Cytological and Ultrastructural Responses of Platanus acerifolia (Ait.) Willd. Leaves to Cerato-Platanin, a Protein from Ceratocystis fimbriata f.sp. platani

Cerato-platanin (CP) is a purified protein isolated from the culture filtrate of the ascomycete Ceratocystis fimbriata f. sp. platani (Cfp), the causal agent of canker stain disease of plane. The responses of cells/tissues of plane leaves to CP was studied by light microscopy (LM) and by transmission electron microscopy (TEM) using two experimental procedures. The most significant responses occurred already at 24 h after treatments, and were also visible at 48 h. The main effects of CP were to cause a great increase in primary starch and a certain degree of intercellular and intracellular disorganization of the spongy parenchyma cells and plasmolysis processes. In addition, an increase of intracellular phenolic compounds was observed in the palisade cells. The effects of Cfp were similar but less evident than those of CP

Caractérisation de quelques provenances de Pinus halepensis Mill. sur la base de la structure anatomique et morphologique des aiguilles

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Geographic variation and bud dormancy in beech seedlings (Fagus sylvatica L)

Italian populations of beech, originating from zones of similar altitudes but different latitudes (38°16'-43°49'N), were studied. The seedlings, 1 and 2 years old, were grown in Florence (43°45') under natural conditions or in climate-controlled chambers with short (SD) or long day (LD) after having been exposed, or not, to winter chilling (CH and NCH, respectively). Differences observed in precociousness of sprouting, thermal time, growth in length and duration of growing season all indicate a variation among the populations tied to the latitude of their zones of origin. Winter chilling was demonstrated to be the principal factor in the removal of dormancy in all the populations studied. In the northernmost populations a significant effect on sprouting was attributable also to photoperiodic regime. The interaction chilling x long day indicates that LD is able to partially substitute winter chilling and that once the need for removal of dormancy has been satisfied, temperature is presumably the principal environmental factor that controls sprouting.Variation géographique et dormance des bourgeons chez de jeunes plants de hêtre (Fagus sylvatica L). Sur de jeunes plantules de hêtre, on a étudié la variation géographique du débourrement printanier et l'influence qu'ont le froid pendant l'hiver et le régime photopériodique sur la sortie de dormance. Les altitudes des lieux de provenance du matériel sont identiques, mais les latitudes sont différentes. Dans la première expérience on a cultivé les plantules des trois populations (Bagno di Romagna, latitude 43° 49'N; Pacentro, latitude 42° 03'N; Aspromonte, latitude 39° 09'N) à Florence (latitude 43° 45'N) aux conditions climatiques naturelles. Avec l'augmentation de la latitude des stations de provenance le débourrement printanier devient plus précoce (fig 1) et la croissance en longueur, le « thermal time » et le temps entre le débourrement du bourgeon apical et celui des bourgeons latéraux raccourcissent (tableau I). D'après la deuxième expérience effectuée sur les plantules de deux provenances (Casentino, latitude 43° 48' N, et Aspromonte, latitude 38° 16' N) exposées ou non au froid hivernal puis cultivées en conditions naturelles à Florence, les résultats de la première expérience ont été confirmés en ce qui concerne le débourrement et la croissance (tableau II, figs 2 et 3). En outre un polycyclisme très net chez la population méridionale et une forte dépendance du débourrement vis-à-vis de la période de froid préalable ont été démontrés (tableau II, figs 2 et 3). Chez les deux provenances les plantules exposées aux froid en hiver présentent un débourrement plus précoce et plus rapide par comparaison avec celles qui n'ont pas été exposées. Cet effet est particulièrement évident dans le cas des bourgeons latéraux (figs 2 et 3). Lorsqu'on élève en chambre climatisée, à jours longs ou courts, les plantules des populations de la deuxième expérience en les ayant exposées ou non au froid hivernal, les différences entre populations sont confirmées en ce qui concerne la précocité du débourrement, la croissance en longueur et la durée de la période de végétation (tableau III et fig 4). L'effet très net du froid hivernal sur la sortie de dormance (tableau III) et sur le débourrement qui s'ensuit des bourgeons apicaux et axillaires (tableau V) est aussi confirmé. En effet la période nécessaire pour obtenir la totalité du débourrement est plus longue de 100-150 jours (fig 4) chez les plantules non exposées au froid. On a aussi observé un effet du photopériodisme, qui semble être une caractéristique de la population la plus septentrionale (tableaux V, VI et VII). Les effets des jours longs sont nets sur les temps moyens et sur le pourcentage de débourrement et sur la somme des degrés-jours. L'interaction entre jour long et froid en hiver laisse penser que le jour long est très impliqué dans la sortie de dormance et peut se substituer partiellement aux besoins en froid. Une fois satisfaites les exigences pour la sortie de dormance, c'est la température qui intervient comme principal facteur du milieu controlant le débourrement. Les différences observées au cours de toutes les expériences en ce qui concerne la précocité de débourrement, la croissance en longueur et la durée de la saison de végétation indiquent toutes l'existence parmi les populations de variations liées à la latitude des lieux d'origine

