Cone (botanical)

Designation

In French-speaking Switzerland, one indicates it by the term pive and in the Landes of Gascogne, by that of pine cone (of the Gascon pinha , the pine cone indicates more precisely). In Quebec, one calls it also casserole .

Body carrying the gamétophytes

It is not a inflorescence strictly speaking, because Gymnospermes do not have a flower. They consist of scale S which recover the ones on the others on the basis of the base of the cone on a central axis. Each base of the scales contains the reproductive bodies of the plant. The male cones are much smaller and transitory that the cones females. The cone female is larger, it is the latter which one can see in the tree during all the year and which one often collects on the ground. It is more solid than the male cone because it ensures the growth of future the Graine of conifer.

They contain the Sporange S or are held the Méïose and the production of Spore S. the cones male produce Spermatozoïde S while the cones female produce Oosphère S. One says that conifers are hétérosporés. But each tree presents usually the two types of cones. The male cones produce small spores which will become Gamétophyte S males. The cones females are larger and more complexes which the male cones and contain the Ovule S.

Position of the cones on the tree

For the majority of the trees, the male and female cones push on different branches. The male cones push on the lower branches of the tree while the cones females are located on the higher branches. This provision makes it possible to cross fecundations. Indeed, as the Pollen has little chance to go up towards the cones females, fecundation is done normally by another tree.

Body carrying seeds

After fecundation, the cones females remain on the tree at least three years, time that it is necessary so that the seed develops. The large cones females are not fed any more by the plant mother and the dryness of the cone causes the opening of the scales. The scales deviate from the central rachis of the cone releasing the Graine S which are generally winged. This wing enables them to traverse long distances thanks to the Vent. One speaks about Anémochorie. That makes it possible the species to conquer new spaces.

Differences between the cones females of the species of conifers

Cone of Pinaceae

The family members of the Pinaceae (pines (Maritime pine, Umbrella pine, etc), fir trees, fir trees, cedars, larches, etc) have cones made up of overlapping scales the ones on the others like the skin of fish. They are the cone most common. The scales are arranged in spiral according to the Suite of Fibonacci.

The cone female has two types of scales, the scales of bractée, derived from a modified Feuille, and the scales at the origin of the Graine (or pinion), located close to the scales of bractée. On each higher side of the seed scales two ovules are which develop out of seeds after fertilization by grains of Pollen. The scales of bractée develop initially, and are mature at the time of the Pollinisation. The seed scales develop later to lock up and protect seeds while the scales of bractée often do not grow any more.

The scales open temporarily to receive the Pollen, then are closed again during the Fertilization and the maturation of seed. They are reopened then still with maturity to make it possible the Graine to escape. Maturation takes 6 to 8 months after pollination in the majority of the kinds of Pinaceae, but 12 months for the cedars and 18 to 24 months (seldom more) for the majority of the pines. The cones open at the level of the seed scales bending behind with drying of the cone, or (in the fir trees, the cedars and the larch of gold) by destruction of the cones.

Cones of Araucariaceae

The family members of the Araucariaceae (araucaria, Agathis, Wollemia) have their completely amalgamated scales of bractée and seed, and have only one ovule on each scale. The cones are spherical or almost, and rather large with a diameter from 5 to 30 centimetre. They mature in 18 months. With maturity, they disaggregate to release the Graine S. At the Agathis, the seeds fly away and separate easily from the scale of seed, but at the araucaria and the wollemia, the seed is without wing and amalgamated with the scale.

Cones of Podocarpaceae

The cones of the family of the Podocarpaceae are identical by their function but not in their development to those of the family of the Taxaceae. They are kinds of bay whose scales are strongly modified to attract the Oiseau X which disperse seeds. The majority of the cones of this kind are made of two to ten or more scales which amalgamated in a fleshy usually inflated Arille, brilliantly coloured, soft and edible. Usually, only one or two scales of the Apex of the cone is fertile. Each bay contains a seed without wing. The fleshy complex of scale measures approximately from 0,5 to 3 centimetre from length and the seeds measure from 4 to 10 millimetres length. At some species like Prumnopitys, the scales are small and nonfleshy, but the envelope of seed develops a fleshy layer with the place, the cone having then the aspect of small plums on a needle stem. The seeds have an envelope lasts to resist the Digestion of the stomach of the bird and can fallen with the excrements from the bird.

Cones of Cupressaceae

The cones of the family members of the Cupressaceae (cypress, tuya, genévriers, sequoias, etc) are different from different because their scales of bractée and seed are completely amalgamated in only one scale reduced to a piece or a simple visible spine. The cones females have one to 20 ovules on each scale. The cones are usually small from 0,3 to 6 long centimetre and often spherical or almost, like those of the cypress of Nootka whereas others, such as the cones of Western red cedar, are narrow. The scales are arranged either in spiral, or in spirals crossed in X of two or three, seldom of four. In the majority of the cases, the cones are made of wood and the seeds have two narrow wings (one along each side of seed), but at three kinds (Platycladus, Microbiota and Juniperus), the seeds are without wings, and at the Juniperus (genévriers), the cones are fleshy and resemble bays.

Cones of Sciadopityaceae

The cones and the seeds of Sciadopitys are similar to those of Cupressaceae, but they are larger measuring from 6 to 11 centimetres length. The scales are overlapping in spiral and have 5 to 9 ovules on each scale.

Cones of Taxaceae and Cephalotaxaceae

The family members of the Yew S and the Cephalotaxaceae have the most modified cones conifers. There is only one female scale per cone with a simple Ovule. The scale develops in a Arille soft, brilliant, coloured, juicy as a bay which contains seed partly. The " baie" with seed is eaten by the birds which digest the scale rich in sugars. The seed resistant to digestion falls on the ground with the excrements from the bird far from the plant mother.

References

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