Water Relations and Growth of Cotton as Influenced by Salinity and Relative Humidity1
- G. J. Hoffman2,
- S. L. Rawlins2,
- M. J. Garber3 and
- E. M. Cullen2
Soil salinity and atmospheric relative humidity influence plant growth, but few data are available showing the interaction between them. This interaction was studied with cotton (Gossypium hirsutum) in four sunlit climate chambers at temperatures cycling daily between 38 and 26 C. Relative humidity was controlled at 25, 40, 65, and 90%. The root medium was maintained at osmotic potentials of −0.4, −5, −10, and −15 bars.
Relative humidity significantly affected shoot growth only in the 90% relative humidity treatment, where growth was increased about 40%. The shoot-to-root ratio at high humidities was at least double the ratio at low humidities. The 50% yield decrement based on leaf area or plant dry weight occurred at an osmotic potential of −5 bars. Because the anthers of the cotton flowers in the 25 and 90% relative humidity treatments did not dehisce, seed cotton yields at these relative humidities were essentially zero. Seed cotton yields per plant at 40 and 65% relative humidities were comparable to or greater than field yields.
Transpiration per unit leaf area for the entire experiment increased an average of 80% for all salinity levels as the relative humidity decreased from 90 to 25% and decreased slightly with increasing salinity in all humidity treatments. Transpiration per unit leaf area decreased as the plants matured and tended to approach the same value for all treatments near the end of the experiment.
The relative yield of dry matter and leaf area as a function of salinity was the same at all relative humidities, indicating that no interaction between salinity and relative humidity occurred.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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