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1.
Oecologia ; 192(1): 55-66, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31932921

RESUMO

Grassland ecosystems are comprised of plants that occupy a wide array of phenological niches and vary considerably in their ability to resist the stress of seasonal soil-water deficits. Yet, the link between plant drought resistance and phenology remains unclear in perennial grassland ecosystems. To evaluate the role of soil water availability and plant drought tolerance in driving phenology, we measured leaf hydraulic conductance (Ksat), resistance to hydraulic failure (P50), leaf gas exchange, plant and soil water stable isotope ratios (δ18O), and several phenology metrics on ten perennial herbaceous species in mixed-grass prairie. The interaction between P50 and δ18O of xylem water explained 67% of differences in phenology, with lower P50 values associated with later season activity, but only among shallow-rooted species. In addition, stomatal control and high water-use efficiency also contributed to the late flowering and late senescence strategies of plants that had low P50 values and relied upon shallow soil water. Alternatively, plants with deeper roots did not possess drought-tolerant leaves, but had high hydraulic efficiency, contributing to their ability to efficiently move water longer distances while maintaining leaf water potential at relatively high values. The suites of traits that characterize these contrasting strategies provide a mechanistic link between phenology and plant-water relations; thus, these traits could help predict grassland community responses to changes in water availability, both temporally and vertically within the soil profile.


Assuntos
Secas , Pradaria , Ecossistema , Folhas de Planta , Água , Xilema
2.
Sci Total Environ ; 698: 133999, 2020 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-31499345

RESUMO

When water and solutes enter the plant root through the epidermis, organic contaminants in solution either cross the root membranes and transport through the vascular pathways to the aerial tissues or accumulate in the plant roots. The accumulation of contaminants in plant roots and edible tissues is measured by root concentration factor (RCF) and fruit concentration factor (FCF). In this paper, 1) a neural network (NN) was applied to model RCF based on physicochemical properties of organic compounds, 2) correlation and significance of physicochemical properties were assessed using statistical analysis, 3) fuzzy logic was used to examine the simultaneous impacts of significant compound properties on RCF and FCF, 4) a clustering algorithm (k-means) was used to identify unique groups and discover hidden relationships within contaminants in various parts of the plants. The physicochemical cutoffs achieved by fuzzy logic for the RCF and the FCF were compared versus the cutoffs for compounds that crossed the plant root membranes and found their way into transpiration stream (measured by transpiration stream concentration factor, TSCF). The NN predicted the RCF with improved accuracy compared to mechanistic models. The analysis indicated that log Kow, molecular weight, and rotatable bonds are the most important properties for predicting the RCF. These significant compound properties are positively correlated with RCF while they are negatively correlated with TSCF. Comparing the relationships between compound properties in various plant tissues showed that compounds detected in the edible parts have physicochemical cutoffs that are more like the compounds crossing the plant root membranes (into xylem tissues) than the compounds accumulating in the plant roots, with clear relationships to food security. The cluster analysis placed the contaminants into three meaningful groups that were in agreement with the results of fuzzy logic.


Assuntos
Abastecimento de Alimentos , Aprendizado de Máquina , Plantas/metabolismo , Poluentes do Solo/metabolismo , Análise por Conglomerados , Lógica Fuzzy , Xilema
3.
Sci Total Environ ; 699: 134285, 2020 Jan 10.
Artigo em Inglês | MEDLINE | ID: mdl-31520941

RESUMO

In the Mediterranean basin, diffuse-porous, semi-ring-porous and ring-porous tree species coexist in the same regions. Climate change might differently affect these types, but a mechanistic understanding of drought effects on their xylem structure is lacking. We investigated tree-ring width and xylem functional traits in ring-porous Quercus boissieri, semi-ring-porous Q. ithaburensis and diffuse-porous Q. calliprinos, at xeric (Galilee) and mesic (Golan) sites in the South-Eastern Mediterranean basin. We quantitatively assessed how dry and wet years affect growth and xylem traits in different porosity type oaks, and evaluated whether porosity type is preserved or altered during these years. We measured, counted or computed tree-ring width, vessel number, maximum lumen area, frequency, tree-ring and xylem theoretical hydraulic conductivity along 40-year ring series of 50 trees in total. We also quantified ring porosity in each year using two indices, the Gini coefficient and the porosity ratio of vessel area, and described vessel area intra-ring variations by distribution profiles. We then compared these parameters in the five driest and five wettest years of the 40-year period. Radial growth and functional trait variations were more similar between species in the same site (strong drought effects in Q. ithaburensis and Q. calliprinos in Galilee, moderate effects in Q. boissieri and Q. calliprinos in Golan) than between sites for the same species (Q. calliprinos was more affected in Galilee than in Golan). Ring porosity indices and distribution profiles showed that diffuse-porous xylem structure of Q. calliprinos was maintained even under dry conditions at both sites. However, Q. boissieri xylem shifted from ring-porous in wet and normal years to semi-ring-porous in dry years, i.e. the porous ring cannot be completely built under water constraint. This suggests that ring porous strategy, typical of temperate regions with strong seasonality, might not be realized under future drier conditions in the Mediterranean basin.


