Morphogenetic Phases Research Articles

Flash-flooding of Ephemeral Streams in the Context of Climate Change

Ephemeral streams, which are more extended than expected, entail a significant flood risk. Historically they have been underestimated due to their intermittent flow and the lack of knowledge on their hydro-geomorphology. Currently, European legislation recognizes their associated risk and supports research into them, adapting the scale and methodology to their characteristics. Based on the compilation of various works carried out in four Valencian catchments (Eastern Spain), this paper approaches the key questions of rainfall-runoff conversion and flood generation in ephemeral streams, taking into account their hydro-geomorphological specificity. Moreover, the consequences which derive from current environmental changes are addressed in the wider scale of Júcar River Water Authority.The study is based on 5-minute data, registered by the SAIH-Júcar network (Authomatic Hydrological Information System). The investigation has been conducted in two phases. Firstly, key issues determining flash-flood generation at basin scale have been addressed, based on the study of 138 floods, registered between 1989 and 2018, in four Valencian ephemeral streams (Barranc del Carraixet, Rambla de Poyo, Riu Vernissa and Rambla de Gallinera). Secondly, concerning a broader scale (Júcar River Water Authority), the evolution of 698 rain episodes (1989-2007) has been analysed. Finally, the consequences that environmental changes (climatic, anthropogenic and morphogenetic) might mean for flash-flood generation have been discussed.The results show how environmental changes point towards an increase in risk to the detriment of resource. Rain episodes tend to increase in intensity and decrease accumulated precipitation. As a consequence, hydrological connectivity will become more dependent on rain intensity, thus reducing runoff thresholds and basin response times. Anthropic changes enhance this behaviour, reducing infiltration and increasing surface runoff and erosion, while accelerating the hydrological cycle. An increase in process-form disequilibrium in Mediterranean catchments can be expected due to the increase in morphogenetic phases (because of the intensification of events) and a decrease in the efficiency of low-magnitude recovery episodes.Consequently, the behaviour of ephemeral-streams under current climate change conditions points firstly to an increase in intense flash-flood events, which will be difficult to manage with the current flood control measures, and secondly an increase in the general aridity conditions of catchments.

Coordinating the morphogenesis-differentiation balance by tweaking the cytokinin-gibberellin equilibrium.

Morphogenesis and differentiation are important stages in organ development and shape determination. However, how they are balanced and tuned during development is not fully understood. In the compound leaved tomato, an extended morphogenesis phase allows for the initiation of leaflets, resulting in the compound form. Maintaining a prolonged morphogenetic phase in early stages of compound-leaf development in tomato is dependent on delayed activity of several factors that promote differentiation, including the CIN-TCP transcription factor (TF) LA, the MYB TF CLAU and the plant hormone Gibberellin (GA), as well as on the morphogenesis-promoting activity of the plant hormone cytokinin (CK). Here, we investigated the genetic regulation of the morphogenesis-differentiation balance by studying the relationship between LA, CLAU, TKN2, CK and GA. Our genetic and molecular examination suggest that LA is expressed earlier and more broadly than CLAU and determines the developmental context of CLAU activity. Genetic interaction analysis indicates that LA and CLAU likely promote differentiation in parallel genetic pathways. These pathways converge downstream on tuning the balance between CK and GA. Comprehensive transcriptomic analyses support the genetic data and provide insights into the broader molecular basis of differentiation and morphogenesis processes in plants.

Dialogic pedagogical innovation: Creating liberating learning practices for first year university students

Liberatory and emancipatory thinking is shaped by a de-colonised approach to university teaching practices supported by literature on dialogic pedagogy. A theoretical framework for this paper is shaped by the critical realism views of Archer’s (2010) presented through the morphogenetic phases. At this particular university the grounding programme is a compulsory first year inter-disciplinary module called Life, Knowledge and Action (LKA) aimed at promoting liberating practices through dialogic pedagogy. Interpretive and critical approaches were adopted, using mixed methods questionnaires, interviews and observations for data collection. The findings show that LKA was extremely liberating when students became contributors to knowledge creation. Students claimed/expressed their views stating that dialogue liberated them as it exposed them to diverse and alternative views and opinions. Considering the LKA aims the study recommends that the course be offered throughout undergraduate duration as it might be difficult to achieve all goals within a year.

