Recent Examples on the WebThe biggest seasonal allergy triggers include: Pollen, which can actually be a problem most of the year, is a powdery seed plant substance released into the air. Marygrace Taylor, SELF, 9 Mar. 2022 Whereas Humboldt had recorded an upper limit for seed plants of 4600 meters, Morueta-Holme and her team found pioneers as high as 5185 meters. Tim Appenzeller, Science | AAAS, 11 Sep. 2019 There's also Brian Atkinson, a postdoctoral researcher at the University of Kansas who focuses on seed plants from the Cretaceous period, which is after the Permian. Danny Uhlmann, National Geographic, 16 Mar. 2018