Ground Tissue Research Articles

Histological Localization of Fungal Endophytes in Healthy Tissues of <i>Adhatoda vasica</i> Nees

A research protocol has been developed to locate endophytic fungi present inside the healthy leaves and stems of Adhatoda vasica using the microtome technique. The surface-sterilized explants after staining with lactophenol cotton blue showed the presence of endophytic fungi in intercellular spaces of ground and dermal tissues. In transverse sections of leaf at 100 magnification, dense blue colonies of endophytic fungi in epidermis and mesophyll region were recorded, while sprinkled colonies were seen in vascular bundles. In transverse sections of stem at 100 magnification, dense colonies of endophytic fungi in phloem and slightly lesser in epidermal region were observed. Scattered colonies were also recorded in xylem and cortex tissues. The fungal colonies were also present in intracellular and extracellular regions of both explants. Further studies will be required to identify these fungal isolates through pure culture on PDA plates to explore their biosynthetic pathway.

Molecular and Evolutionary Mechanisms of Cuticular Wax for Plant Drought Tolerance.

Cuticular wax, the first protective layer of above ground tissues of many plant species, is a key evolutionary innovation in plants. Cuticular wax safeguards the evolution from certain green algae to flowering plants and the diversification of plant taxa during the eras of dry and adverse terrestrial living conditions and global climate changes. Cuticular wax plays significant roles in plant abiotic and biotic stress tolerance and has been implicated in defense mechanisms against excessive ultraviolet radiation, high temperature, bacterial and fungal pathogens, insects, high salinity, and low temperature. Drought, a major type of abiotic stress, poses huge threats to global food security and health of terrestrial ecosystem by limiting plant growth and crop productivity. The composition, biochemistry, structure, biosynthesis, and transport of plant cuticular wax have been reviewed extensively. However, the molecular and evolutionary mechanisms of cuticular wax in plants in response to drought stress are still lacking. In this review, we focus on potential mechanisms, from evolutionary, molecular, and physiological aspects, that control cuticular wax and its roles in plant drought tolerance. We also raise key research questions and propose important directions to be resolved in the future, leading to potential applications of cuticular wax for water use efficiency in agricultural and environmental sustainability.

Dimethylarsenate (DMA) exposure influences germination rates, arsenic uptake and arsenic species formation in wheat

The contamination of cereals with arsenic (As) is a global health and agronomic concern. This study compared the physiological response, As uptake and As speciation in the grains and above ground tissues of 20 wheat cultivars exposed to 5 mg As kg−1 soil as either arsenate (AsV) or dimethylarsenate (DMA) under glasshouse conditions.Germination rates for the majority of cultivars exceeded 80% for the majority of cultivars when exposed to AsV, but fell significantly to 20–40% when exposed to DMA. For a number of cultivars, grain yields were 20–50% lower when plants were exposed to DMA compared to AsV.Grain As concentrations were between 0.6 and 1.6 μg As g−1 grain across the twenty cultivars when exposed to AsV, whereas grain As concentrations were much higher (2.2–4.6 μg As g−1 grain) when exposed to DMA. When plants were exposed to AsV, 100% of the As present in the grain was found as inorganic As while in plants exposed to DMA, 70–90% of As was present as DMA with the remainder found as inorganic As. DMA is believed to be incorporated by plants via silica (Si) acid channels and assessment of grain Si concentrations demonstrated that up to 40% less Si was accumulated in grains when plants were exposed to DMA.The decreased germination rates and grain yields in the presence of DMA is similar to the symptoms described for straight head disease in rice, which has been linked to DMA exposure. The results presented here indicate some analogous processes occur in wheat to those described in rice. We hypothesise that exposure to DMA may have inhibited Si-metabolism and translocation which resulted in both developmental impairment and possibly an increased susceptibility to soil pathogens.

