Leaf and inflorescence peduncle anatomy: a contribution to the taxonomy of Rapateaceae

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Anatomia de folha e eixo da inflorescência: contribuições à taxonomia de Rapateaceae

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Anatomia de folha e eixo da inflorescência: contribuições à taxonomia de Rapateaceae

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Leaf and inflorescence structure and phylogenetics of Tripogon and affiliated genera (Poaceae: Chloridoideae)

This thesis provides new knowledge on an understudied group of grasses, some of which are resurrection grasses (i.e. able to withstand extreme drought). The sole Australian species (Tripogon loliiformis) is morphologically diverse and could be more than one species. This study sought to determine how many species of Tripogon occur in Australia, their relationships to other species in the genus and to two other genera of resurrection grasses (Eragrostiella and Oropetium). Results of the research indicate there is not enough evidence, from DNA sequence data, to warrant splitting up T. loliiformis into multiple species. The extensive morphological diversity seems to be influenced by environmental conditions. The three genera are so closely related that they could be grouped into a single genus. This new knowledge opens up pathways for future investigations, including studying genes responsible for desiccation tolerance and the conservation of native grasses that occur in rocky habitats.

Cynodon transvaalensis x Cynodon dactylon Hybrid Green Couch Grass, Hybrid Bermuda Grass 'MS-Supreme'

Ploidy: triploid interspecific hybrid (3n = 27 chromosomes). Plant: habit prostrate, creeping, type mat-forming, height very short, longevity perennial, spreading laterally by stolons and rhizomes. Stolon: compound nodes with up to 3 leaves, internode length very short, internode thickness very thin, colour grey-brown (RHS N199A) when exposed to sunlight. Culms: length very short. Leaf blade: shape linear-triangular, length short, width narrow, colour dark green (RHS 137B). Ligule: dense row of short white hairs. Inflorescence: digitate with 3(-4) very short spicate racemes, peduncle very short. (All RHS colour chart numbers refer to 2001 edition.) PBR Certificate Number 2641, Application Number 2002/305, granted 24 February 2005.

Low temperature exposure of root system and inflorescence affected flowering and fruit set in 'Chardonnay' grapevines (Vitis vinifera)

The mechanisms by which low temperature affects flowering and fruit set of grapevines are poorly understood, as is the specific response of the grapevine root system and inflorescence to low temperature effects that reduce fruit set. This study aimed to determine the responses of the root system and inflorescence of the grapevine 'Chardonnay' to low temperature (10 degrees C) during flowering, and considered the possible mechanisms of low temperature effects on those parts. Temperature treatments of 10 degrees C or 20 degrees C were imposed to potted 'Chardonnay' grapevines in a glasshouse for up to two weeks during the early stages of flowering. When the root system alone was exposed to 10 degrees C (with the rest of the plant at 20 degrees C) during flowering, the number of attached berries and percentage fruit set were significantly reduced by 50 % than when the root system alone was exposed to 20 degrees C. Whereas, exposure of the inflorescence alone to 10 degrees C (with the rest of the plant at 20 degrees C) delayed flowering, allowed rachis to grow longer, and increased both the number of attached berries (from 22 to 62 per vine) and fruit set (from 8 % to, 20 %), than when the inflorescence alone was exposed to 20 degrees C. This study will enhance our understanding of the possible mechanisms of low temperature effects on grapevine fruit set and productivity.

Revision of the genus Fosterella (Bromeliaceae)

