother root One aspect of the distribution modified by the decapitation was the suppression of an apical zone without LRs which was observed immediately behind the apex in intact roots. In decapitated ones by contrast accumulation of LRs was enhanced in this zone. Moreover, decapitation appeared responsible for successive LRs opposite the same xylem pole developing nearer each other than in intact roots. (4) Changes in the frequency and location of clumps of LRs. In decapitated roots 21.6%, of the total number of LRs were clumped. In intact ARs this figure was only 13.5%. Moreover, intact roots showed a tendency to LR clumping preferentially in their basal zone In contrast, clumps of LRs were noted indistinctly in both basal and distal zones of decapitated ARs. I his fact implies that removal of the root tip enhances the natural tendency toward clumping of LRs, chiefly in distal zones of the AR. Other aspects of the pattern remain unchanged after removing the root apex. Hence in decapitated as well as intact ARs there were two neighbouring xylem poles opposite which large number of LRs were produced, whereas the remaining ones were considerably less prolific. A further aspect which was not altered by the decapitation was the significantly high frequency of formation of neighbour LRs opposite adjacent xylem poles.
Evaluation of factors contributing to diurnal changes in O2 concentrations in floodwater of deepwater rice fields
Authors: SETTER T. L. , KUPKANCHANAKUL T. , WATERS I. , GREENWAY H.
Published: April 2006

Glass chambers were used to isolate 0–75 m deep water columns in situ in deepwater rice fields in Thailand to evaluate the contribution by various factors to the pronounced diurnal changes in O2 concentrations in the floodwater Chambers filled with distilled water provided estimates of O2 flow from the air into the water, indicating the importance of eddy currents associated with wind action and evaporative cooling. Darkening the natural water gave estimates for O2 evolution due to photosynthesis, while comparisons between columns with and without rice distinguished between O2 evolution and consumption by the rice and the biomass other than rice respectively. Removal of the above water portions of the rice shoots showed the importance of the emergent portion of the canopy to O2 movement from the air into the aquatic part of the ecosystem. This flow may be associated with O2 flow through the lacunae and via air envelopes around the leaf, and with turbulence caused by swaying of the rice leaves in the wind.

The changes in O2 concentration were analysed quantitatively using several simplifying assumptions. One major input was a net O2 flow from the air into the water, about half being due to a net flow across the air–water interface and the other half to flow associated with the rice plants. During the night, these flows were less than the O2 uptake by the biomass, hence O2 concentrations decreased. In the underwater portion of the rice stand, about 60 % of the O2 uptake was due to the rice and about 40% due to the biomass other than rice. During the day, the O2 requirements by respiration were more than compensated for by O2 evolution due to photosynthesis, resulting in increases in O2 concentration of the water.
The relationship between changes in photosynthesis and growth for radish plants fumigated with SO2 and O3
Authors: ATKINSON C. J. , ROBE S. V. , WINNER W. E.
Published: April 2006

The effects of possible ambient concentrations of SO2 and O3 on biomass production and gas exchange of radish (Raphanus sativus L, cv. Cherry Belle) are examined, the relationship between photosynthesis and growth is defined and the mechanisms behind pollutant induced changes in growth are elucidated.

Ozone was shown to be considerably more phytotoxic than SO2. Fumigation at a concentration as low as 5 μmol O3 m−3 (0.12μl 1−1) produced ‘visible’ injury. No ‘visible’ injury symptoms were apparent with plants fumigated with SO2. The effect of fumigation with Oa at concentrations greater than 2.5 μmol m−3 (0.06 μl 1−1) was to reduce biomass production and alter carbon partitioning. This was not so for SO2, fumigated plants. Ozone‐fumigated plants showed a significant reduction in their photosynthetic efficiency (NAR) and despite an increase in LAR, RGR was still depressed below control values.

The relationship between photosynthesis and biomass production for fumigated plants was examined and whole plant carbon acquisition was calculated from gas‐exchange measurements. On comparing calculated carbohydrate production with measured biomass accumulation, it was dear that changes in A were closely related to changes in growth.

