Proceedings of the XLVII Italian Society of Agricultural Genetics - SIGA Annual Congress

Verona, Italy - 24/27 September, 2003

ISBN 88-900622-4-X

Oral Communication Abstract - S4a

REGULATION OF PHYLLOTAXIS VIA POLAR AUXIN TRANSPORT

C. KUHLEMEIER

Institute of Plant Sciences, University of Berne, CH-3013 Berne, Switzerland

Leaves and flowers are formed at the shoot apical meristem according to specific patterns, called phyllotaxis. The beauty and regularity of phyllotaxis have for centuries attracted the attention of philosophers, mathematicians and natural scientists, but experimental approaches have been few. Previous studies have shown that the plant hormone auxin triggers organ formation. Auxin undergoes specific polar transport, via cellular influx and efflux carrier proteins. I will discuss our experiments that show how these auxin carriers regulate phyllotaxis. Our data indicate that auxin is acropetally transported into the meristem through the epidermis and the meristem L₁ layer. In the meristem, auxin becomes redistributed by the primordia which function as sinks for auxin. Hence, the pre-existing primordia dictate the position of future primordia by allowing auxin accumulation in the meristem only at certain minimal distances. The emerging model for phyllotaxis accounts for its reiterative nature, as well as for its regularity and stability.