De Luca P, Sabato S, Balduzzi A, Nazzaro R (1980) Coralloid
root regeneration on Macrozamia megagametophytes.
Good, large coralloid
growths, and minute spheroids occur, the spheroids perched on variscite and jahnsite crystals.
While it is well-established that all cycads produce coralloid
roots which host symbiotic nitrogen-fixing cyanobacteria, the impact of this form of nitrogen fixation on nutrient dynamics is unknown (Grobbelaar, 2004; Donaldson, 2008).
In the early years of mining at Jaguaracu, zircon was collected in well-formed fan-shaped groups, coralloid
aggregates and sub-parallel groups reaching more than 15 cm in length.
and grow upward to produce coralloid
root masses at the soil surface.
nitrogen-fixing ability of the coralloid
cycad roots (Dehgan, 1983).
Examples of such structural synapomorphies for the extant Cycadales are girdling leaf traces, an inverted omega pattern of vascular bundle arrangement in petiole and cataphyll bases, protoxylem poles changing from endarch in the stem to exarch in the leaf traces, a primary thickening meristem, a contractile taproot, and ageotropic, coralloid
, lateral roots (Stevenson, 1990b; Norstog & Nicholls, 1998).
They are formed by low Mg calcite and consist of calcite moonmilk and coralloids
. In Krtola Cave carbonates occurs in zone cementing cave sediments, which are up to 15 cm thick.