The Identification of the Seeds and Achenes of the British Plantaginaceae

The morphology of seeds and achenes of the British members ofthe Plantaginaceae has been examined. Keys to the identificationof seeds in the genera Plantago and Littorella are presented.Quantitative data on size and weight, as well as informationabout shape, colour and surface features of the seeds are givenfor: Plantago major L., P. media L., P. lanceolata L., P. martimaL., P. coronopus L., P. indica L., P. sempervirens Crantz, andLittorella uniflora (L.) Aschers. A representative sample ofeach seed is illustrated.     

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     

Germination and Early Growth of Plants Studied Using Neutron Radiography

Seed swelling, germination, root extension, lateral root initiationand shoot growth were studied in soils of different water contents,using non-destructive, serial neutron radiography. Seeds fromthree varieties of soya beans (Glycine max L.) and one varietyeach of maize (Zea mays L.) and vetch (Vicia sativa L.) wereused. The seeds germinated when they had increased in size bya certain amount, if germination is taken as the time when theradicle first appears. The rate at which roots and shoots extendalso depend on soil water content. Glycine max L., Vicia sativa L., Zea mays L., Soya bean vetch, maize, seed germination, root extension, lateral root initiation, neutron radiography     

Desiccation and Freezing Sensitivity in Recalcitrant Seeds of Tea, Cocoa and Jackfruit

Investigations were undertaken on the desiccation and freezingsensitivity of recalcitrant seeds of three species: tea [Camelliasinensis (L.) O. Kuntze], cocoa (Theobroma cacao L.) and jackfruit(Artocarpus heterophyllus Lamk.). All species showed changesin the physiological characteristics, desiccation and freezingsensitivity of both the seed and the embryonic axes with increasingseed maturity. Fully mature seeds of tea, cocoa and jackfruitsurvived desiccation to 24, 35 and 31% moisture content, respectively,but at these moisture levels seeds were not able to toleratefreezing in liquid nitrogen (-196 °C). Some survival ofcryopreservation was, however, achieved for excised embryonicaxes of partially and fully-mature tea and jackfruit seeds afterdrying to 14% moisture content; cocoa axes were totally freezingsensitive at all three stages of physiological maturity studied.Biochemical investigations on fully mature axes after desiccationand freezing showed that the decline in viability with moisturelevel was associated with increased leachate conductivity, lipidperoxidation products and/or soluble carbohydrates. Evidencefor disruption of cell membranes during desiccation and freezingwas supported by ultrastructural studies.Copyright 1995, 1999Academic Press Camellia sinensis (L.) O. Kuntze, Theobroma cacao L., Artocarpus heterophyllus Lamk., Phaseolus vulgaris L., tea, cocoa, jackfruit, french bean, seeds, embryonic axes, desiccation, freezing, cryopreservation     

2-Trans-Abscisic Acid Biosynthesis and Metabolism of ABA-Aldehyde and Xanthoxin in Wild Type and the aba Mutant of Arabidopsis thaliana

Abscisic acid (ABA) and 2-trans-ABA (t-ABA) biosynthesis werestudied in wild type Landsberg erecta and the three allelicaba mutants of Arabidopsis thaliana (L.) Heynh., which are impairedin epoxy-carotenoid biosynthesis. Labelling experiments with¹⁸O₂and mass spectrometric analysis of [¹⁸O]ABA and its catabolitesABA-glucose ester (ABA-GE) and phaseic acid (PA), and t- ABAand t-ABA-GE, showed that t-ABA biosynthesis was less affectedthan ABA biosynthesis by mutations at the ABA locus. The aba-4allele caused the most severe impairment of ABA biosynthesiscompared with the other two mutant alleles aba-1 and aba-3,yet aba-4 plants synthesized as much t-ABA as wild type Landsbergerecta plants. Feeding experiments with RS- [²H₆]ABA-aldehydeisomers and unlabelled xanthoxin isomers suggest that t-xanthoxinand t-ABA-aldehyde are precursors to ABA and t-ABA in Arabidopsis Key words: ABA-alcohol, ABA-aldehyde, ABA-glucose ester, ¹⁸O₂ labelling, phaseic acid     

