................................................................................................................................ 5 Introduction ........................................................................................................................... 6 Traits and Evolution of Species ............................................................................................... 6 Defense responses in plants—Hypersensitive Response and Systemic Acquired Resistance ............... 7 The Abiotic Stress Regulatory Hormone ABA .................................................................................... 9 Thesis Research and Hypotheses .................................................................................................... 12 Materials and Methods ......................................................................................................... 13 Plant Maintenance and Preparation ............................................................................................... 13 ABA Treatment of Moss Samples .................................................................................................... 13 NaCl Addition to Media for Salt Stress Exposure ............................................................................. 14 Chlorophyll Content Analysis .......................................................................................................... 14 Results and Discussion .......................................................................................................... 15 Physcomitrella patens exhibits better desiccation tolerance than Mnium cuspidatum .................... 15 Conclusion ............................................................................................................................. 22 Literature Cited ..................................................................................................................... 24