Light‐ and CO2‐response curves were used to determine maximum light‐saturated photosynthesis (Amax), incident quantum yield (QY) and carboxylation efficiency (d.A/de1), RuBP‐regeneration capacity (Jmax) respectively. The presence of SO2 over a concentration of 2.5–8.3 μmol m−3 (0.12–0.20 μl −1) enhanced Amax. QY and Jmax, However, dA/dc1, was reduced at all concentrations. This reduction was offset by an increase in Jmax. At the smallest O3 concentration (2.5 μmol m−3) Amax was stimulated and at the higher concentration severely reduced. Q Y was not negatively influenced by the presence of O3, but d.A/dc1 and Jmax were reduced, particularly as the dose increased.
The effect of nitric oxide fumigation at two CO2 concentrations on net photosynthesis and stomatal resistance of tomato (Lycopersicon lycopersicum L. cv. Abunda)
Authors: BRUGGINK G. T. , WOLTING H. G. , DASSEN J. H. A. , BUS V. G. M.
Published: April 2006

Net photosynthesis of 5‐week‐old tomato plants (Lycopersicon lycopersicum L. cv. Abunda), was measured in clean air or with NO fumigation, for five consecutive days under simulated winter glasshouse conditions: temperature 22 °C, VPD 04 kPa, irradiance 30 W m−2 and daylength 8–9 h. NO concentrations applied were 0 or 1 μl 1−1 in combination with CO, concentrations of 350 or 1000 μl −1.

A reduction in net photosynthesis due to NO became apparent on the third day of measurement. On the fifth day this reduction was 38%, of the control at 350 μl −1 CO2 and 24%, at 1000 μl −1 CO2. The increase in photosynthesis due to CO, enrichment was initially 40%; this effect was strongly reduced after 5 d in the presence of NO. Plants did not recover in the dark after the daily fumigation treatment, the level to which photosynthesis was reduced at the end of the day being the level at which it started the next day. The decrease in photosynthesis could not be explained by an increased stomatal resistance, and the plants did not show visible symptoms of injury. Practical implications of the results are discussed.
Competition between three species of Glomus used as spatially separated introduced and indigenous mycorrhizal inocula for leek (Allium porrum L.)
Authors: HEPPER CHRISTINE M. , AZCON‐AGUILAR CONCEPCION , ROSENDAHL S. , SEN R.
Published: April 2006

The ability of three vesicular‐arbuscular (VA) mycorrhizal fungi‐Glomus caledonium (Nicol, and Gerd.) Trappe and Gerd., Glomus sp. type E3 and Glomus mosseae (Nicol. and Schenck) Gerd. and Trappe ‐ to infect leek (Allium porrum L.), when used as spatially separated pairs of inocula was assessed by analysing the roots for the presence of diagnostic fungal enzymes alter separation of root proteins by gel electrophoresis. A difference in competitiveness was observed, such that Glomus sp. E3 was unable to infect a root system if either G. caledonium or G. mosseae were also present. When the latter two fungi were used as a pair of inocula, the one which had been placed to simulate an indigenous strain predominated in the root to the almost total exclusion of the one placed as an introduced inoculum. These results suggest that the successful establishment of VA mycorrhizal inocula in field soils will depend on the indigenous species present, the species being introduced and its placement in the soil. The use of diagnostic fungal isozyme analysis offers a method of monitoring the outcome of an inoculation programme by detecting the presence of the introduced species in the host roots.
Influence of glucosinolate content of Brassica (Cruciferae) roots on growth of vesicular–arbuscular mycorrhizal fungi
Authors: GLENN M. G. , CHEW F. S. , WILLIAMS P. H.
Published: April 2006

We tested the hypothesis that failure to establish symbiosis with vesicular‐arbuscular (VA) mycorrhizal fungi is correlated with glucosinolate concentrations in Brassica, a representative genus of the Capparales. Brassica campestris and B. napus cultivars (brassica) with a range of glucosinolate concentrations (7–524 μmol g1 f. wt in roots) were grown together with the VA mycorrhizal fungi Glomus mosseae and Gigaspora gigantea in agar. Fungal growth was observed in situ but fungi did not penetrate brassica roots. However, normal germ tube growth of the VA mycorrhizal fungi occurred near brassica roots when compatible hosts grew nearby. These compatible hosts developed normal mycorrhizal infections. These results suggest that brassica roots do not produce a diffusable inhibitor of VA mycorrhizal fungi, but lack a diffusable growth stimulus present near roots of compatible hosts.
Mycorrhizal associations of isolates of Sebacina vermifera
Authors: WARCUP J. H.
Published: April 2006