Phosphate uptake and translocation in a tropical Canna-based constructed wetland

IntroductionConsidering the problem of eutrophication of the water bodies, phosphate removal from water has emerged as a research of topical interest. The present study aims to investigate the efficacy of Canna lily-based constructed wetland to remove phosphate from wastewater. The translocation of phosphate in plant tissue and its biochemical transformation in sediments is also studied to understand its accumulation and recirculation within the system. ResultsThe removal of phosphate stabilized at around 50% in the present study and plant uptake was found to be the major removal mechanism. Average removal was 167 mg/m2 day for total phosphate and 84 mg/m2 day for available phosphate for an initial loading rate of 200 mg/m2 day and 85 mg/m2 day, respectively, at a HRT of 24 h. Most of the phosphate concentrated in above ground tissue of plant and its relative accumulation was maximum in flowers. Fractionation of phosphate in sediments confirmed removal by sediments with an accumulation of apatite phosphate (Ca and Mg bound), but release of non-apatite form (Fe and Al bound).ConclusionThe study concludes that Canna-based constructed wetland can be an effective tool for phosphate removal from wastewater and sediments particularly under tropical conditions. Regular harvesting of above ground tissue of Canna can result in nutrient export from the system, whereas autochthonous addition may result in recirculation.

Auxin response cell-autonomously controls ground tissue initiation in the early Arabidopsis embryo

Plant organs are typically organized into three main tissue layers. The middle ground tissue layer comprises the majority of the plant body and serves a wide range of functions, including photosynthesis, selective nutrient uptake and storage, and gravity sensing. Ground tissue patterning and maintenance in Arabidopsis are controlled by a well-established gene network revolving around the key regulator SHORT-ROOT (SHR). In contrast, it is completely unknown how ground tissue identity is first specified from totipotent precursor cells in the embryo. The plant signaling molecule auxin, acting through AUXIN RESPONSE FACTOR (ARF) transcription factors, is critical for embryo patterning. The auxin effector ARF5/MONOPTEROS (MP) acts both cell-autonomously and noncell-autonomously to control embryonic vascular tissue formation and root initiation, respectively. Here we show that auxin response and ARF activity cell-autonomously control the asymmetric division of the first ground tissue cells. By identifying embryonic target genes, we show that MP transcriptionally initiates the ground tissue lineage and acts upstream of the regulatory network that controls ground tissue patterning and maintenance. Strikingly, whereas the SHR network depends on MP, this MP function is, at least in part, SHR independent. Our study therefore identifies auxin response as a regulator of ground tissue specification in the embryonic root, and reveals that ground tissue initiation and maintenance use different regulators and mechanisms. Moreover, our data provide a framework for the simultaneous formation of multiple cell types by the same transcriptional regulator.

SHR overexpression induces the formation of supernumerary cell layers with cortex cell identity in rice

The number of root cortex cell layers varies among plants, and many species have several cortical cell layers. We recently demonstrated that the two rice orthologs of the Arabidopsis SHR gene, OsSHR1 and OsSHR2, could complement the A. thaliana shr mutant. Moreover, OsSHR1 and OsSHR2 expression in A. thaliana roots induced the formation of extra root cortical cell layers. In this article, we demonstrate that the overexpression of AtSHR and OsSHR2 in rice roots leads to plants with wide and short roots that contain a high number of extra cortical cell layers. We hypothesize that SHR genes share a conserved function in the control of cortical cell layer division and the number of ground tissue cell layers in land plants.

Non-destructive determination of floral staging in cereals using X-ray micro computed tomography (\xb5CT)

BackgroundAccurate floral staging is required to aid research into pollen and flower development, in particular male development. Pollen development is highly sensitive to stress and is critical for crop yields. Research into male development under environmental change is important to help target increased yields. This is hindered in monocots as the flower develops internally in the pseudostem. Floral staging studies therefore typically rely on destructive analysis, such as removal from the plant, fixation, staining and sectioning. This time-consuming analysis therefore prevents follow up studies and analysis past the point of the floral staging.ResultsThis study focuses on using X-ray µCT scanning to allow quick and detailed non-destructive internal 3D phenotypic information to allow accurate staging of Arabidopsis thaliana L. and Barley (Hordeum vulgare L.) flowers. X-ray µCT has previously relied on fixation methods for above ground tissue, therefore two contrast agents (Lugol’s iodine and Bismuth) were observed in Arabidopsis and Barley in planta to circumvent this step. 3D models and 2D slices were generated from the X-ray µCT images providing insightful information normally only available through destructive time-consuming processes such as sectioning and microscopy. Barley growth and development was also monitored over three weeks by X-ray µCT to observe flower development in situ. By measuring spike size in the developing tillers accurate non-destructive staging at the flower and anther stages could be performed; this staging was confirmed using traditional destructive microscopic analysis.ConclusionThe use of X-ray micro computed tomography (µCT) scanning of living plant tissue offers immense benefits for plant phenotyping, for successive developmental measurements and for accurate developmental timing for scientific measurements. Nevertheless, X-ray µCT remains underused in plant sciences, especially in above-ground organs, despite its unique potential in delivering detailed non-destructive internal 3D phenotypic information. This work represents a novel application of X-ray µCT that could enhance research undertaken in monocot species to enable effective non-destructive staging and developmental analysis for molecular genetic studies and to determine effects of stresses at particular growth stages.

