Does Seed Priming Induce Changes in the Levels of Some Endogenous Plant Hormones in Hexaploid Wheat Plants Under Salt Stress？

In order to assess whether salt tolerance could be Improved In spring wheat （Triticum aestivum L.）, the present study was performed by soaking the seeds of two cultlvars, namely MH-97 （salt sensitive） and Inqlab-91 （salt tolerant）, for 12 h In distilled water or 100 mol/m^3 CaCl2, KCI, or NaCI. Primed seeds from each treatment group and non-primed seeds were sown In a field In which NaCI salinity of 15 dS/m was developed. Priming of seeds with CaCl2, followed by priming with KCI and NaCI, was found to be effective In alleviating the adverse effects of salt stress on both wheat cultivars In terms of shoot fresh and dry weights and grain yield. Priming with CaCl2 alleviated the adverse effects of salt stress on hormonal balance In plants of both cultlvars. In MH-97 plants, CaCl2 pretreatment considerably reduced leaf absclslc acid （ABA） concentrations and Increased leaf free salicylic acid （SA） concentrations under both saline and non-saline conditions. In contrast, In the Inqlab-91 plant, CaCl2 Increased free Indoleacetic acid （IAA） and indolebutyrlc acid （IBA） content. However, priming of seeds with CaCl2 did not alter free polyamlne levels in either cultlvar, although spermldlne levels were considerably lower In plants raised from seeds treated with CaCl2 for both cultlvars under saline conditions. Priming with KCI Increased growth In Inqlab-91 plants, but not In MH-97 plants, under saline conditions. The salinity Induced reducUon In auxins （IAA and IBA） was alleviated by NaCI priming In both cultlvars under saline conditions. However, NaCI Increased leaf free ABA content and lowered leaf SA and putresclne levels In Inqlab-91 plants under saline conditions. In conclusion, although all three priming agents （I.e. CaCl2, KCI, and NaCI） were effective In alleviating the adverse effects of salt stress on wheat plants, their effects on altering the levels of different plant hormones were different In the two cuItlvars.     

Influence of Macroelements’ Uneven Distribution on the Content of Hormones and Extension of the Roots in Wheat Plants

Russian Journal of Plant Physiology - Increase in the level of mineral nutrition reduces the relative growth rate of the roots, which adversely affects the drought resistance of plants. This was...     

Do Polyamines Participate in the Long-Distance Translocation of Stress Signals in Plants?

Accumulation and ethylene-dependent translocation of free polyamines was studied in various organs, the phloem and xylem exudates of common ice plants (Mesembryanthemum crystallinum L.). Under normal conditions (23–25°C), spermidine predominated among polyamines. Cadaverine was found in old leaves, stems, and, in large quantities, in roots. The heat shock treatment (HS; 47°C, 2 h) of intact plant shoots induced intense evolution of ethylene from leaves but reduced the leaf content of polyamines. Under these conditions, the concentration of polyamines in roots, particularly of cadaverine, increased many times. The HS treatment of roots (40°C, 2 h) induced translocation of cadaverine to stems and putrescine to leaves. An enhanced polyamine content after HS treatment was also found in the xylem and phloem exudates. The exposure of detached leaves to ethylene led to a reduction in their putrescine and spermidine and accumulation of cadaverine, which implies the ethylene-dependent formation of cadaverine and a possible relation between the HS-induced translocation of this diamine to roots and the transient ethylene evolution by leaves. To validate this hypothesis, we compared the ethylene evolution rate and interorgan partitioning of cadaverine and other polyamines for two lines of Arabidopsis thaliana: the wild type (Col-0) and ein4 mutant with impaired ethylene reception. In plants grown in light at 20–21°C, the rate of ethylene evolution by rosetted leaves was higher in the mutant than in the wild type. The content of putrescine and spermidine was reduced in mutant leaves, whereas cadaverine concentration increased almost threefold compared with the wild type. In roots, cadaverine was found only in the wild type and not in the mutant line. Our data indicate the ethylene-dependent formation of cadaverine in leaves and possible involvement of cadaverine and ethylene in the long-distance translocation of stress (HS) signal in plants.     

The Role of SV Ion Channels Under the Stress of Mycotoxins Induced in Wheat Cells—Protective Action of Selenium Ions

Journal of Plant Growth Regulation - Mycotoxin stress, one of the currently intensively studied, was stimulated in wheat hypocotyl cells through the application of zearalenone, produced by Fusarium...     

