bluuebunny/crossref_metadata_2025_split huggingface dataset:
Developmental changes in the aperture during pollen grain ontogeny in Olea europaea L.
Authors: FERNÁNDEZ M. C. , RODRÍGUEZ‐GARCÍA M. I. 
Published: April 2006

summaryChanges in both size and form of the structures making up the apertural region, a modified part of the pollen grain wall, were studied during development in Olea europaea L. The very young microspores initially show thickening of the endexine around the apertural zone. This is followed by the appearance of an exinous oncus and subsequently an intinous oncus. The intinous oncus contains tubules derived from evaginations of the plasmalemma. These tubules increase in number and diameter during development.
Biomass production and gas exchange of winter wheat as affected by flag leaf inoculations with Septoria nodorum
Authors: ROONEY J. M. 
Published: April 2006

summaryInoculation of flan leaves of winter wheat with Septoria nodorum (Berk.) Berk was more effective in reducing final grain weight when inoculation was at anthesis than when it was at flag leaf emergence, either during or following leaf expansion; grain number was not significantly affected by the timing of inoculation. The greatest senescence was observed with late inoculations with correspondingly lower flag leaf weight at grain maturity. It is suggested that flag leaves become more susceptible to S. nodorum with increasing time after emergence. Inoculation did not result in any significant redistribution of assimilate from stems to ears as it did not affect stem weight. The reduction in photosynthesis at high irradiance was proportional to infection‐induced senescence. Change in the total resistance to the diffusive flow of carbon dioxide was controlled by the mesophyll resistance, i.e. that remaining following subtraction of boundary layer and stomatal components.
A comparative study of plant responsiveness to the duration of episodes of mineral nutrient enrichment
Authors: Campbell B. D. , Grime J. P. 
Published: April 2006

summaryGrowth, dry matter partitioning and nitrogen capture were compared in two grasses of contrasted ecology, subjected to treatments involving pulses of nutrient enrichment of various durations supplied every 6 d over a period of 6 weeks. The potentially fast‐growing Arrhenatherum elatius ssp. bulbosum (Willd.) Schubler and Martens was superior in rates of nitrogen capture and dry matter production when exposed to long (≥ 10 h) nutrient pulses whereas the slow‐growing species Festuca ovina L. enjoyed an advantage in treatments providing nutrient pulses of between 0.1 and 10 h duration. These results are consistent with differences in mechanisms of resource foraging predicted by the C‐S‐R model of plant strategies and related models. It is concluded that the lower rates of turnover of tissues and the capacity of roots to remain viable under chronic nutrient stress are important components of the ability of Festuca ovina to exploit brief pulses of mineral nutrient enrichment. The range in duration of the pulses advantageous to F. ovina corresponds to that which might be expected to arise from the death and recovery of microbial populations in infertile soils.
The population genetics of Armeria maritima (Mill.) Willd. on the River South Tyne, UK
Authors: RICHARDS A. J. , LEFEBVRE C. , MACKLIN M. G. , NICHOLSON A. , VEKEMANS X. 
Published: April 2006

summary A. maritima inland in England and Wales is largely confined to metal‐rich soils, where it has probably evolved metal tolerance. Similar populations are found in Belgium, Germany and Poland. Numerous large populations occur on river terraces beside the rivers South Tyne and Tyne in Northumberland. These terraces were mostly formed between 1850 and 1940, and have high levels of toxic heavy metals which result from mining activities within the catchment. It is probable that A. maritima occurred on naturally metalliferous soils high in the Pennine catchment prior to mining, and colonized metalliferous river terraces downstream after 1850.In comparison with the British populations of subspecies maritima, the Tyne populations are unique in being polymorphic for scape hairiness. This character is also found in European mine populations. The Tyne populations also share with European mine populations some degree of self‐fertility, but selfing was insufficient to give rise to detectable excesses of the papillate morph. Nevertheless, in at least one population, excesses of papillates may occur. The papillate morphs tend to be more self‐fertile than the cob morph. The recessive homozygous papillate phenotypes flower later, and tend to predominate in the densest parts of the population It is suggested that heterotic genes may be linked to the loci studied. This may account for the late dowering and high density of homozygous phenotypes.
Ultrastructure, development and cytochemistry of storage cells in the‘tubers’of Phaeoceros laevis Prosk. (Anthocerotophyta)
Authors: LIGRONE R. , LOPES C. 
Published: April 2006

