Grain Growth of Tall and Short Spring Wheat Genotypes at Different Assimilate Supplies
- M. Winzeler,
- Ph. Monteil and
- J. Nösberger *
The degree to which grain growth of wheat (Triticum aestivum L.) is influenced by environmental factors differs among genotypes. Two growth chamber experiments investigated the influence of assimilate supply on grain size in spring wheats. In Exp. 1 with two tall and two short genotypes, assimilate production of single plants was varied after anthesis by CO2 concentrations (1000 and 200 μL CO2 L−1) and by removing 56% of the flag leaf. Treatments had a greater effect on final grain size in the short than in the tall genotypes (range 30.4-47.2 and 37.8-42.4 mg/grain, respectively). Under high CO2, photosynthates accumulated as total nonstructural carbohydrates (TNC) in the stems of tall genotypes, indicating that the supply exceeded the demand of the growing grains. Experiment 2 tested the hypothesis that restricted grain growth in tall genotypes is due to a lack of assimilates, either during the last stages of floret development or the early stages of grain growth, resulting from sink competition of stem growth. The CO2 level varied during the 15 d preceding anthesis and the first 20 d after anthesis (1000 and 200 μL CO2 L−1). In plants grown at 1000 μL CO2 L−1 thereafter, the assimilate supply during floret development or early grain growth had no significant influence on final grain size. The TNC accumulated in the stem up to maturity, suggesting that grain growth was restricted by factors other than assimilates. It is concluded that the ability to increase grain weight under a high assimilate supply differs between spring wheat genotypes. In short genotypes, grain growth was less restricted as compared with the tall genotypes. Grain growth in tall genotypes was not limited by lack of assimilates during floret development or early grain growth.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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