FUNCTIONAL-RELATIONSHIP BETWEEN CHLOROPHYLL CONTENT AND LEAF REFLECTANCE, AND LIGHT-CAPTURING EFFICIENCY OF JAPANESE FOREST SPECIES

We examined the functional relationship between chlorophyll concentrat ions and light spectral absorption in 16 species of woody, vine and he rbaceous plants in northern Japan. Leaves of each species from under f orest shade and in more open sites were measured for chlorophyll, spec ific leaf area (SLA) and spectral absorption. In all species, SLA incr eased and the Chi a:b ratio declined in shade- vs open-grown leaves in dicating an adaptive adjustment to forest shade in these leaf characte rs. However, the expected increase in the ratio of 680 to 700 nm absor ption in shade leaves did not occur in all species. Light absorption a t 680 relative to 700 nm was lower in the shade leaves of Acer japonic um, Kalopanax pictus, Panax japonicus and Petasites japonicus even wit h a reduced Chi a:b, a commonly accepted indicator of shade adaptation . Therefore, spectral measurements in these species failed to support Chi concentrations that were expected to confer an improvement in the absorption of red light (<680 nm) deficient relative to far-red light (>700 nm) in the forest shade. Compared with other species, the absorp tion pattern of these four 'non-conforming' species is associated with a higher ratio of shade:open leaves in reflectance spectra in the 600 -750 nm range. This suggests an increased reflectance in shade leaves caused by changes in leaf surface properties which are not immediately apparent. We conclude that adaptive spectral absorption cannot always be inferred from changes in specific leaf area and chlorophyll a and b concentrations.