REPEATED EXPOSURE TO ENHANCED UV-B RADIATION IN SUCCESSIVE GENERATIONS INCREASES DEVELOPMENTAL INSTABILITY (LEAF FLUCTUATING ASYMMETRY) IN A DESERT ANNUAL

Populations of the desert annual Dimorphotheca sinuata, derived from a common seed stock, were exposed concurrently over four successive gen erations to either ambient (representing no stratospheric ozone deplet ion) or elevated (representing 20 % stratospheric ozone depletion) UV- B levels during their complete life cycle. Leaf fluctuating asymmetry (FA) was measured in populations of plants grown from seeds of selecte d generations which had experienced different UV-B exposure histories, and from seeds collected from a wild population of this species which grows in a naturally enhanced UV-B environment. These measured plants had been grown in a greenhouse under essentially UV-B-free conditions . Leaf FA was significantly increased by greater numbers of enhanced W -B exposures in the parentage of the seed. There was a linear to expon ential dose-response relationship between number of UV-B exposure iter ations in seed parentage and leaf FA, suggesting that damage to DNA ca used by UV-B exposure during plant development may not be fully repair ed, and thus be inherited by offspring and accumulated over successive generations in this species, Leaf FA of plants grown from seed from t he wild population was not significantly greater than that of control plants whose parentage experienced only ambient UV-B exposures, althou gh this negative result may have been due to low sampling intensity an d measurement resolution, and the relatively low UV-B enhancement expe rienced by the wild population. We conclude that leaf FA may constitut e a relatively sensitive yet inexpensive means of quantifying UV-B dam age to plants.