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Crop Science Abstract -

Photosynthesis of Plant Parts of Alfalfa Canopies1


This article in CS

  1. Vol. 11 No. 1, p. 55-58
    Received: July 7, 1970

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  1. D. D. Wolf and
  2. R. E. Blaser2



Radioactive carbon from CO2 assimilated by upper leaves of alfalfa, Medicago sativa L., was not detected later in lower leaves. This suggests that the old leaves in dense canopies (low light intensity) were not parasitic. Net carbon exchange (NCE) and specific leaf weight (SLW) were highest for upper leaves and lowest for bottom leaves. NCE of petioles and stipules contributed 0.6 and 0.9% of total NCE of an alfalfa canopy. The upper steur under normal light conditions was near light compensation, while 8% of the photosynthate from leaves appeared to be respired by the lower stem tissue. The data suggest that models for predicting plant growth may need to include respiration from stems of plants in late growth stages. The data do not support the concept that respiration is a linear function of increased leaf area index.

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