Figure 1

Axillary buds released from dormancy compete for dominance in pea.

(a) Scheme of intact plant. Red arrows represent auxin (IAA) flow; red arrows crossed with black X represent disabled auxin flow. Auxin loaded from the apex (as primary source) to the stem prevents auxin canalization and its export from the axillary buds (as potential secondary auxin sources). (b) Scheme of decapitated plant. Red and crossed red arrows as depicted in a). Dashed crossed red arrow represents intermitted auxin flow after temporary activation. Green arrow represents bud outgrowth and dominance, dashed green arrow represents temporary outgrowth. Apex, the primary source for auxin flow, is removed and auxin synthesized in the buds can be exported, resulting in outgrowth of both buds. The initial outgrowth turns into competition leading to upper bud dominance over the lower. (c) Intact control plant 7-DAS (at the beginning of experiment). (d) Plant 5 days after decapitation with outgrowing and dominant upper axillary bud and temporarily outgrown and then arrested lower bud. (e) Intact plant of same age (7-DAS + 5 days); both axillary buds remain arrested. (f) Length of axillary buds and forming shoots, where: (li) lower bud of intact plants; (ui) upper bud of intact plants; (ld) lower bud of decapitated plants; (ud) upper bud of decapitated plants. Statistically significant differences (identified by Student’s t-test): α = 0.05* and α = 0.01**. Error bars represent standard deviations (n = 60). (g) Relative expression of PsDRM1 gene in lower and upper axillary buds following decapitation. Statistically significant differences (identified by Student’s t-test): α = 0.05* and α = 0.01**. Error bars represent standard deviations (n = 4). (h,j) Immunoanalysis of PIN1 auxin efflux carriers (red signal) showed polar localization in the primary stem (h), lack of localization in procambial cells of inhibited axillary buds, (i) and polar localization in procambial cells of outgrowing buds (j). Scale bar, 100 μm.