summaryThe gametophyte of Phaeoceros laevis Prosk. forms small parenchymatous tubers as perennating organs. The development of tuber cells is characterized by marked cytoplasmic proliferation. The chloroplasts are packed with starch and abundant lipid bodies (spherosomes) are produced in the cytoplasm in association with rough endoplasmic reticulum. The vacuoles become pleomorphic and accumulate electron‐dense deposits. These were negative to PATAg staining for carbohydrates and were digested by pronase; therefore they are assumed to be protein. No ultrastructural evidence was found for the participation of either ER or dictyosomes in the biogenesis of the protein‐storing vacuoles. The mature tubers have a distinct layer of epidermal cells with thick external walls, and frequently harbor intercellular cyanobacteria.
Effects of salinity and relative humidity on growth and ionic relations of plants
Authors: SALIM M. 
Published: April 2006

SUMMARYGrowth and ionic relations of mung bean (Vigna radiate L.), sunflower (Helianthus annuus L.), red kidney bean (Phaseolus vulgaris L.), tomato (Lycopersicum esculentum L.) and Atriplex spongiosa L. were studied with three concentrations of NaCl up to 100 mM in the root medium and at either 30% or 90% relative humidity (RH). Two harvests (7 days apart) of all five plant species were taken. Increase in root zone salinity and relative humidity significantly decreased the transpiration rates of all except A. spongiosa. Fresh weight/dry weight ratios of the shoots were unaffected by salinity, except in mung bean, whereas increased RH generally increased the ratios. Shoot/root ratios of mung bean and A. Spongiosa plants were unaffected by both salinity and humidity but increased salinity decreased these ratios in the other three species. In sunflower and tomato greater RH increased the shoot/root ratios at all salt levels. Generally, increased salinity decreased the relative growth rates of mung bean, red kidney bean and sunflower whereas increased RH improved the relative growth rates of mung bean. A. Spongiosa and sunflower.In most of the species, concentrations of [K + Na] and Cl in the shoot tissue water increased, and those of Ca and Mg decreased, with increase in NaCl concentration in the root medium up to 100 mM. However, in some cases, the concentrations of inorganic ions in the shoot tissue water decreased at all levels of NaCl when the RH in the growth cabinet was increased up to 90%. Concentrations of K in root tissue water of all five species decreased and their Na and Cl concentrations generally increased with increasing salinity of the root medium. Although rates of Na transport relative to that of K through the roots of all the species significantly increased with salinity, red kidney bean roots conducted more Na relative to K under low RH compared with high RH. Similarly the roots of sunflower and A. spongiosa conducted more Cl relative to [K + Na] when the RH was decreased. Higher rates of net ion transport from roots to shoot of mung bean and A. spongiosa plants resulted in higher concentrations of K, Na and Cl in their shoot tissue water when the RH was decreased from 90% to 30%.
The response to salinity at the microscopic level of the marine fungus Dendryphiella salina Nicot and Pugh as investigated stereologically
Authors: CLIPSON N. J. W. , JENNINGS D. H. , SMITH J. L. 
Published: April 2006

SUMMARYA stereological analysis of the response of cellular characteristics of hyphae of the marine hyphomycete Dendryphiella salina to salinity is presented. Analyses of volume fractions, compartmental volumes, membrane surface densities and membrane areas have been made. A major finding has been that the wall forms 40 % of the compartment volume. Total hyphal compartment volume was maximal at 200 mM NaCl at 109μm3 with compartments increasing in width and decreasing in length with salinity. Maximal protoplasmic and cytoplasmic volumes were also found at 200 mM. Electron microscopy demonstrated three different vacuolar types differentiated by their staining characteristics. A light‐staining vacuolar type increased in total volume from 4.5 to 12.2μm3 from 0 to 1 M NaCl. Data are considered not only in terms of hyphal anatomical characteristics but also in terms of those physiological processes occuring in D. salina which allow it to grow in saline media.
Vesicular‐arbuscular mycorrhizas increase chloride concentration in citrus seedlings *
Authors: GRAHAM J. H. , SYVERTSEN J. P. 
Published: April 2006