Relationship between anatomy and vibration behaviour of softwoods and hardwoods

The influence of cell type and cell arrangement on the vibration characteristics of 91 softwood and hardwood species was studied under controlled conditions. The vibration of standardized wood plates was measured by means of high-resolution laser sensors with an accuracy of ± 0.02 μm and a sampling frequency of 30 kHz. First and second order waves within the vibration spectra were identified by Fast Fourier Transformation analysis. The amplitudes, the frequencies, and the duration of the waves of the 91 timber species were compared by means of principal component analysis. Special attention was paid to the influence of tracheids, vessels, storied rays, growth rings, and the anatomical direction of the wood on the vibration spectra. Due to significant differences in vibration between samples on which the vibration was induced in the transverse, radial, and tangential plane, a comparison between tree species was only possible if plates with precise and identical orientation of the grain were used. In plates with exactly oriented surfaces along the radial plane, distinct vibration characteristics were found in timber species with tracheids as ground tissue (softwoods), in timbers without distinct growth rings, and in timbers with storied rays. In contrast, no relationship was found between the arrangement of the vessels, the width of the xylem rays and the vibration characteristics of hardwoods.

Comparative anatomical studies on some species of the genus Amaranthus (Family: Amaranthaceae) for the development of an identification guide

A study of anatomical features of mature leaves and stems (at fruiting stage) of 12 Amaranthus taxa (Family: Amaranthaceae) shows high variation between them and supplied new characters. The internal structures were evaluated to clarify their effectiveness in solving taxonomic complexity and identification difficulty in this genus. Observation of the transections of blades showed that the epidermis is uniseriate, ground tissue consists of angular collenchyma and thin parenchyma. The vascular bundles shape has three patterns crescent, ring, ovate. Also they may be united or separated while the midrib shape in cross section has two patterns in which U-shaped, cordate or crescent bundle occurs. All leaves are petiolate. The examination of the petioles exhibits new and varied characters such as petiole shape (cross section), vascular bundles (shape, number, arrangement). While the resulted characters from the observation of the stem structure showed less variation. Nineteen qualitative characters with 38 character states resulted from leaf anatomy. Only (8) characters were sufficient to generate an identification anatomical key. DELTA program was used in key-generation. Also different measurements were carried out by a photo analysis program (Image J), such as lamina thickness, mesophyll thickness, area of upper and lower epidermal cells and thickness of upper and lower epidermal cells to exhibit most possible dissimilarities between the studied species.

Plant potentialities determine anatomical and histochemical diversity in Mikania glomerata Spreng. galls

Arthropod gall super-hosts have distinct developmental responses to each gall inducer species. The taxa and feeding habits of the gall inducers determine each gall’s histological patterns, but the host plant imposes histological constraints on gall differentiation. Mikania glomerata Spreng. (Asteraceae) is a gall super-host, presenting at least six distinct gall morphotypes. The aim of current study was to evaluate how different species of Cecidomyiidae can manipulate the same host plant tissues, demonstrating the potentialities of M. glomerata under distinct external signaling. We compared M. glomerata anatomy and histochemistry in fusiform galls induced by Liodiplosis cylindrica (Gagne 2001) on petioles, globoid galls induced by L. spherica (Gagne 2001) on leaf laminae, and conic galls of Clinodiplosis sp. on leaf laminae as well as in non-galled leaves and petioles. Even though each gall presents several distinct features, they share anatomical and histochemical patterns, determined by the host plant potentialities. We found that the ground and dermal system tissues were manipulated differently by each inducer, generating distinct gall morphotypes. Alterations on epidermal cell shapes and suppression of the capitate glandular trichomes occured in all studied galls. We report for the first time the occurrence of nutritive cells containing starch in globoid galls. The anatomical diversity of the galls on M. glomerata seems to be more related to distinct differentiation pathways of the host plant than to the taxonomic relationships between the gall-inducing species.

