Search

Copyright of Canadian Journal of Botany is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Botany is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Botany is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper examines the question of how the unique shoot architectural pattern of the Vitaceae, typically with leaf-opposed tendrils or inflorescences in a three-node modular repetitive pattern, can be related to the traditional concepts of monopodial and sympodial shoot development. Based on complete comparative morphological developmental studies of 13 species in six genera, supplemented with observations of 21 other taxa, we have found five shoot architectural patterns in the family. The pattern of shoot architecture is consistent within a species, but there may be more than one pattern present within a genus. Species that lack tendrils, thus exhibiting pattern 1, show sympodial growth. Taxa exhibiting patterns 2, 3, and 4, with tendrils at two of three nodes and with progressively one, two, or three axillary buds within the three-node cycle, grow monopodially, and taxa that exhibit pattern 5, with both tendrils and axillary buds at every node, achieve the pattern via either monopodial or sympodial growth, depending on the species. Although rare in the Vitaceae, pattern 1 is the only one shared with the sister family Leeaceae. We conclude that this was the original shoot architectural pattern, and that the monopodial pattern present in most species today is derived, and unique to the Vitaceae. Les auteurs soulèvent la question à savoir comment le patron caulinaire architectural unique des Vitaceae, typiquement avec des inflorescences ou des vrilles opposées aux feuilles selon un patron trinodal, modulaire et répétitif, peut être relié aux concepts traditionnels de développement caulinaire monopodial et sympodial. Sur la base d’études complètes du développement comparé chez 13 espèces et six genres, en plus d’observations chez 21 autres taxons, les auteurs reconnaissent cinq patrons d’architecture caulinaire dans la famille. Le patron d’architecture caulinaire est congruent avec l’espèce, mais on peut retrouver plus d’un patron dans un genre. Les espèces dépourvues de vrilles, appartenant donc au patron 1, ont une croissance sympodiale. Les taxons montrant les patrons 2, 3, 4, avec des vrilles sur deux ou trois nœuds et avec progressivement un, deux, ou trois bourgeons axillaires, dans le cadre d’un cycle trinodal, se développent de façon monopodiale. Les taxons montrant le patron 5, ayant à la fois des vrilles et des bourgeons axillaires sur tous les nœuds, réalisent ce patron par une croissance soit monopodiale ou soit sympodiale, selon l’espèce. Bien qu’il soit rare chez les Vitaceae, le patron 1 est le seul qui soit commun avec la famille sœur des Leeaceae. Les auteurs concluent qu’il s’agit du patron original d’architecture caulinaire, et que le patron monopodial, tel qu’il se présente chez la plupart des espèces actuelles, est dérivé et unique au Vitaceae. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Botany is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Several authors have proposed that the European Hordeum secalinum and the morphologically similar South African Hordeum capense are conspecific. In this paper we provide evidence that the two species differ in their 5S DNA unit class composition. We also report on the diversity of 5S DNA units in Hordeum muticum, a South American species. When the 5S rDNA unit class composition for these three species is compared with the unit class composition for all Hordeum species thus far investigated, it appears that H. capense is more closely related to the American Hordeum species containing the long Y2 unit class, than to H. secalinum, which lacks the long Y2 unit class but contains the long X2 unit class found in H. marinum. This analysis suggests H. capense may have originated from a stock common to the South American species, such as H. muticum. [ABSTRACT FROM AUTHOR]

Resin canals are an important taxonomic characteristic in conifers. In this paper we examined within- and between-needle variation of the cross-sectional number of resin canals in Scots pine (Pinus sylvestris L.). Variation within needles was determined from 12 free-hand sections taken along the whole length of foliage collected from a common crown position. The effect of crown location and tree age on resin-canal density was also examined from the midpoint cross sections of 450 Scots pine needles collected from interior and exterior locations from the top, middle, and bottom of 25 crowns of trees ranging in age from 8 to 70 years. Within-needle resin-canal density varied with needle length. Two resin canals were typical for the basal and the terminal needle cross sections. There were 3.2 and 8.6 resin canals for cross sections taken from 10 and 30% of the needle length from the basal sheath, respectively. Resin-canal density was largest, and relatively constant, between 30 and 80% of the needle length. We found significant differences in the cross-sectional number of needle resin canals, as influenced by crown positions and tree age. Resin-canal density increased with foliage height. Foliage from the top one-third