Mature Stem Research Articles

Evidences for the association between carbon isotope discrimination and grain yield—Ash content and stem carbohydrate in spring wheat grown in Ningxia (Northwest China)

Carbon isotope discrimination (Δ) has been repeatedly reported to positively correlate with grain yield in wheat grown under post-anthesis stress environments. Several hypotheses have been put forward to explain this association. However, there is few reported direct evidence clarified the relationship between Δ and grain yield, which is the objective of the present work. The relationships between Δ and grain yield (GY), harvest index (HI), ash content ( m a), specific stem dry weight (SSDW) and carbohydrate in stem, were studied in a collection of 20 bread wheat cultivars (landraces, released cultivars and advanced lines) in Yinchuan of the Ningxia region (Northwest of China) in three successive years (2006, 2007 and 2008). Relationships between GY, HI, stem specific dry weight, accumulation and mobilization of stem reserved carbohydrate and Δ were analyzed. The effects of year, sampling time and genotypes on measured traits were significant. Positive correlations between grain yield and Δ were noted in 2007 and 2008 when stress occurred after anthesis, but not in 2006 when soil water condition was nearly optimal. Significant and positive correlations among m a L m, grain Δ and harvest index were found. Stem water-soluble carbohydrate content (SWSCC) and specific dry weight 7 days after anthesis was positively associated with Δ. Remobilization efficiency of stem water-soluble carbohydrate and total carbohydrate (the sum of water-soluble carbohydrate and starch) was also found to be significantly and positively correlated to Δ. There were negative relationships between Δ G m, Δ S m, and SSDW at maturity. In conclusion, Δ may predict yield when irrigation does not meet crop's water requirement and wheat experiences a slight water stress after anthesis in central region of Ningxia. Δ or m a L m is related to the efficiency of carbon partitioning to the grain. Basal mature stem Δ seems to be an integrated character reflecting both early carbohydrate assimilation and dry matter remobilization to grain during grain-filling.

Elucidating the Mechanisms of Assembly and Subunit Interaction of the Cellulose Synthase Complex of Arabidopsis Secondary Cell Walls

Cellulose is the most abundant biopolymer in nature; however, questions relating to the biochemistry of its synthesis including the structure of the cellulose synthase complex (CSC) can only be answered by the purification of a fully functional complex. Despite its importance, this goal remains elusive. The work described here utilizes epitope tagging of cellulose synthase A (CESA) proteins that are known components of the CSC. To avoid problems associated with preferential purification of CESA monomers, we developed a strategy based on dual epitope tagging of the CESA7 protein to select for CESA multimers. With this approach, we used a two-step purification that preferentially selected for larger CESA oligomers. These preparations consisted solely of the three known secondary cell wall CESA proteins CESA4, CESA7, and CESA8. No additional CESA isoforms or other proteins were identified. The data are consistent with a model in which CESA protein homodimerization occurs prior to formation of larger CESA oligomers. This suggests that the three different CESA proteins undergo dimerization independently, but the presence of all three subunits is required for higher order oligomerization. Analysis of purified CESA complex and crude extracts suggests that disulfide bonds and noncovalent interactions contribute to the stability of the CESA subunit interactions. These results demonstrate that this approach will provide an excellent framework for future detailed analysis of the CSC.

Tissue specific expression of potent insecticidal, Allium sativum leaf agglutinin (ASAL) in important pulse crop, chickpea (Cicer arietinum L.) to resist the phloem feeding Aphis craccivora

The phloem sap-sucking hemipteran insect, Aphis craccivora, commonly known as cowpea aphid, cause major yield loss of important food legume crop chickpea. Among different plant lectins Allium sativum leaf agglutinin (ASAL), a mannose binding lectin was found to be potent antifeedant for sap sucking insect A. craccivora. Present study describes expression of ASAL in chickpea through Agrobacterium-mediated transformation of "single cotyledon with half embryo" explant. ASAL was expressed under the control of CaMV35S promoter for constitutive expression and phloem specific rolC promoter for specifically targeting the toxin at feeding site, using pCAMBIA2301 vector containing plant selection marker nptII. Southern blot analysis demonstrated the integration and copy number of chimeric ASAL gene in chickpea and its inheritance in T(1) and T(2) progeny plants. Expression of ASAL in T(0) and T(1) plants was confirmed through northern and western blot analysis. The segregation pattern of ASAL transgene was observed in T(1) progenies, which followed the 3:1 Mendelian ratio. Enzyme linked immunosorbant assay (ELISA) determined the level of ASAL expression in different transgenic lines in the range of 0.08-0.38% of total soluble protein. The phloem tissue specific expression of ASAL gene driven by rolC promoter has been monitored by immunolocalization analysis of mature stem sections. Survival and fecundity of A. craccivora decreased to 11-26% and 22-42%, respectively when in planta bioassay conducted on T(1) plants compared to untransformed control plant which showed 85% survival. Thus, through unique approach of phloem specific expression of novel insecticidal lectin (ASAL), aphid resistance has been successfully achieved in chickpea.

