This article develops the basis for a THz laser feedback interferometry application to determine a plant's generic variations. By detecting biochemical and biophysical changes, the dynamics of cell water can be mapped into time-dependent dehydration profiles, much like a fingerprint, and genetic variations of a plant species can be inferred. Quantum cascade lasers are applied for rapid, high resolution acquisition of phase and amplitude images. The impact of cell age and orientation, and spectral differences were investigated to refine the spectroscopy technique. This THz spectroscopy application would potentially improve the quality of agricultural production by accurately distinguish a genetically modified plant from a wild plant of the same genus.