Morphological and anatomical studies inTribulus terrestris I. Phyllotaxis and branching

Phyllotaxis and branching system inTribulus terrestris were studied. Besides three nodal types already known in the species, a new type was found. The four nodal types were designated as A (with one leaf and no flower), B (with one leaf and one flower), C (newly found type, with two leaves of different sizes and no flower) and D (with two leaves of different sizes and one flower). A-type nodes are found only in basal parts of shoots, while distal parts have exclusively D-type nodes. Between the nodes of the two types there is always one node of B-type. Occurrence of C-type is rare and restricted to the first node of the lateral branch. The first leaf of the lateral branch superposes to the leaves of the mother axis at maturity, but it is situated at first more or less laterally. On the basis of anatomy, as well as gross morphology, the branching system at B- and D-type nodes was interpreted as sympodial, the main axis ending in a flower. With regard to the manner of overlapping of sepal margins, right- and left-handed calyces were recognized. The handedness always corresponds to the direction to which the peduncle is inclined.