Na^＋ and Water Uptake in Relation to the Radial Reflection Coefficient of Root in Arrowleaf Saltbush Under Salt Stress

The response of halophyte arrowleaf saltbush (Atriplex triangularis Willd) plants to a gradient of salt stress were investigated with hydroponically cultured seedlings. Under salt stress, both the Na+ uptake into root xylem and negative pressures in xylem vessels increased with the elevation of salinity (up to 500 mol/m3) in the root environment. However, the increment in negative pressures in root xylem far from matches the decrease in the osmotic potential of the root bathing solutions, even when the osmotic potential of xylem sap is taken into consideration. The total water potential of xylem sap in arrowleaf saltbush roots was close to the osmotic potential of root bathing solutions when the salt stress was low, but a progressively increased gap between the water potential of xylem sap and the osmotic potential of root bathing solutions was observed when the salinity in the root environment was enhanced. The maximum gap was 1.4 MPa at a salinity level of 500 mol/m3 without apparent dehydration of the tested plants. This discrepancy could not be explained with the current theories in plant physiology. The radial reflection coefficient of root in arrowleaf saltbush decreased with the enhanced salt stress was and accompanied by an increase in the Na+ uptake into xylem sap. However, the relative Na+ in xylem exudates based on the corresponding NaCl concentration in the root bathing solutions showed a tendency of decrease. The results showed that the reduction in the radial reflection coefficient of roots in the arrowleaf saltbush did not lead to a mass influx of NaCl into xylem when the radial reflection coefficient of the root was considerably small; and that arrowleaf saltbush could use small xylem pressures to counterbalance the salt stresses, either with the uptake of large amounts of salt, or with the development of xylem pressures dangerously negative. This strategy could be one of the mechanisms behind the high resistance of arrowleaf saltbush plants to salt stress.     

Does Apoplastic Sucrose Induce the Ability for Sucrose Loading in Developing Leaves of Sugarbeet?

Dark-grown sugarbeet (Beta vulgaris L.) leaves were used toinvestigate a possible role of apoplastic sucrose in the inductionand development of the putative phloem-located sucrose carrierin relation to minor vein loading and export capacity. Unlabeledsucrose was introduced to the leaf apoplast after which veinaccumulation of [¹⁴C]sucrose was determined by autoradiogra-phy.Western blotting was used to detect the putative carrier. Anaffinity purified antibody against the sucrose binding proteinof soybean did not cross-react with the protein in a plasmalemma-enrichedfraction from sugarbeet leaves. Challenging the apoplast ofleaf discs with buffer plus sucrose for 6 h (induction) resultedin decreased [¹⁴C]sucrose uptake. When induction treatmentswere conducted with detached intact leaves in the dark, sucroseand glucose, but not buffer alone enhanced [¹⁴C]sucrose uptake.Detached leaves induced under laboratory light conditions for24 h showed enhanced [¹⁴C]sucrose uptake even in the absenceof any sugar introduced to the apoplast (buffer only). The datasuggested that in the etiolated tissue, sucrose was not a directand specific inducer of its putative carrier; instead sugarsmay have provided the energy for vein loading. Furthermore,the data suggested a role for light in the development of theputative sucrose carrier and vein accumulation of sucrose intransitional leaves of sugarbeet. The role of light may alsobe related to tissue energy level. ¹Contribution No. D-15192-1-91 from the New Jersey AgriculturalExperiment Station. This work was funded in part by the BeetSugar Development Foundation and Rutgers University ResearchCouncil and was submitted as partial fulfillment for M.S. degreeby Lynne H. Pitcher. (Received February 19, 1991; Accepted May 13, 1991)     

Diurnal Changes in the Regulatory Properties of Phosphoenolpyruvate Carboxylase in CAM Plants: Are Alterations in the Quaternary Structure Involved?

Day — and night-forms of phosphoenolpyruvate carboxylase (EC 4.1.1.31) (PEP-C) were extracted from leaves of the CAM plant Kalanchoë daigremontiana. During storage after extraction, the day-form spontaneously lost its sensitivity towards the allosteric inhibitor l -malate. This effect was accelerated by inorganic phosphate, PEP, 3-PGA and G-6-P. l -Malate however stabilized the malate sensitivity of the day-form of PEP-C. Crude desalted extracts of the day-form and of the night-form of PEP-C were subjected to ultracentrifugation on a continuous sucrose gradient in the presence of malate and of marker enzymes. Both forms of PEP-C were found to have relative molecular masses of about 200,000. This suggests that both forms represent the dimers of the enzyme protein. The result also suggests that reversible dissociation and association of enzyme subunits is not the mechanism which brings about the interconversion of the two PEP-C forms during the diurnal CAM cycle in vivo.     

