THE EFFECT OF POTASSIUM APPLICATION ON LEAF WATER RELATIONS CHARACTERISTICS OF FIELD-GROWN BARLEY PLANTS (HORDEUM-DISTICHUM L)

Leaf water relations characteristics were studied in spring barley fer tilized at low (50 kg ha(-1)) or high (200 kg ha(-1)) levels of potass ium applied as KCI. The leaf water relations characteristics were dete rmined by the pressure volume (PV) technique. Seasonal analysis in ful ly irrigated plants showed that within 2 weeks from leaf emergence the leaf osmotic potential at full turgor (Psi(pi)(100)) decreased from a bout -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. Psi(pi)(100) was 0.05 to 0.10 MPa lo wer in high K than in low K plants. Thus, an ontogenetically determine d accumulation of solutes occurred in the leaves independent of K appl ication. 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 mo dulus of elasticity (epsilon) was increased in high K plants. The main effect of high K application on water relations was an increase in le af water content and a slight decrease in leaf Psi(pi). During drought limited osmotic adjustment and increase in elasticity of the leaf tis sue mediated turgor maintenance. These effects were only slightly modi fied by high potassium application.