The Barley Phytomer
1 SCRI, Invergowrie, Dundee DD2 5DA, Scotland, UK
2 North Dakota State University, Fargo, ND 58105, USA
3 Nordic Gene Bank, PO Box 41, SE-23053 Alnarp, Sweden
* For correspondence. E-mail bforst{at}scri.ac.uk
Received: 27 April 2007 Returned for revision: 25 May 2007 Accepted: 27 June 2007
Background and Aims: Morphological mutants have been useful in elucidating the phytomeric structure of plants. Recently described mutants have shed new light on the ontogeny (development of plant structures) and the phytomeric system of barley (Hordeum vulgare). Since the current model for barley phytomers was not adequate to explain the nature of some mutants, a new model is proposed.
Methods: New phytomer mutants were detected by visual assessment of mutant families in the Optic barley mutation grid population. This was done at various growth stages using laboratory, glasshouse and field screens. Simple explanations were adopted to account for aberrant phytomer phenotypes and a thesis for a new phytomer model was developed.
Key Results and Conclusions: A barley phytomer model is presented, in which the origins of vegetative and generative structures can be explained by a single repeating phytomer unit. Organs on the barley plant are divided into two classes, single or paired, depending on their origin. Paired structures are often fused together to create specific organs. The model can be applied to wheat (Triticum aestivum) and related grasses.
Key words: Barley, Hordeum vulgare, phytomer, floral structure, mutants