RADISH (RAPHANUS-SATIVUS L) - A MODEL FOR STUDYING PLANT-RESPONSES TOAIR-POLLUTANTS AND OTHER ENVIRONMENTAL STRESSES

The use of Raphanus sativus L. as a model crop for studies on plant re sponse to environmental stresses is reviewed with emphasis on the effe cts of different atmospheric pollutants (O3, SO2, NO2, acidic precipit ation) and their combinations. Responses to temperature, light supply, water stress, and atmospheric CO2 are also studied and discussed. In addition, the references reviewed are evaluated in terms of their expe rimental protocols on growth conditions and recommendations for optima l ranges of environmental and cultural variables, i.e. light, temperat ure, nutrient supply are given. Its distinct pattern of biomass partit ioning, the small dimensions along with short and easy culture make ra dish an excellent experimental plant. The fleshy below-ground storage organ, formed by the hypocotyl and upper radicle, acts as the major si nk during vegetative development. Abundant assimilate supply due to el evated levels of CO2 along with high irradiation frequently promote hy pocotyl growth more than shoot growth, whereas under conditions of str ess shoot growth is maintained at the expense of the hypocotyl. This m akes the hypocotyl:shoot ratio of radish a very sensitive and suitable indicator for various environmental stresses. Potential weaknesses an d short-comings of radish in its role as a model crop, particularly th e high variability of injury and growth responses, are discussed along with possible solutions. Future research needs are derived from the s ummarized results presented and from some disparities among findings w ithin the literature reviewed.