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Crop Science Abstract -

Late Season Water Stress in Cotton: II. Leaf Gas Exchange and Assimilation Capacity


This article in CS

  1. Vol. 36 No. 4, p. 922-928
    Received: Mar 27, 1995

    * Corresponding author(s): gerik@brcsun0.tamu.edu
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  1. K. L. Faver,
  2. T. J. Gerik ,
  3. P. M. Thaxton and
  4. K. M. El-Zik
  1. Blackland Research Center,, 808 E.Blackland Rd. Temple, TX, 76502
    Dep. of Soil and Crop Sciences, Texas A&M Univ., College Station, TX 77843-2474



Water stress reduces net CO2 assimilation (A) and yield of cotton (Gossypium hirsutum L.), but our knowledge of the physiology, of water stress on A and assimilation capacity is incomplete. Experiments were conducted in a rain shelter-lysimeter facility in 1990 and 1991 to determine if the yields of two short-season cotton cultivars with common ancestry, TAMCOT HQ95 (HQ95) and G&P74 + (GP74), resulted from intrinsic differences in A and assimilation capacity. Water stress was imposed by withholding 0, 50 or 75, and 100% of the depleted soil water after flowering. Results indicated that both stomatal and nonstomatal factors were important in controlling A. HQ95 bad higher A and g than GP74 over leaf water potentials (ΨL) ranging from − 1.0 to − 3.2 MPa. Nonstomatal limitations to A were more important than stomatal factors when ΨL was > − 1.5 MPa. Stomatal factors limited A when ΨL was < − 1.5 MPa for both cultivars. The initial slope (Si) and the maximum A at high ci (Amax)declined with increasing water stress for both cultivars. The Si was greater for HQ95 than GP74 over the range in ΨL and suggest that HQ95 had higher ribulose-l,5-bisphosphate carboxylase-oxygenase activity than GP74. Increasing water stress reduced Amax equally in both cultivars. This suggests that electron transport processes for ribulose-l,5-bisphosphate regeneration of the cultivars did not differ. Therefore, stomatal and nonstomatal CO2 assimilation processes are important in limiting A of water stressed cotton. Intrinsic differences in these processes enable some cotton cultivars to better tolerate water stress.

Contribution of the Texas Agric. Exp. Stn, Texas A&M University System, College Station, TX.

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