Isolates of Sebacina vermifera Oberwinkler (Tremellaceae), identified by their teleomorphs, from orchid and non‐orchid hosts have been examined for their mycorrhizal associations. All isolates stimulated germination of seed of species of Microtis (Orchidaceae). Three isolates from ectomycorrhizal hosts formed ectomycorrhizas on Melaleuca uneinata R. Br. ex Alton I. and other ectomycorrhizal plants. None of the orchid isolates nor an isolate which was endophytic in Phyllanthus formed ectomycorrhizas but in addition to species of Micron's they stimulated germination of one or more species of Caladenia, Cyrtostylis or Glossodia but not other terrestrial orchids.

Protocorms of Microtis developed at depth in soil in the presence but not the absence of ectomycorrhizal S. vermifera on M. uneinata. Young albino plants of Microtis rara R. Br. grew for 4 months in the presence of ectomycorrhizal S. vermifera with M. uneinata but mycorrhizal albino plants on their own all died, suggesting a possible tripartite mycorrhizal association.
Observations on growth rates and calcium carbonate deposition in the green alga Gongrosira
Authors: PENTECOST ALLAN
Published: April 2006

In vivo growth rates of Gongrosira [probably G. incrustans (Reinsch) Schmidle], a cushion‐forming fresh‐water green alga (Chaetophorales) are reported for the first time. The annual radial growth rate averaged 0.42 mm in a mountain stream from northern England and was positively correlated with water temperature (r=+ 0.919, P < 005). The colonies were heavily incrusted with calcium carbonate (calcite). Photosynthetic activity probably promotes calcification between the closely packed basal filaments, but most of the precipitation appears to be abiogenic from supersaturated stream waters. Calcified Gongrosira bioherms are also described from a subtropical site in Mexico. The survival period for Gongrosira at the English site was approximately one year, and at both sites Gongrosira was a permanent and significant component of the epilithic algal flora.
The biological effects of gamma irradiation on secondary embryoids of Brassica napus ssp. oleifera (Metzg.) Sinsk., winter oilseed rape
Authors: MACDONALD MARY V. , NEWSHOLME D. M. , INGRAM D. S.
Published: April 2006

The effects of gamma irradiation on secondary embryoids of Brassica napus ssp. oleifera (Metzg.) Sinsk., winter oilseed rape, are reported. A kill curve was established, and the secondary embryoids were found to be more tolerant of high doses of irradiation than tissues of many other plant species. Secondary embryoids which had received less than 320 Gy retained their secondary embryogenic potential at subsequent subcultures, although their potential to develop into plantlets was greatly reduced. A haploid line from the cultivar Rapora was found to be more sensitive to gamma irradiation than a diploid line from the cultivar Primor. A number of regenerant plants have been established from irradiated embryoids and grown on to flowering.
Studies on infraspecific variation in Cyperus longus L. from Europe
Authors: COLLINS ROSEMARY P. , McNALLY SHEILA F. , SIMPSON D. A. , JONES M. B.
Published: April 2006

Clonal material of the temperate C4 species Cyperus longus L. (Cyperaceae) sampled from Cornwall, S. W. Great Britain and Mt Pilion, central Greece was grown under the same environmental conditions. Comparisons were made of the pattern of leaf growth, net photosynthesis (Pn) and the characteristics of the isoenzymes of glutamine synthetase (GS). In addition, we studied the morphological characteristics of these clones and 95 herbarium specimens collected from a range of localities throughout Europe.