SUMMARYSeedlings of sour orange (Citrus aurantium L.) and sweet orange (C. sineusis (L.) Osbeck) were grown in a sandy soil low in phosphorus (P) and either inoculated with Glomus intraradices Schenck & Smith (vesicular‐arbuscular mycorrhizal; VAM) and/or fertilized with soluble KH2PO4 (nonmycorrhizal: NM). Eight‐month‐old VAM and NM seedlings of similar shoot size and P concentration were salinized with 30 and 60 mM NaCl in one experiment for 6 weeks until growth reductions were observed, and in another experiment, seedlings were salinized for 4 weeks before growth reductions occurred. Salinization did not affect colonization by G. intraradices but reduced growth, hydraulic conductivity of roots, and transpiration of shoots. There were no significant growth or physiological interactions between mycorrhizas and salinity which indicates that G. intraradices did not affect salinity stress tolerance of either species. In the first experiment, mycorrhizas increased Cl concentration in shoots and total Cl per plant of sweet orange but not sour orange. NM seedlings fertilized with KH2PO4, had significantly higher levels of P and K than in VAM plants which may have led to the observed differences in the leaf concentrations of Cl and cations. In the second experiment, VAM plants were also supplemented with KH2PO4 before salinization. This resulted in similar leaf and root concentrations of P, K, and other cations. Root Mn was lower and leaf Cu and root Cu and Zn were higher in VAM seedlings. Salinization negated the mycorrhizal effect on Cu to an extent depending on NaCl level. Mycorrhizas increased Cl concentration in leaves and roots of salinized sweet orange and sour orange in the apparent absence of a P‐nutritional effect.
Anther dehiscence in Lycopersicon esculentum Mill. I. Structural aspects
Authors: BONNER LYNDA J. , DICKINSON H. G. 
Published: April 2006

SUMMARYThe structure and chemistry of anther dehiscence in Lycopersicon esculentum (Solanaceae) has been examined using a range of microscopic techniques. No Single event or process has been identified as being solely responsible for the release of the pollen grains, instead, an integrated programme of development across a number of tissues appears to be involved. The earliest events in this process are changes in the intersporangial septa and growth of specific epidermal cells. Large numbers of calcium oxalate (druse) crystals accumulate in the septa and may play a part in the weakening and eventual enzymic dissolution of this cell layer. The differential growth of epidermal cells fulfils two roles; firstly it serves to define the point of rupture or stomium and, secondly the enlarged cells generate and transmit the force required to disrupt the unenlarged stomial cells. Adjacent loculi are unified within the anther first by the enzymic degradation of the crystal‐filled septal cells, which is followed by similar degradation of the remaining connective tissue cells and the eventual rupture of the remnants of the tapetal walls.Once the epidermal cell system has been established, and adjacent loculi unified, the endothecium develops in the anther wall, but only in the region adjacent to the stomium in the distal third of the anther. Opening of the anther is achieved by a combination of the mechanical forces generated by tile enlarged epidermal, and possibly the endothecial, cells operating on the previously weakened stomial cells, which at the time of rupture have started to desiccate. Following rupture of the anther wall, the stomium is transformed from a slit to a wide‐mouthed pore via the ordered desiccation and contraction of the endothecial and surrounding tissue. Although these final stages of dehiscence show some sensitivity to ambient vapour pressure differences, there is little doubt that the process of dehiscence is not purely a desiccatory one, indeed only specific localised areas of the anther degenerate and dehydrate, whilst the bulk of the anther tissue remains turgid and metabolically active.This multicomponential type of anther dehiscence is discussed in the perspective of other models proposed to explain anther opening in members of the Solanaceae, as well as systems suggested for other plants which clearly possess very different methods of dehiscence.
Analysis of specific leaf area and photosynthesis of two inbred lines of Plantago major differing in relative growth rate
Authors: DIJKSTRA PAUL , LAMBERS HANS 
Published: April 2006

SUMMARYTwo inbred lines of Plantago major L., differing in relative growth rate (RGR), were studied in order to elucidate physiological factors responsible for this difference. The slow growing inbred line of P. major ssp. major L. (line W9) had a lower specific leaf area (SLA) compared with that of the fast growing P. major ssp. pleiosperma Pilger (line A4). Photosynthetic activity per unit leaf area was higher than that of A4, but expressed per unit leaf dry weight W9 exhibited a lower activity than A4. Photosynthetic capacity (per unit leaf dry weight or nitrogen) was identical for both lines. The amount of chlorophyll a per unit dry weight or leaf area was higher for line W9. Differences in the chemical composition of the leaf dry weight of the two lines did not explain the lower SLA or lower photosynthetic activity per unit leaf dry weight of the slow growing line. The lower SLA of W9 was mainly caused by the lower water content per unit dry weight. A higher amount of cell wall material per unit leaf dry weight was found.We conclude that the lower SLA of W9 resulted in a greater shading within the leaf, a lower light absorption and lower photosynthetic rate per unit leaf dry weight. Consequently, this resulted in a lower RGR. The significance of these characters for growth under trampling and soil compaction is discussed.
Purification and some properties of an aminopeptidase from endosperms of ×Haynaldoticum sardoum Meletti et Onnis
Authors: GALLESCHI L. , PELLEGRINI L. 
Published: April 2006

