STORAGE OF ENVIRONMENTAL SIGNALS IN FLAX - THEIR MORPHOGENETIC EFFECTAS ENABLED BY A TRANSIENT DEPLETION OF CALCIUM

It is possible to induce the formation of epidermal meristems in the h ypocotyl of non-injured and non-hormone-treated plantlets of flax, by combining various sorts of physical stimulations with a transient depl etion of calcium. The characteristic times for the decrease of the tis sue concentration of calcium during calcium depletion and for the reco very of the normal tissue concentration of calcium after resupplying t he latter ion, are close to 1 day. The stimuli may correspond to wind or drought or even to the manipulation stress occurring when the plant lets are transferred from their germination to their growth vessel. Me ristem production is increased by combining several physical stimulati ons. When calcium depletion is delayed relative to the application of the physical stimulation(s), the production of meristems is delayed ac cordingly. This means that the signal induced by the physical stimulat ion(s) may be stored within the plants, without apparent effect, until a calcium depletion finally allows the stored signal to take effect ( formation of meristems). For storage periods of up to 8 days no loss o f the potency of the stored signal was observed. A few other examples of storage of morphogenetic signals in plants have been described in t he literature. The mechanism involved in signal storage is still not c learly understood. However, it seems that the sensing and/or storing o f the signals require that the plant tissues are sufficiently rich in calcium, whereas the licensing of the plants for the translation of si gnals into the final response (meristem production) is done by a trans ient calcium depletion.