Biomedical subjects

D Barthélémy

Publications and source records attributed to D Barthélémy.

7 recordsLinked to original sources

PubMed2006

Relative extents of preformation and neoformation in tree shoots: Analysis by a deconvolution method.

BACKGROUND AND AIMS: Neoformation is the process by which organs not preformed in a bud are developed on a growing shoot, generally after preformation extension. The study of neoformation in trees has been hindered due to methodological reasons. The present report is aimed at assessing the relative importance of preformation and neoformation in the development of shoots of woody species. METHODS: A deconvolution method was applied to estimate the distribution of the number of neoformed organs for eight data sets corresponding to four Nothofagus species and a Juglans hybrid. KEY RESULTS: The number of preformed organs was higher and less variable than the number of neoformed organs. Neoformation contributed more than preformation to explain full-size differences between shoots developed in different positions within the architecture of each tree species. CONCLUSIONS: Differences between the distributions of the numbers of preformed and neoformed organs may be explained by alluding to the duration of differentiation and extension for each of these groups of organs. The deconvolution of distributions is a useful tool for the analysis of neoformation and shoot structure in trees.

Logistic Models↗

PubMed2003

Periods of organogenesis in mono- and bicyclic annual shoots of Juglans regia L. (Juglandaceae).

The organogenetic cycle of shoots on main branches of 4-year-old Juglans regia trees was studied. Mono- and bicyclic floriferous and vegetative annual shoots were analysed. Five parent annual shoot types were sampled between October 1992 and August 1993. Organogenesis of summer growth units was monitored between 16 Jun. and 3 Aug. 1993. Variations over time in the number of nodes, cataphylls and embryonic green leaves of terminal buds were studied. The number of nodes of parent shoot buds was compared with the number of nodes of shoots derived from parent shoot buds. The spring growth units of mono- and bicyclic shoots consist exclusively of preformed leaves which were differentiated, respectively, during the spring flush of growth (mid-April until mid-May) or the summer flush of growth (mid-June until early August) in the previous growing season. Thus, winter buds may consist of flower and leaf primordia differentiated in two different periods during annual shoot extension. The summer growth units of bicyclic shoots consist of preformed leaves that were differentiated in spring buds during the spring flush of growth in the current growing season. Bud morphology is compared between spring and summer shoots.

Juglans↗

PubMed2002

Periods of organogenesis in shoots of Nothofagus dombeyi (Mirb.) oersted (Nothofagaceae).

The organogenetic cycle of main-branch shoots of Nothofagus dombeyi (Nothofagaceae) was studied. Twelve samples of 52-59 parent shoots were collected from a roadside population between September 1999 and October 2000. Variations over time in the number of nodes of terminal and axillary buds, and the length, diameter and number of leaves of shoots derived from these buds (sibling shoots) were analysed. The number of nodes of buds developed by parent shoots was compared with the number of nodes of buds developed, I year later, by sibling shoots. The length, diameter and number of leaves of sibling shoots increased from October 1999 to February 2000 in those shoots with a terminal bud. However, extension of most sibling shoots, including the first five most distal leaf primordia, ceased before February due to abscission of the shoot apex. Axillary buds located most distally on a shoot had more nodes than both terminal buds and more proximal axillary buds. The longest shoots included a preformed part and a neoformed part. The organogenetic event which initiated the neoformed organs continued until early autumn, giving rise to the following year's preformation. The absence of cataphylls in terminal buds could indicate a low intensity of shoot rest. The naked terminal bud of Nothofagus spp. could be interpreted as a structure less specialized than the scaled bud found in genera of Fagaceae and Betulaceae.

Cell Differentiation↗

PubMed2002

Preformation and neoformation in shoots of Nothofagus antarctica (G. Forster) Oerst. (Nothofagaceae) shrubs from northern Patagonia.

The size (length and diameter) and number of leaf primordia of winter buds of Nothofagus antarctica (G. Forster) Oerst. shrubs were compared with the size and number of leaves of shoots derived from buds in equivalent positions. Buds developed in two successive years were compared in terms of size and number of leaf primordia. Bud size and the number of leaf primordia per bud were greater for distal than for proximally positioned buds. Shoots that developed in the five positions closest to the distal end of their parent shoots had significantly more leaves than more proximally positioned shoots of the same parent shoots. The positive relationship between the size of a shoot and that of its parent shoot was stronger for proximal than for distal positions on the parent shoots. For each bud position on the parent shoots there were differences in the number of leaf primordia per bud between consecutive years. The correlations between the number of leaf primordia per bud and bud size, bud position and parent shoot size varied between years. Only shoots produced close to the distal end of a parent shoot developed neoformed leaves; more proximal sibling shoots consisted entirely of preformed leaves. Leaf neoformation, a process usually linked with high shoot vigour in woody plants, seems to be widespread among the relatively small shoots developed in N. antarctica shrubs, which may relate to the species' opportunistic response to disturbance.

Logistic Models↗

PubMed2001

Pattern analysis in branching and axillary flowering sequences.

In the architectural approach to the study of plants, a major issue is to analyse branching and axillary flowering patterns. Due to the structured expression of the branching process and the noisy character of the observed patterns, we propose an analysis framework which is both structural and probabilistic. Data take the form of sequences which naturally represent the underlying structural information of branching and axillary flowering patterns and allow the application of a large number of methods ranging from exploratory analysis to stochastic modeling. The primary aim of the proposed analysis methods is to reveal patterns not directly apparent in the data, and thus to deepen our biological understanding of the underlying mechanisms that control the branching and the axillary flowering of plants over time and space. The proposed approach is illustrated using a set of examples corresponding to different plant species and different biological or agronomic objectives.

Models, Biological↗

PubMed2001

Dioecy in Fitzroya cupressoides (Molina) I.M. Johnst. and Pilgerodendron uviferum (D. Don.) Florin (Cupressaceae).

The aim of this study was to determine the dioecious or monoecious condition of Fitzroya cupressoides and Pilgerodendron uviferum. The study area lies west of the Nahuel Huapi National Park in northern Patagonia (Argentina), where these species form mixed stands. One hundred individuals of each species were studied over three successive years. The nature and position in the crown of their reproductive organs were recorded. Results showed that both species are dioecious. This feature has been confirmed on trees of these species growing in other sites within their natural distribution area in Argentina and Chile.

Argentina↗

PubMed1986

[Alloimmune neonatal neutropenia in homozygotic female twins].

Female homozygous twins presented with alloimmune neonatal neutropenia due to a maternal neutrophil-specific anti-NA2 antibody. The disease is usually benign, but when accompanied by severe infection it may require exchange transfusion and transfusion of granulocytes free of the antigen involved in the immunological conflict. Owing to the risk of relapse in subsequent pregnancies, the haemogram of the following infants must be supervised.

Agranulocytosis↗