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Hairy roots were obtained after infection of Artemisia absinthium shoots with Agrobacterium rhizogenes strains 1855 and LBA 9402. The susceptibility to hairy root transformation varied between plant genotypes and bacterial strains. Hairy roots showed macroscopic differences from control root cultures. Southern blot hybridization confirmed the integration of T-DNA from both p1855 and pBin19, while polymerase chain reaction analysis indicated the presence of the neomycin phosphotransferase gene in the hairy root genome. Subcultured transformed root lines grew well in selective B5 agar-solidified medium containing kanamycin or rifampicin and without hormones. Shake-flask experiments with fast-growing root lines showed that 40 g l-1 was the best sucrose concentration for biomass production, yielding a 463-fold increase in dry weight after 28 days of culture. Great differences were found in the profiles of the essential oils isolated from normal and hairy roots. Gas chromatography/mass spectrometry analysis showed the oil produced by transformed cultures to be a mixture of 50 compounds with only one major component representing 37% of the oil content.

Gypsophilapaniculata L. is among the 10 best selling cut flower species globally and is considered a “target” plant for breeding varieties. The aim of this work was to make the genetic improvement of Gypsophila more rational and focused. The study of basic chromosome number and the reproductive system (potential barriers to intraspecific and interspecific incompatibilities) of the wild species as well as the commercial hybrids forms the basis of crossbreeding and selection of variety. A significant difference in ploidy was found between the species paniculata, its cultivar Flocon de Neige doubles, the species libanotica Boiss. (n = 34) and Pacifica Kom. (n = 68). A significant difference in the chromosome number was found among the commercial hybrids of Gypsophila under investigation, and this difference was observed among them as well as when compared with the wild type species. The flower structure of commercial hybrids can be remarkably complex. Some hybrids such as Biancanieves® and MeryG® showed empt...

An investigation by electron microscopy has been carried out on Nicotiana tabacum L. var. BELW3 callus cells grown in a medium containing different NaCl concentrations (0.1, 0.2, 0.3 M) for 60 days to study the salt effect at cell level. Control N. tabacum callus exhibited parenchymatous cell types with normal cytoplasm, nucleus, organelles and membranes, together to cells forming meristematic zones by normal mitosis and cytokinesis. The callus cells exposed to the lowest salt dose did not show specific structural changes in comparison to control cells. On the contrary, the callus cells treated with the salt at the highest doses showed alterations of chloroplasts, severe damages at nuclear and cytoplasmic level, until to a complete disorganization of the whole protoplast. Also mitochondria and the membranous system appeared injured. However, in all the salt treated callus cells amylopasts were very abundant. A peculiar phenomenon was the presence in these calli under salt stress of cells contiguous to the...

The origin of the sporophyte in land plants represents a fundamental phase in plant evolution. Today this subject is controversial, and scarcely considered in textbooks and journals of botany, in spite of its importance. There are two conflicting theories concerning the origin of the alternating generations in land-plants: the “antithetic” theory and the “homologous” theory. These have never been fully resolved, although, on the ground of the evidences on the probable ancestors of land plants, the antithetic theory is considered more plausible than the homologous theory. However, additional phylogenetic dilemmas are the evolution of bryophytes from algae and the transition from these first land plants to the pteridophytes. All these very large evolutionary jumps are discussed on the basis of the phyletic gradualist neo-Darwinian theory and other genetic evolutionary mechanisms.

Cerato-platanin (CP), a protein previously isolated from the ascomycete Ceratocystis fimbriata f.sp. platani (CJp), the causal agent of plane canker stain, has been studied with regard its phytotoxic effect in plane leaf cells by transmission electron microscopy.When infiltrated in plane leaf mesophyllum, pure cerato-platanin induced, 24 and 48 h after treatment, several negative responses in palisade and spongy tissues.One of the most important responses consisted, already after 24 h, in a great production of primary starch in these tissues. Moreover, the ultrastructural observations evidenced numerous other symptoms, such as strong alterations in chloroplasts, nuclei and in the cytoplasm. These changes were particularly serious in spongy parenchyma cells. In addition, these cells appeared strongly squashed with a reduced and completely disorganized protoplast.