Principal‐components analysis of the morphological characteristics suggested that European material falls into two distinct morphological groups, typical C. longus and ssp. badius (Desf.) Murb. The clonal material from Cornwall corresponded morphologically with ssp. longus and that from Mt Pilion with ssp. badius. Physiological and biochemical measurements of the two clones indicated distinct differences in the phenology, Pn and stomatal conductance at high light levels, their complements of GS1 and GS2 isoforms and associated temperature stability. It appears, therefore, that ssp. badius represents a distinct ecotype of ssp. longus. However, the apparent taxonomic distinction between the groups requires further investigation of population variation, as our studies were performed on a limited amount of clonal material.
The effects of root cooling and excision treatments on the growth of primary leaves of Phaseolus vulgar is L.
Authors: SMITH P. G. , DALE J. E.
Published: April 2006

Seedlings of Phaseolus vulgaris L. were grown in nutrient solution at two temperatures and the free abscisic acid (ABA) content of primary leaves measured by radioimmunoassay with a monoclonal antibody (MAC‐62). Transfer of 7‐day‐old seedlings from solutions at 22.5 °C to 10 °C doubled the ABA content per g fresh weight after 6 h and led to a S‐fold increase by 24 h. Shorter incubations led to a 2.5‐fold rise 2 h after the start of cooling. Root‐cooling restricted leaf expansion rate but both the inhibition of leaf growth and the rise in ABA content were reversed when root temperature was returned to 22.5 °C. 2 h after transfer to control conditions half of the extra free ABA induced per leaf by root‐cooling was no longer present. Excision of seedling lateral roots impeded leaf expansion and led to enhanced ABA content after 24 h. Petiole ringing experiments showed that the rapid rise in ABA was not due to blockage of export from the leaves of root‐cooled plants, although export may have contributed to the fall in ABA when cooled seedlings were returned to 22.5 °C.
Ozone accelerates structural degradation of epicuticular wax on Norway spruce needles
Authors: BARNES J. D. , DAVISON A. W. , BOOTH T. A.
Published: April 2006

Scanning electron microscopy was used to investigate the effects of O., fumigation (70 d of 240 μg O3m−3for 6 h d−1during a 12 h photoperiod) on the condition of the epicuticular wax that fills and surrounds the stomatal antechamber of the needles of seven clones of Norway spruce(Picea abies(L.) Karst.). The rate of change of the physical structure of the wax differed between clones, but in all eases O., accelerated the process on current and previous year's needles. The change consisted of a transition from a crystalline array of fine tubes to an amorphous, ‘melted’ layer with no visible structure. This resulted in a higher frequency of stomata occluded by an apparently continuous plug. In four clones, O3, fumigation resulted in 70–80 %, of the stomata on previous year's needles being occluded, in contrast to 7–28 % in charcoal‐filtered air. Five of the clones showed a greater effect of O3, on the wax of the previous year's needles than on current needles. The physiological consequences of such O.,‐induced effects are discussed. Premature wax degradation induced by O3, and/or acid mist may have contributed to the decline of spruce in high‐altitude forests of continental Europe.
Regulation of gene expression in ectomycorrhizas
Authors: HILBERT J. L. , MARTIN F.
Published: April 2006

In an effort to investigate the presence of any ‘symbiosis‐specific’ genes that are expressed specifically during the development of ectomycorrhizas, the polypeptide content of Eucalyptus‐Pisolithus mycorrhizas, uninfected Eucalyptus globulus (Maid et al.) Kirkp. short roots, and free‐living Pisolithus tinctorius Coker & Couch mycelia have been compared. Analysis of the soluble proteins by two dimensional polyacrylamide gel electrophoresis showed that most of the polypeptides observed in mycorrhizas were already synthesized in free‐living mycelia. The effects of mycorrhizal infection on polypeptide accumulation fell into three distinct categories: (i) decreased amounts of a large number of polypeptides, (ii) increased accumulation of a comparatively few polypeptides and, (iii) appearance of ectomycorrhizins (mycorrhiza‐specific polypeptides). Approximately 50% of the fungal polypeptides and more than 80 % of the plant polypeptides resolved on gels disappeared during the development of ectomycorrhizas. Among 520 polypeptides, 10 polypeptides, called ectomycorrhizins, were ectomycorrhiza‐specific in that they were present in ectomycorrhizas, but not in free living mycelia nor in non‐infected roots. The results showed differential accumulation of ectomycorrhizins during mycorrhiza development. These findings demonstrate that protein synthesis is drastically altered in response to the morphological and physiological changes resulting from the establishment of ectomycorrhiza.
Root and mycorrhizal endophyte development in a chronosequence of restored tallgrass prairie
Authors: COOK B. D. , JASTROW J. D. , MILLER R. M.
Published: April 2006

