Structure of a rice panicle. Schematic representation of a rice panicle comprising a main central axis (blue line) named rachis, to which primary branches (Pb) are attached (black lines); the primary branches bear secondary branches (Sb, green lines), which in turn bear tertiary branches (Tb, orange lines). Spikelets (Sp) are attached to the branches by a peduncle. Nodes are represented by red dots (ARM, Aborted Rachis Meristem). In the P-TRAP output results, the following terms are used instead of botanical terminology: Primary Axis (PA) for the blue line, the secondary axes (SA) for the black lines; the tertiary axes (TA) for the green lines and the quaternary axes (QA) for the orange lines.