A simple and efficient protocol for in vitro shoot regeneration from storage root explants of witloof chicory (Cichorium intybus L.) has been used to study the effect of colchicine at different concentrations, and colchi- cine in combination with kinetin or 2,4-D or with 2,4-D and kinetin, in comparison with kinetin and control (no treatment), upon this type of morphogenic event. The results demonstrated a strong stimulatory effect of colchicine at low concentration on shoot regeneration frequency when compared to the number of shoots formed in the con- trol. This effect was comparable to that of kinetin, a growth regulator that induces shoot differentiation. By contrast, the presence of 2,4-D completely inhibited shoot regeneration. Colchicine at high concentration did not induce shoots, and caused the complete death of the explants. A carefully histological analysis of the explants during the in vitro culture period showed the formation of numerous meristematic zones (precursors of adventitious bud and shoot development) in the parenchyma mass; these meris- tems were present only in the explants subjected to the colchicine and to the other treatments able to stimulate shoot differentiation. Nuclei of different sizes were observed in the explants treated with colchicine at low dose, the largest, probably, polyploids. Polyploid nuclei, in fact, were found in the regenerated plants.

Adventitious root and shoot formation was obtained from cotyledon fragments of chestnut (Castanea sativa Mill.) and these processes followed two phases. In a first stage after detachment of the embryonic axis, the cotyledon fragments in culture formed a cotyledon petiole, which elongated for about 6 d. Thereafter, root primordia arose at the tip of the cotyledon petioles, followed by normal root development. In some cases, the cotyledon petioles showed adventitious shoot regeneration from a nodular structure previously formed at the end of the petioles. The presence or absence of growth regulators did not significantly influence root regeneration, whereas cytokinins stimulated shoot formation. The processes of root and shoot differentiation were studied also at the histological level. Observation with a light microscope showed that the developing root apical meristems were connected with a vascular bundle of the cotyledon petiole. Similarly, shoot bud meristem connections were observed with vascular tissue inside the nodular structure.

Summary The ontogeny and ultrastructure of secretory oil glands in the fruits of Citrus sinensis and Citrus limon were studied with light and electron microscopy (TEM). Oil glands were initiated by cell division in globular/oval clusters of young meristematic cells under or including also the epidermis. Successively, the central oil cells increased greatly in size by growth and coalescence of one or more vacuoles. Starting from these cells the oil cavity formation and enlargment occurred by schizogenous and lysigenous precesses which overlap one another. The separation of the cell walls, in both Citrus species, was accompanied by strong structural disorganization of the cytoplasm, loss of nuclei, plasmolysis, and followed by autolysis processes. Prior these changes a great quantity of oil droplets filled the cells. In Citrus sinensis this material was formed in the plastids; on the contrary, in Citrus limon oil droplets appeared only in the cytoplasm, and no connection with the plastids was observed. The processes of schizogeny and lysigeny occurred in a centrifugal direction. The peripheral oil chamber cells were so pushed outward and flattened with the progressive expansion of the gland cavity. Also these cells became vacuolated, showed schizogenous processes together with cytoplasm and nuclei breakdown. These cell modifications were preceded by an abundant essential oil synthesis. Electron dense material appeared in the cavity near the boundary cells. Among the cell layers surrounding the cavity, the outer peripheral cells showed very thick walls. These cells, probably, had a protective function, while the inner cells continued, at least in part, to produce and secrete oil compounds. In the two Citrus species the pattern of oil gland development was practically the same, except the different plastid behaviour.

Summary Selaginella lepidophylla is a pteridophyte resurrection plant from Central America deserts that has been studied hitherto only for microphyll ultrastructure and photosynthetic activity during rehydration. With the present work the anatomy and cell ultrastructures have been examined during progressive rehydration. Light microscope observations clearly showed the maintenance in the dry condition of chloroplasts although in a crushed form, of chlorophyll content, and the restoration of the normal anatomical structures in stem and microphylls after the complete rehydration process. Electron microscope analyses permitted us to observe a gradual reorganization in the different cells of stem and microphylls of all the cytoplasmic components including the membrane systems present either in the protoplasm or in the organelles. In particular, the chloroplasts appeared to be able to newly accumulate starch, and then to recover the normal photosynthetic capacity. Therefore, it is possible to say that S. lepidophylla retains in the dry condition the cell structures in a well conserved state or, at least, in a functional state by protective mechanisms that permit a total reorganization of the cells after rehydration. This statement is further supported by the absence of any structural disruption effects in the rehydrated cells of S. lepidophylla.

