Anatomical characterization and technological properties of Pterogyne nitens wood, a very interesting species of the Brazilian Caatinga biome.

Pterogyne nitens is commonly known in northeastern Brazil as a lesser-known fast-growing species in the Caatinga biome, which is a difficult place for tree development due to the low natural fertility soils and low availability of water. Due to the importance of expanding information about the anatomical wood properties of Caatinga native species, the aim of this work was to characterize the anatomical elements, to macroscopically describe the wood and make inferences about its possible end-uses. Maceration was performed which enabled measuring fiber dimensions, pore frequency and the following technological indexes: cell wall fraction, slenderness ratio, Runkel index and flexibility coefficient. Histological sections enabled describing the arrangements of the cellular elements in different observation sections and to determine the pore diameter. P. nitens wood has anatomical arrangements characterized by confluent axial parenchyma, being diffuse-porous with the presence of tylosis and heterogeneous/stratified rays (biseriate). The fibers were classified as very short (length 0.81 mm), not flexible and Runkel index 0.82. The pores were few in number with a frequency of 32.9 pores/mm2, distributed in a diffuse format and many were obstructed by tylosis. Based on the anatomical results and considering other technological studies, P. nitens wood is most suitable for charcoal production.

Micrografía analítica de semillas de Cebil (Anadenanthera colubrina var. Cebil (Griseb.) Altschul, Fabaceae) y Chamico (Datura ferox L., Solanaceae), empleadas como drogas alucinógenas en Argentina / Analytical micrography of seeds of Cebil (Anadenanthera colubrina var. Cebil (Griseb.) Altschul, Fabaceae) and Chamico (Datura ferox L., Solanaceae), employed as hallucinogenic drugs in Argentina

Resumen La micrografía analítica es una herramienta útil para la identificación de restos vegetales en muestras de material trozado o molido que no podrían ser identificadas de forma morfológica. El objetivo de este estudio es conocer los caracteres mi- crográficos de las semillas de Cebil (Anadenanthera colubrina var. cebil (Griseb.) Altschul, Leguminosae) y Chamico (Datura ferox L., Solanaceae), con el fin de proporcionar parámetros empleables para su identificación en un contexto forense y toxicológico. Los caracteres micrográficos relacionados con el tegumento exterior y las esclereidas fueron los más indicados para diferenciar entre ambas especies.

Abstract Analytical micrography is a useful tool for the identification of plant parts that can't be identified for its morphological characters. The aim of this work is to obtain micrographic characters of Cebil (Anadenanthera colubrina var. cebil (Griseb.) Altschul, Leguminosae) and Chamico (Datura ferox L., Solanaceae) seeds for its identification in a toxicological and forensic context. The most suitable micrographic features were the ones related with exterior testa and the stone cells.

How do newly matured vessels start conducting water? The significance of lateral pathways for connecting newly matured vessels to the transpiration stream.

Despite the long history of research on xylem structure and function, there are no reports in the literature explaining how xylem vessel elements began conducting water just after their maturation. This study was conducted to demonstrate the anatomical arrangement of newly matured vessels, looking specifically for the first pathways connecting newly matured vessels to the transpiration stream. Using the developing stems of Paraserianthes lophantha (Willd.) I.C.Nielsen as the experimental system, the course of vessel differentiation and maturation along the developing bundles was followed by using the dye-pressure method. Water pathways from newly matured vessels to other functioning vessels were directly visualized by the technique of single-vessel dye injection. Some isolated newly matured vessels from the transpiration stream were detected using two apoplastic tracers. The results of this study converge to support the hypothesis that the movement of water in the newly matured vessels depends completely on lateral contacts with other functioning vessels via vessel-to-vessel paths or vessel relays. In cases where the lateral pathways were absent, the flow within the newly matured vessels was substantially blocked resulting in a significant hydraulic isolation of the newly matured vessels. These results might contribute to a better understanding of the pattern of water movement within the developing xylem systems, and underscore that xylem vessels start conducting water through lateral transport, although their primary function is the axial transport.

Selection of host-plant genotype: the next step to increase grain legume N2 fixation activity.

