Gymnosperms: Definition, Meaning, Examples, Reproduction, Plants, Topics

What Are Gymnosperms?

The term gymnosperm means ‘naked seeds,’ which defines this plant's characteristics in their reproductive arrangements. Thus, the group of gymnosperms were among the most evolutionarily significant throughout the process of plants’ development evolving during the Paleozoic era and existing in more recent epochs. They play an immense role in ecological life because they are parts of the forest systems and help to anchor soil and support multifaceted wildlife. Economically, they are viewed as a source of timber to produce construction and furniture since the gymnosperm produces wood. In the same regard, they offer resins used in varnishes as well as in drugs, hence they are not only ecological. Yet, it is necessary to know about gymnosperms to understand their roles in ecosystems and determine their value for global communities.

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Characteristics Of Gymnosperms

Gymnosperms are characterized by several distinctive features:

General Features

Seed development:

Gymnosperm seeds lack shells, that is they are not protected by fruits as is observed in angiosperms. These seeds also mature on the exterior of partly or wholly distinct organs like cones or modified foliage.

Absence of fruits and flowers:

Gymnosperms have no true fruits and flowers as those found in angiosperms. Instead, their reproductive structures are often cones (strobile) for the production of seeds.

Vascular system:

Most gymnosperms have an advanced xylematic and phylematic system. There is a transport of water and minerals in the plant from roots to staking parts through the xylem while the phloem transports sugars and nutrients from the photosynthetic part of the plant to the assorted tissues.

Morphological Characteristics

Leaf types

Needle-like Leaves: These are leaves that contain cones and they are found in plants like pines, cedars, spruces and firs they are of benefit to them in that they help them reduce their rate of water evaporation plus they are of benefit in a cold climate.

Scale-like Leaves: Some cypresses and junipers have scale-like foliage which helps lessen water loss and resistance to the surrounding stresses.

Root And Stem Structures

Roots:

The taproot is usually highly developed in gymnosperms and it allows the plant to get water from deeper layers of the ground. Some of the species also have what is known as lateral roots which run parallel to the surface of the ground as they expand the area that can be used in the provision of resources.

Stems:

Stems in gymnosperms may be woody and may be erect or may be prostrate or even creeping in some cases. There is tendril protection using a thin layer of the bark cover and the presence of secondary thickening development, allowing an increment in thickness. Stems contain a reproductive organ like cones or strobili in which seeds are formed.

Classification Of Gymnosperms

The gymnosperm class are listed below-

Major Divisions

Cycadophyta (Cycads)

Cycads are prehistoric seed-producing plants belonging to the division Pteridophyta and more commonly grouped under the kingdom Gymnosperms, they have stout stems and large palm-like fronds. They are mostly encountered in the tropical and subtropical areas of the globe and what can be striking about them is the fact that they are nitrogen-fixing cyanobacteria.

Ginkgophyta (Ginkgo)

Gymnosperms are those plants that possess seeds in sporangia which are exposed; ginkgos are a category of gymnosperms and the only living species of this plant is ginkgo biloba. It has large fan-like leaves and is most commonly used as a shade-bearing tree in urban gardens. It is in the presence of ginkgos that both adaptability to pollution and a relatively long evolutionary history stretching from Mesozoic times have been noted.

Coniferophyta (Conifers)

Gymnosperms are seeds plants with naked seeds without special integuments, and the conifers which are the largest and most diverse are trees and shrubs that bear leaves which are usually needle-like or Scot-like. They make cones as reproduction structures, seeds usually appear at the scales of the female cones. Temperate/boreal conifers can be found in most of the areas of the world and are vital in roles such as timber production and paper and resin industries.

Gnetophyta (Gnetum, Ephedra, Welwitschia)

Gnetophytes are a diverse group of gymnosperms comprising three distinct genera: Two of them are Gnetum and Ephedra whereas the third and last one is more of a curiosity as it falls under the category of a gymnosperm called Welwitschia. It ranges from vine-like climbers like Gnetum, mini-shrubs like Ephedra, and the bizarre Welwitschia which has only two ribbon-like leaves that in its lifetime never cease to grow. Gnetophytes are natives of tropical and subtropical areas though some of the species should be adapted to desert conditions.

Life Cycle Of Gymnosperms

Gymnosperms exhibit distinct reproductive structures:

Reproductive Structures

Male Cones (Microsporangia):

Male cones contain microspores derived from meiosis within specialized tissue referred to as microsporangia. They differentiate into pollen grains and bear male gametophytes (sperm cells) in the form of microspores.

Female Cones (Megasporangia):

Female con distinguished from male called strobil, include ovules inside structures, referred to as megasporangia. Within each ovule is a megasporocyte; through meiosis it forms megaspores which are also known as megaspore mother cells. The single functional megaspore was interpreted to give rise to a female gametophyte only.

Pollination And Fertilisation

Pollination:

Pollen grains reach the feminine cone either using wind or animals; as a consequence, they attach themselves to this structure. Furthermore, some gymnosperms feature the formation of pollen tubes together with the transfer of sperm cells into the female gametophyte.

Fertilisation:

When pollen grain sperm cells penetrate the female gametophyte and fertilize eggs, fertilization is said to have taken place. This process helps to form a ‘zygote’ which subsequently begins to grow into an embryo or seed.

Development Of Seeds

After fertilisation, a structure called the zygote forms an embryo, while the outer layer of the ovule forms what is referred to as a seed coat. Inside the cone, the seed is mature showing its protective casing and nutrient supply for embryonic development. Once they have reached maturity, they release seeds either by themselves or with the help of wind or animals that help deposit them on the ground where they can germinate under the right environmental conditions to produce a new gymnosperm plant.

Diagram: Life Cycle Of A Pine Tree

Ecological And Economic Importance

Ecological Roles:

Along with this, the depicted species play an important role in the cycling of carbon through photosynthesis and serve as homes and food providers for animals, thus promoting the richness of fauna in the earth’s systems.

Economic Uses:

Furthermore, some species have been proven to be useful in the treatment of diseases and they are used for decoration and aesthetics, hence they bring in economic value.

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