Different NAA plus kinetin or BA combinations were tested on Francia Pernod fennel seedlings for callus induction and plant regeneration. Callogenesis from hypocotyls was obtained in all auxin/cytokinin-containing media. The organogenic response was observed especially in presence of NAA plus kinetin. The highest frequency of shoot regeneration was found when the auxin and kinetin were used at a 1:1 ratio. Moreover, a prolonged culture period increased shoot formation. Somatic embryogenesis was tested on several fennel populations. The results gave evidence of the genotypic importance. Two different protocols were used for somatic embryo induction. Using the first protocol among the different fennel genotypes tested, only Francia Pernod showed embryogenic capacity. In this case, from a primary non-embryogenic callus cultured for 12 months in presence of 2,4-D, an embryogenic secondary callus was produced. When transferred to the medium without 2,4-D (agarized or liquid), this gave embryogenic plants in high frequency. As far as the second embryogenic method is concerned, secondary embryogenic callus developed only in the presence of 2,4-D plus kinetin in Francia Pernod genotype. Thereafter, the replacement of those growth regulators by GA3 into the medium greatly increased the somatic embryo development, especially in `Francia Pernod', but also in `Aboca erbe' callus, a population with a very poor embryogenic capacity. In Francia Pernod, the primary and secondary (embryogenic) calli showed different morphological and histological responses, either when the secondary callus was induced by 2,4-D alone or by 2,4-D plus kinetin. Ontogenetic processes leading to somatic embryo formation are described in this context.

In Nicotiana bigelovii var. bigelovii the formation of callus habituated for auxin and cytokinin can be induced with high frequency after a very short treatment of the hypocotylar tissues with 2,4-dichlorophenoxyacetic acid (2,4-D). Some habituated callus lines exhibit the capacity to regenerate normal shoots for a period of several months. In this study we report that stem and leaf explants, when excised from N. bigelovii var. bigelovii shoots regenerated from 10 habituated callus lines, were able to dedifferentiate and grow, in hormone-free medium and with a very high frequency, as habituated calluses. The developmental process during the shoot regeneration from the previously habituated callus using 2,4-D in this variety of N. bigelovii , seems to imply the possible irreversibility of the habituated state through the regeneration phase.

The action of several concentrations of an anionic synthetic surfactant alkylbenzene sulphonate (ABS) and a non-ionic surfactant arylalkylpolyglycol ether (Citowett) were studied using as test different in vitro culture systems (Pittosporum tobira Ait. and Nicotiana tabacum L. var. Bel W3). Three parameters were analyzed: i) callus or total biomass increase (P. tobira and N. tabacum, respectively); ii) shoot regeneration frequency (N. tabacum); iii) cell damage. Phytotoxic general effects occurred for ABS and Citowett in both species especially at higher concentrations; however some differences were observed between the two types of surfactants. A clear callus growth stimulation was found in P. tobira cultured in presence of ABS at lower doses whereas Citowett at high concentration induced, in N. tabacum, a light increase of the total number of regenerated shoots in comparison to control. Both surfactants at higher concentrations caused strong damages at cytological level. The effects of these surfactants on cytoplasm and nuclei were determined. The use of in vitro culture as a monitoring system is discussed.