Fossil wood of the Mimosoideae from the early Paleocene of Patagonia, Argentina

Brea, M., Zamuner, A.B., Matheos, S.D., Iglesias, A. & Zucol, A.F., December, 2008. Fossil wood of the Mimosoideae from the early Paleocene of Patagonia, Argentina. Alcheringa 32, 427–441. ISSN 0311-5518. An anatomically preserved mature stem from the Salamanca Formation (early Paleocene) at Palacio de Los Loros, central Patagonia, Argentina, is described and assigned to Paracacioxylon frenguellii sp. nov. The material was preserved by siliceous permineralization and shows features of the secondary xylem typical of subfamily Mimosoideae. This species represents the oldest record of the genus and of the Leguminosae along the western border of Gondwana, and is the world's second oldest record of Leguminosae wood. The species is characterized by ring-porous to semi-ring-porous vessels that are solitary, in multiples of 2–4 and clustered, simple perforation plates, alternate and vestured inter-vessel pitting, homocellular 1–6 seriate rays, tyloses, crystals and diffuse apotracheal, vasicentric paratracheal and confluent axial parenchyma. Paracacioxylon frenguellii has anatomical similarities to Acacia Miller. The presence of Paracacioxylon frenguellii associated with pulvinate leaves suggests that the legumes might have been a component of mesothermal forests developed along the western margin of the Golfo San Jorge Basin during the early Paleocene.

Rooting of the mature and juvenile stem cuttings of Irvingia wombolu (Vemeosen)

Rooting of the mature and juvenile stem cuttings of <i>Irvingia wombolu</i> (Vemeosen)

Annual species abundance in a tidal freshwater marsh: Germination and survival across an elevational gradient

Annual species contribute significantly to the standing biomass of tidal freshwater marshes, but they tend to be distributed unevenly along the elevation gradient, with higher surface elevations supporting greater densities of annual species. We explored the generation of this pattern by evaluating how different life history stages of annual species are related to elevation and to each other. In 2006, we counted seedlings emerging from the seed bank under optimal greenhouse conditions, as well as seedlings and mature stems of annual species in 38 plots located at different elevations in a tidal freshwater marsh near Alexandria, Virginia, USA. Annual species seedling and mature stem density increased with elevation of the marsh surface, but seed density did not change with elevation. Seeds of annual species germinated in saturated rather than flooded conditions (4.50 ±0.54 versus 1.66 ±0.26 species/ greenhouse container ±SE). Germination and survival from seedling to mature stem affected density of annual species across an elevational gradient, but the relative importance of either process differed by species. Amaranthus cannabinus was common and frequent in the seed bank (68% of all plots), and seed density increased with elevation, but seedlings and mature stems were infrequent at any elevation (21% and 5%, respectively), suggesting that germination is limiting its recruitment to standing vegetation. In contrast, Bidens laevis was uncommon in the seed bank (18% of all plots), but was frequently observed as seedlings and mature stems (55% and 34%, respectively). We therefore conclude that B. laevis recruitment was limited by its ephemeral seed bank. Impatiens capensis density did not appear to be limited by germination or survival to maturity as density of the species was high at all life history stages. Rather, its strong positive relationship with elevation at all life stages shows that I. capensis is limited by water inundation, particularly in spring when seeds require oxygen to germinate. Overall, we show that annual species increase in density at higher elevations in a tidal freshwater marsh, but that recruitment of each species may be limited by different intrinsic and extrinsic processes.