One-Leaf Cuttings as a Model to Study Second Growth in the Potato (Solanum tuberosum) Plant

Second growth is an important physiological disorder of thepotato (Solanum tuberosum L.) plant. A model system to studysecond growth was developed using one-leaf cuttings. Photoperiod,temperature, decapitation and leaf removal treatments were carriedout on the plants from which the cuttings were taken and onthe cuttings themselves. Tuberized, one-leaf cuttings takenfrom moderately-induced plants and exposed to 35 °C afterleaf removal showed 95% second growth within 10 d after treatmentinitiation. Conditions that promoted second growth also reducedstarch and dry-matter content, even in tubers that did not developsecond growth. Cuttings, second growth, potato, Solanum tuberosum L, cv, Bintje, Solanum tuberosum L. cv., Désirée, Solanum tuberosum L. cv., Russet Burbank, tuberization, starch content, dry-matter, heat, photoperiod, decapitation, leaf removal     

Seed Development in a Shrunken Endosperm Barley Mutant

Seg8 is one of eight barley (Hordeum vulgare L.) mutants whoseendosperm development is affected by the maternal plant genotype.This study was initiated to determine the nature and onset ofabnormal development to provide a basis for further studiesaimed at understanding the mechanism of genetic control. Seeddevelopment and synthesis and accumulation of reserve substanceswere compared between seg8 and its normal counterpart, cv. Klages.Light microscopic examination showed that the mutant phenotypeappeared as early as 4 d after anthesis (DAA), and seg8 graindry weight was significantly lower than cv. Klages by 8 DAA.Grain cell number was significantly lower in seg8 by 8 DAA,indicating an early termination of cell division. The mutanthad a lower starch concentration and higher sucrose concentration,also evident at 8 DAA. Rates of [¹⁴C]sucrose incorporation intostarch in excised half seeds were similar in both genotypesat 2 and 4 DAA, but at 8 and 12 DAA seg8 had a lower rate. Totalprotein concentration was not significantly different betweenthe two genotypes throughout endosperm development. These resultsindicate that the mutation affects cell division and starchaccumulation prior to 8 DAA. It is not known if the reductionin starch biosynthesis and accumulation results from a reducedcapacity for starch or a defect in starch biosynthesis. Hordeum vulgare L., barley, shrunken endosperm mutant, endosperm development, starch, protein, endosperm cell number     

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.     

Production of a Fungistat and the Role of Fungi during Germination of Digitalis purpurea L.cv. Gloxiniaflora Seeds

The seed coats of Digitalis purpurea L. cv. Gloxiniaflora werecultured for indigenous fungi. Alternaria alternata (Fries)was identified as the sole fungus on seeds freshly harvestedfrom unopened capsules, whereas A. alternata, Rhizopus arrhizus(Fischer), Penicillium sp. and other fungi appeared on storedseeds. The appearance of fungi in seed cultures was seasonal,being more frequent in winter and early spring than in summerand autumn. Alternaria grew well on autoclaved seeds, on dehiscentseed coats, or on seed coats separated from the embryos of ungerminatedseeds. Rhizopus did not grow on these but grew weakly on theculture medium from viable seeds. A. alternata appears to functionas a degradation agent for the seed coat subsequent to germination.Neither fungus was found to be essential to germination of Digitalisseeds. Bioassay of the culture medium from germinating seedsshowed that a fungistat effective against both Alternaria andRhizopus is produced coincident with germination. Based on chromatographicanalysis, the fungistat appears to be a cardenolide. Alternaria alternata (Fries), cardenolides, Digitalis purpurea L. cv, Gloxiniaflora, fungistats, germination, Rhizopus arrhizus (Fischer)     

