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Publications by Jhonathan Ephrath

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.

Papers by Jhonathan Ephrath

Weed Research, Apr 1, 2013

SummaryA new method for non‐destructive monitoring of the subsurface development of Cyperus rotun... more SummaryA new method for non‐destructive monitoring of the subsurface development of Cyperus rotundus (purple nutsedge) is described. A minirhizotron (MR) system was adopted for use to observe vegetative growth of the weed in a net‐house and under field conditions. In particular, the key stages of tuber production and sprouting were monitored and quantified. The MR system allowed non‐destructive repeated measurements of the key stages in C. rotundus subsurface development, serving as a both quantitative and qualitative tool in the study of C. rotundus. A comparison between the MR method and a destructive method revealed that the former reduces experimental variance, thus providing a more accurate prediction of the sprouting process. The techniques presented in the current study offer advanced methodologies for continuous monitoring of C. rotundus development under the soil surface. The novelty of this method lies in its simplicity and efficiency, allowing continuous observation of specific organs of this noxious weed and potentially of other geophytes.

Crop Science, 1985

The penetration of radiation into cotton (Gossypium hirsutum L., ‘Acala SJ‐2’) canopies was inves... more The penetration of radiation into cotton (Gossypium hirsutum L., ‘Acala SJ‐2’) canopies was investigated in two field experiments in Negba (1980, irrigated by sprinklers), and in Nahal‐Oz (1981, three irrigation treatments by a drip system). Photosynthetically active radiation (PAR) below the canopy was measured by a sensor moving on a 2 at track across the rows and integrated for periods of 30 min. The PAR was also measured above the canopy, and the percent of penetration was calculated. Plant height and leaf area index (LAI) were measured together with the radiation measurements. A high correlation was found between plant height and LAI, and both were highly correlated with radiation penetration. Plant height was found to be more useful than LAI as a predictor of radiation penetration, because its measurement in the field is more convenient. During periods of moisture stress, radiation penetration was usually lower than predicted by plant height. An examination of our data by using a model revealed that plant width was an important factor determining radiation penetration. The model accurately predicted radiation penetration into the canopy, provided that reliable estimates of essential plant parameters (e.g., plant height and width, LAI, and leaf angle distribution) had been input. Increased growth in height was usually associated with high rates of irrigation, whereas plant width was not. Plant width increased abruptly as soon as the first bolls began to develop, and this was followed by a rapid decrease in radiation penetration.

Scientia Horticulturae, May 1, 2021

Abstract Grafting with different rootstocks may provide increased tolerance and yield, even under... more Abstract Grafting with different rootstocks may provide increased tolerance and yield, even under poor-quality irrigation conditions. We examined the effects of potato rootstock on physiology, dry mass, and yield of tomato scion in pots irrigated with saline water. Tomato (cv. Ikram), potato (cv. Charlotte) and grafted (cv. Ikram/Charlotte) plants were subjected to saline and non-saline water-irrigation treatments (electrical conductivity 5.0 and 1.0 dS m−1, respectively). Physiological, mineral, dry mass and yield analyses were performed. Potato rootstock unchanged the total plant dry mass without disturbing the physiology of the tomato scion under saline water irrigation. The grafted plants showed differential root trait responses with balanced mineral partitioning across plant parts under saline water irrigation. Grafted plants were superior in water productivity by 56.8 and 70.5 % over the control plants under saline and non-saline water-irrigations, respectively. Potato rootstock could improve the tolerance of tomato scion to saline water irrigation through distinct changes in dry mass allocation, and the induction of mineral-compartmentalization processes. The results of this study suggest that the use of potato rootstock may be a good strategy for increasing tolerance to saline water irrigation, as well as the production of both fruits and tubers in a single plant.

