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Response of Basin Wildrye and Tall Wheatgrass Seedlings to Salination¹

Tall wheatgrass [Agropyron elongatum (Host) Beau. ‘Jose’] and basin wildrye (Elymus cinereus Scribn. & Merr. ‘Magnar’) may have high potential for increasing forage production on degraded, saline/alkaline rangelands in the arid west. To compare their tolerance to salinity and decreasing soil osmotic potentials seedlings of each species were grown in salinized sand cultures in the greenhouse with isosmotic solutions of CaCI₂, NaCI, Na₂S0₄, and equimolar CaCI₂ plus NaCl and Na₂S0₄ plus NaCI. Calcium inhibited growth of both cultivars more than the other salts and was especially toxic to basin wildrye seedlings at osmotic pontentials below - 15 bars. Since Na₂S0₄, and NaCl are the predominant salts on Great Basin saline rangelands, Ca toxicity should not be a problem in field plantings, but high tolerance to Na should have adaptive value for both cultivars. Absolute yield of Jose shoots and roots exceeded that of Magnar at all soil osmotic potentials, but salination reduced root growth of Jose more than Magnar and reduced shoot growth of Magnar more than Jose. Even though both cultivars maintained relatively high turgor at low leaf water potentials small initial losses in turgor were associated with greatly reduced growth. Either the threshold turgor necessary for growth of these cultivars was very high under these experimental conditions or ionic imbalances or energy expenditures associated with osmotic adjustment limited growth despite high turgor pressure. Gradually salinized plants maintained positive turgor at average leaf water potentials of 12 bars lower than did control plants in which water stress developed rapidly due to decreasing soil matric potentials when water was withheld. Both species survived soil osmotic potentials down to -35 bars but grew very little below - 10 bars.

Key Words: Leaf water potential • Osmotic adjustment • Turgor • Salinity tolerance • Yield • Ion toxicity • Elymus cinereus (Scribn. & Merr.) • Agropyron elongatu (Host Beau)

² Range scientist, US. Dep. of Agric., Univ. of Nevada, Reno, NV 89512.

Received for publication May 24, 1982.