Assuntos
Monitoramento Ambiental , Quercus/crescimento & desenvolvimento , Chuva , Mudança Climática , Secas , Porosidade , Árvores/crescimento & desenvolvimento , Xilema
4.
Sci Total Environ ; 699: 134332, 2020 Jan 10.
Artigo em Inglês | MEDLINE | ID: mdl-31629315

RESUMO

Karst environments are unusual because their dry, stony and shallow soils seem to be unfavorable to vegetation, and yet they are often covered with forests. How can trees survive in these environments? Where do they find the water that allows them to survive? This study uses midday and predawn water potentials and xylem water isotopes of branches to assess tree water status and the origin of transpired water. Monitoring was conducted during the summers of 2014 and 2015 in two dissimilar plots of Mediterranean forest located in karst environments. The results show that the three monitored tree species (Abies alba Mill, Fagus sylvatica L, and Quercus ilex L.) use deep water resources present in the karst vadose zone (unsaturated zone) more intensively during drier years. Quercus ilex, a species well- adapted to water stress, which grows at the drier site, uses the deep water resource very early in the summer season. Conversely, the two other species exploit the deep water resource only during severe drought. These results open up new perspectives to a better understanding of ecohydrological equilibrium and to improved water balance modeling in karst forest settings.


Assuntos
Fagus/fisiologia , Quercus/fisiologia , Secas , Florestas , Folhas de Planta , Estações do Ano , Solo , Água , Xilema
5.
Ying Yong Sheng Tai Xue Bao ; 30(11): 3671-3680, 2019 Nov.
Artigo em Chinês | MEDLINE | ID: mdl-31833679

RESUMO

To explore the nutrient source and supply-demand relationship of the female cone deve-lopment and new shoot growth of Pinus koraiensis, reproductive mother branches were experimentally girdled, defoliated, and under the combination of both treatments. The effects of different treatments on the female cones development, branch growth and the content of carbohydrate (NSC), nitrogen (N) and phosphorus (P) in different tissues and organs were measured. The results showed that girdling significantly affected female cone development, new shoot growth, and the contents of NSC, N and P in different tissues and organs, while defoliation treatment had limited effect. The NSC content in the mother branch xylem and phloem after girdling were significantly lower than that of the control (CK, ungirdling+0% defoliation), and decreased significantly with the increases of the degree of defoliation. The NSC content in mother branch xylem and phloem of girdling+100% defoliation was 59.0% and 64.8% lower than that of CK, respectively. The deficiency of NSC resulted in the death of mother branches and new shoots and the abortion of female cone. Under girdling treatment, the contents of N and P in xylem and phloem of mother branches of 0%, 50% and 100% defoliation treatment were significantly higher than that of CK. The contents of N and P in xylem of mother branches were 17.3%, 18.2% and 24.3% and 17.9%, 7.1% and 3.6% higher than those of CK, respectively. The contents of N and P in phloem of mother branches was 39.3%, 35.2% and 48.9% and 31.0%, 28.2% and 14.8% higher than those of CK, respectively. The female cone development and new shoot growth of P. koraiensis consumed a large amount of NSC, N and P. The carbohydrates and mineral nutrients manufactured or stored in the mother branches could not meet the needs of female cone development and new shoot growth, and thus they need to be imported from other tissues.