The Dry Storage of Citrus Seeds

The survival of seeds of lemon (Citrus limon L.), lime [C. arantifolia(Christm.) Swing.] and sour orange (C. aurantium L.) was examinedunder a wide range of constant moisture contents and temperatures.Seed longevity was increased by decreasing the moisture contentand temperature of the storage environment. Maximum viabilitywas maintained in the combination of storage conditions includingthe lowest moisture content (5 per cent) and lowest temperature(–20 °C) investigated. The practicality of dry storageof citrus seed for genetic conservation is discussed. Citrus limon L., lemon, Citrus aurantifolia (Christm.), Swing, lime, Citrus aurantium L., sour orange, dry storage, moisture content, temperature, seed viability, seed longevity     

Density Studies on Lupins. II. Components of Seed Yield

Components of seed yield of cv. Ultra (Lupinus albus L.) andcv. Unicrop (L. angustifolius L.) were measured when grown atthree densities. The low density (10 plants m^–2) Unicropyield (34 g seed per plant) was 1.8 times that of Ultra as ithad more branches, pods and seeds per pod. Ultra seeds (310mg per seed) were heavier than Unicrop seeds (180 mg). The branchingpattern of Ultra was less dependent on plant density, henceat 93 plants m^–2 it gave a higher per plant yield (7.4vs 6.4 g) than Unicrop at lower densities (83 plants m^–2).Density had most influence on pod formation and only small effectson seeds per pod and seed weight. Yield components on the main-steminflorescence were influenced less by density than componentson branch inflorescences. Later formed, higher order generationsof inflorescences were most affected by increased inter- andintra-plant competition. Pod numbers on the main-stem were similarfor both species. Pods formed at higher flower nodes in Unicrop,but the lower flower nodes were less fertile than those in Ultra.Node position of flowers had no influence on seed set in main-stemUnicrop pods, but pods from higher nodes in Ultra formed fewerseeds. Seed weights in Unicrop were similar among main-stemnodes but in Ultra seed weights tended to increase at highernodes. Lupinus spp, lupins, seed yield, planting density     

Legume Nodule Morphology with Regard to Oxygen Diffusion and Nitrogen Fixation

Soybean (Gtycine max (L.) Merr. cv. Fiskeby V), white clover(Trifolium repens L. cv Blanca) and lucerne (Medicago sativaL.cv. Europe) nodules grown in fluid culture of Perlite wereexamined by cryo-scanning electron microscopy. The surfacesof all three species consisted of loosely packed cortical cells,collapsed areas covering intact cells and in soybean, troughswhich lacked the layers of loosely packed cells and were coveredby an amorphous matrix. The superficial cortical cells werehydrophobic and their surfaces were covered by a solvent-extractablestippling. This stippling was absent from the surfaces of underlyingcells. Air-filled intercellular spaces in fractured noduleswere seen throughout the cross-section. Nitrogen fixation, intercellular pathways, hydrophobicity, oxygen diffusion, cryo-SEM, soybean, Glycine max (L.) Merr. cv. Fiskeby V, clover, Trifolium repens L. cv. Blanca, lucerne, Medicago saliva L. cv. Europe.     

CORRIGENDUM

F. W. Andrews: A Study of Nut Grass (Cyperus rotundus L.) inthe Cotton Soil of the Gezira. I. The Maintenance of Life inthe Tuber. To the literature cited should be added: SMITH, E. V., and MAYTON, E. L., 1937: Nut Grass EradicationStudies. II. The Eradication of Nut Grass (Cyperus rotundusL.) by Certain Tillage Treatments. Jour. Amer. Soc. Agron.,xxx. 18.     

Interrelationship between Meristematic Regions of Developing Inflorescences of Four Cereal Species

A cultivar from each of four cereal species (Avena sativa L.,cv. Swan, Hordeum vulgare, L., cv. Clipper, Triticum aestivumL., cv. Gabo, and Secale cereale L., cv. South Australian Rye)was grown in controlled environment chambers in a 10-h photoperiod(short days) or 10-h photoperiod supplemented with a 6-h extensionby incandescent light. The developmental morphology of the inflorescenceswas followed to ascertain whether there were any common developmentalinterrelationships between the species. Inflorescence internodeelongation was initiated when the floret initial first appeared,irrespective of whether it occurred on the most advanced lateralspikelet or on the terminal spikelet of the rachis. The glumes(infertile bracts) of the terminal spikelet of the rachis wereinitiated when the first second-order inflorescence branch appeared,irrespective of whether the second-order inflorescence branchwas a floret initial or a lateral spikelet, as in Triticum sp.,or an inflorescence (panicle) branch, as in Avena sp. Cessationof the activity of the apical meristem, as measured by primordiumformation, was not correlated with any particular stage of floraldevelopment but appeared to be due to a lack of nutrients causedby an increasing competitiveness for the available nutrientsfrom the developing spikelets which are situated closer to thevascular system than the apical meristem.     

