Comparison of Plant Telomere Locations using a PCR-generated Synthetic Probe

We have generated a telomere-specific probe by the polymerasechain reaction and used it to localize chromosome telomeresof ten unrelated angiosperm species in in situ. Concatenationof the simple monomers, 5'-(TTTAGGG)-3', derived from the sequenceof Arabidopsis thaliana telomeres, yielded a stable, versatileand reliable probe that gave a signal of high intensity followingfluorescence in situ hybridization. Most species, includingthose with known karyotype rearrangements, showed telomere labelonly at chromosome termini. These findings are discussed inthe context of the chromosomal events responsible for generatingand stabilizing karyotype change in plants.Copyright 1993, 1999Academic Press PCR, telomere repeat sequence (TRS), in situ hybridization, comparative physical mapping, karyotype evolution, genome organization, Lathyrus sativus L., Vicia sativa L. subsp. nigra (L.) Ehrh., Vigna radiata (L.) R. Wilczek cv. Berken, Nicotiana sylvestris Speg et Comes, Haplopappus gracilis (Nutt.) A. Gray, Gibasis pulchella (Kunth) Rafin., Tradescantia commelinoides Schultes. fil., Hordeum vulgare L. cv. Sultan., Hordeum vulgare L. cv. Tuleen 346, Milium vernale Bieb., Paphiopedilum insigne (Wall.) Pfitz     

Cloning and Characterization of the Ribosomal Protein Genes in the spc Operon of a Prokaryotic Endosymbiont of the Pea Aphid, Acyrthosiphon kondoi

To correlate a prokaryotic endosymbiont in the pea aphid, Acyrthosiphonkondoi, with the endosymbionts in related aphid species as wellas with free-living bacteria and subcellular organelles, andto study the mode of its gene expression within aphid cells,we have cloned and characterized the genes encoding ribosomalproteins S3, L16, L29, S17, L14, L24, L5, S14, S8, L6, L18,S5, L30, L15 and secretion protein Y (Sec Y) from the S10 andspc ribosomal protein gene operons of this endosymbiont. Theorganization of these genes is identical to that in Escherichiacoli, and their nucleotide sequences are highly similar (87%identity) to the corresponding E. coli genes. They are muchless similar to the corresponding chloroplast and mitochondrialgenes. The guanine plus cytosine G+C content of the genes ofthe A. kondoi endosymbiont is much higher than those of theendosymbionts in related aphid species reported so far. It appearseither that the A. kondoi endosymbiont is derived from an ancestralbacterium different from those in other aphids or that its G+Ccontent increased in a relatively short time after the evolutionarydivergence of its host.     

Early Reproductive Ontogeny in Interspecific Crosses of Arachis hypogaea and Section Arachis Species

Wild Arachis species have been recognized as sources of resistanceto pests and pathogens that infect A. hypogaea L. and causesubstantial yield losses. However, utilization of these geneticresources for crop improvement has been difficult. This studywas conducted to (a) understand the processes of early embryogrowth and development in four Arachis species, two A. hypogaeacultivars and their hybrids and (b) identify parental compatibilitiesin reciprocal crosses of A. hypogaea. The results indicatedthat delayed fertilization beyond 24 h, coupled with slow proembryogrowth, leads to embryo abortion in many interspecific crosses.For example, in female A. cardenasii crosses, lack of or delayedfertilization leads to failure to obtain hybrids. When A. batizocoiwas used as a female parent, delayed fertilization and the inabilityof quiescent proembryos to resume growth after soil penetrationcaused abortion. Embryos of A. hypogaea x A. glandulifera crossesdeveloped normally during the first 21 d after fertilization,but then aborted at a later time. In this study, A. hypogaeawas always a better female parent than the wild Arachis species.Increasing the number of pollinations per cross, using the cultivatedspecies as the female parent, utilizing different A. hypogaeavarieties, and embryo rescue techniques are suggested to improvethe probability of obtaining interspecific hybrids in Arachis.Copyright1995, 1999 Academic Press Peanut, interspecific hybrids, Arachis, wild species, incompatibilities     

