title: Sensitivity of duckweed (Lemna major) to ultraviolet-B radiation.
abstract: The sensitivity of an important aquatic macrophyte, duckweed (Lemna major), to UV-B radiation was studied under experimental conditions at three different doses designated as no, mild, and severe injury dose by observing visible injury symptoms and estimating levels of chlorophyll, pheophytin, carotenoids, protein, starch, free sugar, and peroxidase activity. Laboratory-grown duckweed plants were exposed to UV-B radiation at 0.4 mW/cm(2) intensity for different time periods. Mild and severe injury were developed at 6.48 and 8.64 J, respectively. Peroxidase activity increased at all the exposure levels. Dose-dependent decrease in chlorophyll and starch with drastic depletion in protein and free sugar content were observed. Pheophytin and carotenoids content increased at no injury level, but decreased at higher exposure level. The results indicate that ambient UV-B radiation at the indicated level acts as a physiological stress in Lemna major.
authors.affiliation: Photobiology Laboratory, Industrial Toxicology Research Centre, Lucknow, 226 001, India.
authors.forename: M
authors.initials: M
authors.lastname: Farooq
authors.forename: G
authors.initials: G
authors.lastname: Suresh Babu
authors.forename: R S
authors.initials: RS
authors.lastname: Ray
authors.forename: R B
authors.initials: RB
authors.lastname: Misra
authors.forename: U
authors.initials: U
authors.lastname: Shankar
authors.forename: R K
authors.initials: RK
authors.lastname: Hans
mesh_terms: D002338:Carotenoids / Q000378:metabolism; D002734:Chlorophyll / Q000378:metabolism; D004307:Dose-Response Relationship, Radiation; D019684:Magnoliopsida / Q000201:enzymology / Q000378:metabolism / Q000528:radiation effects*; D018384:Oxidative Stress / Q000528:radiation effects; D010544:Peroxidases / Q000378:metabolism; D010674:Pheophytins / Q000378:metabolism; D010935:Plant Diseases / Q000209:etiology; D010940:Plant Proteins / Q000378:metabolism; D011836:Radiation Tolerance; D013057:Spectrum Analysis; D013213:Starch / Q000378:metabolism; D013997:Time Factors; D014466:Ultraviolet Rays / Q000009:adverse effects*
chemical_list: D010674:Pheophytins; D010940:Plant Proteins; D002734:Chlorophyll; D002338:Carotenoids; D013213:Starch; D010544:Peroxidases