Juliana Medeiros and Dennis Stevenson
Cycad RootsAside from the presence of coralloid roots, the morphology and anatomy of the cycad root system is typical of plants with secondary growth, although root contraction has been shown to occur in the primary roots of cycads. Coralloid roots can constitute 1-3.6% of total Cycad biomass (Rai et al., 2000). They can be found at depths of up to 30cm below ground. The portion of the coralloid occupied by cyanobacteria is known as the cyanobacterial zone. Initiated as a new meristematic layer in precoralloids long before cyanobacterial invasion, this specialized tissue is not found in normal lateral roots.More on Coralloid Root Anatomy Within 12 months of germination, cycad seedlings produce adventitious roots at the root shoot junction called precoralloids. These develop as part of the normal growth of the plant, even under sterile culture conditions, and are eventually transformed into coralloid roots upon colonization by cyanobacteria. Like many plants, Cycads have symbiotic fungi inhabiting their normal roots. Opinion is diverse, however, on the presence or absence of non-cyanobacterial microbes within coralloid roots. More on Other Organisms Present in Cycad Roots
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