Plant Growth Analysis: Allometry, Growth and Interference in Orchardgrass and Timothy

A multiple regression procedure was used to evaluate allometricresponses to stand age and species population densities in monoculturesand mixtures of orchardgrass (Dactylis glomerata L., also knownas cocksfoot) and timothy (Phleum pratense L.). In each speciesthe allometry between shoot dry weight and either leaf areaor tiller number per plant was studied. Population density treatmentsaffected allometry by changing allometric exponents expressingthe ratio of relative growth rates of different plant characteristics.Allometric relationships changed as growth proceeded, and thetwo species differed in their allometric responses to treatments. Plant growth analysis, allometry, competition, Dactylis glomerata L., Phleum pratense L.     

On separation and identity of fern antheridiogens

Chromatographic studies show that the hormones controlling antheridiuminduction in the fern species Pteridium aquilinum (Polypodiaceae),Anemia phyllitidis and Lygodium japonicum (Schizaeaceae) aredifferent molecular entities. SCHRAUDOLF's report that gibberellic acid induces antheridiain A. phyllitidis and L. japonicum was confirmed. The activityspectrum of GAs towards species of different fern families stronglyresembles that of the native Anemia antheridiogen. However,the native antheridiogens of A. phyllitidis, and of Lygodiumjaponicum, are more species-selective in their action than isGA₃. Preliminary studies have yielded no conclusive evidenceon whether the native antheridiogens are gibberellins. (Received August 21, 1967; )     

A New Histochemical Method for Localization of the Site of Monoterpene Phenol Accumulation in Plant Secretory Structures

A new method is reported for the histochemical localizationof monoterpene phenols in essential oil secretory structures.The method was adapted from a spot test originally devised forin vitro detection of phenolic compounds in organic analyses.Plant subjects were the Lamiaceae species Thymus vulgaris L.,Oreganum vulgare L. and Mentha x piperita L., which accumulateessential oil in glandular trichomes. A reagent consisting of4-nitrosophenol in conc. H₂SO₄was applied to sample leaves ofeach species. A positive test for phenol was indicated by theproduction of coloured indophenols. Using this method, monoterpenephenols were identified in the trichomes of T. vulgaris(thymol)and O. vulgare(carvacrol), indicated by colour changes to redand green respectively. No phenol was detected in trichomesof M. x piperita. Results were confirmed by GC-MS analysis ofleaf volatile extracts from each species, and in vitro testswith thymol and carvacrol. The method could be used in fieldsurveys for rapid identification of potential medicinal plantsand bioactive compounds. Copyright 2001 Annals of Botany Company Histochemistry, secretory structures, glandular trichomes, Lamiaceae, Thymus vulgaris, Oreganum vulgare, Mentha x piperita, essential oil, aromatic monoterpenes     

Some Effects of Sucrose Concentration on Primordium Development in Excised Primary Roots

The effects of varying the amount of sucrose used to supplementthe culture medium maintaining the growth of excised roots ofPisum sativum L., Vicia faba L., Zea mays L. and Phaseolus vulgarisL., on the rates of primordium initiation and subsequent emergenceas lateral roots and on the duration of the interval betweenprimordium inception and emergence as a secondary root throughthe tissues of the primary have been investigated. Variation in the exogenous concentration of sucrose from 0.5to 8 per cent had little effect on the rate of primordium inceptionin Pisum and Vicia and the rates never reached the values obtainedfor the roots of the corresponding intact plants. Moreover,over the 6 day culture period lateral root emergence did notoccur in any of the excised roots of these two species. In contrast,each of the aspects of primordium development examined in theexcised roots of Zea and Phaseolus was markedly affected bythe amount of sucrose used to supplement the culture medium.In addition, in the presence of about 6 per cent sucrose, primordiumdevelopment in these cultured roots was very similar to thatin roots of the corresponding intact plants. The results indicate either that some factor necessary for primordiumdevelopment is present in adequate amounts in excised rootsof Zea and Phaseolus, but not in those of Pisum and Vicia, orthat the factors controlling such development are differentin the former and latter two species. Vicia faba L., Pisum sativum L., Zea mays L., Phaseolus vulgaris L., broad bean, garden pea, maize, dwarf bean, primordium development, sucrose concentration, cultured roots     