Regulation of Mo-cofactor, NADH- and NAD(P)H-specific nitrate reductase activities in the wild type and two nar-mutant lines of barley (Hordeum vulgare L.)

Seedlings of three genotypes of barley, Hordeum vulgare L.,cv. Winer, were grown in nutrient solutions for 12 d: (a) Wt,the wild type; (b) Chlo19 and (c) Chlo29, two nitrate reductase(NR) deficient nar-mutants. Nar-mutant plants grown in nitratedeveloped about 5–24% of NADH-NR (EC 1.6.6.1 [EC] .) activitylevel characteristic of the Wt. The NR in vitro assays in whichNADH or NADPH were used as electron donors showed that the twomutant lines contained a mixture of NADH-specific and NAD(P)H-bispecific(EC 1.6.6.2 [EC] .) NRs. Chlo19 had a very low level of MoCo activityas compared to Chlo29 and Wt. Chlo19 appeared to be mutatedin a MoCo gene rather than in the genes coding for the nitrateNR apoenzyme. NAD(P)H-NR was found in the shoots and roots of both mutantsbut only in the roots of Wt. Several aspects of the regulationof NADH and NAD(P)H specific NRs in plants of the barley cv.Winer genotypes are discussed. MoCo was a strong limiting factorfor NR biosynthesis in nitrate-fed plants of Chlo19, but lesslimited in N-starved and ammonium-fed plants. Biomass productionby the three genotypes was similar during first 12 d after germination,regardless of the level of NR detected in vitro. Mutant plantsmay be able to supply the nitrogen required for growth withonly 5–24% of the NR level of the WT. Key words: Hordeum vulgare, mutants, nitrate, nitrate reductase, molybdenum cofactor     

Distribution and Accumulation of Thiophenes in Plants and Calli of Different Tagetes Species

The diversity of thiophenes (natural biocides) and the differencesbetween the concentrations of these compounds in the leavesand roots of Tagetes erecta L., T. patula L. cv. Nana furia,and T. minuta L. (marigolds) indicated the presence of at leasttwo different sites of accumulation: leaves and roots. Leafexplants of Tagetes, however, are used by preference to obtaincallus cultures. Once subcultured, secondary (C₂) calli of T.patula obtained from leaves of 4 to 7-week-old plants, containedhigher amounts of accumulated thiophenes (up to 80% of the amountsin the leaves) than original (C₁) or twice subcultured calli(C₃). The concentrations of thiophenes in C₂ calli of T. minutawere about half those of C₁ calli, while the concentrationsof thiophenes of C₁ calli amounted to 1-2% of the leaf values.Most of the C₃ calli of T. minuta did not contain thiophenesat all. Although C₁ calli of T. erecta also contained considerableamounts of thiophenes, the C₂ calli died, most likely owingto high levels of accumulated polyphenolic compounds. The combinationof species effects and the physiological state of plants andcalli provides adequate information to decide whether Tagetescalli are able to produce thiophenes or not. It is concludedthat the ability to produce thiophenes does not depend on theorgan used, but on the genetic information present in the species,and on the physiological state of plants and calli, particularlytheir age. Key words: Callus, explant selection, Tagetes erecta, Tagetes minuta, Tagetes patula, thiophenes     

Direct Organogenesis and Plant Regeneration in Preconditioned Tissue Cultures of Lathyrus cicera L., L. ochrus (L.)DC. and L. sativus L.

