{"id":{"repo_id":"adelaide","oai_identifier":"oai:digital.library.adelaide.edu.au:2440/97381"},"canonical_url":"https://search.dev.ndltd.org/etd/adelaide/oai:digital.library.adelaide.edu.au:2440/97381","repository":{"repo_id":"adelaide","name":"University of Adelaide","base_url":"https://digital.library.adelaide.edu.au/server/oai/request"},"display":{"title":"Nitrate and ammonium interactions in maize.","abstract":"Nitrogen (N) is one of the major mineral nutrients required by a plant for its growth and development. Nitrate (NO₃⁻) and ammonium (NH₄⁺) are the predominant forms of N available to plants in agricultural soils. Plants have the ability to absorb both these forms efficiently from the soil solutions. With soil solution concentrations of NH₄⁺ being much lower (on average 10%) than NO₃⁻, contribution of these small amounts of NH₄⁺ to the overall N budget of crop plants is often overlooked. This research focussed on the contribution of this NH₄⁺ in the nitrogen economy of maize plants. The study also investigated whether NH₄⁺ has any effect on uptake and utilization of other nutrients, and most importantly, NO₃⁻. Growth of maize inbred line B73 was increased when one-third of total nitrogen was supplied as NH₄⁺ with low NO₃⁻, but not for another inbred line Gaspe Flint. Further investigations on B73 found a 20% increase in plant growth when supplied with 10% NH₄⁺ along with sufficient NO₃⁻. Ammonium being a cheaper N source and the low energy and carbon skeleton requirement for its assimilation has contributed in increased shoot dry matter accumulation in these plants. A corresponding increase in total N, total free amino acids and sugars in the leaves of these plants were observed. A positive correlation was seen between transcript levels of putative high affinity NO₃⁻ and NH₄⁺ transporters. This together with an increased activity of N assimilatory enzymes suggested that small amounts of NH₄⁺ can increase the uptake and assimilation of N in these plants. 10% NH₄⁺ in the nutrient solution does not inhibit the NO₃⁻ uptake capacity in plants but when the concentration was increased to 50% there is a reduction in NO₃⁻ uptake capacity for plants growing in low N. This indicates that high concentration of NH₄⁺ limit the absorption of NO₃⁻ which is an important signalling molecule for various metabolic activities in plants. Reduction in NO₃⁻ uptake capacity of plants grown in 10% NH₄⁺ at sufficient N was correlated with higher total free amino acids in the roots, particularly glutamine and asparagine. This reduction in NO₃⁻ uptake capacity when grown in small amounts of NH₄⁺ is a long term effect caused by the products of N assimilation and could be reversed by moving plants to solely NO₃⁻ treatments. Higher concentrations of amino acids in the roots of these plants suggests that NH₄⁺ that enters the root gets first into the assimilatory pathway in the cytosol prior to the assimilation of NH₄⁺ formed by the reduction of NO₃⁻ in the plastids. This study showed that small amounts of NH4 + improve plant growth and lead to major changes in N uptake and assimilation processes. Based on these effects and the fact that plants in the field always have a small amount of N available as NH₄⁺, it is recommended that NH₄⁺ be added to the experimental nutrient solutions with maize and the effect be explored in other major plant species.","abstract_html":"Nitrogen (N) is one of the major mineral nutrients required by a plant for its growth and development. Nitrate (NO₃⁻) and ammonium (NH₄⁺) are the predominant forms of N available to plants in agricultural soils. Plants have the ability to absorb both these forms efficiently from the soil solutions. With soil solution concentrations of NH₄⁺ being much lower (on average 10%) than NO₃⁻, contribution of these small amounts of NH₄⁺ to the overall N budget of crop plants is often overlooked. This research focussed on the contribution of this NH₄⁺ in the nitrogen economy of maize plants. The study also investigated whether NH₄⁺ has any effect on uptake and utilization of other nutrients, and most importantly, NO₃⁻. Growth of maize inbred line B73 was increased when one-third of total nitrogen was supplied as NH₄⁺ with low NO₃⁻, but not for another inbred line Gaspe Flint. Further investigations on B73 found a 20% increase in plant growth when supplied with 10% NH₄⁺ along with sufficient NO₃⁻. Ammonium being a cheaper N source and the low energy and carbon skeleton requirement for its assimilation has contributed in increased shoot dry matter accumulation in these plants. A corresponding increase in total N, total free amino acids and sugars in the leaves of these plants were observed. A positive correlation was seen between transcript levels of putative high affinity NO₃⁻ and NH₄⁺ transporters. This together with an increased activity of N assimilatory enzymes suggested that small amounts of NH₄⁺ can increase the uptake and assimilation of N in these plants. 