The components of lucerne (Medicago sativa) leaf area index respond to temperature and photoperiod in a temperate environment |
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| Institution: | 1. Key Laboratory of Desert and Desertification, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou, Gansu Province, 730000, China;2. Institute of Geography, University of Erlangen-Nürnberg, Kochstrasse 4-4, Erlangen, 91054, Germany;3. Sidalong Protection Station of Qilian Mountain Nature Resever, Zhangye, Guansu Province, China;1. Faculty of Agriculture and Life Science, University of Maribor, SI, Slovenia;2. Horticulture and Product Physiology, Wageningen University, NL, Netherlands;1. NSW Department of Primary Industries, Fisheries Conservation Technology Unit, PO Box 4321, Coffs Harbour, NSW 2450, Australia;2. Marine and Estuarine Ecology Unit, School of Biological Sciences, University of Queensland, Brisbane, QLD 4072, Australia;3. Sterling Trawl Gear Services, 187 Ernest St., Manly, QLD 4179, Australia;4. Department of Statistics, The University of Auckland, Private Bag 92019, Auckland, New Zealand;1. Programa de Pós-Graduação em Genética e Biologia Molecular, Departamento de Genética, Instituto de Biociências, Universidade Federal do Rio Grande do Sul (UFRGS), 91501-970, Porto Alegre, RS, Brazil;2. Programa de Pós-Graduação em Biologia Celular e Molecular, Centro de Biotecnologia, UFRGS, 91501-970, Porto Alegre, RS, Brazil;3. Instituto do Cérebro, Pontifícia Universidade do Rio Grande do Sul (PUCRS), Av. Ipiranga 6690, 90610-000, Porto Alegre, Brazil;1. School of Environment, The University of Auckland, Auckland, New Zealand;2. University College London, Institute of Archaeology, London, UK;3. Oxford Dendrochronology Laboratory, Oxford, UK |
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| Abstract: | Irrigated crops of ‘Grasslands Kaituna’ lucerne were grown for 5 years in a temperate climate at Lincoln University, Canterbury, New Zealand (43°38′S, 172°28′E). From these the response of the components of leaf area index (LAI) to environmental factors was determined. A broken stick temperature threshold with a base temperature (Tb) of 1 °C at air temperatures (Ta) <15 °C and a Tb = 5 °C for Ta ≥ 15 was required to accumulate thermal time (Tt). Using this, the appearance of nodes on the main-stem (phyllochron) was constant in Tt within a re-growth cycle (30–42 days). The phyllochron was 37 ± 7 °Cd but declined from 60 to 37 °Cd as photoperiod decreased from 15.7 to 11.4 h. Branching began at the appearance of the fifth main-stem node with 2.5 secondary nodes produced per main-stem node in spring re-growth cycles but only 1.7 produced in summer. Leaf senescence increased from 0.3 to 1.08 leaves per main-stem node after the appearance of the ninth node. Spring re-growth cycles had a mean individual leaf area of 170 mm2 compared with 400 mm2 for summer re-growth cycles. These results demonstrate systematic variation in LAI components and suggest they need to be considered separately in response to environmental factors to provide a quantitative framework for crop simulation analyses of lucerne canopy development. |
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