Micrometric Study and Random Amplified Polymorphic Deoxyribonucleic Acid Analysis of Wattakaka volubilis (Linn. f.) Stapf. Leaves

The leaves of Jīvantī are considered to be the best among the vegetables in the classical texts of Ayurveda. In some parts of India, Wattakaka volubilis (Linn. f.) Stapf. is used in the name of JTvantT for treatment of pyoderma, fever, cough, cold, rheumatic pain, diabetes, eye diseases, snake bite etc. The present study deals with the micrometric evaluation and molecular characterization of Wattakaka volubilis (Linn. f.) Stapf. leaves by random amplified polymorphic deoxyribonucleic acid (RAPD) markers by following standard parameters. Morphological study showed that leaves are 6.5–14 × 4.5–11 cm, in size, broadly ovate or suborbicular with reticulate venation. Transverse section of petiole measures about 2.7 μm, showing single-layered epidermis with multicellular, warty trichomes. Cortex contains chloroplast and several prismatic and rosette crystals. Section through midrib measures about 3.4 × 3.2 μm, having centrally located bicollateral vascular bundle supported by ground tissue. Powder microscopy showed the presence of multicellular and glandular trichomes, paracytic stomata, rosette crystals of calcium oxalate, oil globules and chlorophyll pigments. In RAPD analysis, all the 10 primers showed good amplification. The unique bright and light bands obtained in polymerase chain reaction amplification along with quantitative pharmacognostical characters can be considered as a measure for authentication and standardization of the plant.

Continuous adsorption of methylene blue dye on the maize stem ground tissue

Continuous adsorption of methylene blue from aqueous solutions onto maize stem ground tissue in column mode was investigated. The study encompassed the effects of important parameters such as flow rate, initial concentration of methylene blue, and bed depth on methylene blue removal from model solutions. The maximum adsorption capacity of the maize stem was 45.9 mg/g at the initial methylene blue concentration of 20 mg/L, bed height of 6.5 cm and flow rate of 8 mL/min. It was found that the breakthrough time for reaching saturation increased with a decrease in the flow rate, and also occurred earlier for a higher influent concentration. The breakthrough times increased with the bed depth, thus allowing a larger volume to be treated. The Adams-Bohart, Yoon-Nelson, Clark and artificial neural network models were used to predict the breakthrough curves. These models gave excellent approximations of the experimental behavior.

Identification of tissular origin of particles based on autofluorescence multispectral image analysis at the macroscopic scale

Powders produced from plant materials are heterogeneous in relation to native plant heterogeneity, and during grinding, dissociation often occurred at the tissue scale. The tissue composition of powdery samples could be modified through dry fractionation diagrams and impact their end-uses properties. If tissue identification is often made on native plant structure, this characterization is not straightforward in destructured samples such powders. Taking advantage of the autofluorescence properties of cell wall components, multispectral image acquisition is envisioned to identify the tissular origin of particles. Images were acquired on maize stem sections and ground tissues isolated from the same stem by hand dissection. The variability in fluorescence intensity profiles was analysed using principal component analysis. The correspondence between fluorescence profiles and the different tissues observed in maize sections was assessed based on histology or known compositional heterogeneity. Similar variability was encountered in fluorescence profiles extracted from powder leading to the potential ability to predict tissular origin based on this autofluorescence multispectral signal.

Totipotent nutritive cells and indeterminate growth in galls of Ditylenchus gallaeformans (Nematoda) on reproductive apices of Miconia

