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A conifer cone, or in formal botanical usage a strobilus, pl.: strobili, is a seed-bearing organ on gymnosperm plants, especially in conifers and cycads. They are usually woody and variously conic, cylindrical, ovoid, to globular, and have scales and bracts arranged around a central axis, but can be fleshy and berry-like.
Most conifers are monoecious, but some are subdioecious or dioecious; all are wind-pollinated. Conifer seeds develop inside a protective cone called a strobilus. The cones take from four months to three years to reach maturity, and vary in size from 2 to 600 millimetres (1 ⁄ 8 to 23 + 5 ⁄ 8 in) long.
The cones are 8–17 cm (3– 6 + 1 ⁄ 2 in) long and 4–6 cm (1 + 1 ⁄ 2 – 2 + 1 ⁄ 4 in) broad, dark purple before maturity; [4] [5] the scale bracts are short, and hidden in the closed cone. The brownish winged seeds are 3.5 mm (1 ⁄ 8 in) long [4] and released when the cones disintegrate at maturity about 6–7 months after pollination.
Strobili are often called cones, but some botanists restrict the use of the term cone to the woody seed strobili of conifers. Strobili are characterized by a central axis (anatomically a stem ) surrounded by spirally arranged or decussate structures that may be modified leaves or modified stems .
The male cones are small, 0.5–6 cm (1 ⁄ 4 – 2 + 1 ⁄ 4 in) long, and fall soon after pollination; pollen dispersal is by wind. Seed dispersal is mostly by wind, but some species have large seeds with reduced wings, and are dispersed by birds.
The multiple cones of Z. integrifolia may develop through three methods: sympodium, forking of the bundle system, and adventitious buds. The most common form of development is the rapid formation of cone domes on the plant's sympodium, which is its main axis. More cones are present when there is a "branching" of the bundles to the cones.
Cross section of ovule in gymnosperms and angiosperms. Gymnosperm pollen is produced in microsporangia borne on the scales of the male cone or microstrobilus.In most species, the plants are wind-pollinated, and the pollen grains of conifers have air bladders that provide buoyancy in air currents.
The cones are small and inconspicuous at pollination in late winter, the pollen cones in clusters of 10–30 together, the female cones singly or 2–3 together. [ 6 ] The seed cones mature in 7–8 months to 2.5–4.5cm long, ovoid to globose, with spirally arranged scales; each scale bears 3–5 seeds .