Detecting shape differences in species of the Littorina saxatilis complex by morphometric analysis

We investigated variation in shell size and shape of marinesnail species of the Littorina saxatilis complex (L. saxatilis,L. compressa and L. arcana) using geometric morphometric methods.These morphologically similar periwinkle species that are commonin the European intertidal have presented many problems fordiagnosis based on morphology alone. A discriminant analysisdemonstrated that geometric morphometrics is very efficientfor diagnosing individuals to species among sympatric populations.We successfully diagnosed an average of 96% of the specimens(with 85.7–100% correct diagnosis for specific comparisons).The diagnosis capability of this method is absolute at the populationlevel. This makes the technique potentially useful for the designof manipulative field or laboratory experiments. Moreover, ageometric-morphometric analysis was also accomplished in twosnail ecotypes (H and M) of L. saxatilis from rocky shores ofNE England which are apparently adapted to different degreesof wave exposure. We found that the H (exposed) ecotype hasa relatively rounded shell shape with a bigger aperture, whereasthe M (protected) ecotype has a smaller aperture. (Received 23 March 2006; accepted 25 January 2007)     

ESTERASE VARIABILITY IN THE GASTROPODS LITTORINA SAXATILIS (OLIVI) AND L. ARCANA ELLIS

The esterase system has been studied using isoelectric focusingin two closely related rough periwinkles, Littorina saxatilisand L. arcana, in an investigation of possible differences betweenthe two species at this level of discrimination. Collectionsof both species were obtained from Yorkshire, north Cornwalland south Devon; L. saxatilis was also obtained from sites insouth Cornwall (in and near the estuary of the Tamar), Dorsetand Scotland, where L. arcana was not present. There is considerablevariation both within and between sites which tends to maskany overall differences between the two species. However, ingeneral there is a much greater degree of heterogeneity withinsamples of L. saxatilis than within samples of L: arcana whenboth species are found together; this is reflected in the ShannonWiener diversity index for bands. Also the number of esterasebands is greater for L. saxatilis than for L. arcana at eachof the five sites where both occurred. A dendrogram derivedfrom the percentage occurrence of each band present in eachsample produced a reasonable degree of separation of the twospecies (Received 8 January 1988; accepted 24 February 1988)     

Effects of soil mechanical impedance on root and shoot growth of Lolium perenne L., Agrostis capillaris and Trifolium repens L.

A method was used for applying a uniform mechanical impedanceto plant roots using sand packed at different bulk densitieswith depth within each growth cylinder. In a growth experiment,replicate cylinders were packed with sand to give the followingmechanical impedances: 0.25 MPa penetration resistance (negligibleimpedance), 1.40 MPa (moderate impedance) and 2.30 MPa (severeimpedance). Seedlings of Lolium perenne L., Trifolium repensL. and Agrostis capillaris were grown for 23 d in each impedancetreatment and effects on both roots and shoots were studied.Severe mechanical impedance affected both root and shoot growthrates for all three species resulting in smaller leaves andshorter roots. For the grasses, the root-to-shoot ratio at harvestwas the same for all the treatments, but a delay in the initiationof both shoots and roots was observed in the severe mechanicalimpedance treatment. The results are discussed in relation tothe possibility that roots penetrating the impeding treatmentsmay have caused signalling that kept shoot and root growth insynchrony. Differences observed in the response to mechanicalimpedance of T. repens compared to the other two species maybe a function of differences in the physiology between mono-and dicotyledonous species. Key words: Mechanical impedance, Lolium perenne, Trifolium repens, roots, shoots     