Die vorliegende Arbeit stellt eine umfassende taxonomische Revision der Gattung Fosterella L.B. Sm. (Bromeliaceae) dar, die alle 31 derzeit akzeptierten Arten umfasst und einen Bestimmungsschlüssel für diese beinhaltet. Die Revision beruht auf der morphologisch-anatomischen Auswertung von Herbarmaterial (über 800 Exsikkate), Lebendpflanzen (ca. 150 Akzessionen) und eigenen vergleichenden Untersuchungen im Freiland. Die Gattung Fosterella ist seit nunmehr etlichen Jahren Forschungsgegenstand einer interdisziplinären Studie, die sowohl molekulrae, als auch anatomische, morphologische und biogeographische Untersuchungen einbezieht. Unser Interesse an der Gattung Fosterella gründet sich auf ihrer enormen ökologischen und biogeographischen Vielfalt, sie gilt als hervorragendes Modellsystem für Artbildungsmechanismen in den Anden. In den letzten Jahren wurde von verschiedenen molekularen Methoden Gebrauch gemacht, um die verwandtschaftlichen Beziehungen innerhalb der Gattung zu untersuchen, so dass mittlerweile gut aufgelöste Stammbäume vorliegen. Diese molekularen Studien, überwiegend durchgeführt von Dr. Martina Rex, wurden ergänzt durch intensive Sammelaktivitäten und eingehende taxonomische Untersuchungen im Rahmen der vorliegenden Revision. Auf diese Weise konnten die morphologische Plastizität der einzelnen Arten erfasst und schließlich ein wohlfundiertes Artkonzept vorgelegt werden. Zunächst wird ein kurzer Überblick über die Familie der Bromeliaceen als auch die Gattung Fosterella gegeben, in dem jeweils Informationen zur Verbreitung, Morphologie, Physiologie, Ökologie und Phylogenie geliefert werden. Im Anschluss an einen historischen Überblick des taxonomischen Werdegangs wird die Abgrenzung der Gattung Fosterella zu den nächstverwandten Gattungen Deuterocohnia, Dyckia und Encholirium erläutert. Die morphologischen Merkmale zur Differenzierung der Arten innerhalb der Gattung werden im Hinblick auf ihre Zuverlässigkeit und ihr Gewicht diskutiert. Der Artschlüssel basiert auf Merkmalen, die leicht auszumachen und gut zu unterscheiden sind. Bei der ausführlichen Beschreibung der Arten wird auch auf ihre jeweilige Verbreitung, Ökologie, taxonomische Abgrenzung, systematische Verwandtschaft sowie die Etymologie des Namens eingegangen. Beigefügt sind jeweils Zeichnungen, ein Foto vom Holo-/Lectotypus, Fotos von Lebendpflanzen sowie eine Verbreitungskarte. Im Rahmen der taxonomischen Arbeit wurden fünf Arten zu Synonymen reduziert: Fosterella chiquitana Ibisch, R. Vásquez & E. Gross und F. latifolia Ibisch, R. Vásquez & E. Gross wurden in die Synonymie von F. penduliflora (C.H. Wright) L.B. Sm. eingezogen; F. fuentesii Ibisch, R. Vásquez & E. Gross als Synonym zu F. albicans (Griseb.) L.B. Sm. gestellt; F. elata H. Luther in die Synonymie von F. rusbyi (Mez) L.B. Sm. verwiesen und F. nowickii Ibisch, R. Vásquez & E. Gross als Synonym zu F. weddelliana (Brongn. ex Baker) L.B. Sm. gestellt. Fosterella schidosperma (Baker) L.B. Sm. var. vestita L.B. Sm. & Read wird zum Synonym von Fosterella weberbaueri (Mez) L.B. Sm. reduziert. Sechs Arten wurden neu beschrieben: Fosterella batistana Ibisch, Leme & J. Peters; F. christophii Ibisch, R. Vásquez & J. Peters; F. elviragrossiae Ibisch, R. Vásquez & J. Peters; F. kroemeri Ibisch, R. Vásquez & J. Peters; F. nicoliana J. Peters & Ibisch und F. robertreadii Ibisch & J. Peters. Das Taxon F. gracilis (Rusby) L.B. Sm. wurde neu etabliert. Um die Evolution von einzelnen morphologischen Merkmalen zu rekonstruieren, wurden die Zustände von zehn ausgewählten Merkmalen kodiert und auf einen molekularen Stammbaum kartiert. Die folgenden Merkmalszustände wurden als ursprünglich innerhalb der Gattung ermittelt: Stammlosigkeit, ganzrandige Blattspreiten, flache Rosetten mit dem Boden aufliegenden Blättern, locker beschuppte Blattunterseiten, schildförmige Haare mit gezähntem Rand, ganzrandige Pedunkel-Brakteen, rispenförmiger Blütenstand, kahle/verkahlende Blütenstandsachsen, weiße Petalen und einfach-aufrechte Narben. Rückschlüsse bezüglich der Evolution und Ausbreitung der Gattung Fosterella werden diskutiert: Die überwiegend kleinen Verbreitungsgebiete der Arten hängen offensichtlich mit ihren fragmentierten, inselartigen Habitaten (z.B. innerandine Trockentäler) zusammen. Die Tatsache, dass die Yungas-Bergregenwälder des Departamento La Paz, Bolivia, die Region mit der größten Artenvielfalt darstellen, lässt sich mit der extrem variablen Topographie und der außerordentlich hohen Vielfalt an Habitaten dieser Region erklären. Aus folgenden Gründen erscheint es sehr wahrscheinlich, dass die Gattung Fosterella ihren Ursprung im Tiefland hat: Die Mehrheit der Arten weist einen eher mesophytischen Habitus auf und ist in mehr oder weniger humiden Habitaten zu finden. Die Gattung ist durch mehrere Arten in sehr alten Habitaten des präkambrischen Schilds im Tiefland von Zentral-Südamerika vertreten. Weiterhin betreiben, soweit bekannt, alle Fosterella Arten C3 Photosynthese, während in den Gattungen der Schwestergruppe, Deuterocohnia, Dyckia and Encholirium, CAM der verbreitete Photosyntheseweg ist. In jedem Fall ist die Besiedelung der Anden und/oder Tieflandhabitate mehrfach unabhängig voneinander geschehen, vielleicht sogar in beiden Richtungen.

