ISHS Acta Horticulturae 710: International Symposium on Greenhouses, Environmental Controls and In-house Mechanization for Crop Production in the Tropics and Sub-Tropics
NONDESTRUCTIVE DETECTION OF PLANT WATER STRESS BY MICROWAVE SENSING |
| Authors: | T. Shimomachi, T. Takemasa, T. Takakura, K. Kurata |
| Keywords: | water stress, permittivity, open-ended coaxial probe, photosynthetic rate, stomatal conductance, water potential |
| Abstract:
The physiological response of a plant to environmental stress can induce changes in physiological and physical conditions of the plant. These changes influence the dielectric properties of the plant, which can be detected by measuring microwave complex dielectric properties of plant materials such as leaves and stems. The objective of this research was to detect these responses of plants to water deficiency stress nondestructively. The complex dielectric properties of tomato leaves under water stress were measured with an open-ended coaxial probe from 0.3 to 3 GHz, as well as changes in gravimetric moisture, photosynthetic rate, stomatal conductance and water potential which reflect the physiological condition of the plants. Experimental results showed that the complex permittivity (both permittivity and loss factor) of tomato leaves increased during water stress. Among the parameters measured, the highest correlation was observed between complex permittivity and water potential. A physiochemical model to describe the complex permittivity of crushed non-stressed and stressed tomato leaves was constructed with pure water, pulp, glycine, and KNO3, and the complex dielectric measurements of crushed tomato leaves were reproduced quite accurately from 0.3 to 3 GHz. | |
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