Volatile profile of perennial leaves of seven cultivated species of Ceratozamia (Cycads)

Ceratozamia (Zamiaceae) is a genus of New World Cycads, containing more than 20 species distributed in eastern and southern Mexico, with extensions into Central America [1]. Morphology, anatomy, and molecular data allowed resolution of some aspects of species relationships, suggesting phytogeographic hypotheses [2]. Renewed interest in cycads has also resulted in works focused on phytochemical topics [3 and literature therein], however data on the volatile emission profiles lack. Seven Ceratozamia species belonging to clade \u201cC\u201d [2] and cultivated in a cold greenhouse at the Florence Botanic Garden were investigated: Ceratozamia fuscoviridis D. Moore, Ceratozamia hildae Landry & M. Wilson, Ceratozamia kuesteriana Regel, Ceratozamia latifolia Miq., Ceratozamia longifolia Miq., Ceratozamia mexicana Brongn., Ceratozamia vulgaris J. Schust. Perennial leaves were screened in February, July and September 2011 for the emission of volatile organic compounds (VOCs) by means of headspace solid phase microextraction coupled with gaschromatography and mass spectrometry (HS-SPME-GC/MS); two leaflets per species were sampled from coetaneous leaves, and analysed. In this study we assessed and compared the volatile profiles among species and across sampling periods, with the main objective to collect preliminary information to evaluate the potentiality of VOCs for taxonomic purposes. The VOC analysis revealed the emission of overall 199 compounds, of which 144 identified. The unknown compounds dominated the volatile profiles, accounting for about 27%, followed by aldehydes, terpenes, alcohols, ketones and esters. The highest number of compounds (115) was found in C. fuscoviridis, the lowest (91) in C. longifolia. In all the examined species, February profiles invariably exhibited the major amount of volatiles in comparison to July and September. Statistical data processing proved: (i) a low level of diversity among the VOC profiles of the examined species referred to each collection time; (ii) a great variability in the temporal emission patterns of all the species across the three sampling periods. These evidences revealed the predominance of the environmental components at the study area in affecting the volatile profiles of Ceratozamia species, at the expense of the metabolic resilience related to the different climatic conditions of the native regions. Possible ecological roles of the VOC temporal variation in relation to the plant phenological stages are discussed

Plant species loss and community nestedness after leguminous tree Acacia pycnantha invasion in a Mediterranean ecosystem

Invasions of ecosystems by alien species are one of the major threats to biodiversity. Among alien plant species, members of the family Fabaceae s.l. represent some of the most dangerous and well known global invaders. In Mediterranean ecosystems, many Australian acacias have been found to establish and rapidly spread, often determining severe impacts on understorey vegetation. In the present work, we report a case study of an Acacia pycnantha invasion in a typical Mediterranean matorral (Elba Island, central Mediterranean Sea, Italy). We conducted a survey of understorey plant communities across an invasion gradient from non-invaded to transitional and invaded areas, aiming to quantify the impacts on the understorey assemblage and to investigate the ecological processes involved in the changes in species composition. The understorey plant community was highly affected starting from the intermediate stage of invasion. Species richness, diversity and total cover were all lower in invaded than in non-invaded plots, with a transition generally in the middle. In addition, plant community composition severely changed along the invasion gradient. The species set we recorded showed a nested structure, with the composition of species in the invaded plots representing a subset of the others. According to our findings, A. pycnantha exerted detrimental impacts on the native vegetation, mainly causing a severe species loss in the understorey assemblage and the impoverishment of the invaded ecosystems

Morphological and ultrastructural aspects of dehydration and rehydration in leaves of Sporobolus stapfianus.

The resurrection species Sporobolus stapfianus Gandoger has been studied by LM, TEM and SEM in order to define the leaf morphology and fine structure and to analyse the cellular changes occurring during the processes of dehydration and rehydration of the plant. Some characteristics of the fully hydrated leaf and some ultrastructural and physiological events which take place during leaf wilting are discussed in relation to their possible role in plant desiccation-tolerance. The leaves of S. stapfianus show several characteristics common among xerophytic species. In the resurrection leaf they could play a role in slowing down the drying rate, thus leaving time to activate the mechanisms protecting the cell structures against drought damage. Actually, the S. stapfianus leaves do not undergo important cellular alterations during dehydration. The chloroplasts, in particular, retain part of their photosynthetic pigments and thylakoid membranes. Upon rewatering leaf recovery is rather fast and the tissue structure and cell organization of the fully hydrated state are already regained after two days