Assuntos
Pinus , Feminino , Nitrogênio , Nutrientes , Folhas de Planta , Árvores , Xilema
6.
Mol Plant Microbe Interact ; 32(12): 1581-1597, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31657672

RESUMO

Vascular wilt bacteria such as Pantoea stewartii, the causal agent of Stewart's bacterial wilt of maize (SW), are destructive pathogens that are difficult to control. These bacteria colonize the xylem, where they form biofilms that block sap flow leading to characteristic wilting symptoms. Heritable forms of SW resistance exist and are used in maize breeding programs but the underlying genes and mechanisms are mostly unknown. Here, we show that seedlings of maize inbred lines with pan1 mutations are highly resistant to SW. However, current evidence suggests that other genes introgressed along with pan1 are responsible for resistance. Genomic analyses of pan1 lines were used to identify candidate resistance genes. In-depth comparison of P. stewartii interaction with susceptible and resistant maize lines revealed an enhanced vascular defense response in pan1 lines characterized by accumulation of electron-dense materials in xylem conduits visible by electron microscopy. We propose that this vascular defense response restricts P. stewartii spread through the vasculature, reducing both systemic bacterial colonization of the xylem network and consequent wilting. Though apparently unrelated to the resistance phenotype of pan1 lines, we also demonstrate that the effector WtsE is essential for P. stewartii xylem dissemination, show evidence for a nutritional immunity response to P. stewartii that alters xylem sap composition, and present the first analysis of maize transcriptional responses to P. stewartii infection.


Assuntos
Resistência à Doença , Pantoea , Zea mays , Resistência à Doença/genética , Genoma de Planta/genética , Pantoea/fisiologia , Plântula/microbiologia , Xilema/microbiologia , Zea mays/genética , Zea mays/microbiologia
7.
Plant Sci ; 289: 110247, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31623795

RESUMO

Conifer trees, including Norway spruce, are threatened by fungi of the Heterobasidion annosum species complex, which severely affect timber quality and cause economic losses to forest owners. The timely detection of infected trees is complicated, as the pathogen resides within the heartwood and sapwood of infected trees. The presence of the disease and the extent of the wood decay often becomes evident only after tree felling. Fourier-transform infrared (FT-IR) spectroscopy is a potential method for non-destructive sample analysis that may be useful for identifying infected trees in this pathosystem. We performed FT-IR analysis of 18 phloem, 18 xylem, and 18 needle samples from asymptomatic and symptomatic Norway spruce trees. FT-IR spectra from 1066 - 912 cm-1 could be used to distinguish phloem, xylem, and needle tissue extracts. FT-IR spectra collected from xylem and needle extracts could also be used to discriminate between asymptomatic and symptomatic trees using spectral bands from 1657 - 994 cm-1 and 1104 - 994 cm-1, respectively. A partial least squares regression model predicted the concentration of condensed tannins, a defense-related compound, in phloem of asymptomatic and symptomatic trees. This work is the first to show that FT-IR spectroscopy can be used for the identification of Norway spruce trees naturally infected with Heterobasidion spp.


Assuntos
Basidiomycota/isolamento & purificação , Picea/microbiologia , Doenças das Plantas/microbiologia , Espectroscopia de Infravermelho com Transformada de Fourier/métodos , Floema/microbiologia , Folhas de Planta/microbiologia , Xilema/microbiologia
8.
Plant Sci ; 288: 110224, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31521213

RESUMO

Patatin-liked phospholipase A (pPLAs) are major lipid acyl hydrolases that participate in various biological functions in plant growth and development. Previously, a ginseng-derived pPLAIII homolog was reported to reduce lignin content in Arabidopsis. This led us to evaluate its possible usefulness as a biomass source in wood plant. Herein, we report that there are six members in the pPLAIII gene family in poplar. Overexpression of pPLAIIIß derived from ginseng resulted in a reduced plant height with radially expanded stem growth in hybrid poplars. Compared with the wild type (WT), the chlorophyll content was increased in the overexpression poplar lines, whereas the leaf size was smaller. The secondary cell wall structure in overexpression lines was also altered, exhibiting reduced lignification in the xylem. Two transcription factors, MYB92 and MYB152, which control lignin biosynthesis, were downregulated in the overexpression lines. The middle xylem of the overexpression line showed heavy thickening, making it thicker than the other xylem parts and the WT xylem, which rather could have been contributed by the presence of more cellulose in the selected surface area. Taken together, the results suggest that PgpPLAIIIß plays a role not only in cell elongation patterns, but also in determining the secondary cell wall composition.


