Abstract
The transductions to initiate and propagate pattern were investigated in the sunflower head. The spiral pattern emerges as new florets form in regular centripetal sequence on the flat disc. The spiral lines of florets arise as rows of simple bumps. Each bump splits to become a small bract and a circular disc flower. This topographical progression was described by a scanning electron microscopic technique applied to living tissue. The suitability of various theories to explain the progression was examined. Because no periodic cell specialization was seen by scanning electron microscopy prior to pattern emergence, a mechanism that produces pattern in uniform tissue by spontaneous physical buckling (folding) was examined further. Key configurational changes of development were reproduced in models using the buckling assumptions. In further testing, a young head was physically constrained to cause it to grow as an oval. Pattern was modified as predicted. Unexpectedly, organ character changed as well. In localized regions, the folding was abnormal; the typical dyad floret, bract and flower, was replaced by a single large bract. This anomaly is known in mutants of sunflower; hence, the physical treatment induced a phenocopy. We concluded that (1) buckling is a strong candidate to be the process producing organ pattern, and (2) the accompanying topographical changes can be prerequisite to organ differentiation.
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Selected References
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- Braam J., Davis R. W. Rain-, wind-, and touch-induced expression of calmodulin and calmodulin-related genes in Arabidopsis. Cell. 1990 Feb 9;60(3):357–364. doi: 10.1016/0092-8674(90)90587-5. [DOI] [PubMed] [Google Scholar]
- Carter D. R., Blenman P. R., Beaupré G. S. Correlations between mechanical stress history and tissue differentiation in initial fracture healing. J Orthop Res. 1988;6(5):736–748. doi: 10.1002/jor.1100060517. [DOI] [PubMed] [Google Scholar]
- Coen E. S., Meyerowitz E. M. The war of the whorls: genetic interactions controlling flower development. Nature. 1991 Sep 5;353(6339):31–37. doi: 10.1038/353031a0. [DOI] [PubMed] [Google Scholar]
- DRONAMRAJU K. R. Y-LINKAGE IN MAN. Nature. 1964 Jan 25;201:424–425. doi: 10.1038/201424b0. [DOI] [PubMed] [Google Scholar]
- Douady S, Couder Y. Phyllotaxis as a physical self-organized growth process. Phys Rev Lett. 1992 Mar 30;68(13):2098–2101. doi: 10.1103/PhysRevLett.68.2098. [DOI] [PubMed] [Google Scholar]
- Holder N. Positional information and pattern formation in plant morphogenesis and a mechanism for the involvement of plant hormones. J Theor Biol. 1979 Mar 21;77(2):195–212. doi: 10.1016/0022-5193(79)90307-2. [DOI] [PubMed] [Google Scholar]
- Hsieh H. J., Li N. Q., Frangos J. A. Shear-induced platelet-derived growth factor gene expression in human endothelial cells is mediated by protein kinase C. J Cell Physiol. 1992 Mar;150(3):552–558. doi: 10.1002/jcp.1041500316. [DOI] [PubMed] [Google Scholar]
- Liu Cm., Xu Zh., Chua N. H. Auxin Polar Transport Is Essential for the Establishment of Bilateral Symmetry during Early Plant Embryogenesis. Plant Cell. 1993 Jun;5(6):621–630. doi: 10.1105/tpc.5.6.621. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Selker J. M., Steucek G. L., Green P. B. Biophysical mechanisms for morphogenetic progressions at the shoot apex. Dev Biol. 1992 Sep;153(1):29–43. doi: 10.1016/0012-1606(92)90089-y. [DOI] [PubMed] [Google Scholar]
- Smith L. G., Hake S. The Initiation and Determination of Leaves. Plant Cell. 1992 Sep;4(9):1017–1027. doi: 10.1105/tpc.4.9.1017. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Spurr A. R. A low-viscosity epoxy resin embedding medium for electron microscopy. J Ultrastruct Res. 1969 Jan;26(1):31–43. doi: 10.1016/s0022-5320(69)90033-1. [DOI] [PubMed] [Google Scholar]
- St Johnston D., Nüsslein-Volhard C. The origin of pattern and polarity in the Drosophila embryo. Cell. 1992 Jan 24;68(2):201–219. doi: 10.1016/0092-8674(92)90466-p. [DOI] [PubMed] [Google Scholar]
- Szymkowiak E. J., Sussex I. M. The internal meristem layer (L3) determines floral meristem size and carpel number in tomato periclinal chimeras. Plant Cell. 1992 Sep;4(9):1089–1100. doi: 10.1105/tpc.4.9.1089. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Wolff T., Ready D. F. The beginning of pattern formation in the Drosophila compound eye: the morphogenetic furrow and the second mitotic wave. Development. 1991 Nov;113(3):841–850. doi: 10.1242/dev.113.3.841. [DOI] [PubMed] [Google Scholar]