Abstract
We investigated two spectral reflectance indices, the normalized difference vegetation index (NDVI) and the photochemical reflectance index (PRI) as indicators of photosynthetic pigments and photosynthesis in Japanese larch (Larix kaempferi Sarg.) needles. Daily courses of spectral reflectance, photosynthetic pigment concentration and photosynthetic activity (net photosynthetic rate and chlorophyll fluorescence) of the needles were measured in a 4-year-old larch plantation in August 2002. No significant correlations were found between needle pigment concentrations and either index. Although the daily course of net photosynthetic rate correlated with that of NDVI, this relationship varied under weak light conditions in the evening. PRI was significantly linked to epoxidation state in xanthophyll cycle, light use efficiency (LUE) of CO2 assimilation and quantum yield of PS II with higher correlation coefficient than NDVI was. We conclude that PRI is usable for estimating daily changing photosynthetic light use efficiency in larch needles.