Effects of Fluctuating Temperatures on Germination

Germination responses to alternating daily cycles involvingtransfers between different temperatures over the range 0 toc. 40?C were investigated in four species: Lycopus europaeusL., Clarkia unguiculata Lindl., Apium graveolens L. cv. GiantRed, and Silene dioica (L.) Clairv. Comparisons of the germination of these species revealed distinctivedifferences which could be related to particular features ofthe geographical regions or ecological habitats in which theyoccur naturally. The effects of fluctuating as opposed to constant temperaturesvaried from one species to another. L. europaeus depended almostabsolutely on fluctuating temperatures for germination. Germinationof S. dioica was greatly increased by fluctuating temperatures.Moderate increases occurred over a restricted temperature rangein A. graveolens cv. Giant Red and C. unguiculata was affectedin only minor ways. These results are discussed in relationto previous attempts to explain the mechanisms responsible forthe frequently beneficial effects of fluctuating temperatureson germination.     

Microsatellite cross-species amplification in the genus Littorina and detection of null alleles in Littorina saxatilis

Microsatellite DNA is widely used as population genetic marker,but the cost of using microsatellites is high, as they usuallyneed to be developed and optimized for each species separately.Cross-species amplification of microsatellites is thereforecommonly applied to bring down the cost, but it can also involvegenotyping errors. We studied cross-species amplification ofmicrosatellites in four species of the Atlantic group of Littorina(Neritrema): L. saxatilis (Olivi, 1792), L. obtusata (Linnaeus,1758), L. fabalis (Turton, 1825) and L. arcana Hannaford Ellis,1978 to investigate whether markers originally developed fora more distantly related Pacific species [L. subrotundata (Carpenter,1864)] suffered from more amplification problems than markersdeveloped for one of the species in the Atlantic group (L. saxatilis).We also compared variation in amplification success among thespecies and among different regions in the NE Atlantic. Approximatelyhalf of the 12 primers developed for L. subrotundata and theseven primers developed for L. saxatilis were successfully amplifiedin other species of the subgenus. The success was dependenton phylogenetic distance among species within the subgenus.On the other hand, the variation in performance of the locibetween geographically remote populations of the same specieswas as high as variation among the species. In earlier studiesstatistical analyses indicated that several loci showed a heterozygotedeficiency due to null alleles. The presence of null alleleswas confirmed by a segregation analysis of the microsatelliteloci in eight half-sib families of L. saxatilis. (Received 2 April 2007; accepted 19 November 2007)     

Activities of Carboxylation Enzymes in Freshwater Macrophytes

Fifteen species of freshwater macrophytes, mainly from cool,temperate waters, were assayed for ribulose bisphosphate carboxylase-oxygenase(RuBPCase) and phosphoenolpyruvate carboxylase (PEPCase) activities.In extracts from all the species RuBPCase was the most activecarboxylation enzyme, and the RuBPCase/PEPCase ratio was atleast 2·0, even for the submersed species Isoetes lacustrisL. and Littorella unifiora (L.) Aschers. which have been reportedto show Crassulacean Acid Metabolism (CAM) activity. The PEPCaseactivity in I.lacustris was lower than that found in some non-CAM-likespecies. In this respect, I.lacustris and L unifiora differfrom most terrestrial CAM plants. However, these two species,along with Potamogeton praelongus Wulf. and Juncus bulbosusvar.fluitans L., had the lowest RuBPCASE/PEPCase ratios, lowerthan found in terrestrial C₃ species; suggesting that the potentialfor substantial photosynthetic metabolism of C₄ acids existsin some temperate, submersed plants. In the three amphibiousspecies (Potamogeton polygonifolius Pourr., Mentha aquaticaL., and Hippuris vulgaris L.) examined, the aerial leaves exhibitedhigher RuBPCase activities than the submersed leaves. Key words: Ribulose bisphosphate carboxylase-oxygenase, phosphoenolpruvate carboxylase, freshwater macrophytes     

Predicting the Growth Interactions between Plants in Mixed Species Stands using a Simple Mechanistic Model

