分光反射率からみた樹木の水ストレス反応

抄録

Unusual weather during the summers of 1990's was detrimental to forests and crops. The scientists responsible for the observed forest decline have not been identified, and still trying to find the causes. In this study, measurements of leaf spectral reflectance, photosynthesis, and stomatal conductance of Stewartia pseudocamellia Maxim. (Natsutsubaki) seedlings were carried to detect an indicator of plant water status. Reflectance on infrared wavelength increased with decreasing leaf water content. The slope and inflection point position of the red edge reflectance feature was determined by calculating the first derivative of the spectral curve. A distinctive blue shift, defined here as a shift of the red edge inflection point to shorter wavelengths, is seen in reflectance data from samples collected of the water deficient seedlings. Stress index (SI) was also derived from leaf spectral reflectance data. The photosynthesis and stomatal conductance were affected by low water potential, and these parameters decreased with increasing SI value. The relationships between the physiological parameters of tree seedlings and SI derived from remote sensing data suggest that SI value is useful for detecting and monitoring stress status of forests.