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This article in AJ

  1. Vol. 71 No. 1, p. 27-31
    Received: July 8, 1977

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Leaf Water Potential and Gaseous Exchange of Wheat and Tomato as Affected by NaCl and P Levels in the Root Medium1

  1. Antonio Cerda,
  2. F. T. Bingham,
  3. G. J. Hoffman and
  4. C. K. Huszar2



The phosphorus nutritional status of some plants has been shown to influence the plant's response to salinity. The objective of this study was to determine if this interaction influenced the plant's water relations, fixation of CO2, and yield. Tomato (Lycopersicon esculentum Mill.) and wheat (Triticum aestivum L.) were grown to maturity in nutrient solution cultures containing low to excessive concentrations of NaCl and P.

Leaf total water potential (Lψt) and its components, osmotic (Lψo) and pressure (Lψp), decreased for both crops as salinity levels increased. Increases in the P concentration tended to increase Lψt and Lψo but decrease Lψp, although the changes were not always consistent. Interactions between salinity and P treatments caused significant differences in Lψt and Lψp for wheat. Statistically significant multiple regression equations were developed for Lψt, Lψo, and Lψp as a function of NaCl and P concentrations for both crops. Plant yields were well-correlated with Lψt and Lψo, indicating that these measurements may provide a good characterization of salt stress.

Measurements of leaf stomatal diffusion resistance to water vapor (rH2O) and carbon dioxide (rCO2) and calculated values of mesophyll resistance (rm) increased significantly as salinity increased for tomato. Although the resistance values for wheat also increased as salinity increased, only the rCO2 measurements rose significantly. The significant increases in rCO2 and rm for tomato with additions of salinity indicate a significant reduction in the rate of photosynthesis. Increasing P values consistently reduced the gaseous resistance levels although the reductions were not always statistically significant. There were no significant interactions between salinity and P treatments for any of these resistance measurements.

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