Whole-plant transpiration in Populus sp.: its determination, nocturnal effects and influence by form of nitrogen

  • Author / Creator
    Cirelli, Damián
  • Water is a crucial factor in the life of land plants. Transpiration (E) is inevitable and it is viewed as the universal cost of accessing a CO2-rich atmosphere. Although we now know that plants lose water at night, it had been assumed that stomata remained closed after dark. Renewed interest has encouraged more research on night-time E. An overlooked challenge in this area is that of measuring water loss. Most of the current research relies on leaf-level measurements using gas analysers. This presents many complications and although the instruments are simple to operate, it is not a trivial task to measure E properly, especially at night. I present a system that includes instructions to build the hardware platform and the software package, which utilises balances to measure E simultaneously and continuously from multiple specimens. The system is particularly suited to measuring nocturnal E of whole plants since it requires minimal interaction and it is not intrusive for the plant. With this system, a survey of whole-plant nocturnal E was carried out on four species of Populus with a range of habitat preference from riparian to upland. This survey characterises night-time water loss in relation to habitat, showing that Populus from drier environments may curtail night-time E more readily than riparian species. The survey also investigates the effect of drought on nocturnal E, arguing that night-time sap flow may be associated with one or more physiological functions. Lastly, the effect of two forms of N (NO3- and NH4+) on whole-plant conductance is analysed in two hybrid poplars with different growth potentials. NH4+ is shown to depress day-time, but not night-time conductance in comparison with NO3-; likely due to a change in stomatal function. Root anatomy was radically changed in a species-dependent manner when grown under different N forms. Some of these changes reflect different metabolic needs associated with each N form, while others may have a direct bearing on plant hydraulics.

  • Subjects / Keywords
  • Graduation date
    Fall 2014
  • Type of Item
  • Degree
    Doctor of Philosophy
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.