Does ABA in the Xylem Control the Rate of Leaf Growth in Soil-Dried Maize and Sunflower Plants?

Maize (Zea mays L.) and sunflower (Helianthus annuus L.) plantswere grown in large volumes of soil and leaf growth rate wasmonitored on a daily basis. Half the plants were given a soildrying treatment and when they showed a significant restrictionof growth rate (compared to both their daily growth rate beforedrying and the average growth rate of well-watered plants onthe same day), leaf water relations were measured and xylemsap was extracted using several techniques. There was a significant negative log-linear relationship betweenthe rate of leaf growth and the concentration of ABA in thexylem for both species. There was no clear relationship betweenleaf growth rate and leaf water potential or turgor for eitherspecies. Assessment of different methods for sampling xylemsap suggests that exudates collected from stem stumps or samplescollected by pressurizing the whole root system are suitablefor estimating ABA concentration in xylem, at least with largeplants of maize or sunflower, provided the first few hundredcubic millimetres of collected sap are used for the assay. Centrifugationof sections of stems resulted in dilution of ABA in the xylemsap with sap squeezed from parenchyma tissue. This is because,at least in plants subjected to mild soil drying, the concentrationof the ABA in the xylem is far higher than that in the cellsap of stem tissue. Results support the proposal that ABA plays a major role asa chemical signal involved in the root-to-shoot communicationof the effects of soil drying. The non-hydraulic restrictionof leaf growth by a chemical signal can be explained by theextra root-sourced ABA in the xylem and may be an importantcomponent of the modification of growth and development whichresults from prolonged soil drought. Key words: Soil drying, ABA, leaf growth, Zea mays L., Helianthus annuus L.     

Changes in the Range of Some Common Rocky Shore Species in Britain – A Response to Climate Change?

Since the 1990s there has been a period of rapid climate warming in Europe. Long-term broad scale datasets coupled with time series at specific locations for rocky intertidal species dating back to the 1950s have been collected in Britain and Ireland. Resurveys of the original locations in 2001–2003 have been undertaken to identify changes in the biogeographical range and abundance of these species. The results show that some ‘southern’ species including Osilinus lineatus da Costa and Gibbula umbilicalis da Costa have undergone north and north-eastern range extensions. Populations have increased in abundance and adult size has decreased since the previous surveys were conducted. These changes have been synchronous throughout Britain, strongly suggesting that climate is responsible. The use of intertidal species as indicators of climate change is proposed.     

Does the Gradualness of Leaf Shedding Govern Nutrient Resorption from Senescing Leaves in Mediterranean Woody Plants?

To reveal the environmental and substrate quality effects on decomposition process and enzyme activities, litterbag experiments containing Nuphar and Carex leaves, Nuphar rhizome, and Ranunculus shoot, were carried in five-subalpine marshes in Lake Tahoe basin, USA. Alkaline phosphatase, β-glucosidase, and β-xylosidase activities were determined by a fluorogenic method using methyumbelliferyl substrates. Carex leaves, Nuphar rhizome and leaves, and Ranunculus shoots lost, respectively, 33, 67, 82 and 93% of original dry weight over 268 days. Decay rates were different among substrates but not among marshes. Nitrogen and carbon contents increased during the first 58 days and subsequently remained stable. Phosphorus content was stable during the experimental period except for a decrease in the first 16 days in Nuphar shoots. Enzyme activities in decomposing Carex and Nuphar leaves in four marshes were not significantly affected by environmental conditions. β-glucosidase and β-xylosidase activities in decomposing Carex leaves increased with time, but in other plant tissue these enzyme activities remained stable during experimental period. Enzyme activities were significantly different among decomposing substrates. Alkaline phosphatase activity was highest in Nuphar leaves (ca. 1286 μ-mole h⁻¹ g DW −1) but lower and similar in other plant tissues (ca. 100 and 10 μ-mole h −1 g DW −1, respectively). This study showed differences in decay rates and enzyme activities rely on substrate and not the environment conditions of the study area. Decomposition rates in the early stage of decomposition were related to cumulative enzyme activities.     