Coastal dune development and morphological changes along the littorals of Garigliano, Italy, and Elis, Greece, during the Holocene

Geomorphological and sedimentological studies were carried out along the Garigliano and Elis littorals with the aim to highlight if similar geoenvironmental features are controlled by same coastal processes. Actually, both sites are in Mediterranean climate regions very far each other, modeled by western winds and storms, characterized by wide sandy coastal dunes parallel to the present shoreline, with abundant pumices, and locally anthropized. The Garigliano littoral is characterized by Holocene dune and Pleistocene aeolian deposits. The beach is bounded landwards by a dune system emplaced during the Holocene. Geoarchaeological surveys highlighted the presence of a Roman road which cut the dune, with age older than Graeco-Roman Period. Since the end of the 1950’s, strong littoral retreat affected the beach-dune system, partly due to human activity. The coastland of Elis is characterized by Quaternary marine deposits. Three significant morphogenetic phases occurred during the Holocene. During the last phase, from Graeco-Roman Period to current, shoreline retreat and deposition of aeolian sands occurred. Geoarchaeological evidences suggest that this phase is related to a sea-level lowstand followed by a slow sea-level rise up to the present position, and by humid-temperate climate. Geomorphological surveys of the dunes of Garigliano and Elis, each other compared, suggest that the main phases of their development are related to the effects of climatic conditions, sea-level changes, and secondly to the recent anthropization. The coarse pumices found on both beaches of Campania and Peloponnese regions show the same mineralogical and petrographic features, so we assumed that they likely originated from the Aeolian Arc, southern Italy, which have same composition. These pumices reached the studied coasts by flotation, under the influence of winds and marine surface currents from the southwest-southeast and northwest-west respectively, participating to local coastal processes and representing a good geoindicator of long-distance drift. Precisely for these morphologically converging aspects, such distant sites have been selected and compared.

Transformation of life forms and ontogenetic structure of Nepeta pulchella Pojark: Coenopopulations in Aksu-Zhabagly State Nature Reserve

This paper presents the results of a study of the ontogenesis and structural and morphological features of various life forms of Nepeta pulchella Pojark. (Lamiaceae). The environmental and coenotic features of the species habitats within the Aksu-Zhabagly State Nature Reserve have been described. It is found that N. pulchella inhabits areas from the middle part of the mountains to the subalpine belt. The status of coenopopulations in two types of plant communities has been examined. Depending on various ecological and coenotic conditions, N. pulchella individuals develop two life forms: taprooted caudex and short-rhizomatous–taprooted ones. Individuals belonging to these biomorphs go through complete sophisticated ontogenesis. The following morphogenetic phases have been described for the first biomorph: primary shoot → main axis → primary bush → clone; for the second one: primary shoot → main axis → primary bush → tillering particle → nontillering particle. The studied coenopopulations were normal, transitional to mature, resistant, and incomplete. The ecocoenotic and structural–morphological analyses made it possible to identify in the N. pulchella morphogenesis a number of features determined by phylogenetic ties with closely related taxa.

CLAUSA Is a MYB Transcription Factor That Promotes Leaf Differentiation by Attenuating Cytokinin Signaling.

Leaf morphogenesis and differentiation are highly flexible processes, resulting in a large diversity of leaf forms. The development of compound leaves involves an extended morphogenesis stage compared with that of simple leaves, and the tomato (Solanum lycopersicum) mutant clausa (clau) exposes a potential for extended morphogenesis in tomato leaves. Here, we report that the CLAU gene encodes a MYB transcription factor that has evolved a unique role in compound-leaf species to promote an exit from the morphogenetic phase of tomato leaf development. We show that CLAU attenuates cytokinin signaling, and that clau plants have increased cytokinin sensitivity. The results suggest that flexible leaf patterning involves a coordinated interplay between transcription factors and hormones.