This study demonstrates the importance of preconditioning ofsource tissue in regeneration of multiple shoot buds from severalspecies of Lathyrus. Preconditioned multiple shoots of Lathyruscicera L., L. ochrus (L.) DC. and L. sativus L. were obtainedby germinating seeds on Murashige and Skoog (MS) medium containing50 µM N⁵-benzylaminopurine (BAP) for 2 to 3 weeks. Multipleshoot bud formation occurred when epicotyl explants of preconditionedshoots were cultured on MS medium containing 5–50 µMBAP. No shoot regeneration was observed from epicotyl explantswhich were obtained from non-preconditioned shoots. Shoot budswere formed directly on explants without an intervening callusphase after 2 to 3 weeks of culture. Regenerated shoot budsformed healthy shoots which developed prolific and strong rootswhen transferred to MS medium supplemented with 2.5 µMnaphthaleneacetic acid (NAA). Lathyrus cicera L., L. ochrus (L.) DC., Ochrus Vetch, L. sativus L., Lathyrus pea, de novo differentiation, epicotyl, preconditioning with BAP     

The Interrelationship of Canavanine and Urease in Seeds of the Lotoideae

Seeds of 29 species of canavanine-synthesizing legumes wereassayed for their urease and canavanine production. All of theexamined species possess detectable urease activity. In general,the leguininous seeds richest in urease also had the most canavanine. The urease content of the jack bean seed, Canavalia ensiformis(L.) DC., is formidable and disproportionally greater than thequantity of stored canavanine. The massive urease content ofthe seed cannot be rationalized by the magnitude of the canavaninepool. Analysis of eight species of Mucuna demonstrated that canavanineis not stored in the seeds of these plants. Mucuna species donot appear to be unique in having seeds that do not concurrentlyproduce urease and canavanine.     

Germination Inhibitors in Fruit Extracts of Red Beet (Beta vulgaris cv. rubra

Germination inhibitors in methanol and water extracts of redbeet fruits (Beta vulgaris cv. rubra L.) have been studied usinglettuce and red beet seed germination as bioassays. The methanolextracts contained substances which inhibited lettuce seed germination,but had no effect on the germination of red beet seeds. Germinationof both lettuce seeds and of water-leached or sulphuric acid-treatedred beet seed balls were inhibited by the water extracts. Theconcentrations of ammonia, ferulic acid, and oxalate in thewater extracts were much lower than required for inhibitionof red beet seed germination. The water extracts contained,however, large amounts of inorganic ions, and the results clearlydemonstrated that the inhibitory effect of the water extractson red beet seed germination was mainly due to the content ofsuch inorganic ions.     

Anaesthetic Enhancement of Echinochloa crus-galli (L.) Beauv. Seed Germination: Possible Membrane Involvement

Taylorson, R. B. 1988. Anaesthetic enhancement of Echinochloacrus-galli (L.) Beauv. seed germination: possible membrane involvement.—J.exp. Bot 39: 50–58. Dormant E. crus-galli seeds can be stimulated to germinate bycontact with solutions of several anaesthetic-like substances.The order of activity was n-pentanol > benzyl alcohol >n-butanol > n-propanol > ethanol. 2-propanol is nearlyinactive. The relative activity of the substances as germinationstimulants is closely related to their membrane-buffer partitioncoefficients in a manner similar to their effectiveness as anaestheticsin animals. Thus, n-pentanol is a more active stimulant of germinationthan ethanol and its increased effectiveness is correlated witha higher membrane-buffer partition coefficient Similarly, ananaesthetic that stimulated germination (n-propanol) causedgreater leakage of electrolytes, U.V. absorbing substances andamino acids from E. crus-galli seeds than a substance that wasnot active as a germination stimulant (2-propanol). In animals,action of anaesthetics can be prevented by application of externalpressure, an argument for membrane action. Action of n-propanolin stimulating germination can be similarly prevented by pressurein E. crus-galli seeds. The several lines of evidence supporta membrane action for anaesthetic-like substances in seeds and,accordingly, a membrane site as the locus of seed dormancy. Key words: Anaesthetics, germination, membranes