Remote Sensing, 2021

Understanding the spectral characteristics of crops in response to stress caused by weeds is a ba... more Understanding the spectral characteristics of crops in response to stress caused by weeds is a basic step in improving the precision of agricultural technologies that manage weeds in the field. This research focused on the competition between corn (Zea mays) and redroot pigweed (Amaranthus retroflexus), a common weed that strongly reduces corn yield. The aim of this research was to characterize the physiological changes that occur in corn during early growth because of crop–weed competition and to examine the ability to detect the effect of competition through hyperspectral measurements. A greenhouse experiment was conducted, and corn plants were examined during early growth, with and without weed competition. Hyperspectral measurements were combined with physiological measurements to examine the reflectance and photosynthetic activity of corn. Changes were expected to appear mainly in the short-wave infrared region (SWIR) due to competition for water. Relative water content (RWC), ...

Physiologia Plantarum, 2018

The parasite Phelipanche aegyptiaca infests tomato, a crop plant that is commonly cultivated in s... more The parasite Phelipanche aegyptiaca infests tomato, a crop plant that is commonly cultivated in semi-arid environments, where tomato may be subject to salt stress. Since the relationship between the two stresses-salinity and parasitism-has been poorly investigated in tomato, the effects of P. aegyptiaca parasitism on tomato growing under moderate salinity were examined. Tomatoes were grown with regular or saline water irrigation (3 and 45 mM Cl − , respectively) in soils infested with P. aegyptiaca. The infested plants accumulated higher levels of sodium and chloride ions in the roots, shoots and leaves (old and young) under both salinity levels vs. non-infected plants. There was a positive linear correlation between P. aegyptiaca biomass and salt accumulation in young tomato leaves, and a negative linear correlation between parasite biomass and the osmotic potential of young tomato leaves. Concentrations of the osmoprotectants proline, myoinositol and sucrose were reduced in infected tomato plants, which impaired the host's osmotic adjustment ability. The sensitivity of P. aegyptiaca to salt stress was manifested as a decrease in biomass. In conclusion, P. aegyptiaca parasitism reduced the salt tolerance of tomato plants by promoting the accumulation of salts from the rhizosphere and impairing the host's osmotic adjustment ability.

Remote Sensing of Environment, 2017

Monitoring vegetation dynamics in hyper-arid zones is important because any decrease in the alrea... more Monitoring vegetation dynamics in hyper-arid zones is important because any decrease in the already sparse vegetation cover in these areas could considerably affect the entire ecosystem. The new generation of high spatial resolution satellite (HSR) sensors is suitable for monitoring trees in arid regions because of the distinct and separate objects that trees represent in these environments. The main limitation of modern HSR sensors is the lack of a historical archive that would otherwise enable meaningful landscape change detection, especially in arid regions where tree population dynamics are naturally very slow. This study uses spatial analysis to gain information regarding the long-and short-term dynamic processes affecting the acacia tree population in Wadi Ktora, in the southern Arava Valley, Israel. The data is extracted from a single HSR aerial photograph composed of three spectral bands in the visible and infrared spectrum (green, red, and near infrared). A map of individual acacia trees that is extracted from a colour infrared aerial photograph of Wadi Ktora from 2010 enables the examination of spatial distribution patterns for both tree size and foliage health. Tree size distribution is used as an indicator of long-term (decades) hydrologic spatial processes affecting the acacia population. The tree health distribution is used as an indicator for short-term (months to a few years) hydrologic spatial processes, such as the paths of recent flash floods events. Comparing the distributions of tree size and normalized difference vegetation index (NDVI) enables differentiation between the long-term and short-term processes that brought the population to its present state. Using spatial statistic grouping, the distribution of the trees in the wadi (ephemeral stream) is divided into three distinct categories: (1) large trees with high NDVI values, (2) large trees with low NDVI values, and (3) small trees with medium NDVI values. Using the resulting classification, we divided the wadi into three sections, each representing a unique combination of long-and short-term hydrologic processes affecting the acacia trees. We suggest that the lack of spatial correlation between tree size and health status is a result of spatio-temporal changes in the water supply.

ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, 2016

High mortality rates and lack of recruitment in the acacia populations throughout the Negev Deser... more High mortality rates and lack of recruitment in the acacia populations throughout the Negev Desert and the Arava rift valley of Israel have been reported in previous studies. However, it is difficult to determine whether these reports can be evidence to a significant decline trend of the trees populations. This is because of the slow dynamic processes of acaia tree populations and the lack of long term continuous monitoring data. We suggest a new data analysis technique that expands the time scope of the field long term monitoring of trees in arid environments. This will enables us to improve our understanding of the spatial and temporal changes of these populations. <br><br> We implemented two different approaches in order to expand the time scope of the acacia population field survey: (1) individual based tree change detection using Corona satellite images and (2) spatial analysis of trees population, converting spatial data into temporal data. The next step was to int...

Acta Horticulturae, 2005

A model is proposed for the simulation of nutrient solution flow in a Nutrient Film Technique (NF... more A model is proposed for the simulation of nutrient solution flow in a Nutrient Film Technique (NFT) system, and uptake by plants. The system is consisted of a channel with a thin layer of a porous material. The nutrient solution would be applied via dripping emitters, uniformly spaced along the channel, and drain to a reservoir. The solution would then be compensated for water and nutrients' losses, and re-pumped to the irrigation system. The model was tested against N and K uptake by growing lettuce (Lactuca sativa L.) plants. Uptake of the major nutrients and the effects of salinity buildup were simulated and discussed.

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.

Weed Research, Apr 1, 2013

SummaryA new method for non‐destructive monitoring of the subsurface development of Cyperus rotun... more SummaryA new method for non‐destructive monitoring of the subsurface development of Cyperus rotundus (purple nutsedge) is described. A minirhizotron (MR) system was adopted for use to observe vegetative growth of the weed in a net‐house and under field conditions. In particular, the key stages of tuber production and sprouting were monitored and quantified. The MR system allowed non‐destructive repeated measurements of the key stages in C. rotundus subsurface development, serving as a both quantitative and qualitative tool in the study of C. rotundus. A comparison between the MR method and a destructive method revealed that the former reduces experimental variance, thus providing a more accurate prediction of the sprouting process. The techniques presented in the current study offer advanced methodologies for continuous monitoring of C. rotundus development under the soil surface. The novelty of this method lies in its simplicity and efficiency, allowing continuous observation of specific organs of this noxious weed and potentially of other geophytes.

Crop Science, 1985

The penetration of radiation into cotton (Gossypium hirsutum L., ‘Acala SJ‐2’) canopies was inves... more The penetration of radiation into cotton (Gossypium hirsutum L., ‘Acala SJ‐2’) canopies was investigated in two field experiments in Negba (1980, irrigated by sprinklers), and in Nahal‐Oz (1981, three irrigation treatments by a drip system). Photosynthetically active radiation (PAR) below the canopy was measured by a sensor moving on a 2 at track across the rows and integrated for periods of 30 min. The PAR was also measured above the canopy, and the percent of penetration was calculated. Plant height and leaf area index (LAI) were measured together with the radiation measurements. A high correlation was found between plant height and LAI, and both were highly correlated with radiation penetration. Plant height was found to be more useful than LAI as a predictor of radiation penetration, because its measurement in the field is more convenient. During periods of moisture stress, radiation penetration was usually lower than predicted by plant height. An examination of our data by using a model revealed that plant width was an important factor determining radiation penetration. The model accurately predicted radiation penetration into the canopy, provided that reliable estimates of essential plant parameters (e.g., plant height and width, LAI, and leaf angle distribution) had been input. Increased growth in height was usually associated with high rates of irrigation, whereas plant width was not. Plant width increased abruptly as soon as the first bolls began to develop, and this was followed by a rapid decrease in radiation penetration.

