How does auxin promote apical dominance

Therefore, excess sucrose exported from photosynthetic leaves to the stem overflow into axillary buds and induces bud outgrowth. B Intrinsic factors such as auxin and strigolactones and environmental factors such as shade promote stem intemode elongation in the main shoot. Elongated intemode, which is a strong sink, inhibits bud outgrowth indirectly by limiting sugar supply to axillary bud. The plant source—sink relations is regulated by intrinsic and environmental factors making shoot branching a complex trait that cannot be predicted easily without considering the growth and developmental status of the whole plant and prevailing environmental conditions.

Reappraisal of the source—sink status in shoot branching mutants and wild-types and systematic study of the effect of source—sink status of the main shoot on dormancy and outgrowth of axillary buds might advance our knowledge of the physiological basis of apical dominance and shoot branching in plants. Future studies should accurately determine the sink or source status of an organ being manipulated. For example, the cotyledons in pea contribute to seed germination. The nutrient reserve and biomass of the cotyledons are exhausted within the first 10 days after sowing, during which the plant transitions from heterotrophic to autotrophic growth Hanley et al.

Experiments involving cotyledon removal or defoliation of young newly formed or old non-photosynthetic leaves assuming that they are source of nutrients or photoassimilates might lead to incorrect conclusions.

Besides their role in shoot branching, sugars are also important in many other aspects of plant growth and development including phase transitions from juvenile to adult and from vegetative to flowering Wahl et al. Therefore, when investigating plant growth and development, sugar demand and supply should be taken into consideration. The author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

The author thanks Dr. Aguilar-Martinez, J. Plant Cell 19, — Albacete, A. Hormonal and metabolic regulation of source-sink relations under salinity and drought: from plant survival to crop yield stability. Barbier, F. Sucrose is an early modulator of the key hormonal mechanisms controlling bud outgrowth in Rosa hybrida.

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Cytokinin is required for escape but not release from auxin mediated apical dominance. Plant J. Prasad, T. Does auxin play a role in the release of apical dominance by shoot inversion in ipomoea-nil. Procko, C. The epidermis coordinates auxin-induced stem growth in response to shade.

Genes Dev. Rabot, A. Insight into the role of sugars in bud burst under light in the rose. Rameau, C. Multiple pathways regulate shoot branching. Seale, M. BRC1 expression regulates bud activation potential but is not necessary or sufficient for bud growth inhibition in Arabidopsis. Development , — Simons, J. Snow, R. On the nature of correlative inhibition. Stirnberg, P. PubMed Abstract Google Scholar. Tao, Y. Rapid synthesis of auxin via a new tryptophan-dependent pathway is required for shade avoidance in plants.

Cell , — Tarancon, C. A conserved carbon starvation response underlies bud dormancy in woody and Herbaceous Species. Thimann, K. Studies on the growth hormone of plants: III. The inhibiting action of the growth substance on bud development. Wahl, V. Regulation of flowering by trehalosephosphate signaling in Arabidopsis thaliana. Science , — Xu, N. Co-regulation of ear growth and internode elongation in corn. The outgrowing axillary bud lower or upper was consistently the bud above which the primary stem auxin flux was interrupted.

This outgrowth pattern was not influenced if nutrient supplies were changed by cotyledon removal. Furthermore, considering the roots as main source of strigolactone SL 27 , 28 , 29 , demonstrated as effective inhibitor of bud outgrowth 21 , it can be hypothesized that incision above the bud could direct more acropetally moving SL into this bud and cause its inhibition. Nonetheless, this bud was released from inhibition and formed a shoot.

This finding supports the hypothesis that SL inhibits bud growth only in the presence of auxin in the main stem 9. In addition, the acropetal flow of cytokinins in the stem 30 restricted by incision could also enter the bud and promote bud outgrowth initiation. These results indicated sustainable auxin flow in the primary stem from the apex was required to maintain axillary bud dormancy and auxin flow interruption or inhibition released the upper bud from dormancy, as demonstrated by bud outgrowth, dormancy markers, and PIN1 auxin carrier polarization.

These results are also congruent with the hypothesis that auxin flow from more apical plant parts controls the dormancy status of axillary buds. Furthermore, the typical result of competition for dominance was initiated by decapitation, where the upper axillary bud outcompeted the lower bud.

This competition pattern was not altered by cotyledon removal. Competition ceased by interruption of auxin flow between upper and lower competing axillary buds, resulting in two long-term equally growing shoots. This result was unexpected, but effective chemical concentrations in plant tissues might be sufficient to inhibit auxin export and initial bud outgrowth, but not affect steady-state PIN localization.

The protein synthesis inhibitor CHX also interferes with auxin transport 33 , These experiments demonstrated that chemical inhibition of auxin export from buds does not necessarily impact PIN1 polarization in treated buds. These results suggested not only PIN polarization, but more importantly the capacity of auxin export from buds is required for sustained outgrowth of axillary shoots.

Based on the auxin canalization theory, establishment of an effective auxin transport channel following interruption of stem auxin flow leads to redirection of the auxin source-sink pattern from the original primary-apex-root pathway to a new secondary-apex-root pathway.

Developmental processes involved in the new vascular strands are consistent with the directed auxin flow. More detailed studies on the influence of other hormones and exogenous factors on auxin flow-mediated bud competition will likely elucidate its mechanisms. Pea plants Pisum sativum L. Following protocols: i axillary bud and apical shoot length measurement; ii axillary bud gene expression analyses; iii PIN1 protein immunolocalization assays; iv polar auxin transport capacity assays were used.

Furthermore, 7 DAS plants or 7 DAS decotyledoned plants were administered with a deep lateral incision above the upper axillary bud or between the lower and upper axillary buds and used for axillary bud length measurements henceforth wounded plants. The upper and lower axillary buds were used to explore gene expression and PIN1 protein localization.

For bud length measurements, 60 plants in two biological replicates were used for each treatment. Bud samples were harvested and ground in liquid nitrogen. Total cDNA was synthesized from 0. Two biological replicates were analyzed in duplicates. The mean value and standard deviations were determined from replications of each variant. The anti-Arabidopsis-PIN1 antibody also recognizes the homologous PIN protein in pea, which is presumed to be a PIN1 functional ortholog based on expression similarity and localization signal to Arabidopsis The following antibodies and dilutions were used: anti-PIN1 and CY3-conjugated anti-rabbit secondary antibody Images were acquired using Fluoview 5.

Plants were treated with 0. For each experimental variant stem segment samples were collected from 10 plants. In all stem segment variants samples were incubated in a dioxane-based liquid scintillator cocktail overnight. Six hours after decapitation, 0. How to cite this article : Balla, J. Auxin flow-mediated competition between axillary buds to restore apical dominance. Rameau, C. Multiple pathways regulate shoot branching. Plant Sci. Article Google Scholar.

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Paciorek, T. Immunocytochemical technique for protein localization in sections of plant tissues. Sauer, M. Download references. You can also search for this author in PubMed Google Scholar. This work is licensed under a Creative Commons Attribution 4. Reprints and Permissions. Sci Rep 6, Download citation. Received : 06 May Accepted : 03 October Published : 08 November Anyone you share the following link with will be able to read this content:. Sorry, a shareable link is not currently available for this article.

Provided by the Springer Nature SharedIt content-sharing initiative. Plant Growth Regulation By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate. Advanced search. Skip to main content Thank you for visiting nature. Download PDF. Subjects Plant development Plant physiology. Abstract Apical dominance is one of the fundamental developmental phenomena in plant biology, which determines the overall architecture of aerial plant parts.