of crowns had significantly more resin canals than foliage from the bottom. Foliage collected from the crown interior (proximal to the stem) had fewer resin canals than samples from the crown edge. Resin-canal density increased from 7.1 to 10.3 as tree age increased from 8 to 70 years. These results suggest that crown position and tree age need to be incorporated into the sampling protocols used to establish species standards in resin-canal density, at least for Scots pine, if meaningful comparisons are to be made.Key words: resin canal, needle age, crown position, needle anatomy, Pinus sylvestris.Les canaux résinifères constituent une caractéristique taxonomique importante chez les conifères. Les auteurs ont examiné la variation dans l'aiguille et entre les aiguilles du nombre de canaux résinifères, en section transverse, chez le pin sylvestre (Pinus sylvestris L.). La variation dans l'aiguille a été évaluée à partir de 12 sections à main levée prélevées le long de l'ensemble de feuillage récolté en un point commun de la cime. L'effet de la localisation sur la cime et de l'âge de l'arbre sur la densité des canaux résinifères à été aussi examiné à partir de sections prélevées au centre de 450 aiguilles de pin sylvestre récoltées à l'intérieur et à l'extérieur du sommet, du centre et de la base de la cime de 25 arbres allant de 8 à 70 ans d'âge. La densité des canaux résinifères dans l'aiguille varie selon la longueur de l'aiguille. Deux canaux résinifères sont typiques pour les sections transverses basales et apicales des aiguilles. On retrouve respectivement 3,2 et 8,6 canaux résinifères dans les sections prises à 10 et 30% de la longueur de l'aiguille, à partir de sa base. La densité des canaux résinifères est plus grande, et relativement constante, entre 30 et 80% de la longueur de l'aiguille. En sections transverses, on observe des différences significatives dans le nombre de canaux résinifères de l'aiguille sous l'influence de la position dans la cime et de l'âge. La densité des canaux résinifères augmente avec la hauteur du feuillage. Le feuillage du tiers supérieur des cimes possède significativement plus de canaux résinifères que celui du bas de la cime. Le feuillage récolté à l'intérieur de la cime (à proximité du tronc) montre moins de canaux résinifères que les échantillons provenant du pourtour de la cime. La densité des canaux résinifères augmente de 7,1 à 10,3 à mesure que l'arbre vieillit, de 8 à 70 ans. Ces résultats suggèrent que la positon dans la cime et l'âge de l'arbre devraient être pris en compte dans les protocoles d'échantillonnage utilisés pour établir les densités standards de l'espèce en canaux résinifère, du moins chez le pin sylvestre, si on veut faire des comparaisons significatives.Mots clés : canal résinifère, âge des aiguilles, position dans la cime, anatomie de l'aiguille, Pinus sylvestris.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

The spatial structure of plant communities as well as the quality and abundance of neighbours can strongly influence the intensity of herbivory suffered by a plant. In this paper, we study the effect of the association with shrubs on the ungulate herbivory suffered by Scots pine (Pinus sylvestris var. nevadensis Christ., Pinaceae) saplings in two isolated, fragmented populations in southeastern Spain. For this, we monitored herbivory on saplings with regard to the microhabitat in which they grew. We distinguished pines growing in open interspaces, on the edge of shrubs and within the canopy of shrubs, and also we distinguished four functional types of shrubs: thorny shrubs, nonthorny shrubs, thorny scrubs, and nonthorny scrubs. Our results show that association with shrubs increases the damage inflicted on Scots pine saplings. In fact, saplings growing in the open patches, far from the shrubs, escaped from herbivory more frequently and incurred less damage than did saplings growing close to shrubs. However, herbivory was also reduced when pine saplings were completely surrounded by shrubs, since then they served as a mechanical barrier. The type of neighbouring shrub did not affect the overall damage suffered by pines, despite the fact that the ungulates damaged the nonthorny scrubs more intensely than the other kinds of shrubs. Consequently, saplings have an advantage when growing within the canopy of shrubs; these constitute key microsites for pine recruitment in these Mediterranean forests.Key words: associational resistance, associational susceptibility, mammalian herbivory, Mediterranean high mountain, neighbouring effects, Pinus sylvestris var. nevadensis.La structure spatiale des communautés végétales ainsi que la qualité et l'abondance des voisins peuvent fortement influencer l'intensité de l'herbivorie subie par les plantes. Les auteurs ont étudié l'effet de l'association avec des arbustes sur l'herbivorie subie de la part des ongulés par de jeunes plants de pin sylvestre (Pinus sylvestris var. nevadensis Christ., Pinaceae) dans deux populations isolées et fragmentées du sud-est de l'Espagne. A cette fin, ils ont suivi l'herbivorie chez les jeunes plants en relation avec le microhabitat où ils poussent. Ils ont distingué les pins poussant dans les espaces ouverts, près