Increasing manganese (Mn) concentrations to 5, 10, 15 and 20 mM caused a significant decrease in callus formation and shoot regeneration in comparison to 0.1 (control medium) and 2 mM in Nicotiana tabacum var. BEL W3 grown on Murashige and Skoog’s medium (MS) with 1 mg l−1 α-naphtaleneacetic acid and 1 mg l−1 kinetin. Concentrations of Mn higher than 5 mM also reduced callus growth in Nicotiana bigelovii bigelovii grown on MS solid medium. Callus cultures of N. tabacum with enhanced tolerance to Mn were selected by progressively elevating the level of MnSO4·4H2O in the culture medium. Selection of Mn-tolerant plants occurred only at 2 and 5 mM, because higher concentrations inhibited callus and shoot growth. Differences in mitotic phase indices in plants grown at 2 and 5 mM Mn were found in comparison to the control. In these plants, several mitotic alterations as well as damaged chloroplasts and a reduction in chloroplast number were also observed, especially for those treated with 5 mM Mn. Mn was also shown to affect the number of xylem elements and the degree of lignification, which differed between plants grown at 2 or 5 mM compared to the control.

The anatomy and ultrastructure of glandular trichomes at different developmental stages were investigated in Phillyrea latifolia L. leaves by transmission electron microscopy and histochemical techniques. The trichome consisted of a multicellular secretory head, a unicellular stalk and a collecting cell surrounded by epidermal cells and spongy mesophyll cells. There were numerous plasmodesmata across the cell walls of trichome cells, and especially between the stalk cell and the collecting cell. The collecting cell and stalk cell contained few chloroplasts. Mitochondria, elements of the endoplasmic reticulum and small vacuoles were abundant in the secretory cells. Crystals were present in the secretory cells and the collecting cell, especially at the mature and senescent stages of trichome development. As the cuticle, which covered the secretory cells, did not show pores or perforations, it is proposed that secretion occurred by accumulation of products in subcuticular spaces followed by diffusion through the cuticle. Callose accumulation was observed between the stalk cell and the collecting cell of senescent trichomes, especially in salt-treated plants. Trichome ontogeny was accelerated in salt-treated plants.

The effects of manganese on the morphology and ultrastructure of root cells were studied in in vitro selected plantlets tolerant to high concentrations (5 mM) of Mn which, in a previous investigation, had shown a significant reduction in root growth when compared to the control (0.1 mM Mn). A decrease in the length of the root cap and meristematic region was observed. The most serious effects of Mn toxicity occurred in the outer root cap and outer meristematic cells where extensive cytoplasmic disorganisation was observed. The plasma membrane, in particular, displayed ruptures associated with the formation of vesicular and multi-lamellar bodies. Mitochondria also revealed strong structural alterations. However, the cells in the inner regions of the meristem showed better preserved subcellular components and exhibited normal mitotic activity. These last conditions suggest a possible resistance strategy which permits root development to continue. The primary root structure was not affected by the m...

In Nicotiana tabacum L. var. BEL W3 copper (Cu) at concentrations higher than 50 μM significantly inhibited callus growth and shoot regeneration. After 5–6 months of culture only a few morphogenic callus lines survived in the presence of 100 μM Cu. These calluses showed the capacity to grow and regenerate shoots through successive subcultures on medium containing 100 μM Cu. The 100 μM Cu-tolerant shoots, in comparison to regenerated control shoots, formed roots only when cultured in the presence of 100 μM Cu. From five independent Cu-tolerant callus lines in a culture period of 4–5 months more than 50 plants (defined ‘tolerant’) able to grow in presence of 100 μM Cu were obtained. These plants showed normal xylem tissue formation while control regenerated plants growing in normal Cu MS content (0.1 μM) had few xylem elements in the central cylinder. No difference as far chlorophyll content and chloroplast structure was found among Cu-tolerant and control plants. In Cu-tolerant plants, dry matter production was higher than in controls, particularly in roots.

A study has been carried out on several Amaranthus L species and breeding lines (A. caudatus, A. cruentus, A. hybridus, A. hypochondriacus), some of which have previously shown poor or no plant regeneration from callusing primary explants. Callus formation occurred from explants from almost all the lines tested. Significant differences in callus growth were observed among the lines depending on the growth regulator combinations used. Cultural conditions such as type and growth regulator combination, as well as age-dependent competence of the explant tissues, also influenced the frequency of shoot (and/or root) regeneration in Amaranthus species that had been shown difficult to regenerate in the past. The results obtained demonstrate that in Amaranthus the genotype, growth regulator dose and combination, the type and the physiological stage of explant are factors of great importance for in vitro plant regeneration.

