PROtocols, METHods, Explanations and Updated Standards Wiki (PrometheusWiki, http://www.publish. ... more PROtocols, METHods, Explanations and Updated Standards Wiki (PrometheusWiki, http://www.publish. csiro.au/prometheuswiki/) is a new open access, fully searchable web resource that contains protocols and methods for plant physiology, ecology and environmental sciences. Contributions can be uploaded by anyone in the community, with attributed authorship, and are open for wiki-style comment. This resource allows the gathering in one place of methods, links to published methods and detailed protocols used by leading laboratories around the world, with annotation. As a web resource, PrometheusWiki is continually evolving and updatable, easily and rapidly searchable and highly accessible. It will also enhance communication, allowing multimedia description of protocols and techniques, with spreadsheet tools, slide shows and video files easily integrated into the text. This resource is anticipated to lead to strong benefits in standardising methods, improving access to training for students and professionals, promoting collaborations and expanding the cutting edge of research.
Demographic growth and economic development are putting unprecedented pressure on renewable, but ... more Demographic growth and economic development are putting unprecedented pressure on renewable, but finite water resources, especially in arid regions. By 2025, 1.8 billion people are expected to be living in countries or regions with "absolute" water scarcity (<500 m 3 per year per capita), and two-thirds of the world population will approach "stress" conditions (between 500 and 1000 m 3 per year per capita). Rapidly growing urban areas, climate change and bio-energy demands will amplify the already complex relationship between world development and water demand. In brief, a large quota of the world is facing progressive water scarcity conditions. Today's agriculture uses 70 per cent of all fresh water withdrawals globally, and up to 95 per cent in several developing countries, to meet the present food demand. Therefore, the agricultural sector offers the larger scope for scrutinizing the options to cope with water scarcity. It remains imperative to demand for more efficient and productive water use of farming systems as large amounts of water is consumed by evapotranspiration. To address these aspects, FAO has developed a model, AquaCrop, which simulates attainable yields of the major herbaceous crops in response to water. As compared to other crop models, AquaCrop has a significantly smaller number of parameters and attempts to strike a balance between simplicity, accuracy and robustness. Root zone water content is simulated by keeping track of incoming and outgoing water fluxes at its boundaries, considering the soil as a water storage reservoir with up to 12 layers. Instead of leaf area index, AquaCrop uses canopy ground cover. Canopy expansion, stomatal conductance, canopy senescence and harvest index are the key physiological processes which respond to water stress. Low and high temperature stresses on pollination and biomass production are considered as well. Evapotranspiration is simulated as crop transpiration and soil evaporation and the daily transpiration is used to calculate the daily biomass gain via the normalized biomass water productivity of the crop. The normalization is for atmospheric evaporative demand and carbon dioxide concentration to make the model applicable to diverse locations and seasons, including future climate scenarios. AquaCrop accommodates different water management systems, including rainfed, supplementary, deficit, and full irrigation. Simulations can be carried out both on calendar and thermal time, and future versions, currently under development, will incorporate effects of soil salinity. AquaCrop is mainly aimed at applications at the level of extension services, consulting firms, governmental agencies, NGOs, farmers associations, and farmers. Conceptual and algorithm features of the AquaCrop are illustrated along with some tests and field validation.
Salinity stress tolerance in durum wheat is strongly associated with a plant's ability to con... more Salinity stress tolerance in durum wheat is strongly associated with a plant's ability to control Na(+) delivery to the shoot. Two loci, termed Nax1 and Nax2, were recently identified as being critical for this process and the sodium transporters HKT1;4 and HKT1;5 were identified as the respective candidate genes. These transporters retrieve Na(+) from the xylem, thus limiting the rates of Na(+) transport from the root to the shoot. In this work, we show that the Nax loci also affect activity and expression levels of the SOS1-like Na(+)/H(+) exchanger in both root cortical and stelar tissues. Net Na(+) efflux measured in isolated steles from salt-treated plants, using the non-invasive ion flux measuring MIFE technique, decreased in the sequence: Tamaroi (parental line)>Nax1=Nax2>Nax1:Nax2 lines. This efflux was sensitive to amiloride (a known inhibitor of the Na(+)/H(+) exchanger) and was mirrored by net H(+) flux changes. TdSOS1 relative transcript levels were 6-10-fold l...
