Differential responses of roots for varying tolerance to salinity stress in wheat with special reference to elasticity

Two salt-sensitive (Yongliang-15, GS-6058) and two salt-tolerant (JS-7, Xinchun-31) wheat cultivars were used to investigate the extension, extensibility (viscoelastic parameters), and chemical composition of the cell walls in their root elongation regions (apical 10 mm-long root segments), under salinity stress. The elasticity of the root cell wall, indicated by E0, significantly decreased in the salt-sensitive cultivars, whereas the E0 in the salt-tolerant cultivars was maintained at the same level as that in the non-saline condition. Root extension and the differences among cultivars were largely dependent on elastic extension, which accounts for one-half to two-thirds of the total extension. Viscosity, indicated by η0, and the plastic extension of the root cell walls did not change across the treatments and cultivars. The significant decrease in cell wall elasticity in the root elongation region was one of the factors that depressed root growth in salt-sensitive cultivars under the saline condition. The well-maintained elasticity of salt-tolerant cultivars alleviated the depression of root growth by NaCl. Cell wall elasticity was positively correlated with the relative pectin and hemicellulose I contents and negatively correlated with the relative cellulose content. Under saline conditions, the relative hemicellulose II content did not change in the salt-sensitive cultivars; however, it decreased in the salt-tolerant ones. Thus, changes in chemical composition of the cell wall were correspond with the cell wall extensibility and root growth in wheat cultivars with different degrees of salt tolerance

Distribution of Three Congeneric Shrub Species Along an Aridity Gradient Is Related to Seed Germination and Seedling Emergence

Environmental tolerance of a species has been shown to correlate positively with its geographical range. On the Ordos Plateau, three Caragana species are distributed sequentially along the precipitation gradient. We hypothesized that this geographical distribution pattern is related to environmental tolerances of the three Caragana species during seed germination and seedling emergence stages. To test this hypothesis, we examined seed germination under different temperature, light and water potentials, and monitored seedling emergence for seeds buried at eight sand depths and given different amounts of water. Seeds of C. korshinskii germinated to high percentages at 5 : 15 to 25 : 35 °C in both light and darkness, while those of C. intermedia and C. microphylla did so only at 15 : 25 and 25 : 35 °C, respectively. Nearly 30 % of the C. korshinskii seeds germinated at -1.4 MPa at 20 and 25 °C, while no seeds of the other two species did so. Under the same treatments, seedling emergence percentages of C. korshinskii were higher than those of the other two species. The rank order of tolerance to drought and sand burial of the three species is C. korshinskii \u3e C. intermedia \u3e C. microphylla. The amount of precipitation and sand burial depth appear to be the main selective forces responsible for the geographical distribution of these species

Responses of plant species to different aboveground removal treatments with implications for vegetation restoration in the Mu Us Sandland (Inner Mongolia)

It is generally assumed that plants can respond to varying degrees of physical damage by growth compensation via resprouting, and resprouting is a key functional trait in many species. Few studies have investigated how grass and shrub species distributed in moving dunes and semifixed dunes in semiarid areas respond to the combined effects of temperature and shoot removal. Medicago sativa, Artemisia ordosica, and Artemisia sphaerocephala plants were grown in a glasshouse for 8 weeks at air temperatures of 10/20°C, 12.5/22.5°C, 15/25°C, and 17.5/27.5°C (night/day) and were subjected to treatments of removing all leaves (LR), removing all leaves followed by cutting at half the plant height (HC), and removing all aboveground tissue (WC). The species, temperature, and damage extent had significant effects on the shoot number, leaf mass ratio, leaf area ratio and ratio of belowground to aboveground dry matter, and the species had a significant effect on the net assimilation rate, specific leaf area, and total biomass. The three species grew well under the HC and LR treatments, and high temperatures (15/25°C and 17.5/27.5°C) significantly promoted the regrowth of the three species. Medicago sativa grew faster than the two Artemisia species. Medicago sativa can be used for fertilizing or vegetation restoration in unimportant conservation areas, and the two Artemisia species can be effectively used for vegetation restoration in the Mu Us Sandland. Due to the low labor costs and the local climate conditions, plants should be clipped before the beginning of the main growing season (end of May or early June) to ensure rapid growth

The overrepresented functional GO terms of the genes specifically or preferentially in the selfed ovules of <i>Xanthoceras sorbifolium</i>.

