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Abstract
Auxin's capacity to regulate aspects of plant development has been well characterized in model plant systems. In contrast, orchids have received considerably less attention, but the realization that many orchid species are endangered has led to culture-based propagation studies which have unveiled some functions for auxin in this system. This mini-review summarizes the many auxin-mediated developmental responses in orchids that are consistent with model systems; however, it also brings to the forefront auxin responses that are unique to orchid development, namely protocorm formation and ovary/ovule maturation. With regard to shoot establishment, we also assess auxin's involvement in orchid germination, PLB formation, and somatic embryogenesis. Further, it makes evident that auxin flow during germination of the undifferentiated, but mature, orchid embryo mirrors late embryogenesis of typical angiosperms. Also discussed is the use of orchid protocorms in future phytohormone studies to better understand the mechanisms behind meristem formation and organogenesis.
Disclosure of Potential Conflicts of Interest
No potential conflicts of interest were disclosed.
Acknowledgments
The authors would like to express their gratitude to Drs Jay Jones and Todd Lorenz for consultation and support in the writing of this manuscript. We would also like to thank Dr. Frantisek Baluska for the invitation to write this review.
Funding
This work was financially supported by the USDA (NIFA award number 2011–38422–30942).