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Industrial Applications of Terahertz Sensing: State of Play
Open AccessArticle

THz Water Transmittance and Leaf Surface Area: An Effective Nondestructive Method for Determining Leaf Water Content

1
CREA—Research Centre for Plant Protection and Certification, Via di Lanciola 12/A, 50125 Firenze, Italy
2
CREA—Research Centre for Viticulture and Enology, Viale Santa Margherita 80, 52100 Arezzo, Italy
3
NEST, CNR—Istituto Nanoscienze and Scuola Normale Superiore, Piazza San Silvestro 12, 56124 Pisa, Italy
4
Dipartimento di Fisica “E. Fermi”, Università di Pisa, Largo Bruno Pontecorvo 3, 56127 Pisa, Italy
5
CREA—Research Centre for Forestry and Wood, Viale Santa Margherita 80, 52100 Arezzo, Italy
*
Author to whom correspondence should be addressed.
These authors contributed equally to this work.
Sensors 2019, 19(22), 4838; https://doi.org/10.3390/s19224838
Received: 28 September 2019 / Revised: 27 October 2019 / Accepted: 29 October 2019 / Published: 6 November 2019
(This article belongs to the Special Issue Advanced Industrial Terahertz Sensing Applications)
Water availability is a major limiting factor in plant productivity and plays a key role in plant species distribution over a given area. New technologies, such as terahertz quantum cascade lasers (THz-QCLs) have proven to be non-invasive, effective, and accurate tools for measuring and monitoring leaf water content. This study explores the feasibility of using an advanced THz-QCL device for measuring the absolute leaf water content in Corylus avellana L., Laurus nobilis L., Ostrya carpinifolia Scop., Quercus ilex L., Quercus suber L., and Vitis vinifera L. (cv. Sangiovese). A recently proposed, simple spectroscopic technique was used, consisting in determining the transmission of the THz light beam through the leaf combined with a photographic measurement of the leaf area. A significant correlation was found between the product of the leaf optical depth (τ) and the leaf surface area (LA) with the leaf water mass (Mw) for all the studied species (Pearson’s r test, p ≤ 0.05). In all cases, the best fit regression line, in the graphs of τLA as a function of Mw, displayed R2 values always greater than 0.85. The method proposed can be combined with water stress indices of plants in order to gain a better understanding of the leaf water management processes or to indirectly monitor the kinetics of leaf invasion by pathogenic bacteria, possibly leading to the development of specific models to study and fight them. View Full-Text
Keywords: leaves; plants; terahertz quantum cascade laser; water content; drought stress leaves; plants; terahertz quantum cascade laser; water content; drought stress
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MDPI and ACS Style

Pagano, M.; Baldacci, L.; Ottomaniello, A.; de Dato, G.; Chianucci, F.; Masini, L.; Carelli, G.; Toncelli, A.; Storchi, P.; Tredicucci, A.; Corona, P. THz Water Transmittance and Leaf Surface Area: An Effective Nondestructive Method for Determining Leaf Water Content. Sensors 2019, 19, 4838.

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