Near-infrared ( 2.2 \mu m ) observations of a sample of 48 elliptical galaxies in the Coma cluster have been carried out and used to study the near-ir fundamental plane ( FP ) of ellipticals in this cluster .
An rms scatter of 0.072 dex was found for this relation , similar to that of its optical counterpart , using the same sample of galaxies .
This corresponds to an uncertainty of 18 \% in distances to individual galaxies derived from this relation .
The sensitivity of the near-infrared FP to the star formation or changes in metallicity and stellar population among the ellipticals was explored and found to be small .
Although , a likely source of scatter in this relation is contributions from the Asymptotic Giant Branch ( AGB ) population to their near-infrared light .
Allowing for observational uncertainties , we find an intrinsic scatter of 0.060 dex in the near-ir FP .
The cluster galaxies presented here , provide the zero-point for the peculiar velocity studies , using the near-infrared FP .

Changes in the slopes of the D - \sigma and L - \sigma relations of ellipticals between the optical and near-infrared wavelengths were investigated and found to be due to variations in metallicity or age ( or a combination of them ) .
However , it was not possible to disentangle the effects of age and metallicity in these relations .

We find M / L \propto M ^ { \alpha } with \alpha = 0.18 \pm 0.01 at the near-ir and \alpha = 0.23 \pm 0.01 at the optical wavelengths , using the same sample of galaxies .
This relation is interpreted as due to a mass-metallicity effect or changes in age or the IMF slope with mass .
Using evolutionary population synthesis models , we find that the effects of age and metallicity decouple on the ( M / L ) _ { K } vs. Mg _ { 2 } and ( M / L ) _ { K } vs. ( V - K ) diagrams .
The models suggest that the observed trends on these relations may be due to an age sequence while metallicity mainly contributing to the scatter .