Modelling polymer interactions of the ‘molecular Velcro’ type in wood under mechanical stress

Trees withstand wind and snow loads by synthesising wood that varies greatly in mechanical properties: flexible in twigs and in the stem of the sapling, and rigid in the outer part of the mature stem. The ‘molecular Velcro’ model of Keckes et al. [2003. Cell-wall recovery after irreversible deformation of wood. Nat. Mater. 2, 810–814] permits the simulation of the tensile properties of water-saturated wood as found in living trees. A basic feature of this model is the presence of non-covalent interactions between hemicellulose chains attached to adjacent cellulose microfibrils, which are disrupted above a threshold level of interfibrillar shear. However, other evidence does not confirm the importance of hemicellulose–hemicellulose association in the cohesion of the interfibrillar matrix. Here, we present an alternative model in which hemicellulose chains bridging continuously from one microfibril aggregate (macrofibril) to the next provide most of the cohesion. We show that such hemicellulose bridges exist and that the stripping of the bridging chains from the cellulose surfaces under the tensile stress component normal to the macrofibrils can provide an alternative triggering mechanism for shear deformation between one macrofibril and the next. When one macrofibril then slides past another, a domain of the wood cell wall can extend but simultaneously it twists until the spacing between macrofibrils is reduced again and contact through hemicelluloses bridges is restored. Overall deformation therefore takes place through a series of local stick–slip events involving temporary twisting of small domains within the wood cell wall. Modelled load–deformation curves for this modified ‘molecular Velcro’ model are similar, although not identical, to those for the original model. However, the mechanism is different and more consistent with current views of the structure of wood cell walls, providing a framework within which the developmental control of rigidity in wood synthesised in different parts of a tree may be considered.

Peptone stimulates in vitro shoot and root regeneration of avocado ( Persea americana Mill.)

The effect of peptone on in vitro regeneration of avocado's shoots and roots from juvenile or mature stem sections was studied. In this study, both mature and juvenile explants were used to study the effect of peptone on shoot regeneration. Explants were necrotized on Murashige and Skoog (MS) medium without or with plant growth regulators. On the MS medium supplemented with both peptone and benzyladenine or dichlorophenoxyacetic acid, explants survived but significantly delayed in shoot regeneration. Addition of peptone alone into the medium with an optimal amount of 2.0% (w/v) induced shoot formation. Shoot formation also occurred in nodal sections from mature plant but the regeneration rate remained low. All juvenile explant-derived shoots formed root on the medium supplemented with peptone and naphthaleneacetic acid.

Plant selection, pre-harvest treatments and post-harvest management to prolong the vase-life of shoot cuttings of Codiaeum variegatum (croton)

Codiaeum variegatum is easily grown under hot and humid field conditions and has a high export potential. However, wilting and senescence during post-harvest operations often reduces its vase-life. To improve this drawback, an investigation was conducted to preserve the export quality of C. variegatum vars. Mariana, Batik and Aucubeafolia. Eight separate experiments were conducted to maintain high quality standards during storage life of three varieties of C. variegatum. Cold treatment with or without hot water dip, leaf morphology, leaf maturity with cutting type, pre-harvest hormonal regulation, de-topping, post-harvest hormonal regulation, commodity treatments and combined treatments of the above were the test criteria. The vase-life of three Codiaeum varieties were significantly different from each other. Similarly their response to individual treatments was also variable. Some of these individual treatments such as hormonal regulation were not compatible to be used as a combined treatment. Selection of mature or partially mature stem cuttings having a full length of purple and elongated leaves, de-topping 1-2 weeks before harvesting, spraying of 0.1 mM of Kinetine 4 days before harvesting, application of 100 ppm of Gibberellic acid (GA 3 ) after harvesting, pre-cooling at 17°C and 79% humidity for one day (after harvesting) and application of commodity treatment of 2mg/L of KMn0 4 with 2.5% of sugar and citric acid were the ideal individual treatments for extending the vase-life of Codiaeum varieties. Except post-harvest hormonal regulation, all the other plant selection criteria and post-harvest treatments that are mentioned above could be practiced in combination to increase the vaselife of all three varieties of Codiaeum without loosing the export standards significantly. The increased vase-life under combined treatment wasl8 days for var. Mariana, 20 days for var. Batick and 24 days for var. Aucubaefolia which was a 36.2% increase. Keywords: Cold treatment, commodity treatments, de-topping, hormonal regulation, shoot morphology. Normal 0 false false false MicrosoftInternetExplorer4 J. Natn.Sci.Foundation Sri Lanka 2007 35(3): 153-159 doi: 10.4038/jnsfsr.v35i3.2013 Normal 0 false false false MicrosoftInternetExplorer4 /