Manganese toxicity to germination, callus induction and shoot regeneration was studied on three cultivars of Nicotiana tabacum: BEL W3, Burley 21, Bright NC 944. All materials were cultured on MS solid medium containing 0.1 (control), 2, 5, 10, 15 and 20 mM Mn, to which 5 µM NAA and 5 µM kinetin were added for callus induction and shoot regeneration. Mn toxicity to callus growth was tested using habituated callus of Nicotiana bigelovii var. bigelovii grown on MS medium without growth regulators. Mn concentrations higher than 2 mM were toxic for germination, and concentrations higher than 5 mM were toxic for callus induction, shoot regeneration and callus growth. Among the cultivars examined, Bright tobacco appeared more tolerant to high Mn concentrations during callus formation and shoot regeneration. However, many regenerated plants capable of growing in vitro in the presence of 2 and 5 mM Mn were obtained.

Callus cultures were initiated from micropropagated Artemisia absinthium plantlets on MS basal medium supplemented with different concentrations of BA, Kn, NAA, IAA and 2,4-d in combination or singly. Supplementing the medium with low doses of both BA in combination with NAA, and Kn in combination with NAA enhanced the growth rate of callus cultures. However, cultures grew slowly following the second subculture and the majority turned brown and died within the next month. Initiation of root and shoot primordia occured directly from leaf explants cultured on 1.81 μM 2,4-d, while adventitious shoot formation from callus was observed occasionally when BA was added to the medium in combination with IAA. Furthermore, medium containing 2.22 μM BA and 2.69 μM NAA stimulated both callus growth and organogenesis on some callus cultures derived from leaves and stems of young stock material. The best results were obtained with leaf explants. Cytological analysis of root meristems revealed that all regenerants were diploid (2n=18), as expected.

Variation in the capacity to regenerate shoots and morphogenetic potential were investigated by cyclic culture and regeneration of Nicotiana tabacum var. BEL W3. Explants were excised from different shoots formed by the same callus line. Differences in the organogenetic in vitro response among regenerated plantlets was observed in two subsequent regenerate ‘generations’. A progressive decrease of the regenerative capacity was observed across callus line ‘generations’.

Callus induction, callus growth and organogenetic processes were investigated in hypocotyl and stem cultures of four species of Amaranthus each of which comprised several varieties. Callus formation occurred in almost all the varieties in 100% of explants. The combinations of naphtaleneacetic acid plus benzylaminopurine or 2,4-dichlorophenoxyacetic acid plus Kinetin were very effective in causing callus formation; the results for callus growth in presence of the same growth regulator combinations revealed in some cases significant differences among the varieties. As far organogenesis-based on a few varieties-only A. caudatus and A. hypochondriacus responded well forming shoots from callus when cultured in presence of indoleacetic acid plus Kinetin and/or indoleacetic acid plus benzylaminopurine. Root regeneration was also observed in several varieties. Complete plantlets were obtained from rooted shoots. The results are discussed in relation to hormonal effect and the genotype importance.

The origin of land plants or embryophytes from the Charophyceae is generally accepted today by the botanists. In fact, numerous morphological, cytological, ultrastructural, biochemical and molecular characters are shared in these organisms. A fundamental problem is still constituted by the evolution of the sporophyte, i.e. the appearance of two different phase cycles (gametophyte/sporophyte alternance), although two theories ("antithetic" and "homologous") try to explain this evolutionary event.However, another phylogenetic dilemma is represented, in my opinion, either by the formation of bryophytes or by the transition from these first land plants to the pteridophytes, considering them at whole organism level. The bryophyte gametophyte is the most elaborate of the land plants. It presents several complex characters, principally the growth developmental form, the appearance of multicellular sex organs, antheridia and archegonia. Also the sporophyte shows a complicated structure that is not found in the other land plants or tracheophytes. The sporangium, in particular, exhibits some intricate morphological traits such as the peristome of true mosses for spore dispersion, the elaters of liverworts and the indeterminate growth in the hornworts. The pteridophytes are represented especially by their dominant sporophyte. This latter has the capacity to produce multiple sporangia and, in many cases, two kinds of spores which develop in male and female gametophyte (heterosporous pteridophytes). Another important characteristic of this sporophyte is its ability to become independent of the gametophyte. However, one of the most innovative character is the formation of true vascular elements (xylem and phloem). All these very large evolutionary jumps are discussed on the basis of the phyletic gradualistic neo-Darwinian theory and the punctuated equilibrium theory of Eldredge and Gould. In this context other genetic evolutionary mechanisms are also considered.Nevertheless, the origin of bryophytes and pteridophytes remain, at the moment, a mystery.

