Biology ETDs

Publication Date

Fall 11-14-2022


Measurements of plant water potential provide fundamental insights into how plants are interacting with the environment to manage water needs. However, monitoring water potential is difficult, time consuming, and frequently destructive. Several methods have been in development that attempt to monitor the water status of plant tissues in a simple, continuous, and non-destructive manner. One of these methods, electrical impedance spectroscopy (EIS), is emerging as a particularly promising tool that has several applications in plant biology. I used a new microneedle system that applies small electrodes to a range of tissues. By utilizing this tool in conjunction with a standard pressure chamber, I sought to understand the relationship between leaf water potential (Ψl) and leaf impedance (Z), on the plant species Vitis vinifera and Helianthus annuus in laboratory, greenhouse, and field conditions. I hypothesized that impedance would track water potential continuously without interference from temperature and other environmental factors. Because existing sensors that can continuously monitor leaf water potential are unreliable, we paired measurements of impedance to destructive, instantaneous point measurements of water potentials to assess functionality of our microneedle system. Linear regression analysis of Ψl versus Z point measurements at 0.1, 1.0, and 100 kHz revealed a weak correlation between Ψl and both Zpetiole and Zlamina due to variability of impedance data collected from instantaneous point measurements. Continuous measurements of impedance from a single attachment point were much less variable through time and could be used to track diurnal patterns in impedance in a range of tissues and species for weeks at a time. Short term measurements of leaf relative water content (RWC) and impedance while drying detached leaves showed a strong correlation between RWC and Ψl, that suggests continuous monitoring of RWC would be a better tool for correlating continuous impedance data with Ψl in these species. In addition, diurnal impedance data indicate there are other factors that can contribute to impedance values and these need to be characterized further for this method to be used effectively to assess diurnal water potential changes.




water potential, Electrical impedance spectroscopy

Document Type


Degree Name


Level of Degree


Department Name

UNM Biology Department

First Committee Member (Chair)

David Hanson

Second Committee Member

William Pockman

Third Committee Member

William Giese Jr

Included in

Biology Commons