d'arbustes et sous la canopée des arbustes, et ont également identifié 4 types fonctionnels d'arbustes : arbustes épineux, arbustes non-épineux, rebuts (scrubs) épineux, rebuts non-épineux. On observe que l'association avec les arbustes augmente le dommage subi par les jeunes plants de pin sylvestre. En fait, les jeunes plants poussant dans les espaces ouverts, loin des arbustes, échappent à l'herbivorie plus souvent et subissent moins de dommages que les jeunes plants poussant près des arbustes. Cependant, l'herbivorie est également réduite lorsque les jeunes plants de pin sont complètement entourés d'arbustes, qui servent alors de barrière mécanique. Le type d'arbuste avoisinant n'affecte pas les dommages en général subis par les pins en dépit du fait que les ongulés s'attaquent plus intensément aux rebuts non-épineux qu'aux autres types d'arbuste. Conséquemment, les plantules ont avantage à pousser sous la canopée des arbustes, qui constitue des microsites déterminants pour le recrutement des pins dans ces forêts méditerranéennes.Mots clés : résistance d'association, susceptibilité d'association, herbivorie des mammifères, hautes montagnes méditerranéennes, effets de voisinage, Pinus sylvestris var. nevadensis.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Botany is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Botany is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Botany is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Botany is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Botany is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Botany is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Botany is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Botany is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Botany is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Botany is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Botany is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Botany is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Botany is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Botany is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Botany is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Botany is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Botany is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Botany is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Botany is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Botany is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Botany is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Botany is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Botany is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Botany is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Botany is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Botany is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Botany is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Botany is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study compares the development of the inflorescences and flowers of Parthenocissus quinquefolia (Virginia creeper) and Parthenocissus tricuspidata (Boston ivy). The development of the reproductive shoots is described from inception to maturity using epi-illumination and scanning electron microscopy. In both species, the shoot apex initiates inflorescence primordia low on the apical flank. An inflorescence primordium produces several bract-opposed branches, which in early development resembles the main shoot. As inflorescence development continues, branch primordia initiate as increasingly larger portions than the inflorescence apical meristem. By late development, branch primordia initiate as larger portions than the apex, which is a process that has been observed in other vitaceous inflorescences. With respect to initiation and early development, the Parthenocissus inflorescence is very similar to the tendril, which has been previously studied; these two organs have never been described to be so similar, and their likeness to the shoot, in early development, provides an idea as to how they may have arisen. An inflorescence branch terminates as a dichasium, which is formed by two nearly simultaneous branching events. Parthenocissus tricuspidata flowers develop a more robust gynoecial disc and stigma than in the P. quinquefolia flower; but the calyx is ring-like in the former and cup-like in the latter. Contrary to the previous assumption that there axe no differences in reproductive biology within genera of the Vitaceae, this study has clearly demonstrated variation between two species of Parthenocissus. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Botany is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Botany is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Botany is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Presents a study that described the colonization observed in three cultivars of Linum usitatissimum L., an important agricultural plant that shows intercellar hyphae and arbuscules characteristics of Arum-type colonization. Colonization patterns; Incidence of different metabolic status in twin arbuscular units of Glomus intraradices; Development of paired arbuscules.