Effects of shoot pruning and inflorescence thinning on plant growth, yield and fruit quality of greenhouse tomatoes in a tropical climate

The combined effects of shoot pruning (one or two stems) and inflorescence thinning (five or ten flowers per inflorescence) on greenhouse tomato yield and fruit quality were studied during the dry season (DS) and rainy season (RS) in Central Thailand. Poor fruit set, development of undersized (mostly parthenocarpic) fruits, as well as the physiological disorders blossom-end rot (BER) and fruit cracking (FC) turned out to be the prevailing causes deteriorating fruit yield and quality. The proportion of marketable fruits was less than 10% in the RS and around 65% in the DS. In both seasons, total yield was significantly increased when plants were cultivated with two stems, resulting in higher marketable yields only in the DS. While the fraction of undersized fruits was increased in both seasons when plants were grown with a secondary stem, the proportions of BER and FC were significantly reduced. Restricting the number of flowers per inflorescence invariably resulted in reduced total yield. However, in neither season did fruit load considerably affect quantity or proportion of the marketable yield fraction. Inflorescence thinning tended to promote BER and FC, an effect which was only significant for BER in the RS. In conclusion, for greenhouse tomato production under climate conditions as they are prevalent in Central Thailand, the cultivation with two stems appears to be highly recommendable whereas the measures to control fruit load tested in this study did not proof to be advisable.

Mechanisms and function of flower and inflorescence reversion

Flower and inflorescence reversion involve a switch from floral development back to vegetative development, thus rendering flowering a phase in an ongoing growth pattern rather than a terminal act of the meristem. Although it can be considered an unusual event, reversion raises questions about the nature and function of flowering. It is linked to environmental conditions and is most often a response to conditions opposite to those that induce flowering. Research on molecular genetic mechanisms underlying plant development over the last 15 years has pinpointed some of the key genes involved in the transition to flowering and flower development. Such investigations have also uncovered mutations which reduce floral maintenance or alter the balance between vegetative and floral features of the plant. How this information contributes to an understanding of floral reversion is assessed here. One issue that arises is whether floral commitment (defined as the ability to continue flowering when inductive conditions no longer exist) is a developmental switch affecting the whole plant or is a mechanism which assigns autonomy to individual meristems. A related question is whether floral or vegetative development is the underlying default pathway of the plant. This review begins by considering how studies of flowering in Arabidopsis thaliana have aided understanding of mechanisms of floral maintenance. Arabidopsis has not been found to revert to leaf production in any of the conditions or genetic backgrounds analysed to date. A clear-cut reversion to leaf production has, however, been described in Impatiens balsamina. It is proposed that a single gene controls whether Impatiens reverts or can maintain flowering when inductive conditions are removed, and it is inferred that this gene functions to control the synthesis or transport of a leaf-generated signal. But it is also argued that the susceptibility of Impatiens to reversion is a consequence of the meristem-based mechanisms controlling development of the flower in this species. Thus, in Impatiens, a leaf-derived signal is critical for completion of flowering and can be considered to be the basis of a plant-wide floral commitment that is achieved without accompanying meristem autonomy. The evidence, derived from in vitro and other studies, that similar mechanisms operate in other species is assessed. It is concluded that most species (including Arabidopsis) are less prone to reversion because signals from the leaf are less ephemeral, and the pathways driving flower development have a high level of redundancy that generates meristem autonomy even when leaf-derived signals are weak. This gives stability to the flowering process, even where its initiation is dependent on environmental cues. On this interpretation, Impatiens reversion appears as an anomaly resulting from an unusual combination of leaf signalling and meristem regulation. Nevertheless, it is shown that the ability to revert can serve a function in the life history strategy (perenniality) or reproductive habit (pseudovivipary) of many plants. In these instances reversion has been assimilated into regular plant development and plays a crucial role there.

