UV-B radiation, its effect and defense mecanisms and Terrestrial Plants

FERNANDO E. PRADO, MARIANA ROSA, CAROLINA PRADO, GRISELDA PODAZZA, ROQUE INTERDONATO, JUAN A. GONZÁLEZ AND MIRNA B. HILAL

Environmental Adptations and Stress Tolerance of Plants in the Era of Climatic Changes

Springer

Año: 2011; p. 57 - 84

Abstract  The UV-B is an important component of solar radiation to which all terrestrial and  aquatic plants were exposed during the early evolutionary phase of the Earth. Hence the  plants, principally terrestrial, have evolved different mechanisms to avoid and repair the  UV-B damage; therefore, it is not surprising that photomorphogenic responses to the  solar UV-B are erroneously assumed to be adaptations to the harmful UV radiation. The  responses to UV-B enhancement includes changes in the leaf area, leaf thickness,  stomatal density, wax deposition, stem elongation and branching pattern, as well as in  the synthesis of secondary metabolites, alterations in plant-pathogen and plant-predator  interactions and in gene expression. However, under field conditions the ambient solar  UV-B provides an important signal for the normal plant development and may be  perceived by the plants through nondestructive processes that involving both UV-B  specific and UV-B nonspecific signaling pathways. The specific signaling pathways  include the components UVR8 and COP1 which regulate the expression of a set of genes that are essential for the plants protection. The nonspecific 25 signaling pathways  involve DNA damage, reactive oxygen species (ROS), hormones and wound/defense  signaling molecules. Indeed under the field conditions the ambient UV-B might more  properly be viewed as a photomorphogenic signal than as a stressor. Therefore, it might  not be appropriate to evaluate the adaptive roles of plant responses to UV-B cues upon  stress tolerance by the simultaneous application of both solar radiation and  supplemental UV-B. In this chapter we analyzed the information regarding  physiological and morphogenic responses of the terrestrial plants to the UV-B radiation,  as well as the events related to UV-B perception, signal transduction, gene expression  and ROS formation from different studies carried out in greenhouses, growth chambers  and field conditions.