Symbiotic N2 fixation research thus far has been primarily focused on selection of bacteria. However, little progress in impacting crop yields has resulted from this approach. Bacteria introduced in field soils rarely compete well with indigenous bacteria, including mutated lines selected for high nitrogen fixation capacity. Consequently, introduction of 'elite' bacteria in fields commonly does not result in crop yield increase. This review highlights that the primary regulation of N2 fixation is a result of response of integrated physiological activity at the plant level. Nitrogen feedback from the host plant plays an important role in regulating the N2 fixation rate. Rapid sequestration of fixed nitrogen by the plant is especially important for high N2 fixation activity. In addition, water cycling in the plant between the shoot and nodules plays a key role in sustaining high N2 fixation activity. Therefore, attention in selecting the host-plant genotype is suggested to be the next step to increasing N2 fixation activity of grain legumes.

Commonalities and Differences in Controlling Multipartite Intracellular Infections of Legume Roots by Symbiotic Microbes.

Legumes have the almost unique ability to establish symbiotic associations with rhizobia and arbuscular mycorrhizal fungi. Forward and reverse genetics have identified a large number of genes that are required for either or both interactions. However, and in sharp contrast to natural soils, these interactions have been almost exclusively investigated under laboratory conditions by using separate inoculation systems, whereas both symbionts are simultaneously present in the field. Considering our recent understanding of the individual symbioses, the community is now promisingly positioned to co-inoculate plants with two or more microbes in order to understand mechanistically how legumes efficiently balance, regulate and potentially separate these symbioses and other endophytic microbes within the same root. Here, we discuss a number of key control layers that should be considered when assessing tri- or multipartite beneficial interactions and that may contribute to colonization patterns in legume roots.

Strain-Specific Symbiotic Genes: A New Level of Control in the Intracellular Accommodation of Rhizobia Within Legume Nodule Cells.

This is a short commentary on the article by Wang et al. published in MPMI Vol. 31, No. 2, pages 240-248.

Cell shape can be uncoupled from formononetin induction in a novel cell line from Callerya speciosa.

KEY MESSAGE: It is the first time that formononetin produced by cell culture and its accumulation was shown to be triggered by specific stress signalling linked jasmonate pathway. Callerya speciosa, an endangered traditional Chinese medicine plant, is intensively used in traditional folk medicine. To develop sustainable alternatives for the overexploitation of natural resources, a suspension cell line was created from C. speciosa. Ingredients of C. speciosa, for instance the isoflavone formononetin, are formed during a peculiar swelling response of the root, which is considered as a quality trait for commercial application. A cell strain with elongated cells was obtained by using synthetic cytokinin 6-benzylaminopurine (6-BA) and synthetic auxin picloram. Both, picloram and 6-BA, promote cell division, whereas picloram was shown to be crucial for the maintenance of axial cell expansion. We addressed the question, whether the loss of axiality observed in the maturating root is necessary and sufficient for the accumulation of formononetin. While we were able to mimic a loss of axiality for cell expansion, either by specific combinations of 6-BA and picloram, or by treatment with the anti-microtubular compound oryzalin, formononetin was not detectable. However, formononetin could be induced by the stress hormone methyl jasmonate (MeJA), as well as by the bacterial elicitor flagellin peptide (flg22), but not by a necrosis inducing protein. Combined the fact that none of these treatments induced the loss of axiality, we conclude that formononetin accumulates in response to basal defence and unrelated with cell swelling.

Digestion of isolated legume cells in a stomach-duodenum model: three mechanisms limit starch and protein hydrolysis.

