Table 2 Advantages and inconveniences of methods, alternative to portable MRI, used to measure water content, plant structure, xylem and phloem fluxes, and cavitation
Parameter measured | Method | Advantages | Disadvantages |
|---|---|---|---|
Anatomy | Microscopy | Affordable; easy to perform; high spatial resolution (from a few hundredths of a nanometer for electronic to a couple of tenths of a micrometer for optic) | Destructive; Limited to laboratory; only a small portion of sample can be observed at once |
X-ray (µ)radiography | High spatial (~ 50–100 μm) and temporal (~ tens of seconds per scan) resolution; non-invasive | Limited to laboratory; possible impact of ionizing radiation; expensive; not easily accessible | |
Neutron radiography | High spatial (~ 100 μm) and temporal (~ tens of seconds per scan) resolution; non-invasive; adapted to dense materials | Limited to laboratory; expensive; not easily accessible; possible impact of neutron radiation on plant tissue; limited to plants that fit in a thin container | |
Dye tracing | Affordable; easy to perform; portable | Destructive | |
Air-coupled ultrasound | Non-invasive; high temporal resolution (a few seconds per scan); easy to perform; affordable; portable | Indirect; large variation in results | |
Laser-based guided waves | High temporal resolution (~ a few seconds per scan); easy to perform; portable | Indirect; large variation in results; laser beam can cause tissue damage | |
High-field MRI | Non-invasive; high spatial (~ 100 μm) and temporal (from a few minutes to a few hours depending upon the experiment) resolution | Limited to laboratory; expensive equipment and maintenance; not easily accessible; mainly horizontal orientation; limited plant size and shape | |
Water content | Fresh weight/Dry weight | Affordable; Easy to perform | Limited to laboratory; Destructive; time consuming (overnight drying required) |
NIRS | Non-invasive; portable; affordable; easy to perform | Indirect, results must be interpreted through models (problem of genericity); calibration particularities for a given species and/or context; limited to outermost layers of sample | |
THz spectroscopy | Non-invasive; easy to perform; affordable; portable | Indirect; results must be interpreted through models; limited to outermost layers of sample | |
High-field MRI | Non-invasive; high spatial (~ 100 μm) and temporal (from a few minutes to a few hours depending upon the experiment) resolution | Limited to laboratory; expensive equipment and maintenance; not easily accessible; mainly horizontal orientation; limited plant size and shape | |
Xylem flux | Sap flow meters | Portable; affordable; easy to perform | Invasive; limited to organs with sufficient diameter |
Porometers | Portable; affordable; easy to perform | Indirect, large margin of error in estimating sap flow due to variation between leaves | |
2D light transmission | Non-invasive; affordable; spatial resolution (~ 200–500 μm), offers real-time data on water uptake by roots | Indirect, limited to laboratory; limited to certain plants that fit in a thin container and sandy soil; no other light sources than the instrument during measurement | |
Gravimetric | Affordable; portable; easy to perform; non-invasive | Indirect | |
Isotopic tracing | Portable | Destructive; results must be interpreted through models; can be expensive (cost of radiotracers and mass spectroscopy analyses) | |
Dye tracing | Affordable; easy to perform; portable | Destructive | |
High-field MRI | Non-invasive; high spatial (~ 100 μm) and temporal (from a few minutes to a few hours depending upon the experiment) resolution | Limited to laboratory; expensive equipment and maintenance; not easily accessible; mainly horizontal orientation; limited plant size and shape | |
Phloem flux | Aphids | Affordable | Limited to laboratory; Indirect, limited to certain plant species; approximative with large margin of error; can be complicated to execute |
11C PET imaging | Non-invasive; sufficient spatial resolution to capture water dynamics (a couple of millimeters) and high temporal (a few minutes) resolution | Limited to laboratory; expensive and cumbersome equipment; possible impact of ionizing radiation | |
High-field MRI | Non-invasive, high spatial (~ 100 μm) and temporal (from a few minutes to a few hours depending upon the experiment) resolution | Limited to laboratory; expensive equipment and maintenance; not easily accessible; mainly horizontal orientation; limited plant size and shape | |
Cavitation | Acoustic emissions | Portable; easy to perform; affordable | Indirect, more qualitative than quantitative, can be destructive |
Dye tracing | Affordable; easy to perform; portable | Destructive | |
Xylem Embolism Meter | Affordable; easy to perform | Indirect, Destructive; limited to laboratory; not suitable for very small (fine roots) or large samples (> 10 cm diameter) | |
Microscopy | Affordable; easy to perform; high spatial resolution (from a few hundredths of a nanometer for electronic to a couple of tenths of a micrometer for optic) | Destructive; Limited to laboratory; only a small portion of sample can be observed at once | |
X-ray (µ)radiography | High spatial (~ 50–100 μm) and temporal (~ tens of seconds per scan) resolution; non-invasive | Limited to laboratory; possible impact of ionizing radiation; expensive; not easily accessible | |
Neutron radiography | High spatial (~ 100 μm) and temporal (~ tens of seconds per scan) resolution; non-invasive; adapted to dense materials | Limited to laboratory; expensive; not easily accessible; possible impact of neutron radiation on plant tissue; limited to plants that fit in a thin container | |
High-field MRI | Non-invasive; high spatial (~ 100 μm) and temporal (from a few minutes to a few hours depending upon the experiment) resolution | Limited to laboratory; expensive equipment and maintenance; not easily accessible; mainly horizontal orientation; limited plant size and shape |