Focuses on the development structure and chemistry of the endodermis and exodermis in plant roots. Functions of a root; Early ontogeny of the endodermis and exodermis; Description of Casparian bands; Information on suberin lamellae.

Presents a study that described an evaluation of growth media used to measure population density of Verticillium (V.) dahliae in naturally infested soil. Background on the comparisons of different growth media for quantifying V. dahliae; Materials and methodology; Novel contributions of the study.

The author outlines the major milestones in his 40-year career in plant research. His research program might be described, broadly, as explorations into the physiology and biochemistry of plants and their cells using physiological, biochemical, genetic, molecular biological and chemical techniques and technologies. The main areas encompassed by the program are the pathways of biosynthesis of branched-chain amino acids, pantothenate, folates and one-carbon units, uptake of organic and inorganic sources of nitrogen by plant cells, and somatic hybridization and genetic transformation of plant protoplasts. Many of these investigations were carried out with the aid of auxotrophic and resistance genetic variants selected either from cultures of Datura innoxia cells or from among mutagenized populations of Arabidopsis thaliana seedlings. Some technologies found to be especially useful were plant cell and tissue culture, detection of [sup 14] C-labelled isotopes in metabolic intermediates, isolation, purification and characterization of enzymes, and most recently, [sup 13] C nuclear magnetic resonance (NMR) spectroscopy.Key words: Arabidopsis, Datura, biochemical genetic variants, tissue culture, nitrogen metabolism.L'auteur souligne les principales étapes de ses 40 années de carrière de recherche sur les plantes. On pourrait décrire l'ensemble de son programme de recherche comme l'exploration de la physiologie et de la biochimie des plantes, et de leurs cellules, en utilisant des techniques et des technologies chimiques, biochimiques, génétiques et bio-moléculaires. Les principaux domaines couverts par ce programme impliquent les sentiers de la biosynthèse des acides aminés en chaînes ramifiées, du panthoténate, des foliates et des unités mono-carbonées, l'absorption des sources d'azote organiques et inorganiques par les cellules végétales, ainsi que l'hybridation somatique et la transformation génétique des protoplastes végétaux. Plusieurs de ces recherches ont été conduites avec l'aide de variants auxotrophes et génétiquement résistants, sélectionnés soit de cultures de cellules du Datura innoxia, ou soit à partir de populations obtenues par mutagénèse de plantules de l'Arabidopsis thaliana. La culture des cellules et des tissus s'est avérée particulièrement utile, tout comme la détection des isotopes du [sup 14] C dans le suivi des métabolites intermédiaires, et l'isolation, la purification et la caractérisation d'enzymes, et plus récemment la spectroscopie par résonance magnétique nucléaire (NMR) [sup 13] C.Mots clés : Arabidopsis thaliana, Datura, variants génétiques biochimiques, culture de tissus, métabolisme de l'azote.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

Hummingbird flower mites and hummingbirds may compete intensely for the nectar secreted by their host plants. Here, we present the results from field experiments in which flower mites were excluded from flowers of six hummingbird-pollinated plants with contrasting flower longevities. Nectar measurements were taken on flowers from which mites were excluded and those without mite exclusion over their lifespans. The exclusion of mites had a significant positive effect on the amount of nectar available in plants with long-lived flowers. In contrast, nectar availability in short-lived flowers was not significantly reduced after mite exclusion. The significance of the mite-exclusion treatment was independent of floral morph and flower age. Results also suggest that the magnitude of the mite-exclusion treatment depends on the volume of nectar produced by the flower throughout its lifetime. The treatment effect was detected when nectar consumption, presumably by flower mites, exceeded 13% of the nectar produced by the flowers; nectar availability was not significantly reduced when nectar volume was < 7 µL per flower. It appears that flower mites consume proportionately more nectar in long-lived flowers than in short-lived flowers. Parasitic hummingbird flower mites seem to be preferentially taking advantage of plant-pollinator interactions in which flowers last several days and produce large volumes of