In wheat (Triticum aestivum) seedlings subjected to a mild water stress (water potential of -0.3 ... more In wheat (Triticum aestivum) seedlings subjected to a mild water stress (water potential of -0.3 MPa), the leaf-elongation rate was reduced by one-half and the mitotic activity of mesophyll cells was reduced to 42% of well-watered controls within 1 d. There was also a reduction in the length of the zone of mesophyll cell division to within 4 mm from the base compared with 8 mm in control leaves. However, the period of division continued longer in the stressed than in the control leaves, and the final cell number in the stressed leaves reached 85% of controls. Cyclin-dependent protein kinase enzymes that are required in vivo for DNA replication and mitosis were recovered from the meristematic zone of leaves by affinity for p13(suc1). Water stress caused a reduction in H1 histone kinase activity to one-half of the control level, although amounts of the enzyme were unaffected. Reduced activity was correlated with an increased proportion of the 34-kD Cdc2-like kinase (an enzyme sharing ...
Interactions between Rising CO2, Soil Salinity, and Plant Growth Rana Munns, Grant R. Cramer, and... more Interactions between Rising CO2, Soil Salinity, and Plant Growth Rana Munns, Grant R. Cramer, and Marilyn C. Ball I. Introduction Much of the saline land in the world has been caused by human activities: by clearing, overgrazing, or the installation of irrigation schemes. ...
Progress in Plant Nutrition: Plenary Lectures of the XIV International Plant Nutrition Colloquium, 2002
Increased salt tolerance is needed for crops grown in areas at risk of salinisation. This require... more Increased salt tolerance is needed for crops grown in areas at risk of salinisation. This requires new genetic sources of salt tolerance, and more efficient techniques for identifying salt-tolerant germplasm, so that new genes for tolerance can be introduced into crop cultivars. Screening a large number of genotypes for salt tolerance is not easy. Salt tolerance is achieved through the control of salt movement into and through the plant, and salt-specific effects on growth are seen only after long periods of time. Early effects on growth and metabolism are likely due to osmotic effects of the salt, that is to the salt in the soil solution. To avoid the necessity of growing plants for long periods of time to measure biomass or yield, practical selection techniques can be based on physiological traits. We illustrate this with current work on durum wheat, on selection for the trait of sodium exclusion. We have explored a wide range of genetic diversity, identified a new source of sodium exclusion, confirmed that the trait has a high heritability, checked for possible penalties associated with the trait, and are currently developing molecular markers. This illustrates the potential for marker-assisted selection based on sound physiological principles in producing salt-tolerant crop cultivars. * FAX No: 61 2 6246 5399.
Bread wheat (Triticum aestivum L.) has a major salt tolerance locus, Kna1, responsible for the ma... more Bread wheat (Triticum aestivum L.) has a major salt tolerance locus, Kna1, responsible for the maintenance of a high cytosolic K + /Na + ratio in the leaves of salt stressed plants. The Kna1 locus encompasses a large DNA fragment, the distal 14% of chromosome 4DL. Limited recombination has been observed at this locus making it difficult to map genetically and identify the causal gene. Here, we decipher the function of TaHKT1;5-D, a candidate gene underlying the Kna1 locus. Transport studies using the heterologous expression systems Saccharomyces cerevisiae and Xenopus laevis oocytes indicated that TaHKT1;5-D is a Na + -selective transporter. Transient expression in Arabidopsis thaliana mesophyll protoplasts and in situ polymerase chain reaction indicated that TaHKT1;5-D is localised on the plasma membrane in the wheat root stele. RNA interference-induced silencing decreased the expression of TaHKT1;5-D in transgenic bread wheat lines which led to an increase in the Na + concentration in the leaves. This indicates that TaHKT1;5-D retrieves Na + from the xylem vessels in the root and has an important role in restricting the transport of Na + from the root to the leaves in bread wheat. Thus, TaHKT1;5-D confers the essential salinity tolerance mechanism in bread wheat associated with the Kna1 locus via shoot Na + exclusion and is critical in maintaining a high K + /Na + ratio in the leaves. These findings show there is potential to increase the salinity tolerance of bread wheat by manipulation of HKT1;5 genes.
