Psychrometric Analysis of Turgor Pressure Response: A Possible Technique for Evaluating Plant Water Strees Resistance1

Abstract

Turgor pressure responses were determined over a range of water stress for Zea mays L., Bromus inermis Leyss., and the following colchicine‐induced Agropyron amphiploid hybrids: A. dasystachyum (Hook.) Scribn. ✕ Acaninum (L.) Beauv., A. spicatum (Pursh) Scribn. & Smith ✕ A. dasystachyum, and A. fibrosum (Schrenk) Nevski ✕ A. trachycaulum (Link) Malte ex H. F. Lewis. These plants were grown in a greenhouse and then allowed to acclimate to a growth chamber for 10 days before turgor pressure was determined. Water potential components of detached leaf samples were measured by a psychrometric technique involving freezing and thawing of the leaf tissue. Water was withheld from the potted plants to determine turgor pressure over a range of water stress levels. Linear regressions of turgor pressure on leaf water potential were statistically significant for all comparisons of regression intercepts. Slope comparisons of Bromus inermis and Zea mays with A. dasystachyum ✕ A. caninum and A. spicatum ✕ A. dasystachyum were also statistically different. Predictions of resistance to water stress based on species ability to maintain positive turgor agreed closely with field observations. The ability of this technique to distinguish differences in turgor response between Agropyron hybrids with a common parent suggests that this technique may be useful for screening plant materials for superior resistance to water stress.