Achene Characters Research Articles

Controle em pós-emergência e características germinativas de agriãozinho

O agriãozinho é uma planta daninha de grande importância em pastagens do Brasil e apresenta destacada agressividade, sendo seu controle, portanto, desejável para o sucesso da produção forrageira. O objetivo deste trabalho foi avaliar o controle químico de Synedrellopsis grisebachii na fase reprodutiva e as suas consequências sobre as características germinativas dos aquênios da planta daninha. Os tratamentos constaram da aplicação dos herbicidas glyphosate (100, 200, 900 e 1.800 g ha-1), paraquat (34, 68, 300 e 600 g ha-1) e triclopyr (75, 150, 667 e 1.334 g ha-1), além da testemunha sem aplicação. Foram coletados aquênios aos 15 dias após a aplicação, sendo estes submetidos ao teste de germinação, determinando-se a porcentagem e o índice de velocidade de germinação. Após 29 dias em germinação, verificou-se a viabilidade dos aquênios não germinados, através do teste de tetrazólio. A eficácia dos herbicidas foi avaliada por meio de notas visuais de controle aos 7, 14, 21 e 28 DAA. Conclui-se que para o controle total de S. grisebachii, em estádio reprodutivo, é necessária a aplicação de 1.334 g ha-1 de triclopyr. Nesse estádio, a planta apresentou grande tolerância ao glyphosate e também ao paraquat. Quanto às características germinativas da progênie, o herbicida triclopyr nas doses de 150 e 667 g ha-1 promoveu redução na velocidade de germinação e na viabilidade, enquanto o glyphosate e paraquat não proporcionaram efeito.

Taraxacum scanicum Dahlst. group (section Erythrosperma) in Poland: chorology and seed and pollen morphology of the microspecies

The genus <em>Taraxacum</em> is taxonomically complicated due to apomixis. Therefore, there are significant differences in knowledge of regional Taraxacum-Floras among European countries. Similarly, some taxa are well characterised with well-known distribution, whereas some ones are known e.g. from a single locality. <em>Taraxacum scanicum</em> of section <em>Erythrosperma</em> is one of the most common microspecies of this section in Europe. Recently, this taxon was split into three microspecies. In this study we map the distribution of three described taxa of this group in Poland, i.e. <em>T. scanicum</em> s.s., <em>T. prunicolor</em> and <em>T. cristatum</em>. The survey showed that <em>T. scanicum</em> has a similar distribution as <em>T. prunicolor</em> in Poland. This is in contrast with the hitherto known distribution of both taxa. <em>T. cristatum</em> was found at a single locality that is quite distant from the distribution in southern central Europe. We also provide with new morphological characteristics of achenes and pollen for <em>T. scanicum</em> s.s. and <em>T. prunicolor</em>.

Germination Patterns of Dimorphic Achenes in Three Related Species ofScorzoneroides(Asteraceae, Lactuceae) Growing in Different Environments

Scorzoneroides palisiae, S. salzmannii, and S. muelleri (Asteraceae) are phylogenetically close annuals with dimorphic achenes. Although these three species are characteristic to areas with some degree of disturbance, S. palisiae and S. salzmannii grow in Mediterranean environments, whereas S. muelleri preferentially grows in semi-arid environments. This study compared the germination characteristics of central and peripheral achenes subjected to different storage times. Both central and peripheral achenes of the three Scorzoneroides species were completely dormant immediately after dispersal. This dormancy was reduced after six months in dry storage, and practically disappeared after more than a year in storage. Six-month central achenes of S. palisiae and S. salzmannii displayed lower dormancy levels than peripheral achenes did, producing a mixed germination pattern. However, 6-month central achenes of S. muelleri displayed the same dormancy levels as those of peripheral achenes. Furthermore, there was a nearly significant negative correlation among germination and the annual aridity index in the studied populations. We suggest that this increase in dormancy may be interpreted as an adaptation to semi-arid ecosystems.