Phyllotaxy

Phyllotaxy, the arrangement of organs along the stem, has puzzled scientists for centuries. The shoot apical meristem plays a crucial role in the formation of this pattern, by initiating organ primordia on its flanks in a temporally and spatially controlled manner. Recent studies have shown that primordium position at the meristem is governed by local auxin gradients, but little is known about the subsequent events leading to the phyllotaxy along the mature stem. In a recent report we showed that deviation from the initial phyllotaxy set-up in the meristem is generated during stem growth of transgenic lines affected in miR164-mediated regulation of CUC2 and, to a smaller extent, of wild-type Arabidopsis. This underlines the requirement of maintaining the pattern initiated at the meristem during stem development. In this addendum, we discuss the importance of this mechanism in different mutants and at different stages of Arabidopsis development.

Plants expressing amiR164-resistantCUC2gene reveal the importance of post-meristematic maintenance of phyllotaxy inArabidopsis

In plants, the arrangement of organs along the stem (phyllotaxy) follows a predictable pattern. Recent studies have shown that primordium position at the meristem is governed by local auxin gradients, but little is known about the subsequent events leading to the phyllotaxy along the mature stem. We show here that plants expressing a miR164-resistant CUP-SHAPED COTYLEDON2 (CUC2) gene have an abnormal phyllotactic pattern in the fully grown stem, despite the pattern of organ initiation by the meristem being normal. This implies that abnormal phyllotaxy is generated during stem growth. These plants ectopically express CUC2 in the stem, suggesting that the proper timing of CUC2 expression is required to maintain the pattern initiated in the meristem. Furthermore, by carefully comparing the phyllotaxy in the meristem and along the mature inflorescence in wild types, we show that such deviation also occurs during wild-type development, although to a smaller extent. We therefore suggest that the phyllotactic pattern in a fully grown stem results not only from the organogenetic activity of the meristem, but also from the subsequent growth pattern during stem development.

Early Selection of Douglas-Fir across South Central Coastal Oregon, USA

Abstract Details are given of three first-generation progeny tests (CB1, CB2 and CB3) of coastal Douglas-fir (Pseudotsuga menziesii [MIRB.] FRANCO var. menziesii) planted in the Coos Bay region of south-central coastal Oregon in 1973. The three tests included 15 polymix families based on a 10-pollen mix, and 27 families openpollinated on the ortet. The present study gives heritabilities and additive genetic correlations for growth measured between two and 17 years after planting. Correlated responses are estimated for volume at 17 years from early selection for height and diameter. Between four and 17 years after planting the individual heritability (h2) of height of coastal Douglas-fir across the Coos Bay tests was quite stable between h2 = 0.18 and 0.22. The heritability of stem diameter age-forage was consistently much lower than for height. In the critical age range for early selection between five and 10 years the individual heritability of diameter ranged from h2 = 0.07 to 0.10. The additive genetic correlations involving volume-17 and height or diameter increased to high values of rA = 0.80 to 0.84 between eight to 10 years after planting. Before seven years the absolute values of juvenilemature correlations were much lower. The higher heritability of height made this trait the best criterion for early indirect selection to improve mature stem volume growth. Across these Coos Bay tests, early selection on stem height measured at 5-8 years after planting was estimated to produce almost 40% more gain per year in volume-17 compared with direct selection at 17 years on volume-17 itself. The recommendation for maximizing gain per year in mature volume of coastal Douglas-fir at Coos Bay is to select on height at 7-8 years when the mean height of trees in tests should be around 4.5 to 5.5 meters.