The Conductance model is a simple mechanistic model used topredict the growth of species in monoculture or mixtures fromparameter values derived from plants grown in isolation. Incontrast to many mechanistic models that require extensive parameterization,the Conductance model is able to capture the growth of a broadrange of species using a few simplified assumptions regardingplant growth and easily derived species-specific parameter values.We examine the assumptions within the Conductance model thattotal leaf area per plant is proportional to total plant weight,and that an isolated plant has a projected crown zone area thatis proportional to the 2/3 power of its weight. Power ratherthan linear relations were found between weight and leaf areafor Brassica oleracea, Daucus carota, Matricaria inodora, Solanumnigrum,Stellaria media , Trifolium repens and Veronica persica.For all seven species, the value of the power was less thanunity. All species also exhibited a power relation between crownzone area and weight, with the slope of this relation beingless than 2/3 for B. oleracea, D. carota and S. media. Althoughmorphology type accounted for some of the variation in the parametervalues relating to light interception, there were considerabledifferences between species within upright or prostrate foliagespecies groups. The Conductance model was used to predict yieldsof B. oleracea, S. nigrum and V. persica grown in both monocultureand binary weed-crop mixtures over a range of temporal and spatialscales. After calibrating the model to non-competing plants,the model was used to predict growth of the weed and crop speciesin contrasting densities and stand types. In some crop-weedcombinations, predicted crop and weed weights were within 17%of observed values, with no systematic deviations. In others,systematic and large deviations occurred.Copyright 2001 Annalsof Botany Company Brassica oleracea L., Daucus carota L., Matricaria inodora L., Solanum nigrum L.,Stellaria media L., Trifolium repens L., Veronica persica L., competition, growth, leaf area, crown zone area, light, shoot morphology, canopy architecture     

Comparative Requirement for Endogenous Ethylene during Seed Germination

Requirement for endogenous ethylene during seed germinationof the following ten species was determined: Lycopersicon esculentumMill, (tomato), Allium cepa L. (onion), Avena fatua L., dormantpure line AN-51 (wild oats), Cucumis sativus L. (cucumber),Sinapis arvensis L. (wild mustard), Tagetes erecta L. (marigold),Raphanus sativus L. (radish), Triticum aeslivum L. (wheat),Catharanthus roseus L. (periwinkle), and Phaseolus aureus L(mung bean). Experiments were done under controlled conditionssuited for the germination of each species. Criteria used todetermine the need for endogenous ethylene were: (i) temporalrelationship between ethylene production and seed germination;(ii) parallel inhibition of ethylene synthesis and seed germinationby L-     

PATTERNS OF REPRODUCTION IN FOUR LITTORINA SPECIES

The reproductive periodicities of four Iittorinids, Littorinaneglecta, L. nigrolineata, L. saxatilis and L. arcana were examinedin sympatric populations at Porth Swtan, Anglesey, North Wales.Three species, L. neglecta, L. nigrolineata and L. arcana, werefound to show marked reproductive periodicity. L. saxatilisshowed no periodicity and large numbers of animals were foundin breeding condition throughout the year. The oviparous speciesL. nigrolineata and L. arcana, came into reproductive conditionin the late summer or early autumn, L. nigrolineata in Augustand L. arcana in September, and their populations at Porth Swtanhad few individuals in breeding condition in the late springand early summer. L. neglecta, however, showed a periodicitywith high numbers of breeding animals throughout the springand summer and very low numbers in the autumn. For L. neglectathe basis of reproductive periodicity is shown to be the synchronizedannual life cycle of individuals of this species. It is thereforebelieved to differ from the other three species in which individualsare longer-lived and are supposed to undergo seasonal periodsof reproductive inactivity. (Received 2 March 1982;     

Comparative Embryo Sac Morphology at Anthesis of Cultivated and Wild Species of Arachis