10% NH₄⁺ in the nutrient solution does not inhibit the NO₃⁻ uptake capacity in plants but when the concentration was increased to 50% there is a reduction in NO₃⁻ uptake capacity for plants growing in low N. This indicates that high concentration of NH₄⁺ limit the absorption of NO₃⁻ which is an important signalling molecule for various metabolic activities in plants. Reduction in NO₃⁻ uptake capacity of plants grown in 10% NH₄⁺ at sufficient N was correlated with higher total free amino acids in the roots, particularly glutamine and asparagine. This reduction in NO₃⁻ uptake capacity when grown in small amounts of NH₄⁺ is a long term effect caused by the products of N assimilation and could be reversed by moving plants to solely NO₃⁻ treatments. Higher concentrations of amino acids in the roots of these plants suggests that NH₄⁺ that enters the root gets first into the assimilatory pathway in the cytosol prior to the assimilation of NH₄⁺ formed by the reduction of NO₃⁻ in the plastids. This study showed that small amounts of NH4 + improve plant growth and lead to major changes in N uptake and assimilation processes. Based on these effects and the fact that plants in the field always have a small amount of N available as NH₄⁺, it is recommended that NH₄⁺ be added to the experimental nutrient solutions with maize and the effect be explored in other major plant species.","abstract_has_math":false,"creators":["George, Jessey"],"institution":null,"degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":["Heuer, Sigrid","Garnett, Trevor Paul","Plett, Darren Craig","Tester, Mark Alfred"],"committee_chairs":[],"committee_members":[],"year":2014,"date_issued":"2014","date_published":"2014","updated_at":"2026-07-24T00:50:56Z","subjects":["nitrate; ammonium; flux capacity; assimilation; glutamine synthetase; nitrate transporter; ammonium transporter"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/2440/97381","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.advisor","label":"Advisor","values":["Heuer, Sigrid","Garnett, Trevor Paul","Plett, Darren Craig","Tester, Mark Alfred"]},{"key":"dc:creator","label":"Author","values":["George, Jessey"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.issued","label":"Date","values":["2014"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["nitrate; ammonium; flux capacity; assimilation; glutamine synthetase; nitrate transporter; ammonium transporter"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["http://hdl.handle.net/2440/97381"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["Nitrogen (N) is one of the major mineral nutrients required by a plant for its growth and development. Nitrate (NO₃⁻) and ammonium (NH₄⁺) are the predominant forms of N available to plants in agricultural soils. Plants have the ability to absorb both these forms efficiently from the soil solutions. With soil solution concentrations of NH₄⁺ being much lower (on average 10%) than NO₃⁻, contribution of these small amounts of NH₄⁺ to the overall N budget of crop plants is often overlooked. This research focussed on the contribution of this NH₄⁺ in the nitrogen economy of maize plants. The study also investigated whether NH₄⁺ has any effect on uptake and utilization of other nutrients, and most importantly, NO₃⁻. Growth of maize inbred line B73 was increased when one-third of total nitrogen was supplied as NH₄⁺ with low NO₃⁻, but not for another inbred line Gaspe Flint. Further investigations on B73 found a 20% increase in plant growth when supplied with 10% NH₄⁺ along with sufficient NO₃⁻. Ammonium being a cheaper N source and the low energy and carbon skeleton requirement for its assimilation has contributed in increased shoot dry matter accumulation in these plants. A corresponding increase in total N, total free amino acids and sugars in the leaves of these plants were observed. A positive correlation was seen between transcript levels of putative high affinity NO₃⁻ and NH₄⁺ transporters. This together with an increased activity of N assimilatory enzymes suggested that small amounts of NH₄⁺ can increase the uptake and assimilation of N in these plants. 