Gibberellins may function as modulators of strigolactone response in the control of apical dominance in pea

The synthetic strigolactone (SL) analog GR24 restores apical dominance by rescuing the bushy phenotype of mutant plants that are defective in SL biosynthesis. We examined the effectiveness of this chemical on pea (Pisum sativum L.) plants with normal SL biosynthesis and signaling, following disruption of apical dominance by decapitation of the stem. The cross-talk between the SL and gibberellins (GAs) was also studied. GR24 was applied to the axillary buds of decapitated climbing and dwarf plants, the latter being defective in GA biosynthesis. The results show that the effect of GR24 changes, depending on plant genotype and apparently related to the concentration of endogenous GA1 in treated buds shortly after decapitation. Following apex removal, the biosynthesis of endogenous SLs in roots changed with genotype and GR24 application and this might contribute to determine the response of axillary buds. Experiments with plants in which GA levels were manipulated by chemical means confirmed the possibility that the level of bioactive GAs might modulate the response of decapitated pea plants to GR24, by changing bud responsiveness to the applied SL.