A new Critically Endangered species of stone breaker (Phyllanthus, Phyllanthaceae) from Central Brazil, with notes on its leaf and stem anatomy

A new species from the state of Goiás, Brazil, Phyllanthus pterocaulis, is described and illustrated, with comments on its geographic distribution and environmental preferences, phenology, morphological relationships, and systematic position. It is morphologically allied with Phyllanthus avicularis, P. heliotropus, and P. hyssopifolioides, but differs from all of them by a set of characters related to cymules sex, presence and types of trichomes on leaves and stems, leaf consistency, numbers of sepals in flower of both sexes, integrity of stamens, capsules and seeds. Additionally, we provide images of the new species in the field, conservation status, mapped distribution, the anatomical description of its stem and leaves, and a key to differentiate it from the other similar species belonging to Phyllanthus sect. Loxopodium occurring in Brazil. The new species is one of the few in the genus that occurs in shaded environments in seasonal dry forests within the Cerrado biome.

Stem anatomy of Apioideae (Apiaceae): effects of habit and reproductive strategy

Apioideae is the biggest and the most diverse of four subfamilies recognised within Apiaceae. Except for a few, likely derived, woody clades, most representatives of this subfamily are herbaceous. In the present study, we assessed stem anatomy of 87, mostly therophytic and hemicryptophytic, species from at least 20 distinct lineages of Apioideae, and juxtaposed them with 67 species from our previous anatomical projects also focused on this subfamily. Comparing our data with the literature, we found that wood anatomy does not allow for a distinction between apioids and their close relatives (Azorelloideae, Saniculoideae), but more distantly related Mackinlayoideae differ from Apioideae in their perforation plate type. Vessel element and fibre length, and vessel diameter were positively correlated with plant height: phenomena already reported in literature. Similar pattern was retrieved for vertical intervessel pit diameter. Wood ground tissue in apioids ranges from entirely fibrous to parenchymatous. The shortening of internodes seems to favour the formation of parenchymatic ground tissue, whereas the early shift to flowering promotes the deposition of fibrous wood in monocarpic species. These results support a hypothesis on interdependence among internode length, reproductive strategy, and wood ground tissue type.

Characterization and analysis of novel natural cellulosic fiber extracted from Strelitzia reginae plant

The purpose of this study is to evaluate in detail the usability of new cellulosic fibers extracted from the stem of the plant Strelitzia reginae, as a potential reinforcement for polymer composites. The morphological, physical, thermal, and mechanical properties of fibers were addressed for the first time in this paper. Both untreated and alkali-treated fibers were characterized, using scanning electron microscopy (SEM), Fourier-transform infrared, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), optical microscope, and X-ray diffraction (XRD) and applying tensile test for determining the mechanical behavior. For both fiber treated at one hour (T1H) and at four hours (T4H), the stem anatomy and fiber SEM micrographs showed a strong presence of fiber cells. Thermogravimetry and DSC showed that the fiber was thermally stable up to 233°C for untreated fiber, 254 and 240°C, respectively, In single-fiber tensile tests, it was observed that the fibers extracted from the stem of Strelitzia reginae were strong. The mean values of Young’s modulus exhibited by untreated fibers and treated (T1H) and (T4H) are, respectively, 9.89 GPa, 12.08, and 18.39 GPa. Also mean values of tensile strength are 271.79, 306.23, and 421.39 MPa. The XRD reveals the presence of cellulose with a Crystallinity Index of 70% for raw fiber and 72% for the treated one. Fourier-transform infrared analysis well demonstrated the effect of chemical treatment. It can be concluded from the results of all above experiments that the Strelitzia reginae fibers (SR) could serve as a possible reinforcement in composite materials.

Structure of the secondary xylem and development of a cambial variant in Serjania mexicana (Sapindaceae)

The lianas in the family Sapindaceae are known for their unique secondary growth which differs from climbing species in other plant families in terms of their cambial variants. The present study deals with the stem anatomy of self-supporting and lianescent habit, development of phloem wedges, the ontogeny of cambial variants and structure of the secondary xylem in the stems of Serjania mexicana (L.) Willd. Thick stems (15–20 mm) were characterized by the presence of distinct phloem wedges and tangentially wide neo-formed cambial cylinders. As the stem diameter increases, there is a proportional increase in the number of phloem wedges and neo-formed vascular cylinders. The parenchymatous (pericyclic) cells external to phloem wedges that are located on the inner margin of the pericyclic fibres undergo dedifferentiation, become meristematic and form small segments of cambial cylinders. These cambia extend tangentially into wide and large segments of neoformations. Structurally, the secondary xylem and phloem of the neo-formed vascular cylinders remain similar to the derivatives produced by the regular vascular cambium. The secondary xylem is composed of vessels (wide and narrow), fibres, axial and ray parenchyma cells. The occurrence of perforated ray cells is a common feature in both regular and variant xylem.