Genetic Architecture of Novel Traits in the Hopi Sunflower

Following domestication, crop lineages typically undergo diversification either to adapt to disparate habitats or to fill novel agricultural roles. This process has produced the numerous varieties found in modern-day crop germplasm collections. Here, we mapped quantitative trait loci (QTLs) underlying unique traits in the Hopi sunflower, a primitive, Native American domesticate. These traits included a variety of achene (i.e., single-seeded fruit) characters as well as the extremely late flowering time of the Hopi sunflower. Composite interval mapping identified 42 QTLs underlying the 12 traits of interest. Although these QTLs were found on 10 of the 17 sunflower linkage groups, strong genetic correlations were evidenced by the clustering of QTLs across traits in certain genomic regions. The number of QTLs per trait ranged from 2 to 6, and the average QTL explained 14.7% of the variance (range: 2.5-46.9%). The apparent contribution of epistasis was minor, as has previously been observed for domestication-related traits. Unlike typical domestication-related traits in sunflower, the traits under consideration here exhibited a relatively simple genetic basis, with 2 QTL clusters being largely responsible for the unique characteristics of the Hopi sunflower. Based on the rarity of these traits in domesticated sunflower, it would appear that they evolved within the Hopi lineage following domestication. The simple genetic architecture of these traits may be a by-product of genetic constraints imposed by the genetically complex nature of domestication-related traits in sunflower, with the large number of domestication-related QTLs limiting the fraction of the genome that is available for subsequent diversification.

Characteristics of heteromorphic achenes of Garhadiolus papposus, an ephemeral Asteraceae species, with reference to their adaptations to desert environment

Characteristics of heteromorphic achenes of Garhadiolus papposus, an ephemeral Asteraceae species, with reference to their adaptations to desert environment

Resolving the native provenance of invasive fireweed (Senecio madagascariensis Poir.) in the Hawaiian Islands as inferred from phylogenetic analysis

ABSTRACTAccurate identification of weedy species is critical to the success of biological control programs seeking host‐specific control agents. Phylogenetic relationships based on internal transcribed spacer region (ITS1, ITS2) DNA sequence data were used to elucidate the most likely origin and taxonomic placement of Senecio madagascariensis Poir. (fireweed; Asteraceae) in the Hawaiian archipelago. Putative S. madagascariensis populations from Madagascar, South Africa, Swaziland, and Hawaii were included in the analysis. Different phylogenetic models (maximum parsimony and maximum likelihood) were congruent in suggesting that Hawaiian fireweed is most closely related to populations from the KwaZulu‐Natal region in South Africa. Phylogenetic divergence and morphological data (achene characteristics) suggest that the S. madagascariensis complex is in need of revised alpha‐level taxonomy. Taxonomic identity of invasive fireweed in Hawaii is important for finding effective biological control agents as native range populations constitute different biotypic variants across a wide geographical area. Based on our phylogenetic results, research directed at biological control of Hawaiian infestations should focus on areas in the KwaZulu‐Natal region in South Africa where host‐specific natural enemies are most likely to be found. Our results show that phylogeographical analysis is a potential powerful and efficient tool to address questions relevant to invasion biology of plants.

Phylogenetic relationships inSaussurea (Compositae, Cardueae)sensu lato, inferred from morphological, ITS andtrnL-trnF sequence data, with a synopsis ofHimalaiellagen. nov.,LipschitziellaandFrolovia

