Gymnosperms

Let us learn about Gymnosperms

The word Gymnosperm is made up of two words. meaning and meaning . It means .

Gymnosperms form an intermediate group between pteridophytes and angiosperms.

Ovules are not enclosed by an ovary wall. They remain exposed before and after fertilization.

Out of 900 species of gymnosperms, cone-bearing plants or conifers form the largest group with 500 species.

It occurs predominantly in northern mountain ranges including the Himalayas. Ex: Pine, Fir, Spruce, Cedar

Araucaria thrives well at lower elevations and in a warmer climate.

Sequoia (redwood tree) is one of the tallest plant species which measures more than 100 meters in height.

Let us acquire the knowledge on General characters of Gymnosperms

The Habitat of gymnosperms is woody.

Perennial plants formed dominant vegetation about 200 million years ago.

Gymnosperms have been replaced by Angiosperms because of the dominant vegetation.

The main plant is Sporophyte and heterosporous.

Male and female gametophytes are inconspicuous and depend for nutrition on the sporophyte.

The growth pattern of gymnosperms is monopodial.

It means lower branches are longer than upper branches.

The root system of Gymnosperms is a well-developed root system.

In pinus, the roots are in symbiotic association with some fungus. They are called .

The cycas roots possess cyanobacterium and blue-green algae.

In Cycas, the stems are unbranched. In Pinus and Cedrus, stems are branched.

Let us discuss the Reproduction in gymnosperms

The main plant is sporophyte and heterosporