Arsic, Maja2025-12-172025-12-172022https://hdl.handle.net/11541.2/290691 ethesis (ix, 130 pages) :colour illustrations.Includes bibliographical references (pages 129-130)Foliar-applied phosphorus could more sustainably meet plant nutrient needs. This thesis developed bioimaging techniques to visualize foliar-applied phosphorus (P) absorption pathways and translocation in barley. LA-ICP-MS scans confirmed that vanadate was an appropriate P tracer. Fiber cells and trichomes were key P entry points, however radioisotopes showed trichome density was not related to quantitative absorption differences in four barley cultivars. A non-photochemical quenching assay was developed as a proxy for leaf P status. Foliar-applied P restored functionality in P-deficient spring barley plants within 24 hours, although P-deficiency returned within a week due to translocation. The methods also revealed that foliar-applied manganese (Mn) was more effective at restoring nutrient functionality in Mn-deficient plants than P applications in P-deficient plants.enphosphorus;plant nutrition;foliar fertiliser;LA-ICP-MSBarleyPhosphorus in agriculture.Plantsthesis