such as "Introduction", "Conclusion"..etc
The water content of leaves, their thickness, their density and other
properties can now be determined without even having to touch them. A
team of researchers from the CSIC Institute of Acoustics and the
Agri-Food Research and Technology Centre (CITA) of Aragón has just
presented an innovative technique that enables plant leaves to be
studied using ultrasound in a quick, simple and non-invasive fashion.
Tomas E. Gómez, one of the authors of the study and researcher at the
CSIC Institute of Acoustics, where a technique has been developed to
analyse these parts of plants without touching them, explains that "The
method involves establishing a silent dialogue with plant leaves,
questioning them and listening to what they say."
The research, recently published in the journal, Applied Physics
Letters, demonstrates that some properties of leaves such as
thickness, density or compressibility can be determined with this
"The voice of the leaves itself is what gives us information about
their status and their properties, all in an innocuous and silent way
since communication is established by ultrasound, with above-audible
frequencies," the scientist indicates.
The technique involves radiating the leaves with broadband ultrasonic
pulses (between 0.2 and 2 megahertz), which are emitted through the air
from portable devices. In doing so, the leaves start to vibrate and an
ultrasonic sensor very similar to the transmitter detects the waves. The
signal is then digitalised and the researchers analyse the resonance
range, which enables the characteristics of the leaves to be assessed.
The entire process is done in a way that is non-intrusive to the
plant. Until now, coupling fluids have been used between the ultrasound
transmitter and the material being studied, as is in the case in
medicine, for example, when gels or oils are applied to perform an
Listening to leaf moisture
Eustaquio Gil-Pelegrín, co-author of the study and researcher at the
Forestry Resources Unit of the Agri-Food Research and Technology Centre
(CITA) in Aragón, which has also taken part in the research, explains
that "With this method we can also directly estimate, without contact or
interference, the water potential of leaves very accurately."
Information about water content enables us to analyse the loss of
turgor in the leaves and the internal morphology of their cell layers,
which in turn makes it possible to assess the level of development and
to see how they are influenced by environmental factors. Research on the
status and water potential of plants helps to diagnose the situation of
agricultural and natural systems.
Gil-Pelegrin emphasises the effectiveness of the technique, "even to
detect critical moments for plants, such as stomatal closure." Gas and
liquid exchange takes places through these pores on the surface of the
leaf, and [stomata] opening is determined by factors such as light, CO2
concentration and water availability. For example, when there is a
drought the stomata close.
Scientists have successfully applied the ultrasound method to the
study of perennial leaves (Prunus laurocerasus and Ligustrum
lucidum) and deciduous leaves (Populus x euroamericana
and Platanus x hispanica).
The team also took cuttings of some leaves to ascertain water loss
over time, and they observed variations in leaf resonance and even water
mass loss as little as 1%. The details of this line of research will
soon be published in the Journal of Experimental Botany.
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