Classification, Characteristics and Life Cycle of Gymnosperms

The term “Gymnosperm” is derived from the Greek words “gymnos” (naked) and “sperma” (seed), and thus refers to “naked seeds.” Gymnosperms are seed-producing plants, but unlike angiosperms, they do not produce fruits. These plants form cone-like structures on the surface of scales or leaves, or at the ends of stalks.

Gymnosperms are members of the kingdom Plantae and the sub-kingdom Embryophyta. The fossil evidence suggested that they appeared around 390 million years ago, during the Paleozoic era.

Gymnosperms are plants in which the ovules, unlike angiosperms, are not enclosed within the ovary wall. It is exposed before, during, and after fertilization, as well as before developing into a seed.

Gymnosperm stems can be branched or unbranched. These plants’ thick cuticle, needle-like leaves, and sunken stomata reduce the rate of water loss.

Conifers, cycads, gnetophytes, and Gynkgophyta division and Ginkgo biloba are members of the gymnosperm family.

Let’s take a look at gymnosperm characteristics, examples, classification, and examples.

Characteristics of Gymnosperm

Gymnosperms have the following important characteristics:

1. They don’t make flowers.
2. Their fruit does not produce seeds. They are completely naked.
3. They are found in colder climates with snowfall.
4. They sprout needle-like leaves.
5. They are either perennial or woody, growing as trees or bushes.
6. They are not classified as ovary, style, or stigma.
7. Because there is no stigma, they are pollinated directly by the wind.
8. Male gametophytes produce two gametes, one of which is functional.
9. They form cones with reproductive structures 
10. The seeds contain endosperm, which stores food for the plant’s growth and development.
11. These plants have vascular tissues that help transport nutrients and water.
12. The xylem lacks vessels, and the phloem lacks companion cells and sieve tubes.

Classifications of Gymnosperm

Gymnosperms are classified into four types, which are listed below:

Cycadophyta

Cycads are dioecious plants (meaning: individual plants that are either all male or female). Cycads are seed-bearing plants, the majority of which have become extinct. They were abundant during the Jurassic and late Triassic periods. The plants are now regarded as historical relics.

Large compound leaves, thick trunks, and small leaflets attached to a single central stem characterize these plants. They range in height from a few centimetres to several meters.

Cycads are found primarily in the tropics and subtropics. Some members have adapted to dry arid conditions, while others have adapted to oxygen-deficient swampy environments.

Ginkgophyta

Ginkgophyta, another Gymnosperm class, has only one living species. All other members of this class have died out.

Ginkgo trees are distinguished by their large size and fan-like leaves. Ginkgo trees also have a wide range of applications, from medicine to cooking. Ginkgo leaves are used to treat memory disorders such as Alzheimer’s.

Ginkgo trees are also extremely resistant to pollution, as well as disease and insect infestations. In fact, after the nuclear bombs were dropped on Hiroshima, six Ginkgo trees were the only living things to survive within a kilometer or two of the blast radius.

Gnetophyta

Gnetophytes, like any other member of the gymnosperm family, are a relic from the past. There are currently only three members of this genus.

Gnetophytes are typically tropical plants, trees, and shrubs. They are distinguished by flowery leaves with a soft coating. This coating reveals an ancestral link to angiosperms.

Gnetophytes are distinguished from other members of this class by the presence of vessel elements in their xylem.

Coniferophyta

These are the most well-known members of the gymnosperm family. Because they are evergreen, they do not shed their leaves in the winter. These are distinguished primarily by male and female cones that form needle-like structures.

Coniferous trees are typically found in temperate zones with average temperatures of 10 degrees Celsius. Conifers include giant sequoia, pines, cedar, and redwood.

Examples of Gymnosperms

The following are some examples of gymnosperms:

1. Cycas
2. Pinus
3. Araucaria
4. Thuja
5. Cedrus
6. Picea
7. Abies
8. Juniperus
9. Larix

Life Cycle of Gymnosperms

Gymnosperms have both haploid and diploid life cycles, which means they reproduce through generational alternation. They go through a sporophyte-dominant cycle.

The gametophyte stage lasts only a few days. Cones are commonly used as reproductive organs.

Male Cones 

Male cones have microsporophylls containing microsporangia. Haploid microspores are produced by Microsporangium. A few microspores mature into male gametes known as pollen grains, while the rest degenerate.

Female Cones

Megasporophylls congregate to form female cones. They have megasporangium-containing ovules. It generates haploid megaspores as well as a megaspore mother cell.

Wind or another pollinating agent transports pollen to the egg, where it releases a sperm. A zygote is formed when the nuclei of male and female gametophytes fuse. This is referred to as fertilization.

The seed is visible as scales on the cones of the gymnosperm.