The utilization of pre-anthesis reserves in grain filling of wheat. Assessment by steady-state 13CO2/12CO2 labelling |
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Authors: | T Gebbing H Schnyder & W KÜhbauch |
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Institution: | Chair of Grassland Science, Technische Universität München, D-85350 Freising-Weihenstephan and,;Institut für Pflanzenbau, Universität Bonn, D-53115 Bonn, Germany |
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Abstract: | δ, C isotope composition relative to Pee Dee BelemniteWSC, water-soluble carbohydratesN, nitrogenC, carboncv, cultivarME, efficiency of mobilized pre-anthesis C utilization in grain filling (g C g–1C)Significant mobilization of protein and carbohydrates in vegetative plant parts of wheat regularly occurs during grain filling. While this suggests a contribution of reserves to grain filling, the actual efficiency of mobilized assimilate conversion into grain mass (ME) is unknown. In the present study the contribution of pre-anthesis C (C fixed prior to anthesis) to grain filling in main stem ears of two spring wheat (Triticum aestivum L.) cultivars was determined by 13C/12C steady-state labelling. Mobilization of pre-anthesis C in vegetative plant parts between anthesis and maturity, and the contributions of water-soluble carbohydrates (WSC) and protein to pre-anthesis C mobilization were also assessed. Experiments were performed with two levels of N fertilizer supply in each of 2 years. Pre-anthesis reserves contributed 11–29% to the total mass of C in grains at maturity. Pre-anthesis C accumulation in grains was dependent on both the mass of pre-anthesis C mobilized in above-ground vegetative plant parts (r2 = 0·87) and ME (defined as g pre-anthesis C deposited in grains per g pre-anthesis C mobilized in above-ground vegetative plant parts; r2 = 0·40). ME varied between 0·48 and 0·75. The effects of years, N fertilizer treatments and cultivars on ME were all related to differences in the fractional contribution of WSC to pre-anthesis C mobilization. Multiple regression analysis indicated that C from mobilized pre-anthesis WSC may be used more efficiently in grain filling than C present in proteins at anthesis and mobilized during grain filling. Possible causes for variability of ME are discussed. |
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Keywords: | Triticum aestivum L carbohydrates carbon carbon isotopes efficiency grain filling mobilization nitrogen protein reserves wheat |
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