The relationships between root and mycorrhizal development were investigated at the community level for a chronosequence consisting of restored tallgrass prairie (including plots in the second, fifth, eighth and eleventh growing season) and a virgin prairie remnant. Fibrous ( 1 mm diameter) root length increased across the chronosequence, with the greatest length occurring in the prairie remnant. After an initial increase between the second and fifth growing seasons, the percentage of fibrous roots colonized by vesicular‐arbuscular mycorrhizal fungi declined. However, this decline did not truly reflect the mycorrhizal association in this system because the length of fibrous roots colonized by mycorrhizal fungi did not decrease after the fifth growing season but instead remained essentially constant throughout the remainder of the chronosequence. Evaluation of the data by fibrous root size classes indicated that increases in root length and colonized root length occurred largely in the smaller size class (< 0.2mm diameter); in contrast, percentage colonization and the density of intraradical fungal structures was greater in the larger size class (0.2–1 mm diameter). The importance of thoroughly evaluating responses of mycorrhizal fungi relative to host responses was demonstrated in a field situation.
A comparative study of Geum rivale L. and G. urbanum L. to determine those factors controlling their altitudinal distribution
Authors: Graves J. D. , Taylor K.
Published: April 2006

The control of germination by temperature was compared in Geum urbanum L. and G. rivale L., two closely related species with contrasting altitudinal and latitudinal distributions. Under constant temperatures only slight differences were observed in the response of germination to temperature in the two species. A model was formulated to predict germination in field temperature conditions on the basis of rates of germination observed at constant temperatures. Comparison of observed and predicted germination under field temperature conditions revealed that the rate of germination was considerably higher than expected in G. urbanum at low temperatures. Calculations indicate that at altitudes above the altitudinal limit of G. urbanum this feature results in the germination of G. urbanum during the frost period of the year whilst seed of G. rivale remains dormant until the advent of milder climatic conditions.
Response of Armeria maritima (Mill.) Willd. and Plantago maritima L. from an Irish salt marsh to nitrogen and salinity
Authors: SHEEHY SKEFFINGTON M. J. , JEFFREY D. W.
Published: April 2006

Two experiments on the interaction between salinity and nitrogen supply were carried out on the halophytes Armeria maritima and Plantago maritima. Water potential values ranged from −0.16 MPa to – 5.0 MPa and nitrogen from 0.28 to 280 mg l−1 N. An increase in nitrogen above 2.8 mg l−1 N in the medium in all cases resulted in an increase in growth, though this was not so great at higher salinities. Armeria growth rate was optimal at a higher nitrogen concentration than Plantago and Armeria also accumulated nitrogen in shoots with increasing salinity. Plantago root nitrogen concentrations increased with increased nitrogen.

Both species accumulated sodium in shoots, but in Armeria concentrations were lowest in the highest nitrogen treatments. Potassium was redistributed from shoots to roots with increasing salinity.

Two populations of Plantago from the salt marsh were examined. Differences in growth response and flowering time were observed. A third, inland population of Plantago showed reduced vigour in water potentials lower than −2.5 MPa.
The Brière Marshlands: a palynological survey*
Authors: VISSET LIONEL
Published: April 2006

The work reported here allows the Holocene evolution of a large west French coastal marshland to be reconstructed and demonstrates the landscape changes associated both with the Flandrian transgression and the impact of human settlement from the Neolithic to the present. A sequence of markedly different stages is described, including estuary, schorre (salt marsh or zone of halophytic vegetation covered by the sea only at spring tides) and oak woodland, eventually yielding place to peat growth.
The palaeoecology of Alnus (alder) and the Postglacial history of floodplain vegetation. Pollen percentage and influx data from the West Midlands, United Kingdom
Authors: BROWN A. G.
Published: April 2006

