Let be a Riemannian symmetric space of non compact type with real rank one. For and an integrable function on the Furstenberg boundary , the Poisson transform of is given by
The aim of this talk is to present a necessary and a suffucient condition on eigenfunctions of the Laplace-Beltrami operator associated to with eigenvalue to have an -Poisson integral representations on the boundary . A special discuss of the case of the exceptional symmetric space.