<p>The overrepresented functional GO terms of the genes specifically or preferentially in the selfed ovules of <i>Xanthoceras sorbifolium</i>.</p

Comparative <i>De Novo</i> Transcriptome Analysis of Fertilized Ovules in <i>Xanthoceras sorbifolium</i> Uncovered a Pool of Genes Expressed Specifically or Preferentially in the Selfed Ovule That Are Potentially Involved in Late-Acting Self-Incompatibility

<div><p><i>Xanthoceras sorbifolium</i>, a tree species endemic to northern China, has high oil content in its seeds and is recognized as an important biodiesel crop. The plant is characterized by late-acting self-incompatibility (LSI). LSI was found to occur in many angiosperm species and plays an important role in reducing inbreeding and its harmful effects, as do gametophytic self-incompatibility (GSI) and sporophytic self-incompatibility (SSI). Molecular mechanisms of conventional GSI and SSI have been well characterized in several families, but no effort has been made to identify the genes involved in the LSI process. The present studies indicated that there were no significant differences in structural and histological features between the self- and cross-pollinated ovules during the early stages of ovule development until 5 days after pollination (DAP). This suggests that 5 DAP is likely to be a turning point for the development of the selfed ovules. Comparative <i>de novo</i> transcriptome analysis of the selfed and crossed ovules at 5 DAP identified 274 genes expressed specifically or preferentially in the selfed ovules. These genes contained a significant proportion of genes predicted to function in the biosynthesis of secondary metabolites, consistent with our histological observations in the fertilized ovules. The genes encoding signal transduction-related components, such as protein kinases and protein phosphatases, are overrepresented in the selfed ovules. <i>X</i>. <i>sorbifolium</i> selfed ovules also specifically or preferentially express many unique transcription factor (TF) genes that could potentially be involved in the novel mechanisms of LSI. We also identified 42 genes significantly up-regulated in the crossed ovules compared to the selfed ovules. The expression of all 16 genes selected from the RNA-seq data was validated using PCR in the selfed and crossed ovules. This study represents the first genome-wide identification of genes expressed in the fertilized ovules of an LSI species. The availability of a pool of specifically or preferentially expressed genes from selfed ovules for <i>X</i>. <i>sorbifolium</i> will be a valuable resource for future genetic analyses of candidate genes involved in the LSI response.</p></div

GO function classification of the identified genes expressed specifically or preferentially in the crossed ovules of <i>Xanthoceras sorbifolium</i>.

<p>GO function classification of the identified genes expressed specifically or preferentially in the crossed ovules of <i>Xanthoceras sorbifolium</i>.</p

KOG function classification of the genes expressed specifically or preferentially in the selfed ovules of <i>Xanthoceras sorbifolium</i>.

<p>The X-axis indicates KOG function classification. The Y-axis indicates number of unigenes.</p

The <i>Xanthoceras sorbifolium</i> selfed ovule specifically or preferentially expressed genes were annotated to BRITE functional hierarchies.

<p>The <i>Xanthoceras sorbifolium</i> selfed ovule specifically or preferentially expressed genes were annotated to BRITE functional hierarchies.</p

Twenty-eight specifically or preferentially expressed unigenes in the selfed ovules of <i>Xanthoceras sorbifolium</i> encode for the putative transcription factors belonging to 12 different families.

<p>RPKM: Reads per Kilobase per Million reads.</p

Mean area of the median longitudinal section of ovule and embryo sac after cross- and self- pollination of <i>Xanthoceras sorbifolium</i>.

<p>A: Ovule area; B: Embryo sac area.</p