Assuntos
Lignina/metabolismo , Panax/genética , Fosfolipases A/genética , Proteínas de Plantas/genética , Populus/genética , Madeira/crescimento & desenvolvimento , Sequência de Aminoácidos , Regulação da Expressão Gênica de Plantas , Lignina/genética , Panax/química , Fosfolipases A/química , Fosfolipases A/metabolismo , Filogenia , Proteínas de Plantas/química , Proteínas de Plantas/metabolismo , Plantas Geneticamente Modificadas/genética , Plantas Geneticamente Modificadas/metabolismo , Populus/crescimento & desenvolvimento , Alinhamento de Sequência , Madeira/genética , Xilema/genética , Xilema/crescimento & desenvolvimento
9.
Genes (Basel) ; 10(9)2019 09 07.
Artigo em Inglês | MEDLINE | ID: mdl-31500311

RESUMO

Wood, the most abundant biomass on Earth, is composed of secondary xylem differentiated from vascular cambium. However, the underlying molecular mechanisms of wood formation remain largely unclear. To gain insight into wood formation, we performed a series of wood-forming tissue-specific transcriptome analyses from a hybrid poplar (Populus alba × P. glandulosa, clone BH) using RNA-seq. Together with shoot apex and leaf tissue, cambium and xylem tissues were isolated from vertical stem segments representing a gradient of secondary growth developmental stages (i.e., immature, intermediate, and mature stem). In a comparative transcriptome analysis of the 'developing xylem' and 'leaf' tissue, we could identify critical players catalyzing each biosynthetic step of secondary wall components (e.g., cellulose, xylan, and lignin). Several candidate genes involved in the initiation of vascular cambium formation were found via a co-expression network analysis using abundantly expressed genes in the 'intermediate stem-derived cambium' tissue. We found that transgenic Arabidopsis plants overexpressing the PtrHAM4-1, a GRAS family transcription factor, resulted in a significant increase of vascular cambium development. This phenotype was successfully reproduced in the transgenic poplars overexpressing the PtrHAM4-1. Taken together, our results may serve as a springboard for further research to unravel the molecular mechanism of wood formation, one of the most important biological processes on this planet.


Assuntos
Câmbio/genética , Parede Celular/genética , Populus/genética , Transcriptoma , Câmbio/crescimento & desenvolvimento , Parede Celular/metabolismo , Lignina/biossíntese , Lignina/genética , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Caules de Planta/genética , Caules de Planta/crescimento & desenvolvimento , Populus/crescimento & desenvolvimento , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Xilanos/biossíntese , Xilanos/genética , Xilema/genética , Xilema/crescimento & desenvolvimento
10.
Int J Mol Sci ; 20(16)2019 Aug 09.
Artigo em Inglês | MEDLINE | ID: mdl-31395813

RESUMO

Vascular tissues essentially regulate water, nutrient, photo-assimilate, and phytohormone logistics throughout the plant body. Boron (B) is crucial for the development of the vascular tissue in many dicotyledonous plant taxa and B deficiency particularly affects the integrity of phloem and xylem vessels, and, therefore, functionality of long-distance transport. We hypothesize that changes in the plants' B nutritional status evoke differential responses of the vasculature and the mesophyll. However, direct analyses of the vasculature in response to B deficiency are lacking, due to the experimental inaccessibility of this tissue. Here, we generated biochemical and physiological understanding of B deficiency response reactions in common plantain (Plantago major L.), from which pure and intact vascular bundles can be extracted. Low soil B concentrations affected quantitative distribution patterns of various phytohormones, sugars and macro-, and micronutrients in a tissue-specific manner. Vascular sucrose levels dropped, and sucrose loading into the phloem was reduced under low B supply. Phytohormones responded selectively to B deprivation. While concentrations of abscisic acid and salicylic acid decreased at low B supply, cytokinins and brassinosteroids increased in the vasculature and the mesophyll, respectively. Our results highlight the biological necessity to analyze nutrient deficiency responses in a tissue- rather organ-specific manner.


