Influence de la qualité de l'éclairement sur les corrélations entre le cotylédon et son bourgeon axillaire chez le Linum usitatissimum

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The precedence of one cotyledonary bud over another, as a result of the removal of one of the cotyledons, can be measured quantitatively using the precedence index, g. When g tends towards +1, it is the bud opposite to the deleted cotyledon that takes the precedence, whereas when it tends toward −1, it is the axillant one. When g is close to 0, it corresponds to a globally symmetrical population of plants, in which the bud opposite to the deleted cotyledon and the axillant bud take the precedence in an approximately equal number of plants. When the flax is taken, after decapitation and removal of one cotyledon, on deficient nutrient solution under photoperiodicity of 9 h light: 15 h dark, index g is not affected if the dark period is replaced totally by a low-energy (3 W∙m−2) red light or partly by four periods of 20 min of red light during the dark period. In contrast, blue or far red light, under the same experimental conditions, caused g to tend towards 0 for all cultivars. This effect of the blue or far red light was antagonized by a following red light treatment, which suggests the interference of phytochrome. These observations were not observed with a Knop, ion-rich nutrient solution and at 18 W∙m−2, where g index remained close to +1. Key words: Linum usitatissimum, photomorphogenesis, bud, cotyledon, correlation.