This paper presents a method for describing plant architecture using topolo
gical and geometric information. This method is based on the use of a multi
scale model of plant topology-called multiscale tree graphs-which is extend
ed to include geometry. The relationships between both multiscale topology
and geometry are explicitly identified and topology and geometry are shown
to contain redundant information. This redundancy is expressed as sets of c
onstraints between the geometrical parameters of plant components that belo
ng either to one scale or to different scales. These within- and between-sc
ale constraints are used to reduce the number of measurements when digitizi
ng plant architecture and to implement the geometrical parameters that are
not specified. Different solutions for simplifying plant architectural desc
riptions are proposed. The method, implemented in software dedicated to pla
nt architecture analysis (AMAPmod), does not depend on the plant species or
on the geometric model used to describe the plant components. The multisca
le approach allows plant architecture to be represented at different levels
of accuracy. This method is illustrated on two plants, a 3-year-old apple
tree and a 20-year-old walnut tree, which correspond to applications of dif
ferent sizes and with different goals for the representation. (C) 1999 Anna
ls of Botany Company.