The control of Na(+) and Cl(-) uptake from soils, and the partitioning of these ions within plant... more The control of Na(+) and Cl(-) uptake from soils, and the partitioning of these ions within plants, is an essential component of salinity tolerance. Genetic variation in the ability of roots to exclude Na(+) and Cl(-) from the transpiration stream flowing to the shoot has been associated with salinity tolerance in many species. The maintenance of a high uptake of K(+) is also essential, so measurements of Na(+), K(+) or Cl(-) are frequently used to screen for genetic variation in salinity tolerance. As these ions are not bound covalently to compounds in cells, they can be readily extracted with dilute acid. Na(+) and K(+) can be measured in a dilute nitric acid extract using a flame photometer, by atomic absorption spectrometry or by inductively coupled plasma (ICP)-atomic emission spectrometry. Cl(-) can be measured in the same acid extract with a chloridometer or colorimetrically using a spectrophotometer.
Sodium exclusion from leaves is an important mechanism for salt tolerance in durum wheat. To char... more Sodium exclusion from leaves is an important mechanism for salt tolerance in durum wheat. To characterize possible control points for Na(+) exclusion, quantitative cryo-analytical scanning electron microscopy was used to determine cell-specific ion profiles across roots of two durum wheat genotypes with contrasting rates of Na(+) transport from root to shoot grown in 50 mm NaCl. The Na(+) concentration in Line 149 (low transport genotype) declined across the cortex, being highest in the epidermal and sub-epidermal cells (48 mm) and lowest in the inner cortical cells (22 mm). Na(+) was high in the pericycle (85 mm) and low in the xylem parenchyma (34 mm). The Na(+) profile in Tamaroi (high transport genotype) had a similar trend but with a high concentration (130 mm) in the xylem parenchyma. The K(+) profiles were generally inverse to those of Na(+). Chloride was only detected in the epidermis. These data suggest that the epidermal and cortical cells removed most of the Na(+) and Cl(-) from the transpiration stream before it reached the endodermis, and that the endodermis is not the control point for salt uptake by the plant. The pericycle as well as the xylem parenchyma may be important in the control of net Na(+) loading of the xylem.
Abstract. Phloem sap was collected from petioles of growing and fully expanded leaves of lupins e... more Abstract. Phloem sap was collected from petioles of growing and fully expanded leaves of lupins exposed to 0150 mol m− 3 [NaCl] ext, for various periods of time. Sap bled from growing leaves only after the turgor of the shoot was raised by applying pneumatic ...
The capacity of plants to tolerate high levels of salinity depends on the ability to exclude salt... more The capacity of plants to tolerate high levels of salinity depends on the ability to exclude salt from the shoot, or to tolerate high concentrations of salt in the leaf (tissue tolerance). It is widely held that a major component of tissue tolerance is the capacity to compartmentalize salt into safe storage places such as vacuoles. This mechanism would avoid toxic effects of salt on photosynthesis and other key metabolic processes. To test this, the relationship between photosynthetic capacity and the cellular and subcellular distribution of Na+, K+ and Cl- was studied in salt-sensitive durum wheat (cv. Wollaroi) and salt-tolerant barley (cv. Franklin) seedlings grown in a range of salinity treatments. Photosynthetic capacity parameters (Vcmax, Jmax) of salt-stressed Wollaroi decreased at a lower leaf Na+ concentration than in Franklin. Vacuolar concentrations of Na+, K+ and Cl- in mesophyll and epidermal cells were measured using cryo-scanning electron microscopy (SEM) X-ray microanalysis. In both species, the vacuolar Na+ concentration was similar in mesophyll and epidermal cells, whereas K+ was at higher concentrations in the mesophyll, and Cl- higher in the epidermis. The calculated cytoplasmic Na+ concentration increased to higher concentrations with increasing bulk leaf Na+ concentration in Wollaroi compared to Franklin. Vacuolar K+ concentration was lower in the epidermal cells of Franklin than Wollaroi, resulting in higher cytoplasmic K+ concentrations and a higher K+ : Na+ ratio. This study indicated that the maintenance of photosynthetic capacity (and the resulting greater salt tolerance) at higher leaf Na+ levels of barley compared to durum wheat was associated with the maintenance of higher K+, lower Na+ and the resulting higher K+ : Na+ in the cytoplasm of mesophyll cells of barley.
