AOBPreview originally published online on May 14, 2004
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Annals of Botany 94: 51-58, 2004
© 2004 Annals of Botany Company
Ficus rubiginosa ‘Variegata’, a Chlorophyll-deficient Chimera with Mosaic Patterns Created by Cell Divisions from the Outer Meristematic Layer
1 Plant Standards Branch, Department of Primary Industries, Private Bag 15, Ferntree Gully Delivery Centre, Victoria 3156, Australia and 2 Royal University of Veterinary and Agricultural Science, Bülowsvej 17, DK-1870 Frederiksberg C, Denmark
* For correspondence. Fax 61 03 92109396, e-mail david.beardsell{at}dpi.vic.gov.au
Received: 25 June 2003; Returned for revision: 5 November 2003; Accepted: 4 March 2004. Published electronically: 14 May 2004
• Background and Aims Sections leaves of Ficus rubiginosa ‘Variegata’ show that it is a chimera with a chlorophyll deficiency in the second layer of the leaf meristem (GWG structure). Like other Ficus species, it has a multiseriate epidermis on the adaxial and abaxial sides of the leaf, formed by periclinal cell divisions as well as anticlinal divisions. The upper and lower laminae of the leaf often exhibit small dark and light green patches of tissue overlying internal leaf tissue.
• Methods The distribution of chlorophyll in transverse sections of typical leaves was determined by fluorescence microscopy.
• Key Results Patches of dark and light green tissue which arise in the otherwise colourless palisade and spongy mesophyll tissue in the entire leaf are due to further cell divisions arising from the bundle sheath which is associated with major vascular bundles or from the green multiseriate epidermis. Leaves produced in winter exhibit more patches of green tissue than leaves which expand in mid-summer. Many leaves produced in summer have no spotting and appear like a typical GWG chimera. There is a strong relationship between the number of patches on the adaxial side of leaves and the number on the abaxial side, showing that the cell division in upper and lower layers of leaves is strongly coordinated. In both winter and summer, there are fewer patches on the abaxial side of leaves compared with the adaxial side, indicating that periclinal and anticlinal cell divisions from the outer meristematic layer are less frequent in the lower layers of leaf tissue. Most of the patches are small (<1 mm in longest dimension) and thus the cell divisions which form them occur late in leaf development. Leaves which exhibit large patches generally have them on both sides of the leaves.
• Conclusion In this cultivar, the outer meristematic layer appears to form vascular bundle sheaths and associated internal leaf tissue in the entire leaf lamina.
Key words: Leaf chimera, leaf development, variegation, periclinal cell divisions, anticlinal cell divisions, mosaic, chorophyll-deficient mutant, Ficus rubiginosa, ornamental plant, vascular bundle, bundle sheath, sheath extension.