Publications by Jhonathan Ephrath
Acta Horticulturae, 2011
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Journal of Experimental Botany, 2012
Knowledge about the root system structure and the uptake efficiency of root orders is critical to... more Knowledge about the root system structure and the uptake efficiency of root orders is critical to understand the adaptive plasticity of plants towards salt stress. Thus, this study describes the phenological and physiological plasticity of Citrus volkameriana rootstocks under severe NaCl stress on the level of root orders. Phenotypic root traits known to influence uptake processes, for example frequency of root orders, specific root area, cortical thickness, and xylem traits, did not change homogeneously throughout the root system, but changes after 6 months under 90 mM NaCl stress were root order specific. Chloride accumulation significantly increased with decreasing root order, and the Cl− concentration in lower root orders exceeded those in leaves. Water flux densities of first-order roots decreased to <20% under salinity and did not recover after stress release. The water flux densities of higher root orders changed marginally under salinity and increased 2- to 6-fold in second and third root orders after short-term stress release. Changes in root order frequency, morphology, and anatomy indicate rapid and major modification of C. volkameriana root systems under salt stress. Reduced water uptake under salinity was related to changes of water flux densities among root orders and to reduced root surface areas. The importance of root orders for water uptake changed under salinity from root tips towards higher root orders. The root order-specific changes reflect differences in vulnerability (indicated by the salt accumulation) and ontogenetic status, and point to functional differences among root orders under high salinity.
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Papers by Jhonathan Ephrath
Australian Journal of Botany, 1999
Acacia saligna (Labill.) H.Wendl, a potential crop for forage and wood production, is considered ... more Acacia saligna (Labill.) H.Wendl, a potential crop for forage and wood production, is considered highly drought-resistant. The aim of this study was to characterise some of the physiological traits contributing to drought resistance in A. saligna. Two experiments were conducted: (i) 4-year-old A. saligna were grown in the field under dryland and irrigated treatments and (ii) 6-month-old A. saligna were grown in pots and irrigated to replenish 100% of the transpiration demand (control), or 75% 50% or 25% of the control. Soil-water deficits in the field elicited an increase in osmotic potential in phyllodes. Stomatal conductance was negatively correlated with air vapor pressure deficit under drought conditions in both experiments, whereas under irrigation in the field it was correlated with solar radiation. In the field, dry matter (DM) production under irrigation was only 14% greater (not significant) than under dryland. In the pot experiment, DM production was significantly reduced,...
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Ecophysiology and Responses of Plants under Salt Stress, 2012
Salinity can cause several challenges for plants, including water stress, mal-nutrition and accum... more Salinity can cause several challenges for plants, including water stress, mal-nutrition and accumulation of excess ions to potentially toxic levels. While salt exclusion, compartmentation and osmoregulation are the mechanisms particularly considered to increase the salt tolerance of plants, tolerance is determined by the integrating effects of several mechanisms at the cell, tissue and organ level. Because roots are in direct contact with the soil solution, they are first to encounter excess salinity and are potentially the first sites of damage or ” line of defence”. However, despite the likelihood that differences among root systems may (partially) underlie distinct salt tolerances, information on the phenotypical and physiological plasticity of root systems under salt stress is scant compared to aboveground organs. This chapter reviews modifications among root size and architecture, morphological and anatomical root traits and root physiology under salinity. Furthermore, root elongation, halotropism and carbon metabolism of roots under salinity are addressed. The review explores the question of whether changes among roots are caused by ion toxicity or whether they could be an active response of plants, which may be of potential adaptive significance. A short overview of the chemical and physical properties of saline soils is given.
