<p>Cadmium is a very toxic heavy metal. We studied cadmium-treated barley plants with an especial focus on rare atypical plants with signs of chlorosis. Cadmium treatment decreased the maximal photochemical activities of both photosystems while the activity of photosystem I decreased more than the activity of photosystem II. In photosystem II, cadmium treatment inhibited non-photochemical quenching that increased portion of unquenched “closed” complexes of photosystem II. The latter effect increased the balance of limitations between the acceptor side of photosystem II (qC) and the donor side of photosystem I (Y(ND)) and raised the ratio qC/Y(ND). All these effects were enhanced in the atypical more damaged plants. Cadmium treatment reduced the potassium content in the first leaves; in atypical plants, the potassium content decreased even more. Cadmium treatment changed a pattern of stomatal conductance possibly by means of reducing the potassium content in the leaves. The untreated barley plants maintained different stomatal conductancees at adaxial and abaxial sides of the leaves and exhibited complicated diurnal dynamics with large ups and downs in stomatal conductance. The typical cadmium-treated plants were less flexible and presented medium values. Stomatal conductance in the untreated plants was higher or lower than that in the typical Cd cadmium-treated plants depending on the time; average daytime stomatal conductance was equal in both variants. At 10.00, the stomatal conductance of the atypical cadmium-treated plants was smaller than that of the typical ones. Levels of 13 chloroplast mRNAs remained unchanged, while 1 mRNA decreased in both types of cadmium-treated plants.</p>