Raab-Straube, E. von: Phylogenetic relationships in Saussurea (Compositae, Cardueae) sensu lato, inferred from morphological, ITS and trnL-trnF sequence data, with a synopsis of Himalaiella gen. nov., Lipschitziella and Frolovia. — Willdenowia 33: 379–402. — ISSN 0511-9618; © 2003 BGBM Berlin-Dahlem.DNA sequences from the nuclear ribosomal ITS and from the chloroplast trnL-trnF regions of 47 species of all six subgenera and 13 sections of Saussurea were analysed. The cladogram resulting from ITS sequence data indicates that Saussurea in its present circumscription is paraphyletic. S. sect. Elatae and S. subg. Jurinocera together are sister to the genus Jurinea. The affinities of S. subg. Frolovia are unclear, while representative species of the remaining four subgenera and ten sections form a strongly supported monophyletic group. Within this clade, the delimitation of S. subg. Eriocoryne and S. subg. Amphilaena against S. subg. Saussurea is not evident. The trnL-trnF intergenic spacer sequences show a remarkable synapomorphy, a 21bp insertion, for Jurinea cyanoides, S. deltoidea, S. ceratocarpa and S. frolovii, supporting the paraphyly of Saussurea. These results correspond to differences in morphological characters of achenes and pappus, which also suggest that S. sect. Elatae, S. subg. Jurinocera and S. subg. Frolovia are not closely related to the remainder of the genus. Consequently, S. sect. Elatae is separated as the new genus Himalaiella, and the small generic segregates Frolovia and Lipschitziella are resurrected. A synopsis of these three genera is presented and the new combinations Himalaiella abnormis, H. afghana, H. albescens, H. auriculata, H. chenopodiifolia, H. chitralica, H. deltoidea, H. foliosa, H. heteromalla, H. nivea, H. peguensis, Frolovia frolovii and F. gorbunovae are validated.

Delineation and phylogeny of Centaurea sect. Acrocentron based on DNA sequences: a restoration of the genus Crocodylium and indirect evidence of introgression

The Mediterranean group Acrocentron of the genus Centaurea is defined mainly on the basis of pollen type, but also by achene characters and involucral bracts morphology. We have revised the delineation of the group by cladistically comparing the sequences of the ITS spacers of the nuclear ribosomal DNA. Our results confirm that the Acrocentron group is a natural one, with a different delimitation from the commonly accepted. The ITS phylogeny supports that Centaurea sect. Chamaecyanus and sect. Stephanochilus belong to the Acrocentron group and suggests that sect. Chamaecyanus should be merged in sect. Acrocentron as a subsection. Contrary, sect. Aegialophila and sect. Crocodylium form a natural group that cannot be placed in the Acrocentron group and should be considered a different genus. The inclusion of Centaurea crocodylium in Aegialophila makes that the prioritary name for the generic level is Crocodylium; thus, two new nomenclatural combinations are proposed: Crocodylium creticum and Crocodylium pumilum. The groups suggested by the ITS sequences are correlated to the main geographical centers of speciation of Acrocentron. However, support for internal nodes of the tree is extremely poor. The low support within the tree and the absence of correlation between karyology and molecular phylogeny suggest that hybridization has played an important role in the diversification of Acrocentron.

Verbesina barrancae (Compositae, Heliantheae), a new species from Jalisco, Mexico

Verbesina barrancae, a new species of Compositae (Heliantheae) from Jalisco, Mexico, is described and illustrated. It is morphologically similar to Verbesina crocata but differs in characteristics of inflorescence, anthers, and achenes as well as in form of pollen, size and number of spinules, size of colpus transversalis, and index of polar area.

QTL analysis reveals different and independent modes of inheritance for diagnostic achene characters in Microseris (Asteraceae)

There are few reliable diagnostic morphological characters for species of the asteracean genus Microseris, and quantitative differences in the shapes of the achenes and the paleaceous pappus parts play a decisive role in species recognition. The genetic basis of species and strain differences in various characters has been studied previously, but little is known about quantitative characters of the achenes. We performed a quantitative trait locus (QTL) analysis in the F2 of an interspecific cross between Microseris douglasii and M. bigelovii for achene length, achene diameter, achene shape, palea length, awn length, and achene pigmentation. Independent inheritance of the main heritable achene characters – achene length, palea length and achene pigmentation – was revealed by the detection of distinct and specific QTLs for these characters. For palea length five QTLs with about equal phenotypic effects were mapped on four different linkage groups. Achene length and achene shape (achene length / achene diameter) were determined by two different genetic systems with one major gene and two modifiers. The detection of QTLs with a polarity of the effects opposite to that in the parental strains for achene length and achene shape reveals genetic variation for a potential increase in species differences. For the highly heritable trait, achene pigmentation, the bimodal F2 distribution suggested single-factor inheritance for absence versus presence of spots, with dominance for the spotted condition. However, only relatively weak QTL effects on that trait could be detected. Additional molecular markers (RAPDs, AFLPs) have to be tested for cosegregation with that major gene. The results are discussed in the context of different theories for the evolution of morphological characters.