SUMMARYAminopeptidase activity was detected in dry and germinating seeds of x Haynaldoticum sardoum. The enzyme was partly purified from germinating seeds and preliminary characterization was carried out.The aminopeptidase showed a pH optimum of 8.0, a molecular weight estimated at 89 000 by Sephadex G‐100 gel filtration and an isoelectric point of 4.5. The enzyme hydrolysed p‐nitroanilides, but was unable to break down exogenous native proteins. Activity was severely inhibited by p‐chloromercuribenzoate, p‐hydroxy‐mercuribenzoate and bestatin, slightly inhibited by iodoacetamide and ethylenediaminetetraacetic acid and not influenced by 2‐mercaptoethanol, phenylmethanesulphonyl fluoride and polyamines.A possible physiological role for the enzyme in the final stages of storage protein degradation is suggested.
Visible foliar injury of red spruce seedlings subjected to simulated acid mist
Authors: LEITH I.D. , MURRAY M. B. , SHEPPARD L. J. , CAPE J. N. , DEANS J. D. , SMITH R. I. , FOWLER D. 
Published: April 2006

SUMMARYTwo‐year‐old red spruce seedlings [Picea rubens Sarg. syn. P. rubra (Du Roi) Link] were subjected to 6 simulated acid mist treatments (pH 2.5, 2.7, 3.0, 3.5, 4.0, 5.0) in a replicated experiment using open‐top chambers. Acid mist solutions containing equimolar (NH4)2SO4, and HNO3 were applied twice weekly for 22 weeks, each application being equivalent to 2 mm of precipitation.Visible symptoms of foliar damage were observed on the 3 most acidic mist treatments (pH 2.5, 2.7, 3.0). The inputs of nitrogen, sulphur and acidity in the most acidic treatment were 55, 42, 1,3 kg ha‐1, respectively, over a 10 week period. The plants subjected to the pH 2.5 treatment were found to be most severely damaged with approximately 40% foliar necrosis after 10 weeks of treatment.On approximately 80% of seedlings, necrosis was confined to current year needles only. These damaged needles were initially light brown or light orange in colour turning a deeper red 3 to 5 weeks after initial necrosis. Percentage foliar damage was linearly related to concentration (of NH4+, NO3‐, SO42– and H+) with 62% foliar damage in the pH 2.5 treatment after a 22–week period.Spray application stopped in December 1987. Observations during the following spring showed that the pH 2.5 and pH 3 treatments induced earlier Hushing, requiring 60 day °C less thermal time than the pH 5–0 treatment. In 1988, this decrease in thermal requirement was equivalent to flushing 11 days earlier. There was no evidence of acid mist treatments inducing bud mortality.
Effects of acid mist on the frost hardiness of red spruce seedlings
Authors: FOWLER D. , CAPE J. N. , DEANS J. D. , LEITH I. D. , MURRAY M. B. , SMITH R. I. , SHEPPARD L. J. , UNSWORTH M. H. 
Published: April 2006

