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Crop Science Abstract -

Net Photosynthesis, Carbon Dioxide Compensation Point, Dark Resperiration, and Ribulose-1,5-bisphosphate Carboxylase Activity in Wheat1


This article in CS

  1. Vol. 26 No. 3, p. 557-563
    Received: Apr 25, 1985

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  1. A. Massachi,
  2. M. T. Giardi,
  3. D. Tricoli and
  4. G. Di Marco2



Net photosynthesis, CO2 compensation point, and ribulose-1,5-bisphosphate carboxylase (RuBPCase) activity were measured in the flag leaves of one hard wheat (Triticum durum Desf.) and one soft wheat (Triticum aestivum L.) from anthesis to an advanced state of senescence. Net photosynthesis was not significantly different in the two cultivars. A linear relation was found between net photosynthesis and RuBPCase attributable to the relatively low enzymatic activity. The slope of the line was found to be similar in the two cultivars, indicating similar carboxylation efficiencies. The CO2 compensation points at 210 mL O2 L−1 air did not differ in the two cultivars while a slight difference was observed between the points measured at 22 mL O2 L−1 air only in mature leaves. The extrapolation of the CO2 compensation points to zero O2 concentration gave positive values indicating that mitochondrial respiration was not completely inhibited by light. Approximate values of this respiration were calculated for the two cultivars, based on a recent model of leaf photosynthesis. Dark respiration, measured as O2 uptake by leaf slices, showed little change through maturation and senescence of the leaves. In mature leaves, this respiration was significantly higher in the soft wheat cultivar, while in senescent leaves, this difference disappeared.

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