Retention of intact plant cells to the end of the small intestine leads to transport of entrapped macronutrients such as starch and protein for colonic microbial fermentation, and is a promising mechanism to increase the content of resistant starch in diets. However, the effect of gastro-intestinal bio-mechanical processing on the intactness of plant cells and the subsequent resistance to enzymatic digestion of intracellular starch and protein are not well understood. In this study, intact cells isolated from legume cotyledons are digested in a laboratory model which mimics the mechanical and biochemical conditions of the rat stomach and duodenum. The resulting digesta are characterised in terms of cell (wall) integrity as well as intracellular starch and protein hydrolysis. The cells remained essentially intact in the model with negligible (ca. 2-3%) starch or protein digestion; however when the cells were mechanically broken and digested in the model, the hydrolysis was increased to 45-50% suggesting that intact cellular structures could survive the mixing regimes in the model stomach and duodenum sufficiently to prevent digestive enzyme access. Apart from intact cell walls providing effective barrier properties, they also limit digestibility by restricting starch gelatinisation during cooking, and significant non-specific binding of α-amylase is observed to both intact and broken cell wall components, providing a third mechanism hindering starch hydrolysis. The study suggests that the preservation of intactness of plant cells, such as from legumes, could be a viable approach to achieve the targeted delivery of resistant starch to the colon.

α-TIP aquaporin distribution and size tonoplast variation in storage cells of Vicia faba cotyledons at seed maturation and germination stages.

Vacuoles have been shown to undergo deep modifications in relation to plant developmental stages and in the maintaining the cellular homeostasis. In this context, we studied the variations of the vacuolar membrane size and α-TIP aquaporin distribution at early and advanced seed stages of maturation, germination and embryo growth in Vicia faba cotyledon storage cells.

Temporal, but not spatial, changes in expression patterns of petal identity genes are associated with loss of papillate conical cells and the shift to bird pollination in Macaronesian Lotus (Leguminosae).

In the generally bee-pollinated genus Lotus a group of four species have evolved bird-pollinated flowers. The floral changes in these species include altered petal orientation, shape and texture. In Lotus these characters are associated with dorsiventral petal identity, suggesting that shifts in the expression of dorsal identity genes may be involved in the evolution of bird pollination. Of particular interest is Lotus japonicus CYCLOIDEA 2 (LjCYC2), known to determine the presence of papillate conical cells on the dorsal petal in L. japonicus. Bird-pollinated species are unusual in not having papillate conical cells on the dorsal petal. Using RT-PCR at various stages of flower development, we determined the timing of expression in all petal types for the three putative petal identity genes (CYC-like genes) in different species with contrasting floral morphology and pollination syndromes. In bird-pollinated species the dorsal identity gene, LjCYC2, is not expressed at the floral stage when papillate conical cells are normally differentiating in bee-pollinated species. In contrast, in bee-pollinated species, LjCYC2 is expressed during conical cell development. Changes in the timing of expression of the above two genes are associated with modifications in petal growth and lateralisation of the dorsal and ventral petals in the bird-pollinated species. This study indicates that changes in the timing, rather than spatial distribution, of expression likely contribute to the modifications of petal micromorphology and petal size during the transition from bee to bird pollination in Macaronesian Lotus species.

Responses of tropical legumes from the Brazilian Atlantic Rainforest to simulated acid rain.

We investigated the morphological and anatomical effects of simulated acid rain on leaves of two species native to the Brazilian Atlantic Rainforest: Paubrasilia echinata and Libidibia ferrea var. leiostachya. Saplings were subjected to acid rain in a simulation chamber during 10 days for 15 min daily, using H2SO4 solution pH 3.0 and, in the control, deionized water. At the end of the experiment, fragments from young and expanding leaves were anatomically analyzed. Although L. ferrea var. leiostachya leaves are more hydrophobic, rain droplets remained in contact with them for a longer time, as in the hydrophilic P. echinata leaves, droplets coalesce and rapidly run off. Visual symptomatology consisted in interveinal and marginal necrotic dots. Microscopic damage found included epicuticular wax flaking, turgor loss and epidermal cell shape alteration, hypertrophy of parenchymatous cells, and epidermal and mesophyll cell collapse. Formation of a wound tissue was observed in P. echinata, and it isolated the necrosis to the adaxial leaf surface. Acid rain increased thickness of all leaf tissues except spongy parenchyma in young leaves of L. ferrea var. leiostachya, and such thickness was maintained throughout leaf expansion. To our knowledge, this is the first report of acidity causing increase in leaf tissue thickness. This could represent the beginning of cell hypertrophy, which was seen in visually affected leaf regions. Paubrasilia echinata was more sensitive, showing earlier symptoms, but the anatomical damage in L. ferrea var. leiostachya was more severe, probably due to the higher time of contact with acid solution in this species.