The majority of gall-inducing nematodes lives in the soil, and induces galls on roots. Nevertheless, some nematodes are able to climb up the stems and induce galls on aerial plant organs. This is the case of Ditylenchus gallaeformans (Oliveira et al., 2013), which induces galls on the inflorescences of Miconia albicans (Sw.) Steud. (1841) and Miconia ibaguensis (Bonpl.) Triana (1871) (Melastomataceae). Under the influence of D. gallaeformans, the flowers of M. albicans and M. ibaguensis do not differentiate in situ. Instead of flowers, the axes of the galled inflorescences are surrounded by emergences with nutritive tissues lining the larval chambers. The nutritive tissues are meristem-like, but distinct from other galls, they have a promeristematic capability. In other words, the nutritive tissues of these galls have totipotent cells, originating new covering emergences with dermal, ground and vascular tissues. Therefore, these galls have an indeterminate growth, which is a novelty for galls in general. Additionally, D. gallaeformans induces a long-distance impact on fruits, which have increased number of carpels. Such long-distance effects indicate that D. gallaeformans is a peculiar colonial parasite, which may compensate the damages of gall inducing mechanisms by favoring, at least partially, its host plant fitness. The number of carpels is a conservative character in most plant species, and the promeristems are maintained only in apical and lateral buds of normal plants. However, D. gallaeformans is capable of manipulating these conservative features in its host plants, and the signaling factors involved in these interactions deserves special attention.

Effect of pulsed electric fields on the structure and frying quality of “kumara” sweet potato tubers

Abstract The aim of this research was to study the effect of pulsed electric fields (PEF) on the microstructure of “kumara” sweet potato ( Ipomoea batatas cv. Owairaka ) and its quality after frying. Whole sweet potato tubers were treated at different electric field strengths ranging from 0.3 to 1.2 kV/cm with specific energy levels between 0.5 and 22 kJ/kg. Cell viability was determined using tetrazolium staining to investigate the uniformity of the PEF effect across tubers. Based on the patterns of viable cells it was observed that the effect of PEF was not homogeneous across the tuber. This result was also supported by the pattern of enzymatic browning due to PEF facilitating the reaction of polyphenoloxidase and phenols. PEF treatment resulted in significant softening of the ground tissues, but not on the dermal tissues, as determined by texture analysis. With respect to frying quality, tubers pre-treated with PEF at electric field strength of 1.2 kV/cm and fried at 190 °C had an 18% lower oil content than non-PEF treated samples. The kinetics of browning as a function of frying time could be described by a fractional conversion model. The activation energy ( Ea ) of the browning rate during frying increased (more temperature sensitive) due to PEF pretreatment at 0.5 kV/cm and 1.2 kV/cm. It implies that PEF pretreatment allows frying the potato chips at lower temperature in order to achieve the same brown colour intensity as the non-PEF treated tubers. This study shows clearly that PEF could reduce the energy required for cutting and frying of kumara. Industrial relevance This study provides evidence that the effect of PEF processing on whole kumara tubers is not uniform, demonstrating heterogenous distribution. These findings provide important information for food industry to design appropriate PEF processing conditions for solid materials. More importantly, PEF treatment reduced the energy required for cutting and frying of kumara, and reduced the oil content in the fried kumara chips.

Establishment of Expression in the SHORTROOT-SCARECROW Transcriptional Cascade through Opposing Activities of Both Activators and Repressors

Tissue-specific gene expression is often thought to arise from spatially restricted transcriptional cascades. However, it is unclear how expression is established at the top of these cascades in the absence of pre-existing specificity. We generated a transcriptional network to explore how transcription factor expression is established in the Arabidopsis thaliana root ground tissue. Regulators of the SHORTROOT-SCARECROW transcriptional cascade were validated in planta. At the top of this cascade, we identified both activators and repressors of SHORTROOT. The aggregate spatial expression of these regulators is not sufficient to predict transcriptional specificity. Instead, modeling, transcriptional reporters, and synthetic promoters support a mechanism whereby expression at the top of the SHORTROOT-SCARECROW cascade is established through opposing activities of activators and repressors.

Differential toxicity of Pb & Hg on the development of modular traits, photosynthetic and biochemical attributes in two varieties of a forage crop species Trifolium alexandrinum L.

Heavy metal stress as result of natural and anthropogenic activities is main environmental problem. Pb and Hg are among non-biodegradable metals thus remaining persistent in soil and water. The present study was carried out to assess growth and biochemical responses of two varieties (Desi and Misri) of Trifolium alexandrinum L. after application of varying levels (25mg/kg, 50mg/kg and 100mg/kg) of Pb and Hg in soil along with control. Seed germination, biomass of above and below ground tissues, number of flowers and leaves, leaf area and nodulation was observed. For biochemical attributes, green pigments, protein and amino acids, were determined. Both varieties (Desi and Misri) showed variable responses in relation to both Pb and Hg. Similarly, the pattern of character expression was independent for metal levels and types. Misri performed consistently better as it showed best threshold for most of the attributes studied. Hg was found to be more toxic as compared to the Pb as it induced more drastic decline in parameters studied. The study showed that biometric traits can be used as good predictors and the biochemical parameters cannot be used as useful biochemical markers as they showed no marked disparity.