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Plant, Cell & Environment, 2010
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Plant and Soil, 2012
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Journal of Experimental Botany, 2012
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Environmental and Experimental Botany, 2011
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Plant and Soil, 2007
The regrowth capacity after pollarding of a short-rotation plantation of Acacia saligna (Labill.)... more The regrowth capacity after pollarding of a short-rotation plantation of Acacia saligna (Labill.) H. Wendl. was investigated in a field trial. This shrub has been proposed as a provider of biomass (fuelwood and fodder) in an arid environment, using local marginal water resources such as surface runoff and brackish groundwater. The specific objective of this study was to examine the
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<p>Container size and fruit load intensity are two common factors manipulated to regulate p... more <p>Container size and fruit load intensity are two common factors manipulated to regulate plant growth and development. As saline water is increasingly used for irrigation in arid and semi-arid regions, it is important to study effects of container size and fruit load intensity on tomato in both aboveground and belowground parts under salt stress. The experiment was conducted in a net house located in Sede Boqer Campus, Israel. Containers of four sizes (8-, 28-, 48-, and 200L with the same depth but vary in diameters), two salinity levels (1.5- and 7.5 dS m<sup>&#8722;1</sup>) and two crop load intensities (0% and 100%) were applied. Gas exchange parameters (i.e., stomatal conductance and CO<sub>2 </sub>assimilation rate), plant growth parameters (i.e., plant height and stem diameter), and root development were monitored periodically. Plant biomass and various root traits were measured at harvest. For aboveground part, results revealed that container size and salinity level significantly influenced gas exchange performance while fruit load intensity had no significant effect. Plants grown in larger containers without salt stress had higher stomatal conductance and CO<sub>2 </sub>assimilation rate. Plant height and stem diameter were significantly greater in plants grown in 200L than those in other containers despite salinity and fruit load levels. Moreover, plants grown in 200L containers exhibited significant increase of 56.3%, 152.9%, and 174.9% respectively in yield compared with those grown in 48-, 28- and 8L under salt stress. The increase magnitudes were greater when there was no salt stress: 109.0%, 430.8%, and 454.0% respectively. For belowground parts, increased container size leads to increased rooting depth. Besides, Minirhizotron data showed that in 200L containers, plants grown under low salinity without fruit developed the greatest total root length. More detailed root data will be presented.&#160; It is concluded that container size has a pronounced effect on physiological behaviours of tomato plants. Therefore, properly increasing container size can alleviate yield reduction under saline irrigation.</p>
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Flowering time of Hippeastrum can be controlled by applying specific thermal regime to large size... more Flowering time of Hippeastrum can be controlled by applying specific thermal regime to large sized bulbs. Due to high-energy costs, the aim of this study was to examine the possibility to reduce soil heating and keep high bulb growth rate by increasing the CO_2 concentration. Two sets of experiments were carried out in a controlled greenhouse at the North-Western Israeli Negev Desert. In both experiments, bulbs of different initial sizes were grown under two levels of CO_2 concentrations (ambient, 350ppm and elevated, 1000ppm) combined with different minimum soil temperature regimes. In the first experiment three temperature regimes (16℃, 22℃ and 24℃) were tested, while in the second experiment only one minimum soil temperature regime (22℃) was investigated. In both experiments, raising CO_2 concentration from the ambient level to elevated one, or increasing soil temperature resulted in a higher bulb growth rate. Temperatures, CO_2 concentration and initial bulb size significantly i...
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Soil Science Society of America Journal - SSSAJ, 1994
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
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&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;p&amp;amp... more &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;p&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;Weed-crop competition is a problem affecting food production leading to&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#160; significant yield losses in various crops. The use of remote sensing technologies in agriculture enables rapid, non-destructive measurements that can be used for research and agronomical management. Previous research has been conducted characterizing the spectral response of crops to the stress caused by weeds but not much progress has been achieved nor has this been fully connected to physiological processes. Understanding the spectral characteristics of this type of stress is a basic step in advancing precision agricultural technologies for managing weeds in the field. This research focuses on corn (Zea mays) with variable densities of redroot pigweed (Amaranthus retroflexus), a common weed that is known to reduce corn yields. The primary research goal is to characterize the physiological changes that occur in the corn during early growth stages in the presence of weeds of different densities. A secondary goal, is to examine the ability to detect those changes by means of proximal and remote sensing.&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;/p&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;p&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;During June to August 2019, a field experiment was conducted in Sede &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#8211; Boker, Israel. Hyperspectral reflectance measurements using an ASD spectrometer,&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;/p&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;p&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;IR images acquired with a thermal camera and multispectral VIS-NIR images from a mounted UAV were taken. We combined the spectral measurements with physiological measurements (photosynthesis, stomatal conductance and transpiration). The data and results were integrated and analyzed to determine whether physiological differences between variable treatments can be detected by the sensing methods.&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#160; Results show that these can be observed, detected and we will provide new explanations associating the competition, spectral response and physiological processes.&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;/p&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;
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Plant and Soil
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Plant and Soil
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Scientia Horticulturae
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Agricultural Water Management
Effects of treated wastewater (TWW) and fresh water (FW) on autotrophic belowground respiration a... more Effects of treated wastewater (TWW) and fresh water (FW) on autotrophic belowground respiration and respiratory coefficients (Q 10) in summer and winter were determined in a commercial citrus orchard. Efflux of CO 2 from soil and the often-ignored CO 2 transported in xylem sap were quantified; the latter derived from sap flux, CO 2 concentration ([CO 2 ]), pH, and temperature. Xylem [CO 2 ] scaled with xylem sap flux, pH and temperature. TWW and summer increased xylem sap pH (by 12% and 19%), soil CO 2 efflux (32% and 65%), and root respired CO 2 (10-15% and 55%) in comparison to FW and winter, respectively. About twice as much CO 2 from the below ground autotrophic portion of respiration moved in xylem sap as compared to that diffused from the roots into the soil, with seasonal variations of about ±10%. Maximum temperature-dependent respiratory coefficients (Q 10) were 4.7 for autotrophic root respiration and 3.8 for bulk soil CO 2 efflux, and values varied with water quality and season. Total below ground respiration exceeds that previously reported and is a large part of the tree&#39;s carbon balance. Increased respiratory losses caused by poor quality water may explain reduced orchard root growth and overall productivity.
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Publications by Jhonathan Ephrath
Papers by Jhonathan Ephrath