How detrimental are seed galls to their hosts? Plant performance, germination, developmental instability and tolerance to herbivory in Inga laurina, a leguminous tree.

Gall inducers use these structures as shelters and sources of nutrition. Consequently, they cause multiple physiological changes in host plants. We studied the impact caused by seed coat galls of a braconid wasp on the performance of fruits, seeds and seedlings of tree Inga laurina. We tested whether these seed galls are 'nutrient sinks' with respect to the fruit/seed of host plant, and so constrain the reproductive ability and reduce seedling longevity. We measured the influence of such galls on the secondary compounds, fruit and seed parameters, seed viability and germination and seedling performance. Inga laurina has indehiscent legumes with polyembryonic seeds surrounded by a fleshy sarcotesta rich in sugars. The galls formed inside the seed coat and galled tissues presented higher phenol concentrations, around 7-fold that of ungalled tissues. Galls caused a significant reduction in parameters such as fruit and seed size, seed weight and the number of embryos. Fluctuating asymmetry (a stress indicator) was 31% higher in leaves of galled seed plants in comparison to ungalled seed plants. However, the negative effects on fruit and seed parameters were not sufficient to reduce seed germination (except the synchronization index) or seedling performance (except leaf area and chlorophyll content). We attributed these results to the ability of I. laurina to tolerate gall attack on seeds without a marked influence on seedling performance. Moreover, because of the intensity of seed galling on host plant, we suggest that polyembryony may play a role in I. laurina reproduction increasing tolerance to seed damage.

Determination of Botanical Origin of Propolis from Monte Region of Argentina by Histological and Chemical Methods.

Propolis production by honey bees is the result of a selective harvest of exudates from plants in the neighborhood of the hive. This product is used in Argentina as a food supplement and alternative medicine. The aim of this study was to determine the botanical origin of propolis from the arid regions of Monte of Argentina using rapid histochemical techniques and by comparison of TLC and HPLC-DAD chromatographic profiles with extract profiles obtained from Zuccagnia punctata, Larrea divaricata and Larrea cuneifolia, plant species that grow in the study area as a natural community named "jarillal". Microscopical analysis revealed the presence of several Z. punctata structures, such as multicellular trichomes, leaflets, stems and young leaves. Remarkable was the richness of the propolis in two bioactive chalcones, also present in Z. punctata resin; these compounds can be regarded as possible markers for propolis identification and justify its use as a dietary supplement, functional food and medicinal product. This study indicates that the source of resin used by honey bees to produce propolis in the Monte region of Argentina is only Z. punctata, a native shrub widespread in this phytogeographical region, while other more abundant species (L. divaricata and L. cuneifolia) in the region were not found, indicating that this propolis could be defined as a mono-resin, type-Zuccagnia.

Hexavalent chromium-induced differential disruption of cortical microtubules in some Fabaceae species is correlated with acetylation of α-tubulin.

The effects of hexavalent chromium [Cr(VI)] on the cortical microtubules (MTs) of five species of the Fabaceae family (Vicia faba, Pisum sativum, Vigna sinensis, Vigna angularis, and Medicago sativa) were investigated by confocal laser scanning microscopy after immunolocalization of total tubulin with conventional immunofluorescence techniques and of acetylated α-tubulin with the specific 6-11B-1 monoclonal antibody. Moreover, total α-tubulin and acetylated α-tubulin were quantified by Western immunoblotting and scanning densitometry. Results showed the universality of Cr(VI) detrimental effects to cortical MTs, which proved to be a sensitive and reliable subcellular marker for monitoring Cr(VI) toxicity in plant cells. However, a species-specific response was recorded, and a correlation of MT disturbance with the acetylation status of α-tubulin was demonstrated. In V. faba, MTs were depolymerized at the gain of cytoplasmic tubulin background and displayed low α-tubulin acetylation, while in P. sativum, V. sinensis, V. angularis, and M. sativa, MTs became bundled and changed orientation from perpendicular to oblique or longitudinal. Bundled MTs were highly acetylated as determined by both immunofluorescence and Western immunoblotting. Tubulin acetylation in P. sativum and M. sativa preceded MT bundling; in V. sinensis it followed MT derangement, while in V. angularis the two phenomena coincided. Total α-tubulin remained constant in all treatments. Should acetylation be an indicator of MT stabilization, it is deduced that bundled MTs became stabilized, lost their dynamic properties, and were rendered inactive. Results of this report allow the conclusion that Cr(VI) toxicity disrupts MTs and deranges the MT-mediated functions either by depolymerizing or stabilizing them.

