At a time of rising global concern about environmental issues remote sensing techniques acquire increasing importance in vegetation state assessment and health diagnostics. Multispectral optical data have proved abilities in vegetation monitoring. The visible and near infrared region reveals significant sensitivity to plant biophysical variables and pigment content. The spectral signatures of leaves in this wavelength range are mostly defined by the composition of photosynthetic pigments and their stress-induced changes. As such, plant spectral response provides valuable information about the physiological status of plants. As far as chlorophyll content is a most important bioindicator of plant condition being responsible for light absorption and the photosynthetic process, techniques for its non-destructive assessment are of prime interest. In our study, multispectral data of reflected, transmitted and emitted by plants radiation have been used to reveal the performance of different spectral signatures in chlorophyll estimation. Vegetation indices, red edge shift, spectral transmittance, fluorescence parameters, and chromaticity features, have been related in a statistical manner to plant chlorophyll in order to examine the statistical significance of plant spectral response changes to chlorophyll variations. High correlations have been found permitting quantitative dependences to be established between chlorophyll in plants and their spectral properties. Empirical relationships have been derived that allow plant condition and stress assessment (in terms of chlorophyll inhibition) to be performed by using different spectral indicators.