production and release of living root cap border cells is a function of root apical meristem type in dicotyledonous angiosperm plants

• Published in: Annals of botany 2006-05, Vol.97 (5), p.917-923
• Main Authors: Hamamoto, L, Hawes, M.C, Rost, T.L
• Format: Article
• Language: English
• Subjects: Angiosperms; Apical meristems; Apoptosis; Arabidopsis thaliana; Border cells; Brassica napus; Capsicum annuum; Citrullus lanatus; Cucumis melo; Cucumis sativus; Cucurbitaceae - physiology; Daucus carota; developmental stages; Fabaceae - physiology; Glycine max; Gossypium hirsutum; Helianthus annuus; Luffa aegyptiaca; Magnoliopsida - physiology; Magnoliopsida - ultrastructure; Microscopy, Electron, Scanning; Nicotiana tabacum; Petunia hybrida; Phaseolus vulgaris; Pisum sativum; plant anatomy; Plant cells; plant development; Plant Root Cap - physiology; Plant Root Cap - ultrastructure; Plant roots; Plants; root apical organization; Root cap; root caps; root growth; root meristem; Root Structure and Function; Root tips; Sesbania; Sesbania exaltata; Sesbania javonica; Soil plant interactions; Solanaceae - physiology; Solanum lycopersicum var. lycopersicum; Solanum melongena; Stem cells; ultrastructure; Vigna unguiculata
• ISSN: 0305-7364; 1095-8290
• DOI: 10.1093/aob/mcj602

• Background and Aims The root apical meristems (RAM) of flowering plant roots are organized into recognizable pattern types. At present, there are no known ecological or physiological benefits to having one RAM organization type over another. Although there are phylogenetic distribution patterns in plant groups, the possible evolutionary advantages of different RAM organization patterns are not understood. Root caps of many flowering plant roots are known to release living border cells into the rhizosphere, where the cells are believed to have the capacity to alter conditions in the soil and to interact with soil micro-organisms. Consequently, high rates of border cell production may have the potential to benefit plant growth and development greatly, and to provide a selective advantage in certain soil environments. This study reports the use of several approaches to elucidate the anatomical and developmental relationships between RAM organization and border cell production. • Methods RAM types from many species were compared with numbers of border cells released in those species. In addition, other species were grown, fixed and sectioned to verify their organization type and capacity to produce border cells. Root tips were examined microscopically to characterize their pattern and some were stained to determine the viability of root cap cells. • Key Results The first report of a correlation between RAM organization type and the production and release of border cells is provided: species exhibiting open RAM organization produce significantly more border cells than species exhibiting closed apical organization. Roots with closed apical organization release peripheral root cap cells in sheets or large groups of dead cells, whereas root caps with open organization release individual living border cells. • Conclusions This study, the first to document a relationship between RAM organization, root cap behaviour and a possible ecological benefit to the plant, may yield a framework to examine the evolutionary causes for the diversification of RAM organization types across taxa.