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Tracheids and Vessels Contribute to Xylem Hydraulic Efficiency and Safety of Five California

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Tracheids and Vessels Contribute to Xylem Hydraulic Efficiency and Safety of Five California Copyright By Marta I. Percolla 2019 i Tracheids and vessels contribute to xylem hydraulic efficiency and safety of five California Quercus species (Fagaceae) along an elevation gradient Marta I. Percolla A thesis submitted to the Department of Biology at California State University, Bakersfield in partial fulfilment for the degree of Master of Science in Biology Spring 2019 ii iii Table of Contents ACKNOWLEDGEMENTS ......................................................................................................................................... VI ABSTRACT ............................................................................................................................................................ VII KEYWORDS ......................................................................................................................................................... VIII LIST OF TABLES ..................................................................................................................................................... IX LIST OF FIGURES ..................................................................................................................................................... X CHAPTER 1. INTRODUCTION ................................................................................................................................ 11 TRACHEARY ELEMENTS AND PLANT WATER TRANSPORT ........................................................................................................ 12 TRACHEARY ELEMENT DIAMETER AND RESISTANCE TO WATER-STRESS AND FREEZE-THAW EMBOLISM ............................................ 14 CALIFORNIA OAKS AS A UNIQUE ECOLOGICAL AND ANATOMICAL STUDY SYSTEM ........................................................................ 16 LITERATURE CITED ........................................................................................................................................................ 18 CHAPTER 2. XYLEM STRUCTURE AND FUNCTION OF FIVE OAK (QUERCUS) SPECIES ALONG AN ELEVATION GRADIENT IN THE SOUTHERN SIERRA NEVADA OF CALIFORNIA .......................................................................... 23 ABSTRACT .................................................................................................................................................................. 23 INTRODUCTION ............................................................................................................................................................ 24 MATERIALS AND METHODS ............................................................................................................................................ 27 Study sites and species ....................................................................................................................................... 27 Hydraulic conductivity and vulnerability to embolism ....................................................................................... 29 Tracheid abundance and size ............................................................................................................................. 32 Vessel diameters, lengths, and pit characteristics ............................................................................................. 33 Statistical analyses ............................................................................................................................................. 35 RESULTS ..................................................................................................................................................................... 36 Characteristics of sites along an elevation transect ........................................................................................... 36 Hydraulic conductivity and vulnerability to embolism ....................................................................................... 36 Within species variation in traits ........................................................................................................................ 37 Among species variation in traits ....................................................................................................................... 37 Comparison of data generated using hydraulic, microCT, and SVAI methods ................................................... 38 DISCUSSION ................................................................................................................................................................ 38 Oak species did not display intra-specific variation ........................................................................................... 38 Oak species exhibited inter-specific differences in many traits .......................................................................... 40 Xylem function of vessels and tracheids in oaks ................................................................................................ 41 LITERATURE CITED ........................................................................................................................................................ 46 TABLES AND FIGURES. ................................................................................................................................................... 52 Table 2.1. ............................................................................................................................................................ 52 Table 2.2. ............................................................................................................................................................ 53 Table 2.3. ............................................................................................................................................................ 54 Table 2.4. ............................................................................................................................................................ 55 Table 2.5. ............................................................................................................................................................ 56 Table 2.6. ............................................................................................................................................................ 57 Table 2.7. ............................................................................................................................................................ 58 Table 2.8. ............................................................................................................................................................ 59 Figure 2.1. .......................................................................................................................................................... 60 Figure 2.2. .......................................................................................................................................................... 61 Figure 2.3. .......................................................................................................................................................... 62 Figure 2.4. .......................................................................................................................................................... 63 Figure 2.5. .......................................................................................................................................................... 64 iv Figure 2.6. .......................................................................................................................................................... 65 Figure 2.7. .......................................................................................................................................................... 66 CHAPTER 3. CONCLUSION .................................................................................................................................... 67 LITERATURE CITED ........................................................................................................................................................ 68 v Acknowledgements I would like to acknowledge and thank my MS thesis committee, Dr. Anna L. Jacobsen, Dr. R. Brandon Pratt, and Dr. L. Maynard Moe for their assistance, guidance and encouragement with this project. Aaron Baumgardner, Mitchell Coleman, Jaycie Fickle, Jessica Valdovinos and Viridiana Castro are thanked for their assistance with field and with anatomical measures. Daniela Rodriguez-Zaccaro is thanked for contributing SVAI measures. Additionally, I would also like to extend my appreciation to Helen Holmlund, for her exceptional positivity and encouragement. Finally, NSF CREST HRD-1547784 and NSF CAREER IOS-1252232 are thanked for support. vi Abstract Climate change studies predict that mediterranean-type climate regions around the world will experience more intense and protracted drought events in the coming years, which could have significant effects on the already seasonally drought-stressed plant communities in these regions. Many studies have quantified recent drought-associated plant mortality and dieback, including in plant communities of California. Although the effect of water stress on plant structure and hydraulic function has been studied, the different roles of xylem tracheary element types (i.e., vessels and tracheids) within some woody angiosperms and the contribution of these cells to plant
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