Co-occurrence of tannin and tannin-less vacuoles in sensitive plants.

Vacuoles of different types frequently coexist in the same plant cell, but the duality of the tannin/tannin-less vacuoles observed in Mimosa pudica L. is rare. In this plant, which is characterized by highly motile leaves, the development and original features of the double vacuolar compartment were detailed in primary pulvini from the young to the mature leaf stage. In young pulvini, the differentiation of tannin vacuoles first occurred in the epidermis and progressively spread toward the inner cortex. In motor cells of nonmotile pulvini, tannin deposits first lined the membranes of small vacuole profiles and then formed opaque clusters that joined together to form a large tannin vacuole (TV), the proportion of which in the cell was approximately 45%. At this stage, transparent vacuole profiles were rare and small, but as the parenchyma cells enlarged, these profiles coalesced to form a transparent vacuole with a convexity toward the larger-sized tannin vacuole. When leaf motility began to occur, the two vacuole types reached the same relative proportion (approximately 30%). Finally, in mature cells displaying maximum motility, the large transparent colloidal vacuole (CV) showed a relative proportion increasing to approximately 50%. At this stage, the proportion of the tannin vacuole, occurring in the vicinity of the nucleus, decreased to approximately 10%. The presence of the condensed type of tannins (proanthocyanidins) was proven by detecting their fluorescence under UV light and by specific chemical staining. This dual vacuolar profile was also observed in nonmotile parts of M. pudica (e.g., the petiole and the stem). Additional observations of leaflet pulvini showing more or less rapid movements showed that this double vacuolar structure was present in certain plants (Mimosa spegazzinii and Desmodium gyrans), but absent in others (Albizzia julibrissin, Biophytum sensitivum, and Cassia fasciculata). Taken together, these observations strongly suggest that a direct correlation cannot be found between the presence of a tannin vacuole and the osmoregulated motility of pulvini.

Induction and identification of Stylosanthes guianensis tetraploids.

Stylosanthes guianensis is an elite and important forage legume species, which is extensively cultivated in tropical areas. Polyploid breeding via exposure to colchicine is a conventional and practical method to improve varieties of S. guianensis. Terminal buds of S. guianensis Reyan No.5 seedlings were treated with different concentrations of colchicine (0.00, 0.05, 0.10, 0.15, 0.20, and 0.25%) for 24, 48, and 72 h. Morphological and cytological variants were observed at a frequency of <96% among transplanted seedlings. The cytogenetic analysis of young leaf cells was conducted on all variants to identify their ploidy levels. The most efficient procedure for tetraploid production was the treatment of seedling apical buds with 20% colchicine for 48 h, with the tetraploid induction rate being 10%. This is a relatively simple and reliable method for the production of tetraploidy in S. guianensis.

Quantification of the In Vitro Radiosensitivity of Mung Bean Sprout Elongation to 6MV X-Ray: A Revised Target Model Study.

