Seasonal Changes in the Photosynthetic Capacity of Winter Rape Plants under Different Nitrogen Regimes Measured in the Field |
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Authors: | L Kappen A Hammler G Schultz |
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Institution: | Lehrstuhl Ökophysiologie, Botanisches Institut der Christian-Albrechts-Universität zu Kiel, Germany |
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Abstract: | Winter rape (cv.'Falcon') grown under different nitrogen regimes (N0, N120; 0 and 120 kg.ha?1, respectively) in northern Germany was investigated over the 1996 spring–summer season. Using a CO2, H2O diffusion porometer, diurnal courses or net photosynthesis and respiration were measured in situ and were related to microclimatic conditions and leaf water relations. Photosynthesis was modelled and daily CO2 gain was calculated. In contrast to the N120 plants, plants of the low nitrogen plot (N0) grew less densely and their leaves behaved more like sun leaves. Increased nitrogen supply had little influence on photosynthetic capacity but it increased productivity through higher leaf area index and an extended period of photosynthetic activity. N120 plants also appeared to be better acclimated to hot, summer conditions. Higher nitrogen supply substantially increased seed production with the yield of the N120 plants being 16% of the N0 plants. |
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Keywords: | Winter rape nitrogen fertilization leaf area index in situ net photosynthesis respiration seasonal course light use efficiency |
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