The effect of potassium application on leaf water relations characteristics of field grown barley plants (Hordeum distichum L.)

Abstract

Leaf water relations characteristics were studied in spring barley fertilized at low (50 kg ha^-1) or high (200 kg ha^-1) levels of potassium applied as KCl. The leaf water relations characteristics were determined by the pressure volume (PV) technique.

Seasonal analysis in fully irrigated plants showed that within 2 weeks from leaf emergence the leaf osmotic potential at full turgor (Ψ_π ¹⁰⁰) decreased from about −0.9 to −1.6 MPa in leaf No 7 (counting the first leaf to emerge as number one) and from about −1.1 to −1.9 MPa in leaf No 8 (the flag leaf) due to solute accumulation. Ψ_π ¹⁰⁰ was 0.05 to 0.10 MPa lower in high K than in low K plants. Thus, an ontogenetically determined accumulation of solutes occurred in the leaves independent of K application. The ratio of leaf weight at full turgor to dry weight (TW/DW) decreased from about 5.5 in leaf No 6 to 4.5 in leaf No 7 and 3.8 in leaf No. 8. The TW/DW ratio was 4 to 10% higher in high K than in low K plants indicating larger leaf cell size in the former. The tissue modulus of elasticity (∈) was increased in high K plants. The main effect of high K application on water relations was an increase in leaf water content and a slight decrease in leaf Ψ_π

During drought limited osmotic adjustment and increase in elasticity of the leaf tissue mediated turgor maintenance. These effects were only slightly modified by high potassium application.