The origin of the sporophyte in land plants represents a fundamental phase in the plant evolution. Today this subject is controversial and, in my opinion, scarcely considered in our textbooks and journals of botany, in spite of its importance. There are two conflicting theories concerning the origin of the alternating generations in land plants: the "antithetic" and the "homologous" theory. These have never been fully resolved. The antithetic theory maintains that the sporophyte and gametophyte generations are fundamentally dissimilar and that the sporophyte originated in an ancestor organism with haplontic cycle by the zygote dividing mitotically rather than meiotically, and with a developmental pattern not copying the developmental events of the gametophyte. The sporophyte generation was an innovation of critical significance for the land-plant evolution. By contrast, the homologous theory simply stated that a mass of cells forming mitotically from the zygote adopted the same developmental plan of the gametophyte, but giving origin to a diploid sporophyte. In this context, a very important question concerns the possible ancestor or ancestors of the land plants. Considerable evidences at morphological, cytological, ultrastructural, biochemical and, especially, molecular level, strongly suggest that the land plants or Embryophyta (both vascular and non-vascular) evolved from green algal ancestor(s), similar to those belonging to the genus Coleochaete, Chara and Nitella, living today. Their organism is haploid for most of their life cycle, and diploid only in the zygote phase (haplontic cycle). On the contrary, the land plants are characterized by a diplo-haplontic life cycle. Several questions are implied in these theories, and numerous problems remain to be solved, such as, for example, the morphological difference between gametophyte and sporophyte (heteromorphism, already present in the first land plants, the bryophytes), and the strong gap existing between these last with a sporophyte dependent on the gametophyte, and the pteridophytes having the gametophyte and sporophyte generations independent. On the ground of all of the evidences on the ancestors of the land plants, the antithetic theory is considered more plausible than the homologous theory. Unfortunately, no phylogenetic relationship exists between some green algae with diplontic life cycle and the land plants. Otherwise, perhaps, it should be possible to hypothesize another scenario in which to place the origin of the alternating generations of the land plants. In this case, could the gametophyte be formed by gametes produced from the sporophyte, through their mitoses or a delayed fertilization process?

After evidencing the great importance of plants for animals and humans in consequence of the photosynthesis, several considerations on plant evolution are made. One of the peculiar characteristics of the plant is the sessile property, due especially to the cell wall. This factor, principally, strengthened by the photosynthetic process, determined the particular developmental pattern of the plant, which is characterized by the continuous formation of new organs. The plant immobility, although negative for its survival, has been, in great part, overcome by the acquisition of the capacity of adaptation (plasticity) to the environmental stresses and changes, and the establishment of more adapted genotypes. This capacity to react to the external signals induced Trewavas to speak of "plant intelligence". The plant movement incapacity and the evolution of the sexual reproduction system were strongly correlated. In this context, the evolution of the flower in the Angiosperms has been particularly important to allow the male gamete to fertilize the immobile female gamete. Moreover, the formation of fruit and seed greatly improved the dispersal and conservation of the progeny in the environment. With the flower, mechanisms to favour the outcrossing among different individuals appeared, which are essential to increase the genetic variability and, then, the plant evolution itself. Although the Angiosperms seem highly evolved, the plant evolution is not surely finished, because many reported morpho-physiological processes may be still considered susceptible of further improvement. In the last years the relationships among humans, plants and environment are becoming closer and closer. This is due to the use of the DNA recombinant techniques with the aim to modify artificially plant characters. Therefore, the risk of a plant evolution strongly directed towards practical or commercial objectives, or "an artificial evolution", may be hypothesized.