Deep-seated gravitational slope deformations in western Sicily: Controlling factors, triggering mechanisms, and morphoevolutionary models

A study of deep-seated gravitational slope deformation (DSGSD) phenomena affecting areas of various geological and geomorphological settings in western Sicily is described. Western Sicily is underlain by a thin-skinned imbricate wedge of Meso–Cenozoic carbonate and siliciclastic rocks that formed by the stacking of several thrust nappes over the Iblean foreland. Locally, the original thrust sheets are folded and cut by high-angle faults. Large areas of western Sicily now display high relief energy due to Plio-Pleistocene block-faulting and uplifting, and the Quaternary morphogenetic phases are characterised by incision, thereby triggering widespread DSGSDs. To identify controlling factors and triggering causes and to develop reliable morphoevolutionary models for the DSGSDs of western Sicily, a geomorphological study based on field surveys and aerial-photography interpretations was performed. Previous geomorphological data relating to well-known examples of DSGSDs were reconsidered, leading to remarkable revisions of the interpretative models in certain cases. New data were subsequently collected, enabling recognition of additional DSGSD phenomena. The whole body of data involves a total of 27 DSGSDs affecting areas in two specific geological settings: (1) areas with flat thrust surfaces, where differential settlements, back-tilting, lateral spreads in competent rocks overlying marls and clays, large topples, and/or block-type slope movements may develop; and (2) areas where deep-rooted carbonate units come into lateral contact with clayey–marly units along high-angle faults, where lateral spreads in brittle homogeneous rocks, sinking, and/or rock flows may occur. These DSGSD phenomena are associated with different evolutionary stages, allowing a morphoevolutionary model to be defined for the two geological conditions. For these two different morphoevolutionary models, the following structural features play an important role in the development of DSGSDs: (1) where carbonate bodies overlie clayey–marly rocks, triggering of the DSGSDs traces back to deformation of a ductile substratum that follows the exhumation of the flat thrust planes and the underlying clayey–marly rocks due to block-faulting and/or stream incision; and (2) where homogeneous carbonate rocks hundreds of metres thick crop out, the DSGSDs are triggered by very high relief energy and tensile stress that follow the combined actions of Quaternary block-faulting and stream deepening associated with differential erosion.

Combinations of Mutations Sufficient to Alter Arabidopsis Leaf Dissection.

Leaves show a wide range of shapes that results from the combinatory variations of two main parameters: the relative duration of the morphogenetic phase and the pattern of dissection of the leaf margin. To further understand the mechanisms controlling leaf shape, we have studied the interactions between several loci leading to increased dissection of the Arabidopsis leaf margins. Thus, we have used (i) mutants in which miR164 regulation of the CUC2 gene is impaired, (ii) plants overexpressing miR319/miRJAW that down-regulates multiple TCP genes and (iii) plants overexpressing the STIMPY/WOX9 gene. Through the analysis of their effects on leaf shape and KNOX I gene expression, we show that these loci act in different pathways. We show, in particular, that they have synergetic effects and that plants combining two or three of these loci show dramatic modifications of their leaf shapes. Finally, we present a working model for the role of these loci during leaf development.

Geoarchaeology of the Burmarrad ria and early Holocene human impacts in western Malta

Holocene sediments from the ria of Burmarrad (western Malta) provide a record of changing geomorphology, relative sea-level rise and human impacts. Chronostratigraphic evidence attests to a fluvial-dominated upper estuarine environment between ~7500cal. BP and ~7000cal. BP, with increasing salinity linked to rising post-glacial sea level. The shift to a marine setting is dated to ~7000cal. BP, characterized by a wave-dominated coastline that accreted up until ~4000cal. BP. During the maximum marine ingression, the Burmarrad floodplain formed a vast 1.8km2 marine bay, ~3000m long by ~650m wide, whose environmental potentiality presented western Malta's early societies with a multiplicity of coastal, terrestrial, and fluvial resources, in addition to a low-energy context favourable to the anchoring of boats. New palynological data show intensified human impact on the landscape beginning ~7300cal. BP, which is broadly consistent with the earliest archaeological traces. Western Malta was already void of a significant vegetation cover by the mid-Holocene. Rapid human-induced sedimentation means that by the Bronze Age, the palaeobay had been reduced by ~40% compared to its mid-Holocene maximum. The final morphogenetic phase constitutes fluvial silts and sands that began accreting after 2700cal. BP. During Punic/Roman times, the ria bay was ~1km2, and was flanked to the south by a well-developed deltaic plain providing fertile land for agriculture. Today, the ria is ~60% smaller than it was 7000years ago.

Impact of Biofield Treatment on Growth and Anatomical Characteristics of Pogostemon cablin (Benth.)

