The cycle of sexual reproduction
The cycle of sexual reproduction in the ontogeny of plants, explained by Pr. Marpha Telepova:
The development of a living being or ontogenesis * covers all phases from an embryo.
All organizations go through "the rise (youth) and loss of function (senescence).
So ontogenesis translates to "the irreversibility of life" functional or morphological, be they animal or plant species (CUENOT 1941; Roberty 1988).
Unlike most animals, which formed during embryogenesis all their organs (including a germline), the formation of organs in the ontogeny of plants remains under the influence of the phenomenon, known as a "Open growth” *.
So the plant by necessity generate additional vegetative organs (leaves, roots, rejection, runners).
For example, the organs of photosynthesis, the leaves are renewable and leaves will be the "replacement organs" in biennial plants (cycle completed in two calendar years).
Annual herbaceous plants after fruiting lose their leaves and this means the end of their life cycle.
For example, the time of ontogeny of a tree can reach 1000 years or more (eg baobab, Juniperus, Sequoia). We must also consider that the sex cells of plants are subject to essentially the environmental constraints.
Finally, following the onset of sexual reproduction in the ontogeny of "flowering plants", they are separated by the formation of various organs of reproduction (flowers) and form different classes and orders of angiosperms (WALTER et al . 2001).
The cycle "from seed to seed" includes an alternation of generations (sporophyte and gametophyte * *). Now and in the case of orchids, individuals, composed of diploid cells (2n) or polyploids (more than 2n) dominate in their life cycle. (Figure 1)
* Oytos: be; genesis: genesis * known phenomenon for organizations set; double * n * n only
by Marpha TELEPOVA-TEXIER
Département des Jardins Botaniques et Zoologiques du Muséum national d’Histoire naturelle, USM 0602, case postale 39, 57 rue Cuvier, 75005 Paris; telepova@gmail.com
The development of a living being or ontogenesis * covers all phases from an embryo.
All organizations go through "the rise (youth) and loss of function (senescence).
So ontogenesis translates to "the irreversibility of life" functional or morphological, be they animal or plant species (CUENOT 1941; Roberty 1988).
Unlike most animals, which formed during embryogenesis all their organs (including a germline), the formation of organs in the ontogeny of plants remains under the influence of the phenomenon, known as a "Open growth” *.
So the plant by necessity generate additional vegetative organs (leaves, roots, rejection, runners).
For example, the organs of photosynthesis, the leaves are renewable and leaves will be the "replacement organs" in biennial plants (cycle completed in two calendar years).
Annual herbaceous plants after fruiting lose their leaves and this means the end of their life cycle.
For example, the time of ontogeny of a tree can reach 1000 years or more (eg baobab, Juniperus, Sequoia). We must also consider that the sex cells of plants are subject to essentially the environmental constraints.
Finally, following the onset of sexual reproduction in the ontogeny of "flowering plants", they are separated by the formation of various organs of reproduction (flowers) and form different classes and orders of angiosperms (WALTER et al . 2001).
The cycle "from seed to seed" includes an alternation of generations (sporophyte and gametophyte * *). Now and in the case of orchids, individuals, composed of diploid cells (2n) or polyploids (more than 2n) dominate in their life cycle. (Figure 1)
* Oytos: be; genesis: genesis * known phenomenon for organizations set; double * n * n only
by Marpha TELEPOVA-TEXIER
Département des Jardins Botaniques et Zoologiques du Muséum national d’Histoire naturelle, USM 0602, case postale 39, 57 rue Cuvier, 75005 Paris; telepova@gmail.com