Functional dynamics of the nitrogen balance of sorghum. II. Grain filling period |
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| Authors: | EJ van Oosterom SC Chapman AK Borrell IJ Broad GL Hammer |
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| Institution: | 1. The University of Queensland, School of Land, Crop and Food Sciences, Brisbane, Qld 4072, Australia;2. CSIRO Plant Industry, Queensland Bioscience Precinct, 306 Carmody Road, St Lucia, Qld 4067, Australia;3. Queensland Primary Industries & Fisheries, Department of Employment, Economic Development and Innovation, Hermitage Research Station, 604 Yangan Road, Warwick, Qld 4370, Australia;4. Queensland Primary Industries & Fisheries, Department of Employment, Economic Development and Innovation, 203 Tor Street, Toowoomba, Qld 4350, Australia;1. College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, China;2. CSIRO Agriculture and Food, Queensland Bioscience Precinct, 306 Carmody Road, St Lucia 4067, Australia;3. School of Agriculture and Food Sciences, The University of Queensland, Gatton, QLD 4343, Australia;4. Queensland Alliance for Agriculture and Food Innovation (QAAFI), The University of Queensland, Hermitage Research Facility, Yangan Rd., Warwick, QLD 4370, Australia;5. Queensland Alliance for Agriculture and Food Innovation (QAAFI), The University of Queensland, 203 Tor St., Toowoomba, QLD 4350, Australia;6. China Transport Telecommunications & Information Center, National Engineering Laboratory for Transportation Safety and Emergency Informatics, No. 1, Anwai Waiguan Houshen, Beijing 100011, China;1. The State Key Laboratory of Grassland Agro-ecosystems, Key Laboratory of Grassland Livestock Industry Innovation, Ministry of Agriculture and Rural Affairs, College of Pastoral Agricultural Science and Technology, Lanzhou University, Lanzhou, Gansu, 730020, China;2. Department of Biology, University of Utah, USA;3. The UWA Institute of Agriculture and School of Agriculture and Environment, The University of Western Australia, LB 5005, Perth, WA, 6001, Australia;1. South Australian Research and Development Institute, Waite Campus, Australia;2. Honorary Researcher, INRA Lusignan, France;1. Texas A&M AgriLife Research and Extension, United States;2. USDA-ARS-CPRL, United States;3. Texas A&M University, United States;1. School of Biological Sciences, Monash University, Wellington Rd, Clayton, VIC 3800, Australia;2. Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, NSW 2751, Australia;3. Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, St. Lucia, QLD, 4072, Australia;1. Department of Agriculture, Fisheries and Forestry (DAFF), PO Box 23, Kingaroy, QLD 4610, Australia;2. Queensland Alliance for Innovation in Food and Agriculture, The University of Queensland, PO Box 23, Kingaroy, QLD 4610, Australia |
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| Abstract: | Maintenance of green leaf area during grain filling can increase grain yield of sorghum grown under terminal water limitation. This ‘stay-green’ trait has been related to the nitrogen (N) supply–demand balance during grain filling. This study quantifies the N demand of grain and N translocation rates from leaves and stem and explores effects of genotype and N stress on onset and rate of leaf senescence during the grain filling period. Three hybrids differing in potential height were grown at three levels of N supply under well-watered conditions. Vertical profiles of biomass, leaf area, and N% of leaves, stem and grain were measured at regular intervals. Weekly SPAD chlorophyll readings on main shoot leaves were correlated with observed specific leaf nitrogen (SLN) to derive seasonal patterns of leaf N content. For all hybrids, individual grain N demand was sink determined and was initially met through N translocation from the stem and rachis. Only if this was insufficient did leaf N translocation occur. Maximum N translocation rates from leaves and stem were dependent on their N status. However, the supply of N at canopy scale was also related to the amount of leaf area senescing at any one time. This supply–demand framework for N dynamics explained effects of N stress and genotype on the onset and rate of leaf senescence. |
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