Dwarf Pines under UV-B Lamps (IMAGE) University of California - Berkeley Caption UC Berkeley researchers subjected dwarf pines (Pinus mugo) to enhanced UV-B radiation in growth chambers for two months. The irradiated pines not only produced malformed pollen, but they dropped all their seed cones, becoming temporarily sterile. Th experiment suggests that enhanced UV-B at the end of the Permian, caused by ozone depletion from volcanic eruptions, could have contributed to Earth's largest mass extinction. Credit Jeffrey Benca, UC Berkeley Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.