In this study, a revised target model for quantifying the in vitro radiosensitivity of mung bean sprout elongation to 6-MV X-rays was developed. The revised target model, which incorporated the Poisson prediction for a low probability of success, provided theoretical estimates that were highly consistent with the actual data measured in this study. The revised target model correlated different in vitro radiosensitivities to various effective target volumes and was successfully confirmed by exposing mung beans in various elongation states to various doses of 6-MV X-rays. For the experiment, 5,000 fresh mung beans were randomly distributed into 100 petri dishes, which were randomly divided into ten groups. Each group received an initial watering at a different time point prior to X-ray exposure, resulting in different effective target volumes. The bean sprouts were measured 70 hr after X-ray exposure, and the average length of the bean sprouts in each group was recorded as an index of the mung bean in vitro radiosensitivity. Mung beans that received an initial watering either six or sixteen hours before X-ray exposure had the shortest sprout length, indicating that the maximum effective target volume was formed within that specific time period. The revised target model could be also expanded to interpret the "two-hit" model of target theory, although the experimental data supported the "one-hit" model. If the "two-hit" model was sustained, theoretically, the target size would be 2.14 times larger than its original size to produce the same results.

[Clonal micropropagation of a rare species Hedysarum theinum Krasnob (Fabaceae) and assessment of the genetic stability of regenerated plants using ISSR markers].

In the present study, a protocol was developed for the in vitro propagation of a rare medicinal plant, Hedysarum theinum (tea sweetvetch), from axillary buds, and identification of the regenerants was performed with the use of ISSR markers. It was demonstrated that Gamborg and Eveleigh medium supplemented with 5 µM 6-benzylaminopurine was the best for H. theinum for initial multiplication. On the other hand, half-strength Murashige and Skoog (MS) basal medium supplemented with 7 µM α-naphthaleneacetic acid proved to be the best for explant rooting. Molecular genetic analysis of the H. theinum mother plants and the obtained regenerants was performed with six ISSR markers. Depending on the primer, four to ten amplified fragments with sizes ranging from 250 to 3000 bp were identified. Our results confirmed the genetic stability of regenerants obtained in five passages and their identity to the mother plant.

Centromeres Off the Hook: Massive Changes in Centromere Size and Structure Following Duplication of CenH3 Gene in Fabeae Species.

In most eukaryotes, centromere is determined by the presence of the centromere-specific histone variant CenH3. Two types of chromosome morphology are generally recognized with respect to centromere organization. Monocentric chromosomes possess a single CenH3-containing domain in primary constriction, whereas holocentric chromosomes lack the primary constriction and display dispersed distribution of CenH3. Recently, metapolycentric chromosomes have been reported in Pisum sativum, representing an intermediate type of centromere organization characterized by multiple CenH3-containing domains distributed across large parts of chromosomes that still form a single constriction. In this work, we show that this type of centromere is also found in other Pisum and closely related Lathyrus species, whereas Vicia and Lens genera, which belong to the same legume tribe Fabeae, possess only monocentric chromosomes. We observed extensive variability in the size of primary constriction and the arrangement of CenH3 domains both between and within individual Pisum and Lathyrus species, with no obvious correlation to genome or chromosome size. Search for CenH3 gene sequences revealed two paralogous variants, CenH3-1 and CenH3-2, which originated from a duplication event in the common ancestor of Fabeae species. The CenH3-1 gene was subsequently lost or silenced in the lineage leading to Vicia and Lens, whereas both genes are retained in Pisum and Lathyrus. Both of these genes appear to have evolved under purifying selection and produce functional CenH3 proteins which are fully colocalized. The findings described here provide the first evidence for a highly dynamic centromere structure within a group of closely related species, challenging previous concepts of centromere evolution.

Inhibition of auxin signaling in Frankia species-infected cells in Casuarina glauca nodules leads to increased nodulation.

Actinorhizal symbioses are mutualistic interactions between plants and the soil bacteria Frankia spp. that lead to the formation of nitrogen-fixing root nodules. The plant hormone auxin has been suggested to play a role in the mechanisms that control the establishment of this symbiosis in the actinorhizal tree Casuarina glauca. Here, we analyzed the role of auxin signaling in Frankia spp.-infected cells. Using a dominant-negative version of an endogenous auxin-signaling regulator, INDOLE-3-ACETIC ACID7, we established that inhibition of auxin signaling in these cells led to increased nodulation and, as a consequence, to higher nitrogen fixation per plant even if nitrogen fixation per nodule mass was similar to that in the wild type. Our results suggest that auxin signaling in Frankia spp.-infected cells is involved in the long-distance regulation of nodulation in actinorhizal symbioses.