Scientia Horticulturae, May 1, 2021

Abstract Grafting with different rootstocks may provide increased tolerance and yield, even under... more Abstract Grafting with different rootstocks may provide increased tolerance and yield, even under poor-quality irrigation conditions. We examined the effects of potato rootstock on physiology, dry mass, and yield of tomato scion in pots irrigated with saline water. Tomato (cv. Ikram), potato (cv. Charlotte) and grafted (cv. Ikram/Charlotte) plants were subjected to saline and non-saline water-irrigation treatments (electrical conductivity 5.0 and 1.0 dS m−1, respectively). Physiological, mineral, dry mass and yield analyses were performed. Potato rootstock unchanged the total plant dry mass without disturbing the physiology of the tomato scion under saline water irrigation. The grafted plants showed differential root trait responses with balanced mineral partitioning across plant parts under saline water irrigation. Grafted plants were superior in water productivity by 56.8 and 70.5 % over the control plants under saline and non-saline water-irrigations, respectively. Potato rootstock could improve the tolerance of tomato scion to saline water irrigation through distinct changes in dry mass allocation, and the induction of mineral-compartmentalization processes. The results of this study suggest that the use of potato rootstock may be a good strategy for increasing tolerance to saline water irrigation, as well as the production of both fruits and tubers in a single plant.

Remote Sensing, 2021

Understanding the spectral characteristics of crops in response to stress caused by weeds is a ba... more Understanding the spectral characteristics of crops in response to stress caused by weeds is a basic step in improving the precision of agricultural technologies that manage weeds in the field. This research focused on the competition between corn (Zea mays) and redroot pigweed (Amaranthus retroflexus), a common weed that strongly reduces corn yield. The aim of this research was to characterize the physiological changes that occur in corn during early growth because of crop–weed competition and to examine the ability to detect the effect of competition through hyperspectral measurements. A greenhouse experiment was conducted, and corn plants were examined during early growth, with and without weed competition. Hyperspectral measurements were combined with physiological measurements to examine the reflectance and photosynthetic activity of corn. Changes were expected to appear mainly in the short-wave infrared region (SWIR) due to competition for water. Relative water content (RWC), ...

Physiologia Plantarum, 2018

The parasite Phelipanche aegyptiaca infests tomato, a crop plant that is commonly cultivated in s... more The parasite Phelipanche aegyptiaca infests tomato, a crop plant that is commonly cultivated in semi-arid environments, where tomato may be subject to salt stress. Since the relationship between the two stresses-salinity and parasitism-has been poorly investigated in tomato, the effects of P. aegyptiaca parasitism on tomato growing under moderate salinity were examined. Tomatoes were grown with regular or saline water irrigation (3 and 45 mM Cl − , respectively) in soils infested with P. aegyptiaca. The infested plants accumulated higher levels of sodium and chloride ions in the roots, shoots and leaves (old and young) under both salinity levels vs. non-infected plants. There was a positive linear correlation between P. aegyptiaca biomass and salt accumulation in young tomato leaves, and a negative linear correlation between parasite biomass and the osmotic potential of young tomato leaves. Concentrations of the osmoprotectants proline, myoinositol and sucrose were reduced in infected tomato plants, which impaired the host's osmotic adjustment ability. The sensitivity of P. aegyptiaca to salt stress was manifested as a decrease in biomass. In conclusion, P. aegyptiaca parasitism reduced the salt tolerance of tomato plants by promoting the accumulation of salts from the rhizosphere and impairing the host's osmotic adjustment ability.

