Leaf water content is one of the most important indicators of the plant growth status. Thus, for a long-term research of the plants, the nondestructive and contactless measurement methods are preferable. Recently, the terahertz (THz) frequency region from 0.1THz to 10THz (or 3-333cm^-1) has seen a flurry of research activity in the fields of physics, chemistry and biology. Terahertz wave is very sensitive to water. This characteristic suggests the capability of THz spectroscopy for monitoring the water content of the plants. In this paper, the influence of varying water content in different zones of the same plant on the absorption and refraction coefficients was given. The influence of varying water content in the different locations of the mesophyll and mid-vein on the absorption and refraction coefficient was described. And the variations mainly result from the different thicknesses of leaf. The absorption and refraction coefficients with different relative water content in the green and yellow leaves were given. These comparisons between green leaf and yellow leaf reveal that the complex permittivity of leaf is as a complex function of the water content of the leaf. So our measurements tend to demonstrate that the dielectric material parameters will be employed to determine the leaf water status in plant leaves. All measurements are in the range of 0.2 to 2.6 THz. These researches will contribute to the future work of a compact and contact-free THz spectrometer to avoid any damage of the leaf surface.

Date Published: 11 August 2011
PDF: 7 pages
Proc. SPIE 8195, International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 81951F (11 August 2011); doi: 10.1117/12.900838

Published in SPIE Proceedings Vol. 8195:
International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications
X.-C. Zhang; Jianquan Yao; Cunlin Zhang; Zhenzhan Wang, Editor(s)