The Postglacial history of Alnus is of particular relevance to the palaeoecology of wetlands and floodplains. The ecological histories of floodplain sites differ from those on dry‐land or from hydroseres. This paper uses pollen percentage and influx data to investigate floodplain succession and woodland development on floodplains in the West Midlands, the primary site being Wilden Marsh near Stourport, Worcestershire. The floodplain at Wilden probably underwent a three‐phase succession during the early Postglacial; Betula was replaced by Salix spp. which were out‐competed by Alnus. Alnus was present prior to its expansion, which is seen as the result of increasing soil stability, pedogenesis and decreased free drainage related to floodplain development and not necessarily to climatic change or anthropogenic disturbance. During the late Postglacial Alnus declines and Salix frequently increases again due to floodplain deforestation and utilisation, which was partly facilitated by altered soil conditions caused by hydrological change. The advantages of small floodplain sites for the differentiation of vegetation pattern is illustrated by the identification of a non‐floodplain pollen component dominated by Tilia.
Ascorbic acid‐induced progression of quiescent centre cells from G1 to S phase
Authors: LISO R. , INNOCENTI A. M. , BITONTI M. B. , ARRIGONI O.
Published: April 2006

summary

Quiescent centre cells, which are known to have their cycle extended mostly in G, and to divide rarely, art‐stimulated to undergo DNA synthesis in root meristems of Allium cepa L. by treatment with ascorbic acid. The effect of ascorbic acid is dramatic: 21% of all the cells in the quiescent centre remain in the G, phase while 79% enter S phase. From a mean value of 2204 × 103μ3 in water‐grown roots, the volume of the quiescent centre drops to a mean value of 167 × 103μ3 following treatment with ascorbic acid. These results indicate that ascorbic‐acid stimulates not only the activity of the quiescent centre cells but also cell proliferation in the entire root meristem. The rate of cell progression through the cycle may be related to cellular ascorbic acid content.
Phenols and bud dormancy
Authors: CODIGNOLA ARNALDO , MAFFEI MASSIMO , FIESCHI MAURIZIO
Published: April 2006

summary

Qualitative analyses of the endogenous phenols of Fagus sylvatica L. were determined separately in leaf primordia and bud scales of dormant buds (apical, subapical and basal) of Fagus sylvatica L. until bud burst.

Qualitative analyses in all leaf primordia showed the presence of phenols which are potential cofactors of IAA oxidase (vanillic acid, 2′4,4′‐trihydroxychalcone), uncoupling agents of oxidative phosphorylation (norwogonin, orobol 7‐O‐rhamnoglucoside, baicalin, 2′4,4′‐trihydroxychalcone and chlorogenic acid), a synergic stimulator of IAA (chlorogenic acid) and others. In all bud scales the qualitative phenol composition includes a mixture of potential IAA oxidase cofactors (vanillic acid and 2′,4,4′‐trihydroxychalcone), uncoupling agents (baicalin and 2′,4,4′‐trihydroxychalcone) and other compounds.

In both leaf primordia and bud scales, the qualitative phenol composition does not change significantly during dormancy. These data do not indicate correlations between phenolic matabolism in bud scales and leaf primordia or between single phenolic compounds and the inception and maintenance of dormancy.
Phosphorus concentrations and chemical fractions in Eucalyptus seedlings grown for a prolonged period under nutrient‐deficient conditions
Authors: MULLIGAN D. R.
Published: April 2006

summary

Seedlings of Eucalyptus grandis Hill ex Maiden, two provenances of E. pilularis Smith (Coffs Harbour (CH) and Myall Lakes (ML)), and E. gummifera (Sol. ex Gaertner) Hochr. were grown for 60 weeks in sand culture under two nutrient‐limiting regimes. Under both levels of nutrient deficiency, E. pilularis (ML) and E. gummifera, the two species from phosphorus‐deficient sites, produced more dry matter than the other two species which originated in more fertile soils. Phosphorus partitioning among different organs, concentrations of phosphorus (and hence efficiencies of phosphorus use) and pool sizes of lipid‐P, Pi, ester‐P, nucleic acid‐P and residue‐P (bound P) were assessed in each organ at harvest. Concentrations were expressed on a per unit protein‐N basis (reflecting the amount of cytoplasm) as well as on a dry weight basis.