Rhynchospora pseudomacrostachya, a new Brazilian species of Cyperaceae

Abstract Rhynchospora pseudomacrostachya, a new Brazilian species of Cyperaceae. Brittonia 54: 340–343. 2002.—Rhynchospora pseudomacrostachya (Cyperaceae) is restricted to the southern Brazil states of Rio Grande do Sul and Santa Catarina. Previously, material of R. pseudomacrostachya had been thought to belong to R. corniculata var. macrostachya (Torr. ex A. Gray) Britton (R. macrostachya Torr. ex A. Gray) of North America. However, R. pseudomacrostachya can be distinguished from the North American taxon on the basis of achene and inflorescence characters.

The taxonomic significance of achene in the genus Ranunculus L. in Egypt

Morphological characters of achenes for nine species of Ranunculus among R. sardous Crantz. is new record tothe flora of Egypt. from Egypt have been investigated using light (LM) and scanning (SEM) microscopy. Carpelwall structure for some studied species has also been searched. The achene morphology showed considerablevariations in shape, size, surface pattern and wall structure. The macrocharacters as well as microcharacters ofachenes are discussed in relation to taxonomy and proved their significance in the distinction between the studiedspecies. A key and SEM micrographs of achenes are provided.

Identidad de dos especies sudamericanas de Rhynchospora (Cyperaceae): R. rostrata y R. organensis

Guaglianone, E. R. & Moore, G. 2001. Identity of two South American species of Rhynchospora (Cyperaceae): R. rostrata and R. organensis. Darwiniana 39(3-4): 239-246. The name Rhynchospora rostrata has been applied to two different species of Rhynchospora (subgn. Haplostylis, sect. Longirostres) from South America. True R. rostrata is known only from Brazil (Distrito Federal, Goias, Minas Gerais). The correct name for the other species going under the name R. rostrata is R. organensis, and it is known from Argentina, Brazil, Paraguay, and Uruguay. R. organensis returns to the status of species after being considered as R. corymbosa var. organensis. R. corymbosa, R. rostrata and R. organensis can be distinguished using inflorescence and achene characters, and a key to differentiate them is provided. R. rostrata and R. organensis are also described and illustrated.

Reinstatement of Clematis petriei (Ranunculaceae), and typification and variation of C. forsteri

Clematis petriei is reinstated at species rank, being distinguished from the widespread and variable C. forsteri by a number of flower and achene characters. In C. petriei the adaxial surface of the sepals and the achenes are glabrous, and the achenes are chestnut brown. C. forsteri has hairy sepals and achenes, and the achenes are usually light to dark brown. A lectotype for C. forsteri is selected from the J. E. Smith Herbarium, and lectotypes are selected for all names placed in synonymy of C. forsteri. Patterns of leaf variation, with a strong geographic basis, are described and illustrated for C. forsteri.

Plate 374. Cephalipterum drummondii

The taxonomic history, distribution, habitat and cultivation requirements of Cephalipterum drummondii A. Gray (Compositae), an Australian endemic, are discussed; a full description and illustrations of the species are provided and achene characters are shown by means of Scanning Electron Micrographs.

The Relationship Between Achene Weight, Embryo Weight and Germination inTaraxacumApomicts

Apomicts provide the opportunity to investigate the variation in achene size and performance that is due to factors other than genetic differences between achenes. Achene characteristics of a single capitulum from each of 15 biotypes of apomicticTaraxacumwere investigated. Within a capitulum, achene fresh weight ranged from 4.45-fold to 13.74-fold. Overall, 59.8% of achenes germinated. The probability of any one achene germinating was influenced both by its source and by its weight and ranged from 0.049 to 0.902 between capitula and from 0.028 to 0.873 between weight classes. An investigation of the relationship between achene parts in three biotypes identified a linear trend for embryos to acquire a greater proportion of total achene weight as achene weight increases. Although the heaviest achenes showed the best germination, it is predicted that, for a given investment of maternal resources, seedling number would be maximized by producing achenes of a single intermediate weight.

