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Gymnosperms

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The term gymnosperms has a unique meaning, since it is translated as naked seeds and is used to designate an important characteristic of all those plants in which the ovules are born in an exposed position on the sporophylls or equivalent structures. They are plants widely used in the manufacture of furniture for their strong stems and in the construction of houses, in addition, they are also used in the production of different cosmetic and medicinal products. The word gymnosperms derives from the Greek term γυμνός “gymnos” and σπέρμα “sperm”, which together mean “ naked seed ”.

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What are gymnosperms?

Gymnosperms are a type of spermatophyte vascular plants that produce seeds and that instead of having a colored flower, they have a growing branch that produces a series of fertile leaves that have exposed seeds .

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  • Definition
  • Gymnosperm characteristics
  • Source
  • Evolution
  • Classification of gymnosperms
  • Reproduction
  • Habitat
  • Lifecycle
  • flowers
  • Fruits
  • Seeds
  • Estate
  • Examples of gymnosperms

Definition

Gymnosperms are the class of spermatophyte plants , in which the seeds are not protected inside the ovary , but on the contrary, they are exposed in the scales of their cones , and hence their name is derived which means ” naked seed ” . They are all vascular plants that have seeds, but are not capable of producing flowers .

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Gymnosperm characteristics

In gymnosperms, the most visible part of the plant body is the growing stem and branches and represents the sporophytic or asexual generation, rather than the sexual generation. Being vascular plants, they contain two conductive tissues, the xylem and the phloem. The xylem is responsible for carrying water and minerals from the roots to the rest of the plant and provides structural support. The phloem is responsible for distributing the sugars, amino acids and organic nutrients that are made in the leaves to the non-photosynthetic tissues of the plant.

They are vascular plants that produce seeds, they are generally woody trees that have evergreen leaves. Its leaves are deep green in color, thin and fine, and needle-shaped with a single vein. Its stem is robust and well developed, it has roots, leaves and seeds exposed in flowers. They do not have true fruits and have a very pleasant smell, which at the same time helps them to scare off insects.

Source

Gymnosperms were plants that dominated the Mesozoic Era , meaning they existed approximately 252.2 million to 66 million years ago, during which time some of the modern families of the same genus originated . Although since the Cretaceous Period these plants have been gradually displaced by more evolved angiosperms , they still inhabit many parts of the world and occupy large areas of the Earth’s surface. In the Permian , 60% of the flora in the world was represented by gymnosperms.

Evolution

In the period known as “Permian” approximately 300 and 250 million years ago, a series of important and great climatic changes occurred, which caused a drier and more arid type of climate, known as tropical climate , causing the disappearance of the great swamps and ending the period of the “Carboniferous” glaciation , and due to this, the extinction of the old gymnosperms occurred, giving rise to the new ones.

Classification of gymnosperms

Gymnosperms are classified into four divisions:

  • Cycadophyta or Cycads : They are palm-like plants in the tropics and subtropics .
  • Ginkgophyta – The only survivor of this type is the well-known Ginkgo biloba plant .
  • Gnetophyta : they are the most numerous and widely distributed of the genus of gymnosperms. It also includes species of great commercial value such as pines.

Reproduction

Gymnosperms are plants that have sexes separated from each other and for this reason they are considered dioecious plants , in other words, female and male plants . They are heterospores and it is through the male gametophytes that they manage to produce the spores, from which the female gametophytes, known as macrospores , develop . These spores unite to form the embryo , producing a type of scales on the seed. In other words, gymnosperm plants reproduce by means of seeds.

Habitat

In general , gymnosperms are distributed and inhabit temperate and cold zones and are capable of reaching great heights in them.

Lifecycle

The life cycle of these plants corresponds to the 2n sporophytic generation and the n gametophytes reside in a small number of cells originating from the sporophyte . Some produce two different types of pineapple-producing spores that are male and female . The female cones have woody haploid spore-forming leaves that give rise to female gametophytes. Male cones have leaf-like structures.

These spores originate pollen grains or male gametophytes that are carried by the wind . When they fall into the female cones, a long pollen tube is formed in the pollen grains that unites the male nucleus with the female nucleus. When the nuclei are fertilized, the 2n zygote is formed that divides mitotically and gives rise to the sporophyte embryo . The female gametophyte surrounds the embryo and this with the nutritive material is surrounded by the integument that protects the seed. When the female cone opens, it lets out the seeds that have an integument wing that facilitates their dispersion.. When the seeds fall on the ground and in a suitable environment, they germinate and originate new sporophytes.

flowers

The flowers of this type of plant are generally very small in size and are not very showy, so they can sometimes go unnoticed . The flowers that present the seminal primordia that are enclosed by a protective covering called carpel, which produces a fruit that contains the seeds , which are the mature seminal primordia.

Fruits

Gymnosperms are plants that do not have fruits. Some of them can produce false fruits , which actually have the function of providing protection to the seeds.

Seeds

They have bare seeds , in other words, the seeds are not enclosed within a fruit .

Estate

The main root of the plant has the ability to produce, by means of elongation and branching , the root system known by the name of allorhizo , which is characterized by a main root and lateral roots that are not morphologically equivalent .

Examples of gymnosperms

  • Gymnosperm plants:  ferns, araucarias, kauris.
  • Gymnosperm trees:  pine, fir, cypress, juniper, dwarf pine, cedar, larch, spruce.

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