nectar. The consequences of this finding concerning plant–hummingbird–mite interactions await further investigation. As a working hypothesis, we propose that nectar production has increased over evolutionary time not only by the selective pressures imposed by the pollinators, but also to compensate for the reduction they suffer after exploitation by nectar robbers and thieves such as flower mites.Key words: Ascidae, flower longevity, hummingbird pollination, multiple-species interactions, mutualism exploitation, nectar theft.Les acariens des oiseaux-mouches et les oiseaux-mouches floricoles sont en forte compétition pour le nectar secrété par leurs plantes hôtes. Les auteurs présentent les résultats d'expériences conduites sur le terrain dans lesquelles les acariens floricoles ont été exclus des fleurs de six plantes pollinisées par des oiseaux-mouches, ces fleurs ayant diverses longévités. Ils ont mesuré le nectar sur des fleurs dont les acariens ont été exclus et des fleurs sans exclusion, au cours de leurs durées de vie. L'exclusion des acariens affecte positivement la quantité de nectar disponible sur les plantes ayant des fleurs longivives. Au contraire, chez les plantes ayant des fleurs à courte durée de vie, l'exclusion des acariens n'a pas d'effet significatif. L'importance du traitement par exclusion des acariens est indépendante de la forme de la fleur et de l'âge de la fleur. Les résultats suggèrent également que l'importance du traitement par exclusion des acariens dépend du volume de nectar produit par la fleur, au cours de sa durée de vie. On détecte l'effet du traitement lorsque la consommation du nectar, probablement par les acariens floricoles, dépasse 13 % du nectar produit par les fleurs; la disponibilité n'est pas significativement réduite lorsque le volume du nectar est < 7 µL par fleur. Il semble que les acariens floricoles consomment proportionnellement plus de nectar chez les fleurs longivives que chez les fleurs à courte durée de vie. Le acariens floricoles parasites des oiseaux-mouches semblent tirer surtout avantage des interactions pollinisateur/plante chez lesquelles les fleurs durent plusieurs jours et produisent de grandes quantités de nectar. Les conséquences de ces observations sur les interactions plantes – oiseaux-mouches – acariens nécessitent plus de recherches. Comme hypothèse de travail, les auteurs proposent que la production de nectar aurait augmenté au cours de l'évolution, non seulement sous l'effet de la pression sélective imposées par les pollinisateurs, mais aussi afin de compenser pour la réduction subie sous l'effet des voleurs de nectar et chapardeurs tels que les acariens floricoles.Mots clés : Ascidae, longévité des fleurs, pollinisation par les oiseaux-mouches, interactions multi-spécifiques, exploitation mutuelle, voleur de nectar.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

Photosynthetic characteristics and their leaf-age dependence were examined to estimate ecophysiological effects on net primary production (NPP) of a polar willow (Salix polaris), a dominant dwarf shrub species in a polar semi-desert area of Ny-Ålesund, Svalbard. Leaves of S. polaris emerged just after snowmelt in early July in 2000; flowers were initiated within 1 week, and fruits in late July. Light-saturated rate of photosynthesis and stomatal conductance to water vapor increased rapidly to their maximum values within 1 week after leaf emergence and then decreased gradually. Depending on the leaf age, photosynthetic rates saturated at photosynthetically active photon flux density (PPFD) of 200–400 µmol·m[sup –2] ·s[sup –1] , which is the light level usually available in the natural habitat. Optimum leaf temperature of photosynthesis ranged from 10 to 18°C, while air temperature in the habitat ranged from 8 to 20°C. These light and temperature responses of photosynthesis of S. polaris would be suitable for efficient carbon gain in the natural habitat characterized by highly variable light and temperature conditions. Using the photosynthetic and respiratory characteristics, biomass distribution, and meteorological data, NPP of S. polaris in the current year was estimated to be 26.1 g C·m[sup –2] . A model simulation of rising temperature conditions predicted a reduction of NPP because of a large increase in respiration. It was suggested that temperature condition and leaf phenological aspects strongly influence the carbon fixation by plants in the high arctic area studied.Key words: arctic semi-desert, climate change, net ecosystem production (NEP), net primary production (NPP), Salix polaris, photosynthesis.L'étude porte sur un saule arctique (Salix