Calcium-Induced Intercellular Adhesion of Keratinocytes Does not Involve Accumulation of β1 Integrins at Cell-Cell Contacts and Does not Involve Changes in the Levels or Phosphorylation of Catenins

On initiation of terminal differentiation human epidermal keratinocytes detach from the underlying basement membrane as a result of inactivation and subsequent loss of integrins from the cell surface. Assembly of keratinocytes into multilayered sheets requires functional E-and P-cadherin and when stratification is inhibited in low calcium medium differentiating keratinocytes continue to express functional integrins. Using immunofluorescence microscopy, we found that on addition of calcium ions to keratinocyte monolayers there was colocalisation of the β₁ integrins and E-cadherin along the lateral membranes except for a zone close to the substratum which exclusively contained integrins. Quantitative immunoelectron microscopy showed that on induction of stable cell-cell contacts the density of β₁ integrins was the same on the apical and lateral membranes, suggesting that the accumulation of integrins on the lateral membranes observed by immunofluorescence microscopy is due to the increased area of contact between adjacent cells and not to an increase in receptor density. There were no changes in the levels of catenins and their degree of phosphorylation after induction of cell-cell contacts. These observations provide new sights into the mechanism of calcium-dependent intercellular adhesion of keratinocytes.     

Does Gibberellic Acid Induce the Transfer of Lipase from Protein Bodies to Lipid Bodies in Barley Aleurone Cells?

We have examined the effect of gibberellic acid (GA₃) on the distribution of the enzyme responsible for mobilizing storage triacylglycerol in aleurone cells of Hordeum vulgare L. cv Himalaya. Using cellular fractionation techniques, we find that, in cells that have not been exposed to hormone, neutral lipase activity is principally associated with a pellet containing the membranes of protein bodies. If the cells are exposed to GA₃ for at least 1 hour, the majority of the lipase activity becomes associated with the lipid body fraction. The nature of the in vivo association between lipid bodies and protein bodies was examined using ultrarapid freezing followed by freeze-fracture electron microscopy. Our analysis indicates that the phospholipid monolayer surrounding the lipid body is directly continuous with the outer leaflet of the bilayer surrounding the protein body. Based on our data, we propose that lipase can be transferred from protein bodies (storage form) to lipid bodies (active form) by lateral diffusion within the plane of the fused phospholipid monolayer, and that the transfer can be controlled by gibberellic acid by an unknown mechanism.     

Facing the Heat: Does Desiccation and Thermal Stress Explain Patterns of Orientation in an Intertidal Invertebrate?

A key challenge for ecologists is to quantify, explain and predict the ecology and behaviour of animals from knowledge of their basic physiology. Compared to our knowledge of many other types of distribution and behaviour, and how these are linked to individual function, we have a poor level of understanding of the causal basis for orientation behaviours. Most explanations for patterns of animal orientation assume that animals will modify their exposure to environmental factors by altering their orientation. We used a keystone grazer on rocky shores, the limpet Cellana tramoserica, to test this idea. Manipulative experiments were done to evaluate whether orientation during emersion affected limpet desiccation or body temperature. Body temperature was determined from infrared thermography, a technique that minimises disturbance to the test organism. No causal relationships were found between orientation and (i) level of desiccation and (ii) their body temperature. These results add to the growing knowledge that responses to desiccation and thermal stress may be less important in modifying the behaviour of intertidal organisms than previously supposed and that thermoregulation does not always reflect patterns of animal orientation. Much of what we understand about orientation comes from studies of animals able to modify orientation over very short time scales. Our data suggests that for animals whose location is less flexible, orientation decisions may have less to do with responses to environmental factors and more to do with structural habitat properties or intrinsic individual attributes. Therefore we suggest future studies into processes affecting orientation must include organisms with differing levels of behavioural plasticity.     

Does Landscape Fragmentation Influence Sex Ratio of Dioecious Plants? A Case Study of Pistacia chinensis in the Thousand-Island Lake Region of China

The Thousand-Island Lake region in Zhejiang Province, China is a highly fragmented landscape with a clear point-in-time of fragmentation as a result of flooding to form the reservoir. Islands in the artificial lake were surveyed to examine how population sex ratio of a dioecious plant specie Pistacia chinensis B. was affected by landscape fragmentation. A natural population on the mainland near the lake was also surveyed for comparison. Population size, sex ratio and diameter at breast height (DBH) of individuals were measured over 2 years. More than 1,500 individuals, distributed in 31 populations, were studied. Soil nitrogen in the different populations was measured to identify the relationship between sex ratio and micro-environmental conditions. In accordance with the results of many other reports on biased sex ratio in relation to environmental gradient, we found that poor soil nitrogen areas fostered male-biased populations. In addition, the degree of sex ratio bias increased with decreasing population size and population connectivity. The biased sex ratios were only found in younger individuals (less than 50 years old) in small populations, while a stable 1∶1 sex ratio was found in the large population on the mainland. We concluded that the effects of landscape fragmentation on the dioecious population sex ratio were mainly achieved in relation to changing soil nitrogen conditions in patches and pollen limitation within and among populations. Large populations could maintain a more suitable environment in terms of nutrient conditions and pollen flow, subsequently maintaining a stable sex ratio in dioecious plant populations. Both micro-environmental factors and spatial structure should be considered in fragmented landscape for the conservation of dioecious plant species.     