The use of cytological and, especially, nuclear DNA and cpDNA molecular analyses in assessing the genetic stability or instability of organogenesis and somatic embryogenesis-derived plants of one fennel (Foeniculum vulgare Mill.) donor plant belonging to Francia Pernod population, was evaluated. Different morphogenic callus types and both organogenic and embryogenic plants showed the normal diploid chromosome number. All regenerated plant types, when examined by RAPD analyses did not show any nuclear DNA polymorphism. No variation was detected in these plants independently from their morphogenic origin in two cpDNA regions which exhibited the same length, base sequence and restriction profiles. Moreover, the study of a cpDNA microsatellite region including a single A/T repeat did not reveal any variation of the repeat numbers in these regenerated plants. These results on the genetic stability and uniformity of organogenic and embryogenic regenerated fennel plants was supported also by a comparison of the cpDNA microsatellite region with other natural fennel plants where variations were found in some of them except Francia Pernod.

Artemisia absinthium L. (wormwood), family Asteraceae, is a perennial under-shrub found in Central Europe, North America, and Asia. The plant presents the following characteristics: to 1 m high, stalks upright, abundant foliage; leaves silky pubescent on both sides, lowest petiolate, tripennate; heads in strong branched panicles, short-stalked, nodding; outer perianth oblong-linear, inner ovate with a broad membranous margin; disk flowers bisexual, the marginal flowers often female, flowering July-September, fruitlets without a pappus (Krussmann 1984). Propagation is mostly by division, but the plant, allogamous, is highly fertile.

In previous research, an in vitro stepwise procedure permitted us to obtain Nicotiana tabacum regenerated plant lines able to grow in the presence of Mn at 2 and 5 mM (Mn-tolerant plants). These plants showed several morpho-physiological and cytological differences in comparison to the Mn-sensitive regenerated plants. In particular, the number of xylem cells and the degree of lignification appeared to be influenced differently by these Mn concentrations. In the present work these Mn-tolerant and Mn-sensitive N. tabacum plants, maintained in the presence of Mn 2 and 5 mM, have been characterized with regards to the uptake of Mn and Fe, the activity of extracellular peroxidases in the stems, and the activity of superoxide dismutase, ascorbate peroxidase, and glutathione reductase in the leaves. The leaf response to an increasing Mn concentration in the medium, corresponded a parallel decrease of Fe content. Plants tolerant of 5 mM Mn showed almost a doubling Mn content over that of the 5 mM Mn-sensitive plants. In the stem, 2 and 5 mM Mn inhibited the extracellular free peroxidases (guaiacol peroxidases) either in the Mn-tolerant plants or in the Mn-sensitive plants. In the Mn-sensitive plants treated with 2 mM Mn the activity of the peroxidases of the ionically and covalently bound wall peroxidases was also depressed. In 5 mM Mn-tolerant plants, an enhanced activity of the covalently bound wall peroxidases was observed. The effect of Mn on the covalently bound wall syringaldazine peroxidases was identical to that observed in the guaiacol peroxidases; the activity was significantly higher in the Mn-tolerant plants grown in the presence of 5 mM Mn. In the leaf, the increase of Mn content inhibited the activity of guaiacol peroxidase, ascorbate peroxidase and superoxide dismutase in the Mn-tolerant as well as in the Mn-sensitive plants. However, the effect was greater in the Mn-sensitive plants. Only glutathione reductase did not show significant variation except for the 2 mM Mn-sensitive plants, where an increased activity was detected.

(1995). Characterization of Nicotiana tabacum var. BEL W3 plants regenerated from resistant to Mn2± callus. Giornale botanico italiano: Vol. 129, No. 4, pp. 1146-1147.

