Development of embryo and endosperm inEragrostis unioloides (Poaceae)

The embryo development conforms to the Asterad type or Megarchetype II. A single cotyledon called scutellum is derived from the entire tierl. The shoot apex, lateral in position, and the coleoptile, originate from the tierl. The remaining parts of the mature embryo are derived from the tiers situated belowl. The short suspensor takes its origin from the lowermost tierp. The endospermab initio is free nuclear in development. It becomes cellular first around the proembryo. Physiologically, the ripe endosperm represents a dead tissue.     

Callose in the walls of mature embryo sac ofTorenia fournieri

Summary During the course of a fluorescence microscopic investigation on the extra-ovular micropylar portion of the embryo sacs ofTorenia fournieri Lind. (Scrophulariaceae) a callosic wall was found which surrounded it almost completely until the time of anthesis. In addition, the walls of young synergids and the filiform apparatus also showed callosic fluorescence. Treatments with PAS reaction revealed a PAS-positive substance filling up the locular cavity. Our attempts to induce fluorochromasia by employing fluorescein diacetate failed, indicating the low permeability of the callosic wall around the embryo sac. It is assumed that the callose wall around the embryo sac isolates the latter from the contents of the locular cavity whereas the callose in the synergid walls may represent an intermediate stage in the maturation of these walls; the filiform apparatus is mainly composed of callose.     

Distinctions betweenHordeum bulbosum andH. murinum s.l. in seed and herbarium collections

It is sometimes necessary to identify eitherH. bulbosum orH. murinum on the basis of the inflorescence or seeds alone. The majority of taxonomic keys use the presence of swollen basal culms for the former against the annual habit for the latter. Confusion is due to similarities in inflorescences and spikelet morphology. Lodicules which always persist and are present beside the fruit in a mature caryopsis, and other characters such as the awns of the lemmas of the lateral spikelets enable conclusive distinction.     

Relationships between five species ofLolium (Poaceae)

Morphological analysis and electrophoresis of seed proteins of fiveLolium species disclosed that they form two distinct groups corresponding to those recognized from compatibility data.Lolium temulentum andL. remotum of the self-pollinated group were shown to be distinct but closely related species. Morphological intergradation and high similarities between protein profiles ofL. perenne, L. multiflorum andL. rigidum (cross-pollinated species) suggest little genetic differentiation between these taxa. This implies that treatment at the infraspecific level might better accomodate the data.     

Species relationships and genetic variation in the diploid wheats (Triticum,Aegilops) as revealed by starch gel electrophoresis

Twenty enzyme loci were examined in the diploid species ofTriticum andAegilops for allelic variation by starch gel electrophoresis. SectionSitopsis, including the five species,Ae. speltoides, Ae. lingissima, Ae. sharonensis, Ae. bicornis andAe. searsii form a close subgroup withAe. speltoides slightly removed from the others.T. monococcum s. lat., was found to be closest to the species of theSitopsis group.Ae. comosa, Ae. umbellulata andAe. uniaristata form a second subgroup withAe. caudata most closely related to these species.Ae. squarrosa appears almost equally related to all of the species, showing no special affinity for any one species group. Nineteen out of twenty loci examined were polymorphic with a mean of 6.7 alleles per locus. Species could be, for most loci, characterized by the presence of predominant alleles. A conspicious genetic characteristic ofTriticum-Aegilops is the sharing of these predominant alleles between species. Within species variation is characterized by a diffuse distribution of secondary alleles.     

Genetic diversity and relationships between nine species of bamboo in Sri Lanka, using Random Amplified Polymorphic DNA

Random Amplified Polymorphic DNA (RAPD) showed a high degree of polymorphism in nine species of bamboo, Dendrocalamus giganteus Wall ex Munro, D. asper Becker ex K. Heyn, D. longispathus (Kurz) Kurz, Bambusa vulgaris `Striata', B. ventricosa, B. bambos (L.) A. Voss, B. atra Lindley, Gigantochloa atroviolacea Wdjaja and Arundinaria hindsii, in Sri Lanka. The lowest mean genetic distance of 0.143 was between B. vulgaris and B. ventricosa. They could however be distinguished morphologically. The genetic distances separating D. longispathus from D. giganteus and D. asper were both greater than that between the latter two species, which had a value of 0.313. Although the genetic distances between Bambusa vulgaris, B. ventricosa and B. bambos were relatively small, B. atra separated from them at greater distances. The smaller genetic distances between G. atroviolacea and B. vulgaris, B. ventricosa and B. bambos indicated that G. atroviolacea had a closer affinity to these three Bambusa species than B. atra. A. hindsii with the greatest genetic distances from all other species in the study, was not related to any of them. RAPD analysis was useful in determining the genetic diversity and relationships and in detecting problematic generic assignments.     