Clonal propagation of guava (Psidium guajava Linn.) by stem cutting from mature stockplants

The study describes the scope of clonal propagation of guava (Psidium guajava Linn.) by stem cutting collected from mature stockplants. Cuttings were treated with 0, 0.2%, 0.4% and 0.8% IBA solution and rooted in the non-mist propagator. Rooted cuttings were allowed to grow in the polybags filled with soil and cow-dung mixed in the ratio of 3: 1 (by volume) for three months to assess the steckling capacity and initial growth performance. The study reveals that the species is amenable for clonal propagation by mature stem cutting. The highest rooting percentage (60%) was observed in the cuttings treated with 0.4% IBA solution followed by 0.2% IBA and the lowest was in controlled cuttings. The maximum number of primary root (32.7) was developed in the cuttings treated with 0.8% IBA solution followed by 0.4% IBA and the lowest was in the cuttings without IBA treatment. The highest survival percentage (70.9) was observed in the cuttings rooted with 0.4% IBA treatment and the lowest (58.3) was in the cuttings without any treatment. However, there was no significant variation in height growth of cutlings due to IBA treatments in rooting.

Short-term disruption of a leafy spurge (Euphorbia esula) biocontrol program following herbicide application

Integrated pest management (IPM) for invasive plant species is being advocated by researchers and implemented by land managers, but few studies have evaluated the success of IPM programs in natural areas. We assessed the relative effects of components of an IPM program for leafy spurge (Euphorbia esula), an invasive plant, at Theodore Roosevelt National Park, North Dakota. Effects of herbicides on leafy spurge abundance and on dynamics of flea beetles (Aphthona spp.) used to control leafy spurge were evaluated over three field seasons following herbicide application. We monitored leafy spurge-infested plots with established flea beetle populations that had received picloram plus 2,4-D in September 1997 or 1998, imazapic in September 1998, versus those with no chemical treatment. Mature stem counts did not differ significantly between treated and untreated plots in 2001, suggesting that leafy spurge stands had recovered from herbicide treatment. Flea beetles were less abundant on plots with a history of herbicide treatment. Structural equation models indicated that in 2000 negative correlations between relative abundances of the two flea beetle species were greater on plots that had received herbicide treatments than on those that had not, but by 2001 no differences were apparent between treated and untreated plots. These results suggest that the most effective component of IPM for leafy spurge at this site is biological control. All herbicide effects we observed were short-lived, but the increased negative correlation between flea beetle relative abundances during 2000 implies that herbicide application may have temporarily disrupted an effective biological control program at this site.

Immunological detection and cellular localization of the phenylalanine ammonia-lyase of a hybrid aspen

The cellular-localization pattern of promoter activities of two phenylalanine ammonia-lyase (PAL; EC 4.3.1.5) genes, palg1 and palg2b, of a hybrid aspen, Populus kitakamiensis, was determined using the GUS reporter system. The strong activities of palg2b promoter were detected in lignified tissues such as xylem and phloem fiber cells of the aspen stem, suggesting the specific function of the PALg2b in lignin biosynthesis. Immunoelectron microscopy and sub-cellular fractionation of xylem cells showed that the PAL activity was detected in both the plastid and cytosol of the xylem ray- parenchyma cells and the cytosol in the developing xylem cells of the aspen mature stem. Our results of the biochemical characterization of xylem PAL protein suggested that the PAL localization was varied during cell differentiation of the aspen xylem to function in lignin biosynthesis.

A fasciclin-domain containing gene, ZeFLA11, is expressed exclusively in xylem elements that have reticulate wall thickenings in the stem vascular system of Zinnia elegans cv Envy

The vascular cylinder of the mature stem of Zinnia elegans cv Envy contains two anatomically distinct sets of vascular bundles, stem bundles and leaf-trace bundles. We isolated a full-length cDNA of ZeFLA11, a fasciclin-domain-containing gene, from a zinnia cDNA library derived from in vitro cultures of mesophyll cells induced to form tracheary elements. Using RNA in situ hybridization, we show that ZeFLA11 is expressed in the differentiating xylem vessels with reticulate type wall thickenings and adjacent parenchyma cells of zinnia stem bundles, but not in the leaf-trace bundles that deposit spiral thickenings. Our results suggest a function for this cell-surface GPI-anchored glycoprotein in secondary wall deposition during differentiation of metaxylem tissue with reticulate vessels.

