Abstract
Roots are discussed less frequently than other plant organs in terms of their phylogenetic origin and evolutionary specialization because of limited paleobotanical information and few broad comparative studies of root structure and development. There is considerable diversity, however, in root structure among the major groups of vascular plants. Roots of many extinct and extant seedless vascular plants have a simple apical meristem (i.e., an apical cell), limited secondary growth, and in some genera, branching is accomplished by a true dichotomy of the apical meristem. Roots of seed plants evolved more complex apical meristems, branching from subterminal tissues, and in some groups extensive vascular cambium activity. Evolutionary developments related to nutrient availability include symbiotic interactions with soil fungi to form mycorrhizae, soil bacteria and cyanobacteria to form nitrogen-fixing nodules, and the modification of branching to form cluster roots. Concomitant with these specializations, root hair frequency and structure are often modified. All roots possess a suberized layer, the endodermis, and in many species, particularly among the angiosperms, a specialized suberized exodermis is present. Roots of aquatic species have evolved mechanisms either to tolerate or to avoid anaerobiosis. Roots growing in continuously wet environments possess constitutive aerenchyma whereas roots of periodically flooded plants are able to respond by forming lysigenous or schizogenous aerenchyma. Key words: roots, evolution, adaptations, structure, symbioses.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.