Fruit dispersal and trypanocarpy in brazilian cerrado grasses

28 grass species from one hectare of cerrado vegetation in Botucatu, State of São Paulo, were studied with regard to the morphology and dispersal of their fruits. 13 species have dispersal units with smooth surfaces which are predominantly dispersed by big herbivorous mammals or birds which swallow them together with their food, e.g., during grazing (accidental endozoochory). On the other hand, smaller animals, including birds, also feed directly on the grains; some of them may escape trituration and digestion or may be even stored (synzoochory). 11 species are principally epizoochorous: 8 of these are ± exclusively adapted to epizoochory, adhering to the animals by scabrid awns or sharply pointed calli, while the rest behave as epizoochores and anemochores. 4 other species are predominantly anemochorous with their dispersal units bearing soft hairs, sometimes together with very small scabrid awns; in a wet state they also can adhere to animals (occasional epizoochory). Beside this, most grass fruits can behave as passive ballists, as passing animals, wind and rain may cause their dispersal units to fall to the ground (passive autochory). — Among the 28 species, 12 have dispersal units which are awned. In 7 of them the awns are spirally twisted; the base of the dispersal unit runs out into a sharply pointed callus and has harpoone-like hairs. These awns show hygroscopical movements which may lead to a drilling of the basal part of the dispersal unit into the sandy cerrado soil. This trypanocarpy is important for establishment but without function for dispersal.     

Maize embryo germination

The cell-cycle progression of germinating embryos of maize (Zea mays L.) was studied from 0 to 72 h after the start of imbibition using DNA flow cytometry on isolated nuclei, and analyses of thymidine kinase activity, histone biosynthesis and levels of proliferating cell nulcear antigen (PCNA). At the start of germination, 75% of the cells were in G1, but this population had decreased to 25% by 72 h. The concomitant increase of cells in S-phase did not occur continuously, but stepwise, indicating that during germination most of the cells enter S-phase as a partially synchronized population. Within the initial 60 h of embryo germination the cells passed through one S-phase; the start and duration of this period of replicative DNA synthesis was further substantiated by the analysis of S-phase-associated events, the biosynthesis of core histones and the enzyme activity of thymidine kinase, which both began to increase at about 12 h after the start of differentiation. Thymidine kinase fluctuated periodically during germination with a transient maximum at 30 h and a second peak at 72 h; histone biosynthesis was not detectable until 12 h after the start of germination. The levels of PCNA protein closely resembled the pattern of thymidine kinase during germination. Together with the cytometric data this allows a clear assignment of cell cycle events to different times of embryo differentiation.Abbreviation PCNA proliferating-cell nuclear antigen Dedicated to Prof. Walter Larcher on the occasion of his 65th birthdayThe authors wish to thank Prof. G. Mikuz (Department of Pathology, University of Innsbruck, Austria) and Prof. G. Stöffler (Department of Microbiology, University of Innsbruck, Austria) for their interest and support. The technical assistance of Mrs. R. Gantschnig is gratefully acknowledged. E.I. Georgieva was recipient of short-term fellowships from the Austrian Academy of Sciences, the Austrian Forschungsgemeinschaft and the Austrian Akademischer Austauschdienst. G. López-Rodas was recipient of a postdoctoral fellowship from the Programa sectorial de Formación de Profesorado y Personal investigador del Ministerio de Educación y Ciencia (Spain). This work was supported in part by Grant SO6011 (to P.L.) from the Austrian Fonds zur Förderung der wissenschaftlichen Forschung and the Dr. Legerlotz-Foundation.     

Relationships between three species ofFestuca sect.Bovinae (Poaceae)

Seed protein electrophoresis confirms the existence of polymorphism among hexaploid populations ofFestuca arundinacea. Both protein and morphological results suggest thatF. pratensis andF. arundinacea should retain independent specific status. High protein homology of these two species withF. gigantea points towards phylogenetic links between these taxa.     

