Pine Life History

The pine tree is a sporophyte. It has roots, stems, and leaves (needles). The roots are usually diarch and develop a vascular cambium and form wood. The young stem has vascular bundles in a ring. The vascular cambium differentiates and annual growth rings of secondary xylem make a woody trunk. The branches (long shoots) have short shoots called fasicles. The fasicles each produce a certain (determinate) number of leaves from 1 to 10 or so.

As a sporophyte, the pine tree produces cones. The microsporangiate cone is a simple strobilus. Each cone scale is a microsporophyll and contains a microsporangium. The megasporangiate cone is a compound strobilus. Each cone scale consists of a megasporophyll and a smaller subtending bract. The ovules are on the upper surface of the megasporophyll.

The important details of the sexual life history are shown below. The basic color code is simple. Sporophyte cells and tissues are usually green. Sporangia are red. The sporocytes are yellow. The spores are cyan. The gametophytes are blue. Nuclei are magenta (when shown).