10% NH₄⁺ in the nutrient solution does not inhibit the NO₃⁻ uptake capacity in plants but when the concentration was increased to 50% there is a reduction in NO₃⁻ uptake capacity for plants growing in low N. This indicates that high concentration of NH₄⁺ limit the absorption of NO₃⁻ which is an important signalling molecule for various metabolic activities in plants. Reduction in NO₃⁻ uptake capacity of plants grown in 10% NH₄⁺ at sufficient N was correlated with higher total free amino acids in the roots, particularly glutamine and asparagine. This reduction in NO₃⁻ uptake capacity when grown in small amounts of NH₄⁺ is a long term effect caused by the products of N assimilation and could be reversed by moving plants to solely NO₃⁻ treatments. Higher concentrations of amino acids in the roots of these plants suggests that NH₄⁺ that enters the root gets first into the assimilatory pathway in the cytosol prior to the assimilation of NH₄⁺ formed by the reduction of NO₃⁻ in the plastids. This study showed that small amounts of NH4 + improve plant growth and lead to major changes in N uptake and assimilation processes. Based on these effects and the fact that plants in the field always have a small amount of N available as NH₄⁺, it is recommended that NH₄⁺ be added to the experimental nutrient solutions with maize and the effect be explored in other major plant species."]},{"key":"dc:title","label":"Title","values":["Nitrate and ammonium interactions in maize."]}]}],"canonical_facts":{"dc:contributor.advisor":["Heuer, Sigrid","Garnett, Trevor Paul","Plett, Darren Craig","Tester, Mark Alfred"],"dc:creator":["George, Jessey"],"dc:date.issued":["2014"],"dc:description.abstract":["Nitrogen (N) is one of the major mineral nutrients required by a plant for its growth and development. Nitrate (NO₃⁻) and ammonium (NH₄⁺) are the predominant forms of N available to plants in agricultural soils. Plants have the ability to absorb both these forms efficiently from the soil solutions. With soil solution concentrations of NH₄⁺ being much lower (on average 10%) than NO₃⁻, contribution of these small amounts of NH₄⁺ to the overall N budget of crop plants is often overlooked. This research focussed on the contribution of this NH₄⁺ in the nitrogen economy of maize plants. The study also investigated whether NH₄⁺ has any effect on uptake and utilization of other nutrients, and most importantly, NO₃⁻. Growth of maize inbred line B73 was increased when one-third of total nitrogen was supplied as NH₄⁺ with low NO₃⁻, but not for another inbred line Gaspe Flint. Further investigations on B73 found a 20% increase in plant growth when supplied with 10% NH₄⁺ along with sufficient NO₃⁻. Ammonium being a cheaper N source and the low energy and carbon skeleton requirement for its assimilation has contributed in increased shoot dry matter accumulation in these plants. A corresponding increase in total N, total free amino acids and sugars in the leaves of these plants were observed. A positive correlation was seen between transcript levels of putative high affinity NO₃⁻ and NH₄⁺ transporters. This together with an increased activity of N assimilatory enzymes suggested that small amounts of NH₄⁺ can increase the uptake and assimilation of N in these plants. 10% NH₄⁺ in the nutrient solution does not inhibit the NO₃⁻ uptake capacity in plants but when the concentration was increased to 50% there is a reduction in NO₃⁻ uptake capacity for plants growing in low N. This indicates that high concentration of NH₄⁺ limit the absorption of NO₃⁻ which is an important signalling molecule for various metabolic activities in plants. Reduction in NO₃⁻ uptake capacity of plants grown in 10% NH₄⁺ at sufficient N was correlated with higher total free amino acids in the roots, particularly glutamine and asparagine. This reduction in NO₃⁻ uptake capacity when grown in small amounts of NH₄⁺ is a long term effect caused by the products of N assimilation and could be reversed by moving plants to solely NO₃⁻ treatments. Higher concentrations of amino acids in the roots of these plants suggests that NH₄⁺ that enters the root gets first into the assimilatory pathway in the cytosol prior to the assimilation of NH₄⁺ formed by the reduction of NO₃⁻ in the plastids. This study showed that small amounts of NH4 + improve plant growth and lead to major changes in N uptake and assimilation processes. Based on these effects and the fact that plants in the field always have a small amount of N available as NH₄⁺, it is recommended that NH₄⁺ be added to the experimental nutrient solutions with maize and the effect be explored in other major plant species."],"dc:identifier.uri":["http://hdl.handle.net/2440/97381"],"dc:subject":["nitrate; ammonium; flux capacity; assimilation; glutamine synthetase; nitrate transporter; ammonium transporter"],"dc:title":["Nitrate and ammonium interactions in maize."],"dc:type":["Thesis"]},"updated_at":"2026-07-24T00:50:56Z"}