Assuntos
Boro/metabolismo , Reguladores de Crescimento de Planta/metabolismo , Folhas de Planta/metabolismo , Plantago/metabolismo , Sacarose/metabolismo , Brassinosteroides/metabolismo , Citocininas/metabolismo , Floema/metabolismo , Xilema/metabolismo
11.
Plant Physiol Biochem ; 142: 482-489, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31437742

RESUMO

Knowledge of the characteristics of chemical components transported in the xylem sap of trunks remains deficient and limited because no appropriate method exists to extract the xylem sap from this part of the tree. We thus explored the differences in xylem sap components extracted by means of centrifugation and water displacement methods and depicted the level and behavior of chemical components in the xylem sap of trunks and branches of different aged trees from a pine forest in northern China. There were no significant differences between the two methods with respect to nitrogen (N) compounds and inorganic ions in the xylem sap. Potassium concentrations obtained by the methods were similar and consistent with the values obtained from earlier publications on woody species. This suggests that contamination of the xylem sap by the centrifugation method is negligible, and this method would be a reliable and robust tool for collection of the trunk xylem sap. Dissolved organic N was the dominant component of total N followed by nitrate (NO3-) and ammonium (NH4+). Potassium and chloride were the predominant cation and anion, respectively, of the xylem sap. The NO3- concentration basically did not change, whereas the NH4+ concentration was larger transported from the trunk to branches for the large tree class during foliage senescence. More inorganic N components (mainly NO3-) were found in young trees than in old trees. Our study contributes to improve the diagnostic assessments of tree physiological processes and growth in mature forest trees under environmental changes.


Assuntos
Centrifugação/métodos , Pinus/química , Caules de Planta/química , Xilema/química , Compostos de Amônio/análise , Cloretos/análise , Nitratos/análise , Nitrogênio/análise , Potássio/análise
12.
J Plant Physiol ; 240: 153010, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31352021

RESUMO

Plant-growth-promoting rhizobacteria (PGPR) improve plant growth by altering the root architecture, although the mechanisms underlying this alteration have yet to be unravelled. Through microarray analysis of PGPR-treated rice roots, a large number of differentially regulated genes were identified. Ectopic expression of one of these genes, OsASR6 (ABA STRESS RIPENING6), had a remarkable effect on plant growth in Arabidopsis. Transgenic lines over-expressing OsASR6 had larger leaves, taller inflorescence bolts and greater numbers of siliques and seeds. The most prominent effect was observed in root growth, with the root biomass increasing four-fold compared with the shoot biomass increase of 1.7-fold. Transgenic OsASR6 over-expressing plants showed higher conductance, transpiration and photosynthesis rates, leading to an ˜30% higher seed yield compared with the control. Interestingly, OsASR6 expression led to alterations in the xylem structure, an increase in the xylem vessel size and altered lignification, which correlated with higher conductance. OsASR6 is activated by auxin and, in turn, increases auxin responses and root auxin sensitivity, as observed by the increased expression of auxin-responsive genes, such as SAUR32 and PINOID, and the key auxin transcription factor, ARF5. Collectively, these phenomena led to an increased root density. The effects of OsASR6 expression largely mimic the beneficial effects of PGPRs in rice, indicating that OsASR6 activation may be a key factor governing PGPR-mediated changes in rice. OsASR6 is a potential candidate for the manipulation of rice for improved productivity.


Assuntos
Arabidopsis/crescimento & desenvolvimento , Ácidos Indolacéticos/metabolismo , Oryza/genética , Reguladores de Crescimento de Planta/metabolismo , Proteínas de Plantas/genética , Xilema/anatomia & histologia , Sequência de Aminoácidos , Arabidopsis/genética , Arabidopsis/metabolismo , Oryza/química , Oryza/metabolismo , Proteínas de Plantas/química , Proteínas de Plantas/metabolismo , Raízes de Plantas/metabolismo , Plantas Geneticamente Modificadas/genética , Plantas Geneticamente Modificadas/crescimento & desenvolvimento , Plantas Geneticamente Modificadas/metabolismo , Alinhamento de Sequência
13.
Int J Mol Sci ; 20(14)2019 Jul 13.
Artigo em Inglês | MEDLINE | ID: mdl-31337083

RESUMO

Histone acetylation and deacetylation play essential roles in eukaryotic gene regulation. HD2 (HD-tuins) proteins were previously identified as plant-specific histone deacetylases. In this study, we investigated the function of the HDT1 gene in the formation of stem vascular tissue in Arabidopsis thaliana. The height and thickness of the inflorescence stems in the hdt1 mutant was lower than that of wild-type plants. Paraffin sections showed that the cell number increased compared to the wild type, while transmission electron microscopy showed that the size of individual tracheary elements and fiber cells significantly decreased in the hdt1 mutant. In addition, the cell wall thickness of tracheary elements and fiber cells increased. We also found that the lignin content in the stem of the hdt1 mutants increased compared to that of the wild type. Transcriptomic data revealed that the expression levels of many biosynthetic genes related to secondary wall components, including cellulose, lignin biosynthesis, and hormone-related genes, were altered, which may lead to the altered phenotype in vascular tissue of the hdt1 mutant. These results suggested that HDT1 is involved in development of the vascular tissue of the stem by affecting cell proliferation and differentiation.


