title: Effects of ultraviolet-B radiation on cotton (Gossypium hirsutum L.) morphology and anatomy.
abstract: Cotton (Gossypium hirsutum L.) crop, cultivated between 40 degrees N and 40 degrees S, is currently experiencing 2-11 kJ m-2 d-1 of UV-B radiation. This is predicted to increase in the near future. An experiment was conducted to study the effect of enhanced UV-B radiation on vegetative and reproductive morphology and leaf anatomy of cotton in sunlit, controlled environment chambers. From emergence to harvest, cotton plants were exposed to 0, 8 or 16 kJ m-2 d-1 of UV-B in a square wave approach for 8 h from 0800 to 1600 h. Changes in plant height, internode and branch length, mainstem node number, leaf area, length and area of petals and bracts, and anther number per flower were recorded. Epidermal cell and stomatal density, stomatal index, leaf thickness, and epidermal, palisade and mesophyll tissue thickness were also measured. Initial chlorotic symptoms on leaves turned into necrotic patches on continued exposure to enhanced UV-B. Exposure to high UV-B reduced both vegetative and reproductive parameters and resulted in a smaller canopy indicating sensitivity of cotton to UV-B radiation. Enhanced UV-B radiation increased epicuticular wax content on adaxial leaf surfaces, and stomatal index on both adaxial and abaxial leaf surfaces. Leaf thickness was reduced following exposure to UV-B owing to a decrease in thickness of both the palisade and mesophyll tissue, while the epidermal thickness remained unchanged. The vegetative parameters studied were affected only by high levels of UV-B (16 kJ m-2 d-1), whereas the reproductive parameters were reduced at both ambient (8 kJ m-2 d-1) and high UV-B levels. The study shows that cotton plants are sensitive to UV-B at both the whole plant and anatomical level.
authors.affiliation: Department of Plant and Soil Sciences, Box 9555, Mississippi State University, Mississippi State, MS 39762, USA. vgk3@ra.msstate.edu
authors.forename: V G
authors.initials: VG
authors.lastname: Kakani
authors.forename: K R
authors.initials: KR
authors.lastname: Reddy
authors.forename: D
authors.initials: D
authors.lastname: Zhao
authors.forename: A R
authors.initials: AR
authors.lastname: Mohammed
mesh_terms: D017209:Apoptosis / Q000502:physiology / Q000528:radiation effects; D035264:Flowers / Q000033:anatomy & histology / Q000254:growth & development* / Q000528:radiation effects; D003368:Gossypium / Q000033:anatomy & histology / Q000254:growth & development* / Q000528:radiation effects; D008855:Microscopy, Electron, Scanning; D009336:Necrosis; D019441:Plant Epidermis / Q000528:radiation effects / Q000648:ultrastructure; D018515:Plant Leaves / Q000502:physiology / Q000528:radiation effects; D012098:Reproduction / Q000502:physiology / Q000528:radiation effects; D014466:Ultraviolet Rays; D014885:Waxes / Q000378:metabolism / Q000528:radiation effects
chemical_list: D014885:Waxes