polaris), une espèce d'arbre nain dominant dans une région polaire semi-désertique du Ny-Ålesund, Svalbard. Afin d'évaluer les effets de facteurs éco-physiologiques sur la production primaire nette (NPP) de cette plante, les auteurs en ont examiné les caractéristiques photosynthétiques et leur dépendance par rapport à l'âge des feuilles. Le S. polaris développe ses feuilles immédiatement après la fonte de la neige au début de juillet (2000), fleurit en moins d'une semaine et fructifie à la fin de juillet. Le taux de photosynthèse en lumière saturante et la conductance stomatale pour l'évaporation de l'eau augmentent rapidement et atteignent leurs valeurs maximales moins d'une semaine après l'émergence des feuilles, puis diminuent graduellement par la suite. Selon l'âge des feuilles, les taux photosynthétiques sont saturés à une densité de flux de photons photosynthétiquement actifs de 200–400 µmol·m[sup –2] ·s[sup –1] , ce qui est égal à l'intensité lumineuse prévalant naturellement dans leur habitat. La température optimale pour la photosynthèse va de 10 à 18°C, alors que la température de l'air dans cet habitat se situe entre 8 et 29°C. Ces réactions de la photosynthèse du S. polaris, en relation avec la lumière et la température, semblent convenir pour assurer un gain en carbone efficace dans cet habitat naturel caractérisé par des conditions de lumière et de température fortement variables. Sur la base des caractéristiques photosynthétiques et respiratoires, ainsi que de la distribution de la biomasse et des données météorologiques, les auteurs estiment que le NPP du S. polaris a été de 26,1 g C·m[sup –2] , au cours de la saison d'observation. Un modèle simulant une élévation des conditions de température permet de prédire une réduction du NPP attribuable à une importante augmentation de la respiration. On suggère que les conditions de température et des aspects phénologiques de la feuille influencent fortement la fixation du carbone par les plantes, dans la région étudiée du Haut arctique.Mots clés : semi-désert, changement climatique, production nette des écosystème (NEP), production primaire nette (NPP), Salix polaris, photosynthèse.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

The early stages of development of the inflorescence of Philodendron insigne were examined using scanning electron microscopy. Pistillate flowers are initiated on the lower portion of the inflorescence and staminate flowers are initiated on the distal portion. The male flowers have three to five stamens. The female flowers have a multilocular ovary consisting of three to five locules. A transition zone consisting of sterile male flowers and atypical bisexual flowers with fused or free carpels and staminodes is located between the male and female floral zones. Generally, the portion of the bisexual flower facing the male zone forms stamens, and the portion facing the female zone develops one or two carpels. In P. insigne, the incomplete separation of staminodes from the gynoecial portion of the whorl shows that the staminodes and carpels belong to the same whorl. The atypical bisexual flowers of P. insigne are believed to be a case of homeosis where carpels have been replaced by sterile stamens on the same whorl. However, there is no regularity in the number of organs involved in the homeotic transformation taking place in atypical bisexual flowers. The presence of atypical bisexual flowers may correspond to a morphogenetic gradient at the level of the inflorescence as a whole.Key words: flower, development, gradient, inflorescence.Les auteurs ont examiné les premiers stades du développement de l'inflorescence du Philodendron insigne, en utilisant la microscopie électronique par balayage. Les fleurs pistillées débutent sur la portion inférieure de l'inflorescence et les fleurs staminées débutent sur la portion distale. Les fleurs mâles portent de trois à cinq étamines. Les fleurs femelles développent un ovaire multiloculaire constitué de trois à cinq loges. Entre les zones florales mâles et femelles, on observe une zone de transition constituée de fleurs mâles stériles et de fleurs bisexuées possédant des carpelles libres ou fusionnés ainsi que des staminodes. Généralement, la portion portant les fleurs bisexuées faisant face à la zone mâle forme des étamines, et la portion faisant face à la zone femelle développe un ou deux carpelles. Chez le P. insigne, la séparation incomplète des staminodes de la portion gynéciale du verticille montre que les staminodes et les carpelles appartiennent au même verticille. On croit que les fleurs bisexuelles atypiques du P. insigne constituent un cas d'homéosis où les carpelles ont été remplacés par des étamines stériles sur le même verticille. Cependant, il n'y a pas de régularité dans le nombre d'organes impliqués dans la transformation homéotique se manifestant dans les fleurs bisexuelles atypiques. La présence de fleurs bisexuelles atypiques pourrait correspondre à un gradient morphogénétique au niveau de l'inflorescence dans son ensemble.Mots clés : fleur, développement, gradient, inflorescence.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

