Influence of increased solar UV-B radiation on magnesium deficient cowpea seedlings: Changes in growth and foliar constituents

The influence of increased solar UV-B radiation (UV-B-IS) equivalent to 20% ozone depletion at Madurai (10 degreesN: India) on growth and various foli ar components of Mg-sufficient (Mg, 0.65 mM MgSO4) and Mg-deficient (Mg-d 0 .02 mM MgSO4) cowpea (Vigna unguiculata L. Walp cv. Pusa-152) was examined after 20 days of stress imposition in the field. The combination of Mg-d an d UV-B-IS stimulated stem elongation as compared with either stresses impos ed independently, while such inductive influence was not manifested in leaf growth. Both stresses, when imposed independently or jointly, produced an increase or decrease in photosynthetic and non-photosynthetic pigment level s to various extents. Concentrations of some macro and microelements in sho ot and leaves (both primary and trifoliate) suggest that Mg-d-mediated phys iological nutritional imbalance was minimized when both Mg-d and UV-B-IS we re given simultaneously. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.