Effet du refroidissement local de la tige sur le transport du AIA exogène en provenance du bourgeon apical et sur la croissance des bourgeons axillaires

Effect of local cooling of the stem on exogenous 1AA transport from the apical bud and on the growth rate of axillary buds .
Local cooling (1.5°C) of the stem (on 2 or 4 cm) of Vicia faba L. cv. Aguadulce for 15 h stops the exogenous IAA transport from the apical bud and causes a high accumulation of tracers above and at the level of the cooled zone. This clamping effect is reversed after removal of the cooling system. If the cooling system is maintained for 48 h, about 25% of the exported radioactivity passes the cooled zone. However, the percentage IAA transmitted decreases to about 6.6% if the cooled zone is sufficiently wide (4 cm) and the temperature lowered to 0.7°C±0.3°C. Using a cooling system of 4 cm (0.7±0.3°C) partially releases the lowermost axillary buds (ax₁ and ax₂) from apical dominance. Yet, the rate of growth of the axillary buds is generally lower than the growth rate after decapitation of the plant.