PROtocols, METHods, Explanations and Updated Standards Wiki (PrometheusWiki, http://www.publish. ... more PROtocols, METHods, Explanations and Updated Standards Wiki (PrometheusWiki, http://www.publish. csiro.au/prometheuswiki/) is a new open access, fully searchable web resource that contains protocols and methods for plant physiology, ecology and environmental sciences. Contributions can be uploaded by anyone in the community, with attributed authorship, and are open for wiki-style comment. This resource allows the gathering in one place of methods, links to published methods and detailed protocols used by leading laboratories around the world, with annotation. As a web resource, PrometheusWiki is continually evolving and updatable, easily and rapidly searchable and highly accessible. It will also enhance communication, allowing multimedia description of protocols and techniques, with spreadsheet tools, slide shows and video files easily integrated into the text. This resource is anticipated to lead to strong benefits in standardising methods, improving access to training for students and professionals, promoting collaborations and expanding the cutting edge of research.
Demographic growth and economic development are putting unprecedented pressure on renewable, but ... more Demographic growth and economic development are putting unprecedented pressure on renewable, but finite water resources, especially in arid regions. By 2025, 1.8 billion people are expected to be living in countries or regions with "absolute" water scarcity (<500 m 3 per year per capita), and two-thirds of the world population will approach "stress" conditions (between 500 and 1000 m 3 per year per capita). Rapidly growing urban areas, climate change and bio-energy demands will amplify the already complex relationship between world development and water demand. In brief, a large quota of the world is facing progressive water scarcity conditions. Today's agriculture uses 70 per cent of all fresh water withdrawals globally, and up to 95 per cent in several developing countries, to meet the present food demand. Therefore, the agricultural sector offers the larger scope for scrutinizing the options to cope with water scarcity. It remains imperative to demand for more efficient and productive water use of farming systems as large amounts of water is consumed by evapotranspiration. To address these aspects, FAO has developed a model, AquaCrop, which simulates attainable yields of the major herbaceous crops in response to water. As compared to other crop models, AquaCrop has a significantly smaller number of parameters and attempts to strike a balance between simplicity, accuracy and robustness. Root zone water content is simulated by keeping track of incoming and outgoing water fluxes at its boundaries, considering the soil as a water storage reservoir with up to 12 layers. Instead of leaf area index, AquaCrop uses canopy ground cover. Canopy expansion, stomatal conductance, canopy senescence and harvest index are the key physiological processes which respond to water stress. Low and high temperature stresses on pollination and biomass production are considered as well. Evapotranspiration is simulated as crop transpiration and soil evaporation and the daily transpiration is used to calculate the daily biomass gain via the normalized biomass water productivity of the crop. The normalization is for atmospheric evaporative demand and carbon dioxide concentration to make the model applicable to diverse locations and seasons, including future climate scenarios. AquaCrop accommodates different water management systems, including rainfed, supplementary, deficit, and full irrigation. Simulations can be carried out both on calendar and thermal time, and future versions, currently under development, will incorporate effects of soil salinity. AquaCrop is mainly aimed at applications at the level of extension services, consulting firms, governmental agencies, NGOs, farmers associations, and farmers. Conceptual and algorithm features of the AquaCrop are illustrated along with some tests and field validation.
Salinity stress tolerance in durum wheat is strongly associated with a plant's ability to con... more Salinity stress tolerance in durum wheat is strongly associated with a plant's ability to control Na(+) delivery to the shoot. Two loci, termed Nax1 and Nax2, were recently identified as being critical for this process and the sodium transporters HKT1;4 and HKT1;5 were identified as the respective candidate genes. These transporters retrieve Na(+) from the xylem, thus limiting the rates of Na(+) transport from the root to the shoot. In this work, we show that the Nax loci also affect activity and expression levels of the SOS1-like Na(+)/H(+) exchanger in both root cortical and stelar tissues. Net Na(+) efflux measured in isolated steles from salt-treated plants, using the non-invasive ion flux measuring MIFE technique, decreased in the sequence: Tamaroi (parental line)>Nax1=Nax2>Nax1:Nax2 lines. This efflux was sensitive to amiloride (a known inhibitor of the Na(+)/H(+) exchanger) and was mirrored by net H(+) flux changes. TdSOS1 relative transcript levels were 6-10-fold l...
