Memorization of Abiotic Stimuli in Plants: A Complex Role for Calcium

Plants are sensitive to various abiotic stimuli (including electromagnetic radiations), to which they respond by modifying their development. The response is sometimes delayed, relative to the reception of the stimulus, which implies that the corresponding information is memorized. A few cases of such behavior are described, including that controlling the induction of meristems in the hypocotyl of flax seedlings. Using this model system, calcium has been shown to play a key role not only in stimulus sensing and the possible storage of that information, but also in its final expression. Modifications of genome expression, as well as posttranslational modifications (e.g., phosphorylation) of proteins, are involved in signal transduction and the possible memorization of information. SIMS methodology provides us with interesting experimental possibilities. The process of “ion condensation,” which has been practically ignored by biologists so far, may be involved in the memorization mechanism. A few cases of the application of plant sensitivity and information memorization to agronomical or research problems are described. The role of memorization mechanisms in the elaboration of an integrated response from plants to the many, varied stimuli that they receive permanently from their environment is discussed.