Assuntos
Proteínas de Arabidopsis/genética , Arabidopsis/genética , Histona Desacetilases/genética , Desenvolvimento Vegetal/genética , Caules de Planta/genética , Feixe Vascular de Plantas/genética , Arabidopsis/metabolismo , Proteínas de Arabidopsis/metabolismo , Parede Celular/genética , Parede Celular/metabolismo , Perfilação da Expressão Gênica , Regulação da Expressão Gênica de Plantas , Histona Desacetilases/metabolismo , Lignina/metabolismo , Mutação , Fenótipo , Caules de Planta/metabolismo , Feixe Vascular de Plantas/metabolismo , Xilema/citologia , Xilema/genética , Xilema/metabolismo
14.
Glob Chang Biol ; 25(11): 3793-3802, 2019 11.
Artigo em Inglês | MEDLINE | ID: mdl-31323157

RESUMO

Drought-induced tree mortality is projected to increase due to climate change, which will have manifold ecological and societal impacts including the potential to weaken or reverse the terrestrial carbon sink. Predictions of tree mortality remain limited, in large part because within-species variations in ecophysiology due to plasticity or adaptation and ecosystem adjustments could buffer mortality in dry locations. Here, we conduct a meta-analysis of 50 studies spanning >100 woody plant species globally to quantify how populations within species vary in vulnerability to drought mortality and whether functional traits or climate mediate mortality patterns. We find that mortality predominantly occurs in drier populations and this pattern is more pronounced in species with xylem that can tolerate highly negative water potentials, typically considered to be an adaptive trait for dry regions, and species that experience higher variability in water stress. Our results indicate that climate stress has exceeded physiological and ecosystem-level tolerance or compensating mechanisms by triggering extensive mortality at dry range edges and provides a foundation for future mortality projections in empirical distribution and mechanistic vegetation models.


Assuntos
Secas , Árvores , Mudança Climática , Ecossistema , Xilema
15.
Plant Physiol Biochem ; 142: 217-223, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31310944

RESUMO

Cell wall architecture of tension wood fibres represents a suitable biological system to study the mechanism of growth and maintenance of posture of trees growing under various physical and physiological growth constraints. In the present study, we investigated the spatial distributions of ß-(1-4)-D-galactan, xyloglucan and xylans (both less and highly substituted) in the opposite and tension wood fibres of bent Leucaena leucocephala by immunolabelling with monoclonal antibodies LM5, CCRCM1, LM10 and LM11 specific to these carbohydrate epitopes. The presence of non-lignified, tertiary wall layer is the typical tension wood characteristic associated with the reaction xylem fibres in Leucaena. LM5 labelling of opposite fibres showed weak labelling in the cell walls indicating less concentration of ß-(1-4)-D-galactans while tension wood showed strong labelling in the tertiary wall layer suggesting the gelatinous layer (G-layer) has a strong cross linking with ß-(1-4)-D-galactans. Xyloglucan distribution was more in the compound middle lamellae and the primary wall-S1 layer boundary of tension wood fibres as compared to that of opposite wood. A weak labelling was also evident near the boundary between the G-layer and the secondary wall of tension wood fibres. The secondary wall of opposite and tension wood fibres showed a strong distribution of both ls ACG Xs (LM10) and hs ACG Xs (LM11) while a weak labelling was noticed in the compound middle lamella. Tension wood fibres also showed strong xylan labelling mainly confined to the lignified secondary walls while the G-layer showed weak xylan labelling. In conclusion, our results suggest that ß-(1-4)-D-galactans and xyloglucans could be implicated in the tensile stress generation within the G-layer of tension wood fibres of Leucaena leucocephala.