Symplastic signaling instructs cell division, cell expansion, and cell polarity in the ground tissue of Arabidopsis thaliana roots

Cell-to-cell communication is essential for the development and patterning of multicellular organisms. In plants, plasmodesmata (PD) provide direct routes for intercellular signaling. However, the role that PD-mediated signaling plays in plant development has not been fully investigated. To gain a comprehensive view of the role that symplastic signaling plays in Arabidopsis thaliana, we have taken advantage of a synthetic allele of CALLOSE SYNTHASE3 (icals3m) that inducibly disrupts cell-to-cell communication specifically at PD. Our results show that loss of symplastic signaling to and from the endodermis has very significant effects on the root, including an increase in the number of cell layers in the root and a misspecification of stele cells, as well as ground tissue. Surprisingly, loss of endodermal signaling also results in a loss of anisotropic elongation in all cells within the root, similar to what is seen in radially swollen mutants. Our results suggest that symplastic signals to and from the endodermis are critical in the coordinated growth and development of the root.

English

A hydroponic greenhouse study was carried out to evaluate the effects of increasing cadmium (Cd) concentration on plant growth, mineral nutrition and Cd distribution of H-250 sunflower genotype. Exposure to increasing Cd concentrations reduced plant biomass by 40, 34, 47 and 42% of the total, leaves, stem and roots dry weights as compared to the control. Regardless of the treatment most of Cd uptake by the genotype was allocated in the root, followed by leaf and stem. The higher bioconcentration factors values in both above ground and underground plant tissues and low transfer factor value indicated that this genotype may be an alternative for use in phytostabilization programs. The results also showed that increasing Cd concentration disrupted plant homeostasis as it increased the concentration of some nutrients and had adverse effect on others, impacting plant growth. In this context, the results suggest that the low magnesium, iron and manganese concentrations in the leaves were the main cause for plant biomass reduction and leaf chlorosis and necrosis, as each one of these elements plays a key role on the chlorophyll molecule and on photosynthesis process.   Key words: Bioremediation, bioaccumulation factor, heavy metal stress, Helianthus annuus, transfer factor.

Analysis of plant growth-promoting properties of Bacillusamyloliquefaciens UCMB5113 using Arabidopsis thaliana as host plant

Main conclusionThis study showed thatBacillusamyloliquefaciensUCMB5113 colonizingArabidopsisroots changed root structure and promoted growth implying the usability of this strain as a novel tool to support sustainable crop production.Root architecture plays a crucial role for plants to ensure uptake of water, minerals and nutrients and to provide anchorage in the soil. The root is a dynamic structure with plastic growth and branching depending on the continuous integration of internal and environmental factors. The rhizosphere contains a complex microbiota, where some microbes can colonize plant roots and support growth and stress tolerance. Here, we report that the rhizobacterium Bacillus amyloliquefaciens subsp. plantarum UCMB5113 stimulated the growth of Arabidopsisthaliana Col-0 by increased lateral root outgrowth and elongation and root-hair formation, although primary root elongation was inhibited. In addition, the growth of the above ground tissues was stimulated by UCMB5113. Specific hormone reporter gene lines were tested which suggested a role for at least auxin and cytokinin signaling during rhizobacterial modulation of Arabidopsis root architecture. UCMB5113 produced cytokinins and indole-3-acetic acid, and the formation of the latter was stimulated by root exudates and tryptophan. The plant growth promotion effect by UCMB5113 did not appear to depend on jasmonic acid in contrast to the disease suppression effect in plants. UCMB5113 exudates inhibited primary root growth, while a semi-purified lipopeptide fraction did not and resulted in the overall growth promotion indicating an interplay of many different bacterial compounds that affect the root growth of the host plant. This study illustrates that beneficial microbes interact with plants in root development via classic and novel signals.