The effects of Enhanced Ultraviolet-B Radiation and Heavy Metal Cadmium on Some Physiological Parameters of Lettuce (Lactuca sativa)

Global stratospheric ozone depletion is elevating surface ultraviolet-B (UV-B) levels. Increase in UV-B levels can alter crop productivity as it affects photosystem II, pigments, and growth regulators. Cadmium is a potentially toxic heavy metal that hampers plant productivity by interfering with their photochemistry and physiological processes of plants. The changes in gas exchange and pigment contents in lettuce seedlings (Lactucca sativa) exposed to an 8.2 kJ m-2 day-1 biologically effective UV-B radiation (UV-B, 280-315 nm) and 40 μmol Cd2 (as Cd3O12S3*8H2O) either alone or in combination were investigated under greenhouse conditions. Compared to the control, photosynthesis rates (PN), stomatal conductance (Gs), transpiration rate (E) and content of photosynthetic pigments decreased significantly (P