Assuntos
Fabaceae/metabolismo , Galactanos/metabolismo , Glucanos/metabolismo , Xilanos/metabolismo , Xilema/metabolismo , Microscopia Imunoeletrônica , Resistência à Tração , Madeira/metabolismo
16.
Int J Biol Macromol ; 137: 703-711, 2019 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-31279878

RESUMO

The vacuolar processing enzyme (VPE) plays an important role in PCD and was originally identified as the proteinase responsible for the maturation and activation of vacuolar proteins in plants. We found that γVPE is involved in PCD of xylem fiber cells through the activation of CEP1 proproteases into mature protease in Arabidopsis. The γVPE protein was expressed specifically in cambium cells cambium, the primary phloem and the primary xylem during stem development. The recombinant γVPE appearing as a proenzyme at pH 7.0, and then transforming into a 40-kD mature enzyme at pH 5.5 in vitro by self-cleaving. The mature γVPE protein activated CEP1 maturation in vitro, whereas this activity was inhibited in the γvpe mutant. Transmission electron microscopy showed delayed PCD in fiber cells and thickening of secondary fiber cell walls in the γvpe mutant. Transcriptome analysis showed that the expression of 2001 genes was significantly altered expression in the γvpe mutants, and most of them are important for secondary cell wall formation and PCD. Our results demonstrate that γVPE is a crucial processing enzyme for xylem fiber cells PCD during stem development.


Assuntos
Apoptose , Arabidopsis/citologia , Arabidopsis/enzimologia , Cisteína Endopeptidases/metabolismo , Xilema/citologia , Arabidopsis/genética , Arabidopsis/metabolismo , Cisteína Endopeptidases/genética , Perfilação da Expressão Gênica , Regulação da Expressão Gênica de Plantas , Concentração de Íons de Hidrogênio , Mutação , Biossíntese de Proteínas
17.
Molecules ; 24(13)2019 Jul 02.
Artigo em Inglês | MEDLINE | ID: mdl-31269661

RESUMO

Scutellaria baicalensis Georgi (SBG) is not just as a traditional herbal medicine but also a popular functional food in China and other Asian countries. A sensitive simple strategy was developed for the first time to analyze SBG from eight different geographical sources using high-performance liquid chromatography (HPLC) coupled with multivariate chemometric methods. Two unsupervised pattern recognition models, hierarchical cluster analysis (HCA) and principal components analysis (PCA), and a supervised pattern recognition model, partial least squares discriminant analysis (PLS-DA), were used to analyze the chemical compositions and physical traits of SBG. The important chemical markers baicalin, baicalein, and wogonoside were analyzed quantitatively and with PLS-DA. These methods distinguished rotten xylem (kuqin) and strip types (tiaoqin) of SBG and found that the thickness of the slice had a significant impact on the classification of SBG. Two classes of strip types were identified: one as the uncut pharmaceutical, which was sectioned with a thickness >3 mm; the other as a thin-sectioned strip type, with a thickness of <2 mm. This fingerprinting technique coupled to a chemometric analysis was used for the simultaneous quantitation of three components (chemical markers) of SBG, and greatly simplified the complicated identification of the multiple components of this plant relative to traditional methods. The strategy can clearly distinguish between kuqin and tiaoqin of SBG, and suggests that the thickness of the slice can be used as the basis for evaluation of SBG. These data provide a theoretical basis and scientific evidence for the development and utilization of SBG.


Assuntos
Análise de Componente Principal , Scutellaria baicalensis/química , Xilema/química , Análise por Conglomerados , Análise Discriminante , Flavanonas/análise , Flavonoides/análise , Glucosídeos/análise , Análise dos Mínimos Quadrados
18.
J Plant Res ; 132(5): 655-665, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31289959

RESUMO

XSP25, previously shown to be the most abundant hydrophilic protein in xylem sap of Populus nigra in winter, belongs to a secretory protein family in which the arrangement of basic and acidic amino acids is conserved between dicotyledonous and monocotyledonous species. Its gene expression was observed at the same level in roots and shoots under long-day conditions, but highly induced under short-day conditions and at low temperatures in roots, especially in endodermis and xylem parenchyma in the root hair region of Populus trichocarpa, and its protein level was high in dormant buds, but not in roots or branches. Addition of recombinant PtXSP25 protein mitigated the denaturation of lactate dehydrogenase by drying, but showed only a slight effect on that caused by freeze-thaw cycling. Recombinant PtXSP25 protein also showed ice recrystallization inhibition activity to reduce the size of ice crystals, but had no antifreezing activity. We suggest that PtXSP25 protein produced in shoots and/or in roots under short-day conditions and at non-freezing low temperatures followed by translocation via xylem sap to shoot apoplast may protect the integrity of the plasma membrane and cell wall functions from freezing and drying damage in winter environmental conditions.


