Andrea Andreucci

Glandular Hairs and Secretory Ducts of Matricaria chamomilla (Asteraceae): Morphology and Histochemistry

The aim of the present work is to characterize the glandular hairs and the secretory ducts of Matricaria chamomilla (Asteraceae) morphologically, anatomically and histochemically. The glandular hairs are multicellular and biseriate with two basal cells, two peduncle cells and a secretory head composed of six cells. The histochemical tests show that the glands are positive for lipids, essential oils, sesquiterpene lactones, and pectic—like substances. The secretory ducts show a lumen surrounded by a layer of specialized cells, with the exception in the root where the ducts do not show any secretory epithelium. The histochemical tests show that the ducts are always positive for lipids, while the tests for the presence of essential oils and sesquiterpene lactones are heterogeneous in the plant organs considered.

Phylogenetic relationships of Italian Bellevalia species (Asparagaceae), inferred from morphology, karyology and molecular systematics

The seven Bellevalia species and subspecies known from Italy, representing about 10% of the genus and three out of six sections, were studied. An integrated morphological, karyological and molecular approach was used to infer phylogenetic and systematic relationships among them. B. romana (the generitype) is the most distinctive species on karyotype asymmetry grounds. B. boissieri and B.dubia, usually considered as subspecies of one species (the latter endemic to Sicily), deserve specific status based on biparental nrDNA markers (internal transcribed spacer, ITS), since they do not form a single clade. The allotetraploid endemic B. pelagica, morphologically similar to B. romana, is sister to the latter under parsimony, both in morphological and ITS trees; it is also related with B. dubia, based on karyotype asymmetry and a uniparental cpDNA marker (trnL(UAA)–trnF(GAA) IGS (intergenic spacer)). A second allotetraploid endemic, B. webbiana, is closely related, on morphological, karyological and molecular grounds, with B. boissieri and B. ciliata, and also with B. trifoliata, three species that might all involved in its origin. B. sect. Conicae Feinbr. and sect. Nutantes Feinbr. are here typified, the former (type: B. ciliata) is most likely a synonym of the latter (type: B. trifoliata).

The “black nodules” of Hypericum perforatum L. subsp. perforatum : Morphological,anatomical, and histochemical studies during the course of ontogenesis

Hypericum perforatum L., traditionally used in folk medicine as a therapeutic plant, is today investigated for its antidepressant and antiretroviral activities. This species is characterized by the presence of different types of secretory structures: translucent glands or cavities, black nodules, and secretory canals. The aim of the present work is to characterize the black nodules on both the floral and vegetative parts, morphologically, anatomically, and histochemically. Nodules consist of a cluster of irregularly shaped cells surrounded by a single- or double-layered sheath. Histochemical tests show that the nodules are negative for the presence of lipids, essential oils, sesquiterpene lactones, steroids, and proteins and positive for pectic-like substances, tannins, and alkaloids. Our results show that the inflorescences are richest in nodules and are, there f ore, the best sites for the extraction of the secondary metabolites.

Homoploid hybrid speciation in Doronicum L. (Asteraceae)? Morphological, karyological and molecular evidences

Abstract The first unambiguous documentation of hybridism in the genus Doronicum (Senecioneae – Asteraceae) is reported. All our morphological, karyological and molecular data concur to indicate that Doronicum × minutilloi Peruzzi hybr. nov. (2n = 60) is a hybrid growing in Monti Aurunci (Central Italy), originated from the spontaneous crossing D. orientale Hoffm. (2n = 60) × D. columnae Ten. (2n = 60). This new hybrid shows a slightly higher morphological, karyotypic and ribotypic affinity with D. columnae, but shares a trnL-trnF IGS haplotype with D. orientale, and co-occurs with the latter species only; it has reduced fertility and a high potential for vegetative propagation through rhizome fragmentation. Our results led us to suspect in fieri homoploid hybrid speciation.

Arsenic-induced morphogenic response in roots of arsenic hyperaccumulator fern Pteris vittata

On the assumption that arsenic induces stress morphogenetic responses involved in As tolerance and hyperaccumulation in the Pteris vittata fern, we analyzed the root system of young sporophytes grown in 250, 334, and 500 μM As for five days and for 14 days. Anatomical and histological analyses were performed in plants grown for five days to evaluate the number, position, length and differentiation pattern of root hairs. AgNOR staining, employed to study nucleolus behavior in root apices, showed that arsenic influences nucleolar activity (evaluated by nucleolus size, number and absorbance) in the root meristem. In plants treated with 250 and 334 μM As an acropetal shift of root hair development and an increase in hair length and density were observed, linked to an ectopic pattern of differentiation. The opposite trend was recorded in plants treated with 500 μM As. It is worth noting the presence of living border-like cells, not yet observed in ferns, and their increase following As treatments. Analysis and vitality of border-like cells were surveyed after 14 days of treatments. In conclusion As treatments elicited a stress-induced morphogenic response which, by modifying the differentiation pattern, number and length of root hairs, modulating nucleolar activity and interacting with the rhizosphere by inducing border-like cell production, may adjust the rate of root uptake and its metabolic activity.