Activation of the WUS Gene Induces Ectopic Initiation of Floral Meristems on Mature Stem Surface in Arabidopsis thaliana

Activation of the WUS Gene Induces Ectopic Initiation of Floral Meristems on Mature Stem Surface in Arabidopsis thaliana

Validation and Development of a Predictive Paradigm for Hemotoxicology Using a Multifunctional Bioluminescence Colony-Forming Proliferation Assay

The lympho-hematopoietic colony-forming assay has been redesigned into a rapid, nonsubjective and standardized proliferation assay that can measure the effects of compounds on multiple stem and progenitor cell populations from different species simultaneously using a sensitive, high-throughput bioluminescence readout. Eleven reference compounds from the Registry of Cytotoxicity (RC) and eight other compounds, including anticancer drugs, were studied over an 8- to 9-log dose range for their effects on seven cell populations from both human and mouse bone marrow simultaneously. The cell populations studied included a primitive (HPP-SP) and mature (CFC-GEMM) stem cell, three hematopoietic (BFU-E, GM-CFC, Mk-CFC) and two lymphopoietic (T-CFC, B-CFC) populations. The results reveal a five-point prediction paradigm for lympho-hematotoxicity. Depending on how and which populations are affected, the resulting effects in the periphery can be predicted. Validation against the RC Prediction Model produces a high degree of correlation between the in vitro IC(50) values and known in vivo LD(50) values, thereby allowing preclinical dosing to be predicted. If primary human hematopoietic target tissue is used, inhibitory concentration (IC(50)/IC(75)/IC(90)) values of anticancer and other drugs can be converted into predicted clinical doses which, when compared to published chemotherapeutic dosing regimen, are very similar. When performed during early drug screening, the prediction value of the assay should help reduce time and cost, but above all, provide increase efficacy and safety for the patient.

Constitutive and phloem specific expression of Allium sativum leaf agglutinin (ASAL) to engineer aphid ( Lipaphis erysimi) resistance in transgenic Indian mustard ( Brassica juncea)

Lipaphis erysimi, commonly known as mustard aphid is a seriously damaging pest of important oilseed crop, Brassica juncea. In previous study we reported using artificial diet bioassay that Allium sativum leaf lectin, ASAL shows insecticidal activity against sap sucking L. erysimi. A gut receptor protein having binding affinity to ASAL was purified from L. erysimi. The receptor protein was further identified as a SymL, playing role in aphid mediated virus transmission. To develop resistance against the above pest, ASAL had been expressed in mustard both in constitutive and phloem tissue specific manner. Stable integration and inheritance of ASAL gene has been shown through Southern hybridization. Expression of ASAL has been confirmed in T 0 and T 1 plants through northern and western blot analyses. The segregation pattern of ASAL transgene and hygromycin selection marker gene were observed in T 1 progenies which followed the 3:1 Mendelian ratio. The phloem tissue specific expression of ASAL gene driven by rice sucrose synthase promoter (RSs-1) has also been monitored by immunohistochemical analysis of mature stem and petiole sections. In-planta bioassays on T 0 plants and their progenies exhibited the efficacy of expressed ASAL to reduce the survival and fecundity of L. erysimi. This is the first report showing sustainable resistance in transgenic B. juncea with ASAL gene against the target pest, mustard aphid.

Activation of the WUS gene induces ectopic initiation of floral meristems on mature stem surface in Arabidopsis thaliana

A gain-of-function Arabidopsis mutant was identified via activation tagging genetic screening. The mutant exhibited clustered ectopic floral buds on the surface of inflorescence stems. The mutant was designated as sef for stem ectopic flowers. Our detailed studies indicate that the ectopic flower meristems are initiated from the differentiated cortex cells. Inverse PCR and sequence analysis indicated that the enhancer-containing T-DNA from the activation tagging construct, SKI015, was inserted upstream of the previously cloned WUS gene encoding a homeodomain protein. Studies from RT-PCR, RNA in situ hybridization and transgenic plant analysis further confirmed that the phenotypes of sef are caused by the overexpression of WUS. Our results suggest that overexpression of WUS could trigger the cell pluripotence and reestablish a new meristem in cortex. The type of new meristems caused by WUS overexpression was dependent upon the developmental and physiological stages of a plant. With the help of some undefined factors in the reproductive organs the new meristems differentiated into floral buds. In a vegetative growth plant, however, only the new vegetative buds can be initiated upon the overexpression of WUS. These studies provide new insights of WUS on flower development.