Ultrastructural investigations of mature embryo sacs of Daaucus carota,D. aureus and D. muricatus — possible cytological explanations of paternal plastid inheritance

Summary The embryo sacs of Daucus carota, D. Aureus and D. muricatus are of the Polygonum-type. They contain one egg cell, two synergids, a giant central cell and three antipodal cells that are to a great extent degenerated. The species of Daucus investigated have an egg cell with a vacuole that is large in comparison to the amount of cytoplasm. The most extreme case of reduced cytoplasm with respect to the volume of the vacuole occurs in D. muricatus. The egg cell of this species contains only very few intact plastids and other cytoplasmic organelles. Paternal plastid inheritance in the cross D. muricatus × D. carota is discussed in connection with the small number of cytoplasmic organelles in the female gamete of D. muricatus.     

Variation at isozyme loci inTriticeae

An electrophoretic comparison of variation at 16 presumptive isozyme gene loci was performed for 17 species from the tribeTriticeae. Included in the analysis were annuals and perennials, and self- and cross-pollinating species, representing the H, I, P, N, R, V, S, E, J, J₁J₂, A, B, and D genomes. Perennial species were found to contain a significantly (marginally, at the 5% level) higher proportion of polymorphic loci and level of heterozygosity, than annual species. There were no significant differences between self- and crosspollinating species. Across all species, mean heterozygosity levels ranged from 0–0.225 and the % polymorphic loci from 6.3–56.3%. Genetic distance estimates varied from 0.08–0.39 for congeneric species. Relationships were deduced between the 17 species using phenetic and cladistic analyses and compared with relationships inferred from other parameters such as morphology and nucleotide sequence data. In general, the trees derived from the various relationships were concordant; the evolutionary basis for minor discrepancies between trees is also discussed.     

Amplification and dispersion of repeated DNA sequences in theTriticeae

Four representatives of a family of dispersed repetitive sequences which were prominent and dispersed in the E genome ofThinopyrum elongatum but poorly represented in wheat, were studied in detail. The 1.4kb sequences were present both as part of tandem and more complex arrays and appeared to have resulted from repeated amplification of the sequence and their dispersion throughout the genome. Subcloning of sections of the 1.4 kb sequences resulted in probes which improved the resolution of the E genome from the genomes in wheat and enabled identification of single E genome chromosomes introduced into wheat. The generality of these types of sequences in the tribeTriticeae was confirmed by isolating analogous sequences from the R (rye,Secale cereale), V (Dasypyrum villosum), and N (Psathyrostachys juncea) genomes. — The cloned repetitive sequences from the R, V, and N genomes each showed characteristic fluctuations in amount within the grasses examined in addition to being virtually absent from wheat. It is thus possible that these sequences may provide useful taxonomic indicators for establishing relationships within theTriticeae, as well as valuable probes for tracing alien chromatin introduced into wheat.     

Hybridization in the genus Lens by means of embryo culture

Summary The cultivated lentil L. culinaris and the wild lentil L. ervoides are reproductively isolated from one another due to their hybrid embryo breakdowns. Using embryo culture, vegetatively normal hybrids were obtained. One specific hybrid, heterozygous for a reciprocal translocation, had about 50% gamete viability and produced aborted and viable embryos in a 11 ratio. In the F₂, vegetatively normal and highly fertile plants were selected. With the aid of embryo culture techniques, L. ervoides can be included in the wild gene pool of the cultivated lentil.     

Chloroplast DNA reassociation and grass phylogeny

Sequence variation in chloroplast DNA (cpDNA) as measured by DNA reassociation was examined in 12 grass species to address systematic problems in thePoaceae at the subfamilial and tribal levels. Two species,Petunia (Solanaceae) andGlycine (Leguminosae), were included to determine degrees of sequence divergence in cpDNA between monocots and dicots. The data were analyzed phenetically and phylogenetically. Species were segregated into four major groups that corresponded to the subfamiliesPooideae, Oryzoideae, Chloridoideae, andPanicoideae. Representatives of thePooideae andOryzoideae grouped together as did members of theChloridoideae andPanicoideae. ThePooideae split into two major groups corresponding to the recently recognized supertribesTriticanae andPoanae. Internodes between subfamily branches were short which might indicate a burst of divergence in the family early in its evolution. Sequence similarity values between the monocot grass species and the two dicot taxa ranged from 0.15 to 0.27, representing the highly conserved sequences of the chloroplast genome.     