Pogostemon cablin is a known aromatic plant which is cultivated for its essential oil widely applicated in perfumery and cosmetic industries. In the present study, the effect of biofield treatment was studied on the growth of P. cablin. For this study an in vitro culture system was set up in two groups, viz., control and treatment, each of which was derived from three different explant sources, namely leaf, node and petiole. Further these in vitro plantlets were hardened and transferred to external environment. The stomatal cells and epidermal hair growth were also studied at various morphogenetic stages. The study revealed that a single spell of biofield energy treatment produced significant increase in growth in treated group throughout all the morphogenetic phases from in vitro to in vivo level. A remarkable increase in stomatal cells and epidermal hair was also seen in treated group.

The effect of retinyl-palmitate on brain regeneration of larval Xenopus laevis

In this work we have studied the effect of treatment with retinyl-palmitate (RP) upon brain regeneration of Xenopus laevis larvae submitted to partial removal of telencephalon, mesencephalon and cerebellum. Results demonstrated a specific inhibitory effect on brain regeneration. At the level of the telencephalon, the inhibition took place above all in the proliferative phase of the regenerative process, delaying, as a consequence, the evolution of the same process. Nevertheless, the morphogenetic phase suffered a very modest inhibition resulting in a moderate accentuation of the hypomorphosis observed in the operated controls raised in water. At the level of the cerebellum, the inhibitory action exercised by RP treatment was much greater than that observed in the telencephalon and continued not only in the proliferative phase, but also the morphogenetic phase of the regenerative process. As a result of such an inhibition, the animals treated with RP either regenerated an extremely hypomorphic cerebellum or did not regenerate at all. At the level of the mesencephalon, RP treatment did not produce a sharp inhibition of proliferative activity, but slightly influenced the morphogenesis of the regenerated optic tectum, which was thinner but more extended. In conclusion, the data of the present work demonstrate that the stem cells responsible for the regenerative processes of the larval brain have a sensitivity to retinoids that is region-specific.

Neurogenesis during optic tectum regeneration in Xenopus laevis

The regenerative neurogenesis of the optic tectum of larval Xenopus laevis has been studied analyzing the proliferative and morphogenetic phases of the regeneration process after removal of one optic lobe. To this end, short-term and long-term pulses were carried out using the thymidine analog BrdU, selectively incorporated into cells during the S phase of the cell cycle. Results indicate that while in early larvae (stage 49/50, according to Nieuwkoop & Faber 1967) regeneration occurs mainly at the expense of the stem cells present in extensive proliferation zones ("matrix areas") of the midbrain, in late larvae (stage 55/56) regeneration occurs at the expense of stem cells present in very limited matrix areas of the brain and of quiescent cells, which re-enter the cell cycle following trauma. Moreover, in early larvae, morphogenesis of the optic tectum is carried out according to a precise spatio-temporal order from rostro-caudal to latero-medial. By contrast, in late larvae, the topographical order of the regenerative morphogenesis of the optic lobe is completely altered. As a consequence, the regenerated optic tectum in early larvae has an apparently normal structure, while the regenerated optic tectum in late larvae lacks stratification.

A quantitative analysis of leaf growth parameters in Myriophyllum aquaticum (Haloragaceae)

This quantitative developmental study examines various parameters associated with the growth of leaves of Myriophyllum aquaticum (Vell.) Verdc. on different shoot systems from a single clonal plant to determine the dynamics of growth processes during the development of a normal, typical leaf. Early stages of development, representing the morphogenetic phase of leaf formation, were used to document the growth rate of leaves, the dynamics of leaf lobe formation, the location of initiation of leaf lobes, and allometric relationship between leaves and leaf lobes. Even though there were variations in maximum leaf length between shoot systems, similar growth patterns were observed. In addition, during the exponential phase of growth, the location of initiation of those lobes was constant in each shoot system. There was a positive correlation between the rate of growth of leaves and the rhythm of initiation of lobes resulting in the formation of strikingly similar leaf morphologies regardless of whether the leaf is long with more lobes or short with fewer lobes. An allometric relationship between leaf length and the length of its lobes was observed. To our knowledge, this has never been noted in a system like this. The existence of constant parameters of growth is essential to maintain some degree of consistency but variations in the modalities of those parameters allow for flexibility within the system. For example, the interplay between rates of leaf growth and duration of growth can explain the range of maximum leaf length observed or can be viewed as a way of using different means to achieve similar end products (fast rate of growth and short duration versus slower rate of growth and longer duration).

