{"id":{"repo_id":"lancaster","oai_identifier":"oai:eprints.lancs.ac.uk:76874"},"canonical_url":"https://search.dev.ndltd.org/etd/lancaster/oai:eprints.lancs.ac.uk:76874","repository":{"repo_id":"lancaster","name":"Lancaster University","base_url":"https://eprints.lancs.ac.uk/cgi/oai2"},"display":{"title":"Effects of deficit irrigation frequency on plant growth, water use and physiology of Pelargonium x hortorum and tomato (Solanum lycopersicum L. cv. Ailsa Craig)","abstract":"In horticultural sectors where water is a threatened resource, altering irrigation frequency may present a viable approach to reduce water use, without any negative effect on crop yield and/or quality. However, our understanding of the physiological impact of this approach in containers in a peat based substrate is limited. Pelargonium x hortorum Bullseye plants were grown in glasshouse conditions under well-watered (WW; daily replacement of 100% of evapotranspiration (ET)), frequent (FDI), or infrequent (IDI) deficit irrigation regimes (50% of ET supplied daily or cumulatively every 4 days, respectively) for four weeks. Both FDI and IDI resulted in short-term increases in water use efficiency, and longer term increases in plant quality (canopy compactness) compared to WW plants. From a physiological perspective, stomatal conductance (gs) decreased similarly under both FDI and IDI, but there were treatment differences in leaf water potential (Ψleaf). FDI resulted in a more positive Ψleaf compared to WW plants, whilst Ψleaf under IDI was typically the lowest. Given the lack of a consistent response for Ψleaf, this suggested another mechanism was regulating stomata in P.hortorum. Under a single drying cycle, different components of the xylem sap were measured. Xylem sap pH, Ca2+ and NO3 - did not change, but the plant hormone abscisic acid (ABA) increased in the xylem sap ([X-ABA]leaf) under both irrigation treatments as soil moisture decreased, and showed a strong relationship with gs both in vivo and in a detached leaf transpiration bioassay. However, when plants were irrigated daily at a percentage of daily ET (adapted from FDI), plants showed an attenuated ABA response compared to when irrigation was withheld (adapted from IDI). It was hypothesised that this may have been a root-derived response due to spatial variation in soil moisture distribution, which was investigated in tomato (Solanum lycopersicum). Similar results were found where gs decreased as [X-ABA]leaf increased, but again the ABA response was attenuated. Furthermore, stomata showed similar sensitivity to ABA under both irrigation treatments. However, similar results were found for root tissue ([ABA]root) and xylem ([X-ABA]root) ABA, and modelling revealed that both localised root water uptake and soil moisture content are important for explaining the variation in [X-ABA]root between irrigation treatments. This research furthers the fundamental understanding of ABA signalling and suggests that irrigation frequency can be altered for a short period of the growing cycle to deliver specific grower objectives.","abstract_html":"In horticultural sectors where water is a threatened resource, altering irrigation frequency may present a viable approach to reduce water use, without any negative effect on crop yield and/or quality. However, our understanding of the physiological impact of this approach in containers in a peat based substrate is limited. Pelargonium x hortorum Bullseye plants were grown in glasshouse conditions under well-watered (WW; daily replacement of 100% of evapotranspiration (ET)), frequent (FDI), or infrequent (IDI) deficit irrigation regimes (50% of ET supplied daily or cumulatively every 4 days, respectively) for four weeks. Both FDI and IDI resulted in short-term increases in water use efficiency, and longer term increases in plant quality (canopy compactness) compared to WW plants. From a physiological perspective, stomatal conductance (gs) decreased similarly under both FDI and IDI, but there were treatment differences in leaf water potential (Ψleaf). FDI resulted in a more positive Ψleaf compared to WW plants, whilst Ψleaf under IDI was typically the lowest. Given the lack of a consistent response for Ψleaf, this suggested another mechanism was regulating stomata in P.hortorum. Under a single drying cycle, different components of the xylem sap were measured. Xylem sap pH, Ca2+ and NO3 - did not change, but the plant hormone abscisic acid (ABA) increased in the xylem sap ([X-ABA]leaf) under both