Inconsistencies in the root biology terminology: Let’s communicate better

Plant and Soil - Root biology is an actively developing field that includes ecological, morphological, anatomical, developmental, and evolutionary aspects. I focus this opinion paper entirely on...     

The effect of cytokinins on shoot proliferation,biochemical changes and genetic stability of Rhododendron ‘Kazimierz Odnowiciel’ in the in vitro cultures

Plant Cell, Tissue and Organ Culture (PCTOC) - Shoot proliferation is a very important micropropagation phase, decisive for economic efficiency of this method for a given taxon. To obtain a high...     

The role of topolins in micropropagation and somaclonal variation of banana cultivars ‘Williams’ and ‘Grand Naine’ (<Emphasis Type="Italic">Musa</Emphasis> spp. AAA)

The effect of the cytokinins mT (meta-topolin), mTR (meta-topolin riboside), MemT (meta-methoxy topolin) and MemTR (meta-methoxy topolin riboside) on micropropagation of banana cultivars ‘Williams’ and ‘Grand Naine’ was studied and compared to BA (6-benzylaminopurine). In vitro cultures, at the third sub-culture level, were purchased from African Biotechnologies (Pty) Ltd., South Africa. These were then sub-cultured on MS media containing 7.5, 15 and 30 μM of all the cytokinins tested. Results recorded after 6 weeks of growth demonstrated that there were statistically significant differences between the parameters analyzed for the treatments. Superior multiplication rates were recorded for mT and mTR treatments. This result was consistent when compared to BA at 22.2 μM (previously published standard concentration). Contrary to previous findings with other species, these cytokinins inhibited rooting. The effect on somaclonal variation was not significantly different when BA, mT and mTR were tested at the seventh multiplication cycle for ‘Williams’ banana. These results support the possible use of topolins as an alternative to BA for Cavendish banana tissue culture. The role of these cytokinins on somaclonal variation however, requires a more stringent investigation as the results obtained in this investigation could have been influenced by carry-over effects from the initial cultures.     

Aliens or natives: who are the ‘thugs’ in British woods?

The invasion of native habitats by exotic, or alien, plant species has received considerable attention recently from policy, research, and practical conservation management perspectives. However, a new hypothesis for species dynamics in Britain suggests that a small number of aggressive native plant species (termed ‘thugs’) may have an equal, or greater, impact on native species and habitats than exotic species. Here, we examine this hypothesis using multivariate techniques with field-layer cover data collected during a country-wide survey of British woodlands. Multivariate analysis of these data identified a north-south gradient on the first axis, and that 20 of the 25 National Vegetation Classification woodland types were sampled within the study. The most abundant field-layer species included three of the proposed native ‘thugs’, i.e. Rubus fruticosus, Pteridium aquilinum and Hedera helix in addition to the native woodland indicator species Mercurialis perennis. Variation partitioning was used to compare the relative importance of native field-layer ‘thug’ species with invading alien shrub and tree species relative to other environmental drivers. The variation in the field-layer data-set explained by the three native ‘thug’ species was significant, but they explained a relatively small proportion of the variation relative to other environmental variables (climate, soil, management factors etc.). They did, however, explain almost four times as much variation as the three alien species that were significantly correlated with field-layer species composition (Acer pseudoplatanus, Impatiens glandulifera, Rhododendron ponticum). The results of this analysis suggest that the field-layer of British woodlands is impacted as much by native ‘thug’ species, as it is from ‘aliens’. Concern about the impact of these native ‘thug’ species has been reported previously, but their impact has not previously been compared to the impact of invading aliens. It is hoped that this analysis will do two things, first to act as a sound baseline for assessing any changing balance that should occur in the future, and second, to prompt both ecologists and conservationists to develop woodland management policies based on sound science.     

Postmitotic ‘isodiametric’ cell growth in the maize root apex

The onset of rapid cell elongation occurred at different distances from the apex in various tissues of the primary root of maize (Zea mays L.). Furthermore, the comparison of these distances with those determined for the cessation of mitotic divisions revealed a considerable discrepancy. The onset of rapid cell elongation was realized much farther from the root apex than the cessation of cell divisions and therefore a distinct region could be distinguished in every examined maize root tissue. This region was denoted the region of postmitotic isodiametric cell growth. Cells in this region grew in width as well as in length and obtained approximately a square-isodiametric shape. They were also characterized, as are cells in the meristem, by intense nucleic-acid metabolism. This prominent postmitotic isodiametric cell growth was observed in both polyploid and diploid tissues, and indicates that postmitotic isodiametric cell growth, like mitotic division and cell elongation growth, represents an important developmental stage in plant cell ontogeny.The authors dedicate this paper to Dr. M. Luxová on the occasion of her 65th birthday     

Insulin-like growth factor-I stimulates cell proliferation in the outer layer of Hertwig’s epithelial root sheath and elongation of the tooth root in mouse molars in vitro