Hierarchical Developmental Morphology: The Case of the Inflorescence ofPhilodendron ornatum(Araceae)

This study deals specifically with floral organogenesis and the development of the inflorescence of Philodendron ornatum. The development of the inflorescence of P. ornatum can be divided into two morphogenetic phases: (i) before and (ii) after the initiation of the floral organs. Before the initiation of the floral organs, the ratio between the width and the length of the inflorescence is greater than after their initiation. The first phase corresponds to the establishment of the phyllotactic pattern, and the second phase corresponds to the differentiation of floral organs. Pistillate flowers are initiated on the lower portion of the inflorescence, and the staminate flowers are initiated on the distal portion. An intermediate zone consisting of sterile male flowers and atypical bisexual flowers (ABFs) with carpels and staminodes inserted on the same whorl is also present. The portion of the ABFs facing the male zone forms staminodes, and the portion facing the female zone develops an incomplete gynoecium with a few carpels. This phenomenon raises the issue of relationships between hierarchical levels and their mutual influence on the developmental morphology of ABFs. In this article, this question is addressed in the context of the basic triadic system developed by Salthe.

14C age anomalies in modern land snails shell carbonate from Southern Italy

Radiocarbon dating based on geomorphological, archaeological and biological data is widely used in geomorphological studies to reconstruct sequences of climatic variations and coastal evolution during the Holocene. The coastal area of Southern Italy is characterized by aeolian dune belts shaped during the Holocene that crop out along the present shoreline. Archaeological data and previous radiocarbon results suggest three aeolian morphogenetic phases. The first phase corresponds to the end of the rapid post-glacial transgression (7.0–6.0kaBP); the second to the aeolian sand deposition during the “Greek–Roman” period (2.5–1.9kaBP); and the most recent phase occurred in the period from the Middle Ages to the present time. The reconstruction of the sequence of the morphogenetic phases was mainly based on radiocarbon analyses carried out on both terrestrial gastropods and marine bivalves. The reliability of the radiocarbon analyses on terrestrial gastropod shells has been questioned by several Authors and a closer understanding of the carbon uptake mechanism in this kind of organisms is needed.A systematic study was carried out by performing Accelerator Mass Spectrometry (AMS) 14C dating on the shells of terrestrial gastropods sampled alive in different geomorphological settings along the Adriatic and Ionian coasts of Southern Italy. The results show significant anomalies in the radiocarbon content and in the carbon stable isotopic ratio. This can be due to the ingestion of 14C-depleted calcium carbonate in the diet of these organisms. We also calculated the carbon fraction from air Xa (between 16% and 48%), plants Xv (between 36% and 73%) and limestone Xc (between 3% and 23%) giving insight to the origin of the age anomalies.

Holocene aeolian morphogenetic phases in Southern Italy: Problems in 14C age determinations using terrestrial gastropods

Radiocarbon age determination is one of the most important methods for dating Holocene events. In particular, it has been used to reconstruct the sequence of aeolian morphogenetic phases along the Apulia and Basilicata coasts (Southern Italy). In these areas, three main Holocene morphogenetic phases have been recognized using radiocarbon data obtained from sub-fossil terrestrial gastropods, archaeological data and OSL analyses: those of the Middle Holocene period, of the Greek–Roman time and of the Middle Ages. Sub-fossil terrestrial gastropods have been considered suitable indicators in the detecting Holocene climate–environmental changes. However, it is well-known that they could show problems as chronological indicators mainly due to aging effects induced by: (i) micro-particles of calcite/aragonite in the shell structure, derived from the local substratum and (ii) a variation of CO 2 content in the plants eaten. In order to verify these hypotheses, living terrestrial gastropods were collected from coastal areas and analysed using AMS. The results indicate that many living gastropods gave ages of 1500 years older than those expected, thus confirming the aging effect. As 14C ages of Middle and Late Holocene aeolian morphogenetic phases, obtained from terrestrial gastropods, seem to be confirmed by archaeological data and OSL analyses. The aim of this work is to verify if the age anomalies obtained from modern gastropods could be extended to the entire Holocene period.