irrigation treatments as soil moisture decreased, and showed a strong relationship with gs both in vivo and in a detached leaf transpiration bioassay. However, when plants were irrigated daily at a percentage of daily ET (adapted from FDI), plants showed an attenuated ABA response compared to when irrigation was withheld (adapted from IDI). It was hypothesised that this may have been a root-derived response due to spatial variation in soil moisture distribution, which was investigated in tomato (Solanum lycopersicum). Similar results were found where gs decreased as [X-ABA]leaf increased, but again the ABA response was attenuated. Furthermore, stomata showed similar sensitivity to ABA under both irrigation treatments. However, similar results were found for root tissue ([ABA]root) and xylem ([X-ABA]root) ABA, and modelling revealed that both localised root water uptake and soil moisture content are important for explaining the variation in [X-ABA]root between irrigation treatments. This research furthers the fundamental understanding of ABA signalling and suggests that irrigation frequency can be altered for a short period of the growing cycle to deliver specific grower objectives.","abstract_has_math":false,"creators":["Boyle, Richard","Dodd, Ian","McAinsh, Martin"],"institution":"Lancaster University","degree_name":"Ph.D.","degree_level":"doctoral","degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2015,"date_issued":"2015","date_published":"2015","updated_at":"2026-07-24T02:48:27Z","subjects":[],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":null,"outbound_label":null,"outbound_source":null},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:creator","label":"Author","values":["Boyle, Richard","Dodd, Ian","McAinsh, Martin"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2015"]},{"key":"dc:date.issued","label":"Date","values":["2015"]},{"key":"dc:publisher.commercial","label":"Dc Publisher Commercial","values":["Lancaster University"]},{"key":"dc:publisher.department","label":"Dc Publisher Department","values":["Lancaster Environment Centre"]},{"key":"dc:publisher.institution","label":"Dc Publisher Institution","values":["Lancaster University"]},{"key":"dc:relation.isreferencedby","label":"Dc Relation Isreferencedby","values":["https://eprints.lancs.ac.uk/id/eprint/76874/"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]},{"key":"dc:type.qualificationlevel","label":"Dc Type Qualificationlevel","values":["doctoral"]},{"key":"dc:type.qualificationname","label":"Dc Type Qualificationname","values":["Ph.D."]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["https://eprints.lancs.ac.uk/id/eprint/76874/1/2015BoylePhD.pdf"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["In horticultural sectors where water is a threatened resource, altering irrigation frequency may present a viable approach to reduce water use, without any negative effect on crop yield and/or quality. However, our understanding of the physiological impact of this approach in containers in a peat based substrate is limited. Pelargonium x hortorum Bullseye plants were grown in glasshouse conditions under well-watered (WW; daily replacement of 100% of evapotranspiration (ET)), frequent (FDI), or infrequent (IDI) deficit irrigation regimes (50% of ET supplied daily or cumulatively every 4 days, respectively) for four weeks. Both FDI and IDI resulted in short-term increases in water use efficiency, and longer term increases in plant quality (canopy compactness) compared to WW plants. From a physiological perspective, stomatal conductance (gs) decreased similarly under both FDI and IDI, but there were treatment differences in leaf water potential (Ψleaf). FDI resulted in a more positive Ψleaf compared to WW plants, whilst Ψleaf under IDI was typically the lowest. Given the lack of a consistent response for Ψleaf, this suggested another mechanism was regulating stomata in P.hortorum. Under a single drying cycle, different components of the xylem sap were measured. Xylem sap pH, Ca2+ and NO3 - did not change, but the plant hormone abscisic acid (ABA) increased in the xylem sap ([X-ABA]leaf) under both irrigation treatments as soil moisture decreased, and showed a strong relationship with gs both in vivo and in a detached leaf transpiration bioassay. However, when plants were irrigated daily at a percentage of daily ET (adapted from FDI), plants showed an attenuated ABA response compared to when irrigation was withheld (adapted from IDI). It was hypothesised that this