Anatomical differences of poplar (Populus × euramericana clone I-214) roots exposed to zinc excess

Poplar is one of the suitable candidates for phytoremediation due to extensive root system, fast growth rate, easy propagation and high biomass production. Zinc (Zn) is an essential element, but at high concentration becomes toxic to plants, similarly like cadmium (Cd). In order to evaluate the effect of Zn on root tissue development we conducted experiments with poplar (Populus × euramericana clone I-214) grown in hydroponics. Plants were treated with low (control) and excess level of Zn (1 mM). Changes in the development of apoplasmic barriers — Casparian bands and suberin lamellae in endodermis, as well as lignification of xylem vessels have been investigated. We found that both apoplasmic barriers developed closer to the root apex in higher Zn-treated root when compared with control root. Similar changes were observed in lignification of xylem vessels. For localization of Zn within root tissues, cryo-SEM/EDXMA analyses were used. Most of Zn was localized in the cortical tissues and four-time less Zn was determined in the inner part of the root below the endodermis. This indicates that endodermis serves as efficient barrier of apoplasmic Zn transport across the poplar root.

RNA sequencing of Populus x canadensis roots identifies key molecular mechanisms underlying physiological adaption to excess zinc

Populus x canadensis clone I-214 exhibits a general indicator phenotype in response to excess Zn, and a higher metal uptake in roots than in shoots with a reduced translocation to aerial parts under hydroponic conditions. This physiological adaptation seems mainly regulated by roots, although the molecular mechanisms that underlie these processes are still poorly understood. Here, differential expression analysis using RNA-sequencing technology was used to identify the molecular mechanisms involved in the response to excess Zn in root. In order to maximize specificity of detection of differentially expressed (DE) genes, we consider the intersection of genes identified by three distinct statistical approaches (61 up- and 19 down-regulated) and validate them by RT-qPCR, yielding an agreement of 93% between the two experimental techniques. Gene Ontology (GO) terms related to oxidation-reduction processes, transport and cellular iron ion homeostasis were enriched among DE genes, highlighting the importance of metal homeostasis in adaptation to excess Zn by P. x canadensis clone I-214. We identified the up-regulation of two Populus metal transporters (ZIP2 and NRAMP1) probably involved in metal uptake, and the down-regulation of a NAS4 gene involved in metal translocation. We identified also four Fe-homeostasis transcription factors (two bHLH38 genes, FIT and BTS) that were differentially expressed, probably for reducing Zn-induced Fe-deficiency. In particular, we suggest that the down-regulation of FIT transcription factor could be a mechanism to cope with Zn-induced Fe-deficiency in Populus. These results provide insight into the molecular mechanisms involved in adaption to excess Zn in Populus spp., but could also constitute a starting point for the identification and characterization of molecular markers or biotechnological targets for possible improvement of phytoremediation performances of poplar trees.

Structure, DNA content and DNA methylation of synergids during ovule development in Malus domestica Borkh

Abstract DNA content and DNA methylation of synergids of Malus domestica Borkh have been evaluated in two different stages before fertilization. A monoclonal antibody against 5-methylcytidine has been used to evidence the level and distribution of DNA methylation. In the first stage, both synergids were alike in structure, with a large chalazal vacuole, a large nucleus and nucleolus and a well developed filiform apparatus. One of the two cells was localized closer the mycropilar region of embryo sac. At this stage both cells showed a 2C DNA content and a similar level and pattern of DNA methylation. The two synergids in Malus had different fates. In the second stage, near the time of fertilization, the mycropilar synergid showed signs of degeneration: a reduced size, a compact chromatin and a more darkly stained cytoplasm. DNA methylation of this synergid was twice as much as the other cell and a different distribution of DNA methylation was also evidenced between the two cells, while their DNA content was unaltered. These observations are discussed in relation to the hypothesis of a different gene expression in the two synergids, thus supporting the assumption of a preprogramming for the degeneration of one of the two cells.

Ontogeny of secretory cavities in vegetative parts of Myrtus communis L. (Myrtaceae): an example of schizolysigenous development

Myrtus communis L. is an evergreen shrub, typical of the Mediterranean scrub. This species is characterized by the presence of secretory cavities, the vegetative parts of which have been investigated morphologically and anatomically. The ontogenesis of secretory cavities is schizolysigenous: a combination of schizogenous and lysigenous development. At maturity, glands are made up of a sheath of flattened cells, and secretory cells are completely degenerated.

Three new hybrids of Ophioglossum (Ophioglossaceae) from Monte Pisano, Tuscany (Central Italy)

Based on general morphology, spore measurements and ornamentation (scanning electron microscope), genome size estimation, and molecular systematics (trnL-trnF IGS), we show the extreme systematic complexity within the European representatives of the genus Ophioglossum. In particular, three hybrids from Tuscany are described: the tetraploid O. × pierinii Peruzzi, Magrini, Marchetti & Viane, seen as the hybrid between diploid O. lusitanicum L. and hexaploid O. azoricum C.Presl; the tetraploid O. × giovanninii Peruzzi, Pierini, Magrini, Marchetti & Viane, seen as the homoploid hybrid between tetraploid O. vulgatum L. and tetraploid O. × pierinii Peruzzi, Magrini, Marchetti & Viane; the pentaploid O. × pseudoazoricum Peruzzi, Pierini, Magrini, Marchetti & Viane, seen as the hybrid between hexaploid O. azoricum C.Presl and tetraploid O. vulgatum L. All the three new taxa grow in different localities in the Monte Pisano mountain range.