In wheat (Triticum aestivum) seedlings subjected to a mild water stress (water potential of -0.3 ... more In wheat (Triticum aestivum) seedlings subjected to a mild water stress (water potential of -0.3 MPa), the leaf-elongation rate was reduced by one-half and the mitotic activity of mesophyll cells was reduced to 42% of well-watered controls within 1 d. There was also a reduction in the length of the zone of mesophyll cell division to within 4 mm from the base compared with 8 mm in control leaves. However, the period of division continued longer in the stressed than in the control leaves, and the final cell number in the stressed leaves reached 85% of controls. Cyclin-dependent protein kinase enzymes that are required in vivo for DNA replication and mitosis were recovered from the meristematic zone of leaves by affinity for p13(suc1). Water stress caused a reduction in H1 histone kinase activity to one-half of the control level, although amounts of the enzyme were unaffected. Reduced activity was correlated with an increased proportion of the 34-kD Cdc2-like kinase (an enzyme sharing ...
Interactions between Rising CO2, Soil Salinity, and Plant Growth Rana Munns, Grant R. Cramer, and... more Interactions between Rising CO2, Soil Salinity, and Plant Growth Rana Munns, Grant R. Cramer, and Marilyn C. Ball I. Introduction Much of the saline land in the world has been caused by human activities: by clearing, overgrazing, or the installation of irrigation schemes. ...
Progress in Plant Nutrition: Plenary Lectures of the XIV International Plant Nutrition Colloquium, 2002
Increased salt tolerance is needed for crops grown in areas at risk of salinisation. This require... more Increased salt tolerance is needed for crops grown in areas at risk of salinisation. This requires new genetic sources of salt tolerance, and more efficient techniques for identifying salt-tolerant germplasm, so that new genes for tolerance can be introduced into crop cultivars. Screening a large number of genotypes for salt tolerance is not easy. Salt tolerance is achieved through the control of salt movement into and through the plant, and salt-specific effects on growth are seen only after long periods of time. Early effects on growth and metabolism are likely due to osmotic effects of the salt, that is to the salt in the soil solution. To avoid the necessity of growing plants for long periods of time to measure biomass or yield, practical selection techniques can be based on physiological traits. We illustrate this with current work on durum wheat, on selection for the trait of sodium exclusion. We have explored a wide range of genetic diversity, identified a new source of sodium exclusion, confirmed that the trait has a high heritability, checked for possible penalties associated with the trait, and are currently developing molecular markers. This illustrates the potential for marker-assisted selection based on sound physiological principles in producing salt-tolerant crop cultivars. * FAX No: 61 2 6246 5399.
Bread wheat (Triticum aestivum L.) has a major salt tolerance locus, Kna1, responsible for the ma... more Bread wheat (Triticum aestivum L.) has a major salt tolerance locus, Kna1, responsible for the maintenance of a high cytosolic K + /Na + ratio in the leaves of salt stressed plants. The Kna1 locus encompasses a large DNA fragment, the distal 14% of chromosome 4DL. Limited recombination has been observed at this locus making it difficult to map genetically and identify the causal gene. Here, we decipher the function of TaHKT1;5-D, a candidate gene underlying the Kna1 locus. Transport studies using the heterologous expression systems Saccharomyces cerevisiae and Xenopus laevis oocytes indicated that TaHKT1;5-D is a Na + -selective transporter. Transient expression in Arabidopsis thaliana mesophyll protoplasts and in situ polymerase chain reaction indicated that TaHKT1;5-D is localised on the plasma membrane in the wheat root stele. RNA interference-induced silencing decreased the expression of TaHKT1;5-D in transgenic bread wheat lines which led to an increase in the Na + concentration in the leaves. This indicates that TaHKT1;5-D retrieves Na + from the xylem vessels in the root and has an important role in restricting the transport of Na + from the root to the leaves in bread wheat. Thus, TaHKT1;5-D confers the essential salinity tolerance mechanism in bread wheat associated with the Kna1 locus via shoot Na + exclusion and is critical in maintaining a high K + /Na + ratio in the leaves. These findings show there is potential to increase the salinity tolerance of bread wheat by manipulation of HKT1;5 genes.