may have been a root-derived response due to spatial variation in soil moisture distribution, which was investigated in tomato (Solanum lycopersicum). Similar results were found where gs decreased as [X-ABA]leaf increased, but again the ABA response was attenuated. Furthermore, stomata showed similar sensitivity to ABA under both irrigation treatments. However, similar results were found for root tissue ([ABA]root) and xylem ([X-ABA]root) ABA, and modelling revealed that both localised root water uptake and soil moisture content are important for explaining the variation in [X-ABA]root between irrigation treatments. This research furthers the fundamental understanding of ABA signalling and suggests that irrigation frequency can be altered for a short period of the growing cycle to deliver specific grower objectives."]},{"key":"dc:format","label":"Dc Format","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Effects of deficit irrigation frequency on plant growth, water use and physiology of Pelargonium x hortorum and tomato (Solanum lycopersicum L. cv. Ailsa Craig)"]}]}],"canonical_facts":{"dc:creator":["Boyle, Richard","Dodd, Ian","McAinsh, Martin"],"dc:date":["2015"],"dc:date.issued":["2015"],"dc:description.abstract":["In horticultural sectors where water is a threatened resource, altering irrigation frequency may present a viable approach to reduce water use, without any negative effect on crop yield and/or quality. However, our understanding of the physiological impact of this approach in containers in a peat based substrate is limited. Pelargonium x hortorum Bullseye plants were grown in glasshouse conditions under well-watered (WW; daily replacement of 100% of evapotranspiration (ET)), frequent (FDI), or infrequent (IDI) deficit irrigation regimes (50% of ET supplied daily or cumulatively every 4 days, respectively) for four weeks. Both FDI and IDI resulted in short-term increases in water use efficiency, and longer term increases in plant quality (canopy compactness) compared to WW plants. From a physiological perspective, stomatal conductance (gs) decreased similarly under both FDI and IDI, but there were treatment differences in leaf water potential (Ψleaf). FDI resulted in a more positive Ψleaf compared to WW plants, whilst Ψleaf under IDI was typically the lowest. Given the lack of a consistent response for Ψleaf, this suggested another mechanism was regulating stomata in P.hortorum. Under a single drying cycle, different components of the xylem sap were measured. Xylem sap pH, Ca2+ and NO3 - did not change, but the plant hormone abscisic acid (ABA) increased in the xylem sap ([X-ABA]leaf) under both irrigation treatments as soil moisture decreased, and showed a strong relationship with gs both in vivo and in a detached leaf transpiration bioassay. However, when plants were irrigated daily at a percentage of daily ET (adapted from FDI), plants showed an attenuated ABA response compared to when irrigation was withheld (adapted from IDI). It was hypothesised that this may have been a root-derived response due to spatial variation in soil moisture distribution, which was investigated in tomato (Solanum lycopersicum). Similar results were found where gs decreased as [X-ABA]leaf increased, but again the ABA response was attenuated. Furthermore, stomata showed similar sensitivity to ABA under both irrigation treatments. However, similar results were found for root tissue ([ABA]root) and xylem ([X-ABA]root) ABA, and modelling revealed that both localised root water uptake and soil moisture content are important for explaining the variation in [X-ABA]root between irrigation treatments. This research furthers the fundamental understanding of ABA signalling and suggests that irrigation frequency can be altered for a short period of the growing cycle to deliver specific grower objectives."],"dc:format":["application/pdf"],"dc:identifier.uri":["https://eprints.lancs.ac.uk/id/eprint/76874/1/2015BoylePhD.pdf"],"dc:publisher.commercial":["Lancaster University"],"dc:publisher.department":["Lancaster Environment Centre"],"dc:publisher.institution":["Lancaster University"],"dc:relation.isreferencedby":["https://eprints.lancs.ac.uk/id/eprint/76874/"],"dc:title":["Effects of deficit irrigation frequency on plant growth, water use and physiology of Pelargonium x hortorum and tomato (Solanum lycopersicum L. cv. Ailsa Craig)"],"dc:type":["Thesis"],"dc:type.qualificationlevel":["doctoral"],"dc:type.qualificationname":["Ph.D."]},"updated_at":"2026-07-24T02:48:27Z"}