Does Stress Increase the Risk of Atopic Dermatitis in Adolescents? Results of the Korea Youth Risk Behavior Web-Based Survey (KYRBWS-VI)

This study investigated the relationship between level of stress in middle and high school students aged 12–18 and risk of atopic dermatitis. Data from the Sixth Korea Youth Risk Behavior Web-based Survey (KYRBWS-VI), a cross-sectional study among 74,980 students in 800 middle schools and high schools with a response rate of 97.7%, were analyzed. Ordinal logistic regression analyses were conducted to determine the relationship between stress and atopic dermatitis with severity. A total of 5,550 boys and 6,964 girls reported having been diagnosed with atopic dermatitis. Younger students were more likely to have atopic dermatitis. Interestingly, the educational level of parents was found to be associated with having atopic dermatitis and having more severe condition. In particular, girls with mothers with at least college education had a 41% higher risk of having atopic dermatitis and severe atopic condition (odds ratio (OR)) = 1.41, 95% CI, 1.22–1.63; P<0.0001) compared with those with mothers who had attended middle school at most. Similar trend was shown among both boys and girls for their father''s education level. The stress level was found to be significantly associated with the risk of atopic dermatitis. Compared to boys with who reported “no stress”, boys with “very high” stress had 46% higher the risk of having more severe atopic dermatitis (OR = 1.46, 95% CI, 1.20–1.78; P<0.0001), 44% higher (OR = 1.44, 95% CI, 1.19–1.73; P<0.0001) with “high” stress, and 21% higher (OR = 1.21, 95% CI, 1.00–1.45; P = 0.05) with “moderate” stress. In contrast, we found no statistically significant relationship between stress and atopic dermatitis in girls. This study suggests that stress and parents'' education level were associated with atopic dermatitis. Specifically, degree of stress is positively correlated with likelihood of being diagnosed with this condition and increasing the severity.     

Salinity and Bacterial Diversity: To What Extent Does the Concentration of Salt Affect the Bacterial Community in a Saline Soil?

In this study, the evaluation of soil characteristics was coupled with a pyrosequencing analysis of the V2-V3 16S rRNA gene region in order to investigate the bacterial community structure and diversity in the A horizon of a natural saline soil located in Sicily (Italy). The main aim of the research was to assess the organisation and diversity of microbial taxa using a spatial scale that revealed physical and chemical heterogeneity of the habitat under investigation. The results provided information on the type of distribution of different bacterial groups as a function of spatial gradients of soil salinity and pH. The analysis of bacterial 16S rRNA showed differences in bacterial composition and diversity due to a variable salt concentration in the soil. The bacterial community showed a statistically significant spatial variability. Some bacterial phyla appeared spread in the whole area, whatever the salinity gradient. It emerged therefore that a patchy saline soil can not contain just a single microbial community selected to withstand extreme osmotic phenomena, but many communities that can be variously correlated to one or more environmental parameters. Sequences have been deposited to the SRA database and can be accessed on ID Project PRJNA241061.     

Does Environmental Instability Favor the Production and Horizontal Transmission of Knowledge regarding Medicinal Plants? A Study in Southeast Brazil

Greater socio-environmental instability favors the individual production of knowledge because innovations are adapted to new circumstances. Furthermore, instability stimulates the horizontal transmission of knowledge because this mechanism disseminates adapted information. This study investigates the following hypothesis: Greater socio-environmental instability favors the production of knowledge (innovation) to adapt to new situations, and socio-environmental instability stimulates the horizontal transmission of knowledge, which is a mechanism that diffuses adapted information. In addition, the present study describes “how”, “when”, “from whom” and the “stimulus/context”, in which knowledge regarding medicinal plants is gained or transferred. Data were collected through semi-structured interviews from three groups that represented different levels of socio-environmental instability. Socio-environmental instability did not favor individual knowledge production or any cultural transmission modes, including vertical to horizontal, despite increasing the frequency of horizontal pathways. Vertical transmission was the most important knowledge transmission strategy in all of the groups in which mothers were the most common models (knowledge sources). Significantly, childhood was the most important learning stage, although learning also occurred throughout life. Direct teaching using language was notable as a knowledge transmission strategy. Illness was the main stimulus that triggered local learning. Learning modes about medicinal plants were influenced by the knowledge itself, particularly the dynamic uses of therapeutic resources.