Arteries define the position of the thyroid gland during its developmental relocalisation

During vertebrate development, the thyroid gland undergoes a unique relocalisation from its site of induction to a distant species-specific position in the cervical mesenchyme. We have analysed thyroid morphogenesis in wild-type and mutant zebrafish and mice, and find that localisation of growing thyroid tissue along the anteroposterior axis in zebrafish is linked to the development of the ventral aorta. In grafting experiments, ectopic vascular cells influence the localisation of thyroid tissue cell non-autonomously, showing that vessels provide guidance cues in zebrafish thyroid morphogenesis. In mouse thyroid development, the midline primordium bifurcates and two lobes relocalise cranially along the bilateral pair of carotid arteries. In hedgehog-deficient mice, thyroid tissue always develops along the ectopically and asymmetrically positioned carotid arteries, suggesting that, in mice (as in zebrafish), co-developing major arteries define the position of the thyroid. The similarity between zebrafish and mouse mutant phenotypes further indicates that thyroid relocalisation involves two morphogenetic phases, and that variation in the second phase accounts for species-specific differences in thyroid morphology. Moreover, the involvement of vessels in thyroid relocalisation sheds new light on the interpretation of congenital thyroid defects in humans.

The Caenorhabditis elegans ortholog of human PHF5a shows a muscle-specific expression domain and is essential for C. elegans morphogenetic development

We have recently described a novel human and murine multigene-family that is highly conserved during evolution and shows a PHD-finger-like domain present in the deduced protein sequences. Here, we describe the cloning and characterization of the Caenorhabditis elegans ortholog of human PHF5a. Transgenic phf-5::yfp-reporter techniques in C. elegans identified temporal C. elegans phf-5 expression being restricted to late C. elegans development. The phf-5::yfp expression starts within the morphogenetic phase of embryonic development and lasts to the stage of adult worms. Spatial phf-5 expression is muscle-specific with an expression in the developing pharynx, in body wall muscular structures, and in the anal muscles. By phf-5 RNAi we further demonstrated that PHF-5 is essential in the morphogenetic phase of C. elegans embryonic development as well as in young larvae. In contrast, phf-5 RNAi does not show an evident phenotype to adult worms. Taken together, this is the first report providing evidence for a tissue and stage-specific expression of a PHF5a ortholog, named phf-5, in C. elegans while our data further suggest an essential role of the encoded PHF-5 protein in morphogenetic development and muscle function.

Developmental Changes Underlying the Formation of the Specialized Time Coding Circuits in Barn Owls (Tyto alba)

Barn owls are capable of great accuracy in detecting the interaural time differences (ITDs) that underlie azimuthal sound localization. They compute ITDs in a circuit in nucleus laminaris (NL) that is reorganized with respect to birds like the chicken. The events that lead to the reorganization of the barn owl NL take place during embryonic development, shortly after the cochlear and laminaris nuclei have differentiated morphologically. At first the developing owl's auditory brainstem exhibits morphology reminiscent of that of the developing chicken. Later, the two systems diverge, and the owl's brainstem auditory nuclei undergo a secondary morphogenetic phase during which NL dendrites retract, the laminar organization is lost, and synapses are redistributed. These events lead to the restructuring of the ITD coding circuit and the consequent reorganization of the hindbrain map of ITDs and azimuthal space.

Holocene coastal dune development and environmental changes in Apulia (southern Italy)

Abstract The coastal area of southern Apulia is characterised by marine deposits of Pleistocene and Holocene ages. It shows the effects of different phases of coastal morphology evolution. During the Middle and Upper Pleistocene, a number of marine terraces were shaped. In some places, they are characterised by thin beach deposits along with a dune belt and relative back dune deposits. Two important morphogenetic phases occurred during the Holocene. The former was characterised by deposition of beach deposits placed slightly above present mean sea level, and by formation of dune belts which were radiometrically aged about 6000 years BP. This event marks the end of the rapid postglacial transgression that occurred during the Holocene Climatic Optimum. During the younger phase, dated at about 2500 years BP, deposition of aeolian sands occurred. Archaeological and morphological evidences suggest that this phase should be related to a low sea-level stand followed by a slow sea-level rise up to the present position and by humid-temperate climatic conditions. The collected data about the Holocene dune belts occurring along the Apulian coastline suggest that main phases of dune development could be related to the effects of sea-level changes, climatic conditions, and in a subordinate way, to human activity.