Fig. 1. Nutritional interpretations of directional changes with time in dry mass, nutrient content, and nutrient concentration during plant development. The reference point (R) represents an initial plant sample taken at time T₀ (usually normalized to 100). Vector orientation and magnitude characterize parameter relationships [increase (+), decrease (-), or unchanging (0)] relative to seedlings sampled at subsequent time intervals. Arrow direction also depicts time progression from time T₀ to T₁, T₂... A new Shift G, characterizing net depletion often associated with retranslocation, is included in the box (Modified from Imo and Timmer, 1997; Malik, 1998)