Introgression of germplasm from wild to cultivated species ofArachis is severely impeded because abortion processes oftenoccur as a prepeg-, peg-(gynophore), or postpeg-elongation event.A comparative study of embryo sac morphology at anthesis wasundertaken to determine if observable differences were presentthat could possibly explain abortion prior to peg tip swellingfollowing soil penetration. Two wild Arachis species (A. duranensisand A. stenosperma) plus A. hypogaea cultivars NC 6 and Argentinewere studied. Differences in starch grain concentration andcytoplasmic stranding organization were observed between A.hypogaea cultivars and the wild Arachis species. These differencesprobably have a significant impact on energy availability atsyngamy and the subsequent early cell division of the embryo.An improper energy balance could contribute to the onset ofabortion in interspecific hybrids. Modification in egg apparatusorganization among all species was also observed which may accountfor low percentages of seed recovery resulting from interspecifichybridization attempts. Embryo sac morphology, interspecific hybridization, Arachis hypogaea L., Arachis species, light microscopy, scanning electron microscopy, embryo abortion, fertilization incompatibility, peanuts, groundnut     

AUTOTOMY IN ARIONID AND LIMACID SLUGS

The occurrence of autotomy was investigated in five terrestrialslug species. Half of the Dcroceras reticulatum and 80 per centof the Limax tenellus slugs which were stimulated mechanicallyin the tail, autotomized the tail. Anon fasciatus, Anon subfuscusand Limax cinereoniger did not show any signs of being ableto autotomize. The autotomized tail of D. rcticulatum and L.tenellus was small compared to the total body weight and alsoto the weight of many predaceous beetles. D. reticulatum andL. tenellus escaped in a few seconds after the beginning ofmechanical stimulation; the reaction time was significantlyshorter than that used by species which did not autotomize theirtail. Comparison between A. fasciatus and D. reticulatum alsoshowed that D. reticulatum sought for refuges significantlymore effectively than A. fasciatus. The exposure of D. reticulatumto the beetle Ptero-stichus mger indicated that autotomy canstop a beetle long enough to let the slug escape. It seems thatautotomy has evolved more frequently in those species whichrely to a great extent on escaping and hiding when defendingthemselves, than in species whose physiology and/or environmentdo not enable them to hide quickly after an attack. (Received 18 February 1993; accepted 19 March 1993)     

Short- and Long-Term Inhibition of Respiratory Carbon Dioxide Efflux by Elevated Carbon Dioxide

Dark carbon dioxide efflux rates of recently fully expandedleaves and whole plants of Amaranthus hypochondriacus L., Glycinemax (L.) Merr., and Lycopersicon esculentum Mill. grown in controlledenvironments at 35 and 70 Pa carbon dioxide pressure were measuredat 35 and 70 Pa carbon dioxide pressure. Harvest data and whole-plant24-h carbon dioxide exchange were used to determine relativegrowth rates, net assimilation rates, leaf area ratios, andthe ratio of respiration to photosynthesis under the growthconditions. Biomass at a given time after planting was greaterat the higher carbon dioxide pressure in G. max and L. esculentum,but not the C₄ species, A. hypochondriacus. Relative growthrates for the same range of masses were not different betweencarbon dioxide treatments in the two C₃ species, because highernet assimilation rates at the higher carbon dioxide pressurewere offset by lower leaf area ratios. Whole plant carbon dioxideefflux rates per unit of mass were lower in plants grown andmeasured at the higher carbon dioxide pressure in both G. maxand L. esculentum, and were also smaller in relation to daytimenet carbon dioxide influx. Short-term responses of respirationrate to carbon dioxide pressure were found in all species, withcarbon dioxide efflux rates of leaves and whole plants lowerwhen measured at higher carbon dioxide pressure in almost allcases. Amaranthus hypochondriacus L., Glycine max L. Merr., Lycopersicon esculentum Mill., soybean, tomato, carbon dioxide, respiration, growth     

BARNACLE-DWELLING EGOTYPES OF THREE BRITISH LITTORINA SPECIES AND THE STATUS OF LITTORINA NEGLECTA BEAN

On the basis of collections from SW Wales and W Ireland it isshown that small (<5 mm) black and/or white Littorina occurringin the barnacle zone on exposed shores, of the L. neglecta shelltype, comprise three species. From their reproductive anatomythese correspond to L. saxatilis, L. arcana and L. nigrolineata,and are interpreted as analogous barnacle-dwelling ecotypesof these species. This adds to the evidence that L. neglectais not a distinct species, but an ecotype of L. saxatilis. (Received 1 June 1992; accepted 23 June 1992)