<Emphasis Type="Italic">Phuphanochloa,</Emphasis> a new bamboo genus (<Emphasis Type="Italic">Poaceae</Emphasis>: <Emphasis Type="Italic">Bambusoideae</Emphasis>) from Thailand

Summary  A new monotypic bamboo genus Phuphanochloa (Poaceae: Bambusoideae) from north-eastern Thailand is described, together with a new species, P. speciosa.     

The grass megagametophyte and its possible phylogenetic implications

The structure of the grasses megagametophyte is considered to be characteristic enough as to deserve a particular place in the megagametophyte typology. Furthermore, it is compared with those of other Monocotyledonous families to point out embryological affinities.Both are members of the Carrera del Investigador (Conicet, Argentina).     

Plant regeneration through callus initiation from thin mature embryo fragments of wheat

A wheat regeneration system was developed using mature embryos. Embryos were removed from surface-sterilised mature caryopses (winter wheat Odeon cultivar and spring wheat Minaret cultivar) and ground to pieces through a sterile nylon mesh. The fragments were characterised by means of the image analysis technique. They were 500 M mean diameter and most of them were elongated. They were used as explants to initiate embryogenic calli on solid medium supplemented with 10 M 2,4-dichlorophenoxyacetic acid. The morphogenic pathway of the initiated calli was followed for a 40-day culture period. Active cellular division occurred within 24 hours of cultivation. Several hundred calli were produced from 100 fragmented embryos within 3 days. A 90% callus induction rate was achieved and proembryos appeared by the 8th day of culture. The highest embryogenic calli induction rate of 47% was obtained when 2,4-dichlorophenoxyacetic acid was suppressed after a 3–4 week induction period. Two regeneration methods were finally compared. A total of 513 plantlets were produced. The optimal protocol produced 25–30 plants per 100 embryos. This regeneration method may be suitable for transformation applications.     

Alfalfa embryo production in airlift vessels via direct somatic embryogenesis

A procedure for the development of alfalfa (Medicago falcata L.) somatic embryos to the torpedo stage in air-lift vessels is described. Embryos were initiated from chopped leaf explants and were formed by direct somatic embryogensis. The system produced a high number of torpedo stage embryos. The effect of various inoculation densities on embryo development was studied. A procedure for the development and maturation of embryos in aerated liquid media was established. The rate of conversion of the torpedo stage embryos formed in the vessels was 83%.Abbreviations ABA abscisic acid - B5 Gamborgs B5 medium (Gamborg et al. 1968) - COT cotyledon embryo state - 2,4-d 2,4-dichlorophenoxyacetic acid - FW fresh weight - ID internal diameter - MS Murashige and Skoog medium (Murashige & Skoog 1962) - PEG polyethylene glycol - POLY polyembryos - VVM volume of gas/volume of bioreactor     

Kinetic studies of embryo development and nutrient utilization in an alfalfa direct somatic embryogenic system

A method for direct somatic embryogenesis in alfalfa (Medicago falcata) is described. The time course in the development phase has been followed for fresh weight, cell density, pH, sugar uptake and embryo number and type. The method of disrupting the explant material has also been shown to influence subsequent embryo formation.     

Identification of gibberellin A1 in the embryo suspensor of Phaseolus coccineus

By combined gas chromatography-mass spectrometry the gibberellin present in suspensors of heart-shaped embryos of Phaseolus coccineus has been identified as Gibberellin A₁ (GA₁). The amount of GA₁ in 2000 suspensors (452 mg), as estimated by gas chromatography. was 4g. The presence of GA₁ in suspensors of P. coccineus is discussed in relation to our present knowledge of the occurrence of many gibberellins in developing seeds and immature fruits of the same species.Abbreviations FID flame ionization detector - GA gibberellin - GC gas chromatography - MS mass spectrometry - PGC preparative gas chromatography - Stage A heart-shaped embryo - Stage B cotytedonary embryo - TMS trimethylsilyl