Canopy nodulation of the endemic tree legume acacia koa in the mesic forests of hawaii
2004
Leary, James J. K. | Singleton, Paul W. | Borthakur, Dulal
Canopy nodulation of Acacia koa (koa) is the result of a unique symbiosis between the host adventitious root system and the bradyrhizobia residing in “pockets” within the canopy of koa. These canopy pockets contain trapped organic soils that are mainly derived from decomposing heartwood and phyllode litter of the host tree. These canopy soils have significantly higher levels of exchangeable cations, total nitrogen content, and significantly lower aluminum levels than the terrestrial soils. Canopy Bradyrhizobium isolates from separate koa trees of different locations do not share matching box‐polymerase chain reaction (PCR) fingerprints, showing that there is no single type that is specific to canopy nodulation. Within the canopy pocket of a single tree, however, we observed a homogenous Bradyrhizobium population that was distinct from the proximal terrestrial population. Canopy nodulation has only been observed on mature koa trees and may function in maintaining symbiosis under stresses occurring within the rhizosphere of the terrestrial environment.
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