At the more extreme conditions of nutrient deficiency (Treatment A), there was little difference between the leaves of the species in terms of efficiency of phosphorus use, but under the less severe conditions (Treatment B) efficiency was in the order E. gummifera > E. pilularis > E. grandis. Most of the foliar phosphorus (up to 70%) was present in a nucleic acid and ester form, although E. gummifera (and E. grandis for Treatment B) had a substantial phospholipid pool (approx. 25% of total leaf phosphorus). In the former case at least, this difference in phosphorus distribution among the chemical fractions may be of ecological significance. The stems and roots showed no species differences but noteworthy findings included the high residue‐P pool in the roots of Treatment A seedlings (up to 41% of root phosphorus) and the high concentrations of Pi in the stems of Treatment B plants (67–87 % of stem phosphorus).

The ecologically distinct provenances of E. pilularis differed neither in phosphorus utilization efficiency nor in distribution among the molecular fractions examined. Their differing productivities were thus related to differences in phosphorus acquisition. The comparatively lower productivity of E. grandis was due to a combination of less efficient acquisition and less efficient internal utilization. The success of E. gummifera could be attributed to increased uptake and possibly increased utilization efficiency that in turn may have been related to its different phosphorus allocation pattern among the major chemical fractions.
Phosphate and nitrate movement in the clonal plants Lycopodium annotinum L. and Diphasiastrum complanatum (L.) Holub
Authors: HEADLEY A. D. , CALLAGHAN T. V. , LEE J. A.
Published: April 2006

summary

The uptake and movement of phosphate by Lycopodium annotinum L. in the field was studied using 32P‐labelled orthophosphate. Although over 90% of the phosphate taken up was retained in the incubated roots, the phosphate transported to the aboveground tissues showed extensive movements both distally and proximally along the horizontal branch system. Root systems up to 12 years old could transport phosphate as far as the stolon apex over one metre distally along the horizontal branch. The movement of phosphate is preferentially to the main sinks for phosphorus, the current year's horizontal and vertical branch segments.

Nitrate uptake and movement was studied in Diphasiastrum complanatum (L.) Holub by measuring the induction of in vivo nitrate reductase activity in current year's growth in different parts of the clone. There was equal induction of in vivo nitrate reductase activity in 1–4 year old root systems incubated in nitrate, but absorption by 3 and 4 year old root systems induced the highest activities in the vertical branches. Nitrate movement to the stolon apex was only detectable from root systems up to 3 years old. There was considerable induction of nitrate reductase activity in vertical branch apices proximal to the 3 and 4 year old root systems supplied with nitrate.

L. annotinum and D. complanatum show considerable inter‐module integration for nitrate and phosphate supply. This means that the plant can adopt an effective ‘foraging’ strategy for nutrients. The movement of resources from sites of absorption to their sites of utilisation means that there is extensive recycling of nutrients spatially, as well as temporally, within the habitats colonised by these plants.
Water uptake and movement in the clonal plants, Lycopodium annotinum L. and Diphasiastrum complanatum (L.) Holub
Authors: HEADLEY A. D. , CALLAGHAN T. V. , LEE J. A.
Published: April 2006

summary

Lycopodium L, sensu stricto and Diphasiastrum complanatum (L.) Holub demonstrate a ‘guerilla’ growth strategy whereby the growth of the stolon apex is subsidized by resources from root systems several years old. In the dry sub‐arctic/sub‐alpine birch forests of Swedish Lapland where the soil cover is very heterogeneous and the annual precipitation is low, the subsidized water balance of the stolon apex is critical to the survival of the plant. Some aspects of water relations of L. annotinum L. and D. complanatum (L.) Holub were studied in the field.

Water potentials were more negative towards the stolon apex, and water movement, traced using acid fuchsin dye, showed that the dye moved 14 times further from an isolated root system in a distal direction towards the stolon apex than in the proximal direction. A single root system initiated 8 years previously, and 65 cm from the stolon apex, was shown to be capable of supporting the growth of this apex. The excision of 3 and 4 year old root systems resulted in the greatest effect on depression of the water potential of the stolon apex, suggesting that these provided most of the water used by the stolon apex.

The preferential allocation of water to the stolon apex was very effective, and the functional morphology of the plants seems to be related to harsh, patchy environments. However, when crossing large patches of inhospitable terrain, or under periods of drought, those stolon apices dependent on old, distant root systems for their water supply can experience lethal water stress. As the health of the stolon apex effects its degree of correlative inhibition of sub‐dominant stolons, the architecture and foraging ability of the clone is affected.