Assuntos
Proteínas de Plantas/genética , Populus/fisiologia , Estresse Fisiológico/genética , Dessecação , Congelamento , Proteínas de Plantas/metabolismo , Brotos de Planta/fisiologia , Populus/genética , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Estações do Ano , Xilema/fisiologia
19.
Planta ; 250(5): 1423-1432, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31290031

RESUMO

MAIN CONCLUSION: Nitrogen and CO2 supply interactively regulate whole plant nitrogen partitioning and root anatomical and morphological development in tomato plants. Nitrogen (N) and carbon (C) are the key elements in plant growth and constitute the majority of plant dry matter. Growing at CO2 enrichment has the potential to stimulate the growth of C3 plants, however, growth is often limited by N availability. Thus, the interactive effects of CO2 under different N fertilization rates can affect growth, acclimation to elevated CO2, and yield. However, the majority of research in this field has focused on shoot traits, while neglecting plants' hidden half-the roots. We hypothesize that elevated CO2 and low N effects on transpiration will interactively affect root vascular development and plant N partitioning. Here we studied the effects of elevated CO2 and N concentrations on greenhouse-grown tomato plants, a C3 crop. Our main objective was to determine in what manner the N fertilization rate and elevated CO2 affected root development and nitrogen partitioning among plant organs. Our results indicate that N interacting with the CO2 level affects the development of the root system in terms of the length, anatomy, and partitioning of the N concentration between the roots and shoot. Both CO2 and N concentrations were found to affect xylem size in an opposite manner, elevated CO2 found to repressed, whereas ample N stimulated xylem development. We found that under limiting N and eCO2, the N% increase in the root, while it decreased in the shoot. Under eCO2, the root system size increased with a coordinated decrease in root xylem area. We suggest that tomato root response to elevated CO2 depends on N fertilization rates, and that a decrease in xylem size is a possible underlying response that limits nitrogen allocation from the root into the shoot. Additionally, the greater abundance of root amino acids suggests increased root nitrogen metabolism at eCO2 conditions with ample N.


Assuntos
Aclimatação , Dióxido de Carbono/metabolismo , Lycopersicon esculentum/fisiologia , Nitrogênio/metabolismo , Transporte Biológico , Carbono/metabolismo , Lycopersicon esculentum/anatomia & histologia , Lycopersicon esculentum/crescimento & desenvolvimento , Fotossíntese , Raízes de Plantas/anatomia & histologia , Raízes de Plantas/crescimento & desenvolvimento , Raízes de Plantas/fisiologia , Transpiração Vegetal , Xilema/anatomia & histologia , Xilema/crescimento & desenvolvimento , Xilema/fisiologia
20.
Int J Mol Sci ; 20(13)2019 Jul 06.
Artigo em Inglês | MEDLINE | ID: mdl-31284596

RESUMO

Tall fescue (Festuca arundinacea), an accumulator that is able to accumulate and excrete cadmium (Cd), has attracted much attention for its possible use in phytoremediation of heavy metal contaminated soils. In the present study, the interaction between Cd and Zn, and their uptake, translocation and accumulation under external Cd and Zn treatment in tall fescue were investigated. The concentrations of K, Ca, Mg in xylem sap under Cd and Zn treatment were measured to determine the level of mineral nutrients and their relationship with Cd alleviation. The result showed that Cd and Zn antagonized each other in the roots, while Cd antagonized Zn and Zn synergized Cd in the shoots of tall fescue. Compared with Cd only treatment, the concentrations of Ca, Mg and K in xylem sap increased after the addition of Zn, and they increased the most in the guttation. This result indicated that the addition of Zn facilitates the level of mineral elements to alleviate Cd toxicity, which might be used to improve the phytoremediation efficiency of Cd contaminated soils by tall fescue.


Assuntos
Festuca/metabolismo , Minerais/metabolismo , Fenômenos Fisiológicos da Nutrição , Zinco/metabolismo , Transporte Biológico , Biomassa , Cádmio , Festuca/anatomia & histologia , Festuca/crescimento & desenvolvimento , Raízes de Plantas/metabolismo , Brotos de Planta/metabolismo , Xilema/metabolismo
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