A mathematical model for the dynamics of Banana Xanthomonas Wilt with vertical transmission and inflorescence infection

A mathematical model for Banana Xanthomonas Wilt (BXW) spread by insect is presented. The model incorporates inflorescence infection and vertical transmission from the mother corm to attached suckers, but not tool-based transmission by humans. Expressions for the basic reproduction number R0 are obtained and it is verified that disease persists, at a unique endemic level, when R0 > 1. From sensitivity analysis, inflorescence infection rate and roguing rate were the parameters with most influence on disease persistence and equilibrium level. Vertical transmission parameters had less effect on persistence threshold values. Parameters were approximately estimated from field data. The model indicates that single stem removal is a feasible approach to eradication if spread is mainly via inflorescence infection. This requires continuous surveillance and debudding such that a 50% reduction in inflorescence infection and 2–3 weeks interval of surveillance would eventually lead to full recovery of banana plantations and hence improved production.

Morphology and anatomy of inflorescence and inflorescence axis in Paepalanthus sect. Diphyomene Ruhland (Eriocaulaceae, Poales) and its taxonomic implications

Paepalanthus sect. Diphyomene has inflorescences arranged in umbels. The underlying bauplan seems however to be more complex and composed of several distinct subunits. Despite appearing superficially very similar, the morphology and anatomy of the inflorescences can supply useful information for the understanding of the phylogeny and taxonomy of the group. Inflorescences of Paepalanthus erectifolius, Paepalanthus flaccidus, Paepalanthus giganteus, and Paepalanthus polycladus were analyzed in regard to branching pattern and anatomy. In P. erectifolius, P. giganteus and P. polycladus the structure is a tribotryum, with terminal dibotryum, and with pherophylls bearing lateral dibotrya. In P. flaccidus, the inflorescence is a pleiobotryum, with terminal subunit, and without pherophylls. Secondary inflorescences may occur in all species without regular pattern. Especially when grown in sites without a pronounced seasonality, the distinction between enrichment zone (part of the same inflorescence) and new inflorescences may be obscured. The main anatomical features supplying diagnostic and phylogenetic information are as follows: (a) in the elongated axis, the thickness of the epidermal cell walls and the cortex size; (b) in the bracts, the quantity of parenchyma cells (c) in the scapes, the shape and the presence of a pith tissue. Therefore, P. sect. Diphyomene can be divided in two groups; group A is represented by P. erectifolius, P. giganteus and P. polycladus, and group B is represented by P. flaccidus. The differentiation is based in both, inflorescence structure and anatomy. Group A presents a life cycle and anatomical features similar to species of Actinocephalus. Molecular trees also point that these two groups are closely related. However, inflorescence morphology and blooming sequence are different. Species of group B present an inflorescence structure and anatomical features shared with many genera and species in Eriocaulaceae. The available molecular and morphology based phylogenies still do not allow a precise allocation of the group in the bulk of basal species of Paepalanthus collocated in P. sect. Variabiles. The characters described and used here supply however important information towards this goal. (C) 2009 Elsevier GmbH. All rights reserved.