To elucidate the mechanism of root formation in tooth development, we examined the role of insulin-like growth factor I (IGF-I) on early root formation in mandibular first molar teeth from 5-day-old mice. Immunohistochemistry revealed the specific localization of the IGF-I receptor in Hertwigs epithelial root sheath (HERS) in the tooth root. The effect of IGF-I on root development, especially on HERS, was subsequently examined in vitro. The control culture showed normal development of HERS and the periodontium, resembling that in vivo. However, the presence of 100 ng/ml IGF-I resulted in elongation of HERS and increased cell proliferation in its outer layer. These effects were negated by the addition of antibodies specific for IGF-I. Thus, we propose that IGF-I is involved in early root formation by regulating the mitotic activity in the outer layer of HERS.This study was partly supported by grants to N.F. from KAKENHI (no. 13671909), to N.F. and M.J.T. from the Promotion of 2001-Multidisciplinary Research Projects in 2001–2005, and to N.F. and K.I. from Iwate Medical University—Keiryokai Research Foundation (no. 64).     

Rethinking the ‘everyday’ in ‘ethnicity and everyday life’

While ‘ethnicity and everyday life’ is a familiar collocation, sociologists concerned with racism and ethnicity have not engaged very much with the extensive body of social theory that takes the ‘everyday’ as its central problematic. In this essay, I consider some of the ways in which the sociology of the everyday might be of use to those concerned with investigating ethnicity and racism. For its part, however, the sociology of the everyday has tended to be remarkably blind to the role played by racism and racialization in the modern world. It is thus no less crucial to consider how the experiences of racialized groups might help us rethink influential accounts of the everyday. To this end, I provide a discussion of pioneering texts by C. L. R. James and W. E. B. du Bois, both of whom were driven by their reflections on racism and resistance to recognize the everyday not as an unremarked context, but as, precisely, a problematic one.     

The ‘Psychic Surgeon’ and the schizophrenic patient: Crisis in a ‘Medicodrama’

This paper is concerned with a Filipino psychic surgeon confronted by a particularly challenging case of a kind perhaps unprecedented in his practice. The paper describes and analyzes how the practitioner modified his usual clinical performance and adapted his actions to demands of an extremely difficult situation. The case is viewed in wider perspective relative to the significance of performative acts of healing in a pluralistic medical setting.     

Hyoscyamine and proline accumulation in water-stressed Hyoscyamus muticus ‘hairy root’ cultures

Summary The patterns of hyoscyamine and proline accumulation were studied in Agrobacterium-transformed ‘hairy root’ cultures of Hyoscyamus muticus to determine if proline is a metabolic precursor of hyoscyamine. Root cultures were stressed osmotically with mannitol and the subsequent growth, hyoscyamine levels, and proline levels were measured after each transfer to fresh experimental medium for a total of four transfers. H. muticus ‘hairy roots’ were also treated with [U-¹⁴C] proline or [1,4-¹⁴C] putrescine and analyzed for radioactive hyoscyamine. Growth of ‘hairy root’ cultures was reduced by up to 90% in 0.4 M mannitol, and this inhibition persisted for at least four transfers. ‘Hairy root’ cultures of H. muticus accumulated hyoscyamine and free proline (up to 6-fold and 25-fold, respectively) when osmotically stressed with mannitol, and this effect also persisted for four transfers when grown in the same mannitol concentration. Because the total production of hyoscyamine was also increased by twofold, we conclude that the elevated hyoscyamine concentration results from increased hyoscyamine synthesis and not from reduced growth. H. muticus ‘hairy roots’ incorporated radioactivity from [1,4-¹⁴C] putrescine efficiently into hyoscyamine in both treatments, but failed to convert [U-¹⁴C] proline into hyoscyamine. We thus conclude that accumulated proline does not serve as a precursor for hyoscyamine.     

‘So you are a mestiza’: Exploring the consequences of ethnic and racial clumping in the US academy

This paper intends to open a dialogue about the use of two specific labels in the US (i.e. ‘Chicanas’ and ‘Latinas’), with a special emphasis on how they are used in the US academy as both markers and identities. More specifically, this paper explores recent trends in the US academy by which women of Latin American descent are lumped together under the rubric Latinas, and in many cases assumed to be equivalent to Chicanas. Arguing that academia must learn to be more thoughtful when creating, defining and adopting categories, the article warns against recreating the very power dynamics we find in mainstream US society by way of these specific labels. Finally, ‘So you are a mestiza’ reminds its readers that, as a practice, social justice asks for a fundamental recognition of a culturally pluralist, democratic society. In this kind of society, histories must endure and multiple realities must be acknowledged.     