Linking the Evolution of Development of Stem Vascular System in Nyctaginaceae and Its Correlation to Habit and Species Diversification

Background: The presence of alternative patterns of secondary growth in stems of Nyctaginaceae has been known for a long time. Still, the interpretation of types of cambial variants are controversial. The knowledge on stem anatomical diversity in Nyctaginaceae, which is diverse also in habits, offers the unique opportunity not only to investigate the evolution of complex developments, but also to address how these anatomies shifted within habits and how the acquisition of novel cambial variants and habit transitions impacted the diversification of the family. Methods: We integrated developmental data with a phylogenetic framework to investigate the diversity and evolution of stem anatomy in Nyctaginaceae using phylogenetic comparative methods, reconstructing ancestral states, and examining whether anatomical shifts correspond to species diversification rate shifts in the family. Results: Two types of cambial variants, interxylary phloem and successive cambia, were recorded in Nyctaginaceae, which result from four different ontogenies. These ontogenetic trajectories depart from two distinct primary vascular structures (regular or polycyclic eustele) yet, they contain shared developmental stages which generate stem morphologies with deconstructed boundaries of morphological categories (continuum morphology). Unlike our a priori hypotheses, interxylary phloem is reconstructed as the ancestral character for the family, with three ontogenies characterized as successive cambia evolving in few taxa. Cambial variants are not contingent in habits, and their transitions are independent from species diversification.Conclusions: Our findings suggests that multiple developmental mechanisms, such as heterochrony and heterotopy generate the transitions between interxylary phloem and successive cambia. Intermediate between these two extremes are present in Nyctaginaceae, suggesting a continuum morphology across the family as a generator of anatomical diversity.

Anatomy of the main stem of soybean plants submitted to the removal of the stem apical meristem

Some plant species allow the cutting of the apical meristem in order to assist activities of genetic improvement programs, among them is the soybean. The objective was to verify if the removal of the apical meristem of soybean plants induces any alteration in the stem anatomy, since it was verified that the removal of the apical meristem reduces the need for tutoring of the plants cultivated under greenhouse conditions. The experiment was conducted with plants of the BRSMG 752S cultivar and the treatments consisted of sections of the hypocotyl region of plants that had undergone apical meristem removal at the V2 development stage and of plants without apical meristem removal. The permanent slides were processed following the usual methodologies in plant anatomy. Descriptions and measurements of anatomical tissues were made for comparison between treatments. Plants with removal presented epidermis as a covering tissue until 20 days after the V2 development stage, while plants without removal of the apical meristem presented it until 30 days after V2. Periderm was observed only in plants with removal, and this feature was not evident in plants without removal until 30 days after V2. There was formation of secondary vascular tissues in the collections 30 days after removal (V2 stage). Thus, we conclude that the removal of the apical meristem accelerates the secondary development in hypocotyls of soybean plants grown under greenhouse conditions.

Effects of Complex Heavy Metal Stress on the Hydrodynamic Parameters, Stem Anatomy and Photosynthetic Properties of Three Desert Species in the Jinchang Mining Area

PurposeThe physiological mechanism and phytoremediation effects of heavy metal pollution by local desert plants, namely, Kochia scoparia, Chenopodium glaucum and Atriplex centralasiatica, around tailings were investigated. MethodsTwo different types of local soils (native soil and native soil + tailings, which are labeled CK and T, respectively) were used for potting experiments in the open, and the photosynthesis performance, chlorophyll content, hydraulics and stem anatomy of the potted plants were analyzed. The collection of soil samples has been approved by the soil resources management department of the local government.ResultsIt was found that the chlorophyll content, photosynthetic rate and transpiration rate decreased but the chlorophyll a and b (Chl a/b) and intercellular CO2 concentration (Ci) values increased in Kochia scoparia under complex heavy metal stress. Nonstomatal restriction led to a decrease in the net photosynthetic rate (Pn) and damage to the chloroplasts. Additionally, four hydrodynamic parameters were elevated under heavy metal stress along with a decrease in duct density and diameter and a significant thickening of the duct wall. Under heavy metal stress, the changes in the chlorophyll parameters of Chenopodium glaucum, Atriplex centralasiatica and Kochia scoparia exhibited the same pattern, with stomatal restriction causing a decrease in Pn and Ci and a significant increase in the leaf specific conductance, hydraulic conductivity, and duct diameter. ConclusionsAtriplex centralasiatica is the dominant desert plant in the region and demonstrates good adaptability and heavy metal accumulation under the stress of heavy metal tailings; therefore, it is a good candidate for tailings remediation in the Jinchang desert mining area.