The separation of Eleocharis obtusa and Eleocharis ovata (Cyperaceae) in eastern Canada

Eleocharis obtusa and Eleocharis ovata are recognized as distinct species or combined in recent taxonomic literature. To assess their morphological relationship and to evaluate all morphological characters potentially useful for their separation, 11 floral and achene characters were measured on 130 eastern Canadian herbarium specimens. Tubercle width was bimodally distributed and completely separated groups established on the basis of stamen number: plants referable to E. ovata had tubercles less than 0.5 mm wide and two stamens, whereas plants referable to E. obtusa had tubercles greater than 0.5 mm wide and three stamens. Since determination of stamen number requires dissection under a microscope and tubercle width requires accurate measurement, the most readily utilized character was found to be the ratio of tubercle width to achene width, which can be measured or estimated. The tubercle was less than 2/3 the width of the achene in E. ovata and more than 2/3 in E. obtusa. Differences in these characters were associated with significant but less dramatic differences in other characters, suggesting that the two taxa should be treated as distinct species. Keywords: Eleocharis obtusa, Eleocharis ovata, Cyperaceae, taxonomy, classification, Canada.

Association of sunflower achene color with other achene characters and bird preference

The association of achene color with other achene characters and bird preference was investigated in segregates of a striped Yugoslavian line NS 39 and in 12 crosses of various genotypes. In the NS 39 segregates, the strongest association of achene color was with kernel content (r = 0.606), bird preference (r = 0.610) and achene oil (r = 0.445). Birds preferred lines with darker achene color which in turn was linked with higher oil and nutmeat content. In the crosses of various genotypes, achene color was strongly associated with achene oil content in segregates of two grey × black achene color crosses (r = 0.436 and 0.292) and in segregates of anthocyanin-containing × black achene color cross (r = 0.419). Key words: Sunflower, color association, achene characters, bird preference, achene oil, nutmeat anthocyanin

Regression model relating decortication of oilseed sunflower hybrids with achene characteristics

Multiple regression equations relating decortication with such achene characteristics as oil content, achene weight and density, in three sets of oilseed sunflowers were developed. Hull content and wax content were included in one set of hybrids. Good prediction of decortication could be obtained from the achene characteristics that are routinely determined, i.e., oil content, achene weight and density. Oil content was the most significant factor, followed by achene density. Key words: Decortication, sunflower

Genetic and Morphological Divergence Among Varieties of Aphanostephus skirrhobasis (Asteraceae-Astereae) and Related Species with Different Chromosome Numbers

Thirty-seven populations representing Aphanostephus riddellii (n = 5), A. ramosissimus (n = 4), and all three varieties of A. skirrhobasis (n = 3), were examined for allozyme differentiation at 17 loci to test hypotheses of hybridization between A. skirrhobasis and A. ramosissimus, and to assess genetic divergence within A. skirrhobasis and among congeneric species with different chro- mosome base numbers. Thirteen populations of A. skirrhobasis were examined also for variation in achene and pappus characters. The species are differentiated easily using isozymes, chromosome numbers, and achene hair types. In contrast to relationships suggested by a hypothesized aneuploid reduction series, A. riddellii is more similar genetically to A. skirrhobasis than to A. ramosissimus. Within A. skirrhobasis, populations of vars. skirrhobasis, thalassius, and kidderi are intermixed in analyses based on allozyme variation, but var. kidderi is differentiated readily using achene length, awn/achene length ratio, and awn number. Average genetic identities within and among varieties are similar, reflecting an isozyme pattern characterized by minor frequency differences among shared alleles. Varieties of A. skirrhobasis apparently have incomplete reproductive barriers in areas of sympatry, and may be in the early stages of regional differentiation initiated during the Pleistocene. Isozyme data do not support purported hybridization between A. skirrhobasis and A. ramosissimus. Varieties of A. skirrhobasis are partially autogamous, but diversity levels suggest a mixed to outcrossing mating system.