Callus induction and morphogenic response of several fennel populations were determined by genotype and hormonal treatment. 100% callus formation occurred only in the Francia Pernod population under the action of 2, 4-dichlorophenoxyacetic acid or α-naphthaleneacetic acid and kinetin. Only this last hormonal treatment induced shoot regeneration. Plant regeneration was observed especially in Francia Pernod population. Ths calluses grown in presence of 2,4-dichlorophenoxyacetic acid or α-naphthaleneacetic acid plus kinetin, showed considerable differences at cytological and histological level which were correlated to their different morphogenic capability.

(1994). In Vitro Tests to Select Plants of Foeniculum Vulgare Miller (Umbelliferae) for Resistance to Phomopsis Foeniculi du Manoir et Vegh (Sphaeropsidaceae) Giornale botanico italiano: Vol. 128, No. 1, pp. 325-325.

A method for callus induction, adventitious bud regeneration, shoot multiplication and rooting of in vitro formed shoots of Helianthus annuus L. var. Argentario is described. Hypocotyl and cotyledon explants formed callus on medium containing 2 mgl−1 naphthalene acetic acid and 0.5 mgl−1 benzyladenine. Adventitious buds were formed on hypocotyl segments on medium containing 0.5–2 mgl−1 benzyladenine. The optimal level of sucrose concentration for shoot regeneration from hypocotyls was 1.5%. Multiplication from shoot apices was promoted by kinetin (2 mgl−1) plus gibberellic acid (5 mgl−1), benzyladenine (2 mgl−1) plus gibberellic acid (10 mgl−1) or at lower frequency by benzyladenine (1 mgl−1). A general feature of the plantlets formed in vitro was the “precocious flowering”.

Experiments upon in vitro culture of immature durum wheat embryos, harvested at different growth stages, were made in two consecutive years. Callus formation and plantlet regeneration were obtained. The ability to form callus and the degree of morphogenetic processes varied with the different hormonal treatments used and with the age of the embryos. In the first year the best response for callus growth was observed with 2,4-D 2 mg l-1 plus adenine 50 mg l-1 or 2,4-D 5 mg l-1 alone in the more mature embryos (15 and 20 days after anthesis). On the contrary, NAA 5 mg l-1 had a greater shoot regeneration effect. In the next year, at all 2,4-D concentrations and for the two different ages of the embryos tested, all embryos formed callus. Regeneration of plantlets was obtained in higher percentage in calli originated from the more developed embryos. The effect of changed media upon plantlet regeneration was studied after callus transplant. Investigation by cytophotometry and chromosome counts on different calli showed, practically in all cells, a diploid condition. A histological analysis demonstrated embryogenic somatic characteristics in many samples of callus. The pattern of organogenesis seemed to be via adventitious bud formation but structures resembling embryoids were also observed in the callus.

Callus formation of Nicotiana glauca pith tissue grown in vitro was studied with cytological and autoradiographic methods during the first 144 hr of culture. A high frequency of prospective proliferating cells showed nuclear fragmentation and nucleolar extrusion. Experiments with tritiated thymidine showed that DNA was synthesized in cells with fragmented nuclei and that fragmentation could be considered a step in the formation of multinucleate cells appearing at 144 hr of culture. No metaphase accumulation was induced at any time with colchicine indicating that mitoses could not be accounted for the rapid onset of cellularization. Evidences of extra DNA synthesis at the nucleolar region and of the presence of cytoplasmic DNA at earlier times of culture are reported.

Polyamines (spermine, spermidine, and putrescine) and nucleic acids were studied during the first cell cycle after the break of dormancy of tuber slices of Helianthus tuberosus L., cv. OB1. Immediately after the break of dormancy, a marked decrease in stored arginine and glutamine and a corresponding increase of polyamines were observed. This first synthesis of polyamines were observed. This firs synthesis of polyamines occurred very early during the G1 phase, concomitant to the synthesis of RNAs. A RNA, probably messenger-like RNA, was synthesized very actively only during the first hours of activation in the culture medium plus 2,4-dichlorophenoxyacetic acid, or in water. At the onset of the S phase, after 12h of activation, an incorporation of [(3)H] thymidine was also detected. A second putrescine synthesis and polyamine accumulation began during the progression of the S phase. During the progression of mitosis, there was a decrease of polyamine synthesis and accumulation.