SUMMARYSeedlings of red spruce [Picea rubens Sarg. syn. P. rubra (Du Roi) Link] were exposed to mists containing equimolar (NH4, SO4 and HNO3 at pHs of 2.5, 2.7, 3.0, 35, 4.0 or 5.0. The mists were applied twice each week, amounting to 2 mm precipitation equivalent on each occasion, between July and December, to open‐top chambers supplied with charcoal‐filtered air.Frost hardiness of shoots excised from seedlings was determined on 6 occasions starting on 21 September, and was found to be strongly influenced by acid mist treatments, seedlings subject to the most acidic mists being the least frost hardy. On 21 September when the first sample was taken the lethal temperature for killing 50% of shoots (LT50) was – 11 °C for the least acidic (pH 5.0) mist and – 7 °C for the most acidic (pH 2.5). By 19 October, the LT50s of pH 5.0 and pH 2.5 mists were –27 and –15 °C respectively. All intermediate treatments ranked according to treatment concentration, with the smaller concentrations causing lower LT.50 values.The treatment at pH 30 provided S and N inputs to the seedlings similar to those experienced by red spruce at elevations of about 1000 m in the southern Appalachians. At pH 3.0, the frost hardiness LT10 during October was typically 8 °C higher than the pH 5.0 treatment, leading to a significant increase in the probability of frost damage at the LT10 level in an average October.The proximity of minimum night temperatures during September to December to the LT10 temperatures of red spruce shoots receiving large inputs of SO42‐, NO3‐, NH4+ and H+ suggests that decreases in frost hardiness caused by intercepted cloud water containing large concentrations of these ions may play a significant part in the observed decline at mountain‐top locations.
Interaction ofGlomusspecies andVigna unguiculatain an oxisol subjected to simulated erosion
Authors: AZIZ T. , HABTE M. 
Published: April 2006

SUMMARYAn experiment was conducted in the greenhouse to determine the effectiveness of three species of vesicular‐arbuscular (VA) mycorrhizal fungi in an oxisol subjected to simulated erosion using cowpea [Vigtta unguiculata(L.) Walp, cv.‘California Black Eye’] as an indicator host. Inoculation of the eroded soil resulted in increased VA mycorrhizal colonization of roots without enhancing shoot P concentration and dry matter yields. Inoculation of the uneroded soil, however, led to significant improvement in infection level as well as in symbiotic effectiveness. Based on the results of this study, it appears that the lack of expression of mycorrhizal effectivness in the eroded soil is a result of nutrient deficiency. The results thus suggest the importance of restoring lost nutrients before the benefits of VA mycorrhizal inoculation could be effectively exploited for a successful establishment of a mycorrhizal cowpea in eroded soils.
Control of stomatal aperture by calcium in isolated epidermal tissue and whole leaves of Commelina communis L.
Authors: ATKINSON C. J. , MANSFIELD T. A. , KEAN A. M. , DAVIES W. J. 
Published: April 2006

SUMMARYPlants of Commelina communis L. were grown in media containing different concentrations of calcium from 1 to 8 mol m −3. After 4 weeks' growth stomatal behaviour was studied both on the intact plants and on isolated abaxial epidermis. The effect of Ca nutrition on stomatal opening was apparently different according to these two methods of observation. The apertures measured in light and in absence of CO2 were smaller on abaxial epidermal strips from plants grown at larger Ca concentrations than those grown at smaller concentrations. The inhibition of opening was thought to be due to the presence of free Ca2+ ions because inhibition was not found when EGTA was included in the medium used for incubating the isolated epidermis, and significant quantities of Ca were lost to the medium by epidermal tissue from plants grown on high concentrations of Ca.Studies on the leaves of intact plants were made with a diffusion porometer and by gas exchange techniques using a leaf cuvette in which the environment was closely controlled. A/c1 curves were used to partition non‐stomatal and stomatal limitations to gas exchange. Porometer measurements of stomatal conductance, determined within the growth room, indicated reduced values for plants grown at low Ca compared with those grown at high Ca, i.e. the observations contradicted those obtained with isolated epidermis.Biomass production increased with Ca up to 4 mol m −3. Analysis of A/c1 curves indicated that plants grown at the larger Ca concentration showed significantly greater values for carboxylation efficiency (dA/dc1). Partitioning of stomatal and non‐stomatal limitations to carbon fixation indicated that the gas‐phase limitations of CO2 were similar at different Ca concentrations. Differences in carboxylation efficiency could account for the greater biomass accumulation found at the larger Ca concentration.Calcium analysis indicated that plants grown at high Ca contained greater bulk leaf Ca concentrations, and a difference in Ca concentration was also evident in epidermal tissue, but the relative distribution of fractionated epidermal Ca was similar. Xylem sap Ca analysis also revealed more Ca in the apoplast of high Ca grown plants.The differences in stomatal behaviour in isolated epidermis and in the intact leaves suggest that in Ca‐rich plants, the level of free Ca2+ ions in the vicinity of guard cells is controlled, thus preventing inhibition of stomatal opening and interference with gas exchange. The loss of this control when epidermis is detached implies that the presence of the mesophyll tissue is important.