Leaf Osmotic Potential and Morphological Traits of 43 Cotton Varieties Growing in a Rainfall Gradient from Southwest to Central Texas

Drought tolerance strongly influences the growth, development and production of cotton under both dryland and irrigated systems. With the rapid release of new cotton varieties, up-to-date information on the fundamental relations between leaf morpho-physiological traits and drought tolerance is needed for both cotton farmers and researchers. Leaf osmotic potential has been shown to predict leaf osmotic potential at the turgor loss point (ψπ,TLP) for field plants. This rapid method provides an opportunity for characterizing drought tolerance capacity of crops in large-scale screening programs of crop improvement. Using a VAPRO 5520 vapor pressure osmometer, this study attempts to evaluate drought tolerance capacity of the selected cotton varieties growing in six fields within a rainfall gradient from southwest to central Texas. The annual rainfalls across the field sites vary from 508 mm to 889 mm. Forty-three cotton varieties were planted either under irrigated or dryland management. Of these, 12 varieties are common in at least two locations. Leaf samples were collected twice during the growing season - first bloom and maximum bloom - for determining selected leaf water-relations variables, including osmotic potential at full turgor (ψ_π,0), specific leaf area (SLA, defined as leaf area per unit leaf mass) and leaf dry matter content (LDMC, defined as leaf matter per unit leaf saturate mass). Leaf water relations parameters will be related to the measured cotton yield and fiber quality.