The control of Na(+) and Cl(-) uptake from soils, and the partitioning of these ions within plant... more The control of Na(+) and Cl(-) uptake from soils, and the partitioning of these ions within plants, is an essential component of salinity tolerance. Genetic variation in the ability of roots to exclude Na(+) and Cl(-) from the transpiration stream flowing to the shoot has been associated with salinity tolerance in many species. The maintenance of a high uptake of K(+) is also essential, so measurements of Na(+), K(+) or Cl(-) are frequently used to screen for genetic variation in salinity tolerance. As these ions are not bound covalently to compounds in cells, they can be readily extracted with dilute acid. Na(+) and K(+) can be measured in a dilute nitric acid extract using a flame photometer, by atomic absorption spectrometry or by inductively coupled plasma (ICP)-atomic emission spectrometry. Cl(-) can be measured in the same acid extract with a chloridometer or colorimetrically using a spectrophotometer.
Sodium exclusion from leaves is an important mechanism for salt tolerance in durum wheat. To char... more Sodium exclusion from leaves is an important mechanism for salt tolerance in durum wheat. To characterize possible control points for Na(+) exclusion, quantitative cryo-analytical scanning electron microscopy was used to determine cell-specific ion profiles across roots of two durum wheat genotypes with contrasting rates of Na(+) transport from root to shoot grown in 50 mm NaCl. The Na(+) concentration in Line 149 (low transport genotype) declined across the cortex, being highest in the epidermal and sub-epidermal cells (48 mm) and lowest in the inner cortical cells (22 mm). Na(+) was high in the pericycle (85 mm) and low in the xylem parenchyma (34 mm). The Na(+) profile in Tamaroi (high transport genotype) had a similar trend but with a high concentration (130 mm) in the xylem parenchyma. The K(+) profiles were generally inverse to those of Na(+). Chloride was only detected in the epidermis. These data suggest that the epidermal and cortical cells removed most of the Na(+) and Cl(-) from the transpiration stream before it reached the endodermis, and that the endodermis is not the control point for salt uptake by the plant. The pericycle as well as the xylem parenchyma may be important in the control of net Na(+) loading of the xylem.
Abstract. Phloem sap was collected from petioles of growing and fully expanded leaves of lupins e... more Abstract. Phloem sap was collected from petioles of growing and fully expanded leaves of lupins exposed to 0150 mol m− 3 [NaCl] ext, for various periods of time. Sap bled from growing leaves only after the turgor of the shoot was raised by applying pneumatic ...
The capacity of plants to tolerate high levels of salinity depends on the ability to exclude salt... more The capacity of plants to tolerate high levels of salinity depends on the ability to exclude salt from the shoot, or to tolerate high concentrations of salt in the leaf (tissue tolerance). It is widely held that a major component of tissue tolerance is the capacity to compartmentalize salt into safe storage places such as vacuoles. This mechanism would avoid toxic effects of salt on photosynthesis and other key metabolic processes. To test this, the relationship between photosynthetic capacity and the cellular and subcellular distribution of Na+, K+ and Cl- was studied in salt-sensitive durum wheat (cv. Wollaroi) and salt-tolerant barley (cv. Franklin) seedlings grown in a range of salinity treatments. Photosynthetic capacity parameters (Vcmax, Jmax) of salt-stressed Wollaroi decreased at a lower leaf Na+ concentration than in Franklin. Vacuolar concentrations of Na+, K+ and Cl- in mesophyll and epidermal cells were measured using cryo-scanning electron microscopy (SEM) X-ray microanalysis. In both species, the vacuolar Na+ concentration was similar in mesophyll and epidermal cells, whereas K+ was at higher concentrations in the mesophyll, and Cl- higher in the epidermis. The calculated cytoplasmic Na+ concentration increased to higher concentrations with increasing bulk leaf Na+ concentration in Wollaroi compared to Franklin. Vacuolar K+ concentration was lower in the epidermal cells of Franklin than Wollaroi, resulting in higher cytoplasmic K+ concentrations and a higher K+ : Na+ ratio. This study indicated that the maintenance of photosynthetic capacity (and the resulting greater salt tolerance) at higher leaf Na+ levels of barley compared to durum wheat was associated with the maintenance of higher K+, lower Na+ and the resulting higher K+ : Na+ in the cytoplasm of mesophyll cells of barley.
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