Endophytic bacterial diversity in banana ‘Prata An?’ (Musa spp.) roots

The genetic diversity of endophytic bacteria in banana ‘Prata Anã’ roots was characterized. Two hundred and one endophytic bacteria were isolated, 151 of which were classified as Gram-positive and 50 as Gram-negative. No hypersensitivity response was observed in any of the isolates. The rep-PCR technique generated different molecular profiles for each primer set (REP, ERIC and BOX). Fifty readable loci were obtained and all of the fragments were polymorphic. Amplified ribosomal DNA restriction analysis (ARDRA) of the isolates based on cleavage with four restriction enzymes yielded 45 polymorphic bands and no monomorphic bands. PCR amplified the nifH gene in 24 isolates. 16S rDNA sequencing of the 201 bacterial isolates yielded 102 high-quality sequences. Sequence analyses revealed that the isolates were distributed among ten bacterial genera (Agrobacterium, Aneurinibacillus, Bacillus, Enterobacter, Klebsiella, Lysinibacillus, Micrococcus, Paenibacillus, Rhizobium and Sporolactobacillus) and included 15 species. The greatest number of isolates belonged to the genus Bacillus. The bacteria identified in this study may be involved in promoting growth, phosphate solubilization, biological control and nitrogen fixation in bananas.     

Oddity and the ‘confusion effect’ in predation

We report on two sets of experiments designed to clarify the roles of sensory ‘confusion’ and prey ‘oddity’ as they interact to influence the hunting success of a pursuit predator, the largemouth bass (Micropterus salmoides), on silvery minnows (Hybognathus nuchalis). Bass quickly captured solitary minnows, but performed many unsuccessful attacks and took much longer to make a capture as prey school size was increased. At school sizes of eight and above, bass were effectively stymied, demonstrating the ‘confusion effect’. The inclusion of one or two ‘odd’ (blue-dyed) minnows in a school of eight greatly increased the ability of bass to capture both normal and odd prey, but this effect of oddity disappeared at a school size of 15. The implications of these results for understanding the adaptive basis of mixed species flocks, herds and schools is discussed.     

How are proliferation and differentiation of melanocytes regulated?

Coat colors are determined by melanin (eumelanin and pheomelanin). Melanin is synthesized in melanocytes and accumulates in special organelles, melanosomes, which upon maturation are transferred to keratinocytes. Melanocytes differentiate from undifferentiated precursors, called melanoblasts, which are derived from neural crest cells. Melanoblast/melanocyte proliferation and differentiation are regulated by the tissue environment, especially by keratinocytes, which synthesize endothelins, steel factor, hepatocyte growth factor, leukemia inhibitory factor and granulocyte-macrophage colony-stimulating factor. Melanocyte differentiation is also stimulated by alpha-melanocyte stimulating hormone; in the mouse, however, this hormone is likely carried through the bloodstream and not produced locally in the skin. Melanoblast migration, proliferation and differentiation are also regulated by many coat color genes otherwise known for their ability to regulate melanosome formation and maturation, pigment type switching and melanosome distribution and transfer. Thus, melanocyte proliferation and differentiation are not only regulated by genes encoding typical growth factors and their receptors but also by genes classically known for their role in pigment formation.     

‘Slaughter in the suburbs’: livestock slaughter and race in post-apartheid cities

The slaughter of animals is a fundamental aspect of the economic, social and spiritual life of many people in South Africa. Under apartheid, these events generally occurred in rural areas or urban townships designated for black people. Since the transition to democracy in the 1990s, increased suburban mixing has exposed established middle-class residents, notably white people, to cattle slaughter. The article explores the resulting public discourses on these events, such as condemnations, liberal appeals for tolerance and Africanist claims to citizenship and space. In addition, the article examines anxieties that some white people express in relation to the materiality of the slaughter of animals in residential areas. The article offers a multi-layered analysis of reactions to animal slaughter in relation to race, identity, difference, space and the place of animals and meat production in cities.     

On hotshots and lotteries: are the best males on larger leks better than expected?

Leks are clusters of males that hold territories containingno special resources except for the males themselves (Höglundand Alatalo, 1995). Among hypotheses put forth to explain whysuch clusters form, the hotshot hypothesis posits that leksform by males that would otherwise receive little attentionfrom females taking up positions next to males that would receivea great deal of female attention in any case (Beehler and Foster,1988; Höglund and Alatalo, 1995). Although this ideamight well be true, we still face the task of evaluating theevidence. In this note I question the efficacy of testing forhotshots by observing the success of males at leks of different sizes. Several authors have noted that the males most successful inattracting mates on larger leks are more successful than thebest males on smaller leks (Westcott and Smith, 1997     

Genomic imprinting and kinship in the social Hymenoptera: what are the predictions?

The kinship theory of genomic imprinting predicts that conflicts of interest between parents can promote the evolution of opposed expression patterns of maternally and paternally derived alleles in the offspring. The social Hymenoptera (ants, some bees, and some wasps) are particularly suitable to test this theory, because a variety of social conflicts are predicted due to relatedness asymmetries between female and male nestmates that are a corollary of haplo-diploid sex determination. Here I argue that the kin-selection predictions for genomic imprinting in social Hymenoptera might in many cases be more complex than previously suggested, because the optimal strategy will have to take fitness effects in different castes and sexes into account.