Remote Sensing of Environment, 2017

Monitoring vegetation dynamics in hyper-arid zones is important because any decrease in the alrea... more Monitoring vegetation dynamics in hyper-arid zones is important because any decrease in the already sparse vegetation cover in these areas could considerably affect the entire ecosystem. The new generation of high spatial resolution satellite (HSR) sensors is suitable for monitoring trees in arid regions because of the distinct and separate objects that trees represent in these environments. The main limitation of modern HSR sensors is the lack of a historical archive that would otherwise enable meaningful landscape change detection, especially in arid regions where tree population dynamics are naturally very slow. This study uses spatial analysis to gain information regarding the long-and short-term dynamic processes affecting the acacia tree population in Wadi Ktora, in the southern Arava Valley, Israel. The data is extracted from a single HSR aerial photograph composed of three spectral bands in the visible and infrared spectrum (green, red, and near infrared). A map of individual acacia trees that is extracted from a colour infrared aerial photograph of Wadi Ktora from 2010 enables the examination of spatial distribution patterns for both tree size and foliage health. Tree size distribution is used as an indicator of long-term (decades) hydrologic spatial processes affecting the acacia population. The tree health distribution is used as an indicator for short-term (months to a few years) hydrologic spatial processes, such as the paths of recent flash floods events. Comparing the distributions of tree size and normalized difference vegetation index (NDVI) enables differentiation between the long-term and short-term processes that brought the population to its present state. Using spatial statistic grouping, the distribution of the trees in the wadi (ephemeral stream) is divided into three distinct categories: (1) large trees with high NDVI values, (2) large trees with low NDVI values, and (3) small trees with medium NDVI values. Using the resulting classification, we divided the wadi into three sections, each representing a unique combination of long-and short-term hydrologic processes affecting the acacia trees. We suggest that the lack of spatial correlation between tree size and health status is a result of spatio-temporal changes in the water supply.

ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, 2016

High mortality rates and lack of recruitment in the acacia populations throughout the Negev Deser... more High mortality rates and lack of recruitment in the acacia populations throughout the Negev Desert and the Arava rift valley of Israel have been reported in previous studies. However, it is difficult to determine whether these reports can be evidence to a significant decline trend of the trees populations. This is because of the slow dynamic processes of acaia tree populations and the lack of long term continuous monitoring data. We suggest a new data analysis technique that expands the time scope of the field long term monitoring of trees in arid environments. This will enables us to improve our understanding of the spatial and temporal changes of these populations. <br><br> We implemented two different approaches in order to expand the time scope of the acacia population field survey: (1) individual based tree change detection using Corona satellite images and (2) spatial analysis of trees population, converting spatial data into temporal data. The next step was to int...

Acta Horticulturae, 2005

A model is proposed for the simulation of nutrient solution flow in a Nutrient Film Technique (NF... more A model is proposed for the simulation of nutrient solution flow in a Nutrient Film Technique (NFT) system, and uptake by plants. The system is consisted of a channel with a thin layer of a porous material. The nutrient solution would be applied via dripping emitters, uniformly spaced along the channel, and drain to a reservoir. The solution would then be compensated for water and nutrients' losses, and re-pumped to the irrigation system. The model was tested against N and K uptake by growing lettuce (Lactuca sativa L.) plants. Uptake of the major nutrients and the effects of salinity buildup were simulated and discussed.

Plant Biosystems - An International Journal Dealing with all Aspects of Plant Biology, 2012

ABSTRACT Canopy temperature (Tc) provides an easy-to-acquire indication of crop water deficit tha... more ABSTRACT Canopy temperature (Tc) provides an easy-to-acquire indication of crop water deficit that has been used in irrigation scheduling systems, but interpretation of this measurement has proven difficult. We compared the timing of irrigation application of the Stress Time (ST) method of irrigation scheduling with the Stress Degree Hours (SDH) method on deficit irrigated cotton (Gossypium hirsutum L.) where each irrigation event delivered 5 mm of water through subsurface drip tape. A well-watered (WW) control and a dry land (DL) treatment were also part of the experimental design. We used data collected from the WW and DL treatments to develop upper and lower baselines for the Crop Water Stress Index (CWSI) appropriate for cotton grown at our location. The ST method detected drought stress earlier in the growing season when both the SDH and CWSI indicated very little drought stress. The SDH method resulted in the application of irrigations relatively later in the growing season when the CWSI also detected higher levels of drought stress. These results suggest that the adding certain micrometeorological variables to simple Tc methods of deficit irrigation scheduling may improve the ability to detect and quantify the degree of crop drought stress.