In dioecious and monoecious plants that depend on animal vectors for reproduction, pollinators have to be attracted to male and female flowers for pollination to be effective. In the monoecious Cucurbita maxima ssp. andreana, male flowers are produced in greater quantity, are spatially more exposed to pollinators and offer pollen in addition to nectar as floral rewards. Nectar traits were compared between male and female flowers to determine any differences in the characteristics of the main reward offered to pollinators. Nectar chemical composition and sugar proportions were similar between flower types. Total nectar sugar production per female flower was threefold higher than per male flower, and nectar removal did not have any effect on total nectar production in both flower morphs. Pollinators reduced nectar standing crops to similar and very scarce amounts in both flower types. Results indicate indirectly that pollinators are consuming more nectar from female flowers, suggesting that the higher nectar production in female flowers may be a reward-based strategy to achieve the high female reproductive output observed in this species.Key words: Cucurbitaceae, Cucurbita maxima ssp. andreana, nectar production, nectar sugar composition, removal effects, standing crop.Chez les plantes dioïques et monoïques qui dépendent de vecteurs animaux pour leur reproduction, les pollinisateurs doivent être attirés vers les fleurs mâles et femelles pour assurer leur fécondation. Chez le Cucurbita maxima ssp. andreana, les fleurs mâles sont plus nombreuses, sont plus exposées dans l'espace aux pollinisateurs, et offrent du nectar en plus du pollen comme récompense. Les auteurs ont comparé les caractéristiques du nectar des fleurs femelles avec celles des fleurs mâles, afin de déceler toute différence dans les caractéristiques de la principale récompense offerte aux pollinisateurs. La composition chimique du nectar et les proportions de sucre sont semblables chez les deux types de fleur. La production totale de sucre dans le nectar de la fleur femelle est trois fois plus élevée que dans la fleur mâle, et la récolte du nectar est sans effet sur la production totale de nectar, chez les deux types de fleur. Les pollinisateurs réduisent la présence de nectar à des quantités minimes et similaires chez deux types de fleur. Les résultat indiquent indirectement que les pollinisateurs consomment plus de nectar sur les fleurs femelles, ce qui suggère que la plus forte production de nectar chez les fleurs femelles pourrait être une stratégie basée sur la récompense pour assurer l'important effort de reproduction femelle observé chez cette espèce.Mots clés : Cucurbitaceae, Cucurbita maxima spp. andreana, production de nectar, composition en sucre du nectar, effet de la récolte, production sur pied.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

Basal reiteration (epicormic shoot production from older branch axes) occurred continuously and repeatedly in branches of 450-year-old Pseudotsuga menziesii (Mirb.) Franco var. menziesii (coastal Douglas-fir) trees reproducing sections of branches comprising less than 100 to as many as 10 000 foliated shoots. Basal reiteration occurred mostly from primary and secondary branch axes but also occurred from higher-order axes if lower-order axes had died back. Basal reiteration occurred in distal sections of upper-crown branches, while it occurred in more proximal sections of middle- and lower-crown branches, indicating that basal reiteration works to distribute foliage more uniformly within branches that have reached maximum size. Basal reiteration occurred repeatedly producing two to six generations of reiterated axes within branches. Less than 22.5% of foliated shoots on branches were produced by sequential branching of the primary axis. Basal reiteration also maintained a constant rate of new shoot production within the branch. Growth-ring analysis showed that basal reiteration occurred over a wide range of axis ages (5–58 years). In conjunction with previous studies, we showed that adaptive reiteration of various architectural units by epicormic shoot production is an inherent process that maintains foliage in the crown of old P. menziesii trees.Key words: branch growth, branching pattern, crown maintenance, longevity.La réitération basale (production épicormique de tiges sur les vieux axes de branches) est survenue continuellement et répétitivement sur les branches de Pseudotsuga menziesii (Mirb.) Franco var. Menziesii (Douglas taxifolié de la côte) âgés de 450 ans, produisant des sections de branches comprenant moins de 100 jusqu'à 10 000 tiges foliées. La réitération basale se produit surtout à partir d'axes raméaux primaires et secondaires, mais survient également sur des axes d'ordre supérieur, si les axes d'ordres inférieurs ont dépéri. La réitération basale se produit dans les sections distales des branches de la couronne supérieure, alors qu'on la retrouve dans les sections plus proximales des branches de la couronne médiane et inférieure, ce qui indique que la fonction de la réitération basale est de distribuer le feuillage plus uniformément sur les branches qui ont les plus fortes dimensions. La réitération basale survient répétitivement, produisant de deux à six générations d'axes réitérés par branche. Moins de 22.5 % des tiges foliées formées sur les branches ont été produites par ramification séquentielle de l'axe primaire. La réitération basale maintient également un taux constant de production de nouvelles tiges sur la branche. L'analyse des anneaux de croissance montre que la réitération basale se produit sur une large gamme d'âges (5–58 ans). En concordance avec des études antérieures, les données montrent que la réitération adaptative de différentes unités architecturales par production de tiges épicormiques est un processus inhérent, qui maintient le feuillage dans la couronne des Douglas taxifoliés âgés.Mots clés : croissance des branches, patron de ramification, maintient de la couronne, longévité.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

Transgenic Nicotiana tabacum L. (tobacco) plants expressing an unregulated gene for pyrophosphate-dependent fructose-6-phosphate 1-phosphotransferase (PFP) from the fermentor protist Giardia lamblia were produced. Independently transformed lines revealed a high level of Giardia PFP activity but unaltered activities of native plant PFP, phosphofructokinase, and fructose-1,6-bisphosphatase. Transgenic plants exhibited a decrease in total biomass but no dramatic physiological or morphological alterations or significant reduction of seed yield. Both source and sink tissues demonstrated altered partitioning: leaf starch was significantly lower at the beginning and end of the daily light period and young seeds had lower starch but higher lipid levels, and these changes were correlated with PFP activity. Transgenic seeds had significantly higher percentages of germination, and microscopic examination of these seeds showed a temporal enhancement in growth of the young embryo. The significance of these results as they relate to our current understanding of PFP is discussed.Key words: pyrophosphate-dependent fructose-6-phosphate 1-phosphotransferase (PFP), transgenic, Nicotiana tabacum, glycolysis, photosynthate partitioning.Les auteurs ont produit des plants transgéniques de tabac (Nicotianum tabacum L.) exprimant un gène non régularisé provenant du protiste de fermentation Giardia lamblia, et codant pour la fructose-6-phosphate 1-phosphotransférase dépendante du pyrophosphate (PFP). Des lignées transformées indépendamment montrent un degré élevé d'activité PFP du Giardia, sans que les activités PFP, phosphofructokinase et fructose-biphosphatase de la plante d'origine ne soient altérées. Les plantes transgéniques montrent une diminution de leur biomasse totale, mais aucune altération physiologique ou morphologique importante, ni réduction de la production des graines. Les tissus sources aussi bien que puits montrent une modification des allocations: l'amidon foliaire est significativement plus faible au début et à la fin de la période lumineuse quotidienne, et les jeunes graines possèdent moins d'amidon mais des teneurs en lipides plus élevées, changement qui sont corrélés avec l'activité PFP. Les graines transgéniques ont des pourcentages de germination significativement plus élevés; l'examen microscopique de ces graines montre une stimulation temporaire de croissance du jeune embryon. Les auteurs discutent de la signification de ces résultats en relation avec les connaissances actuelles sur la PFP.Mots clés : fructose-6-phosphate 1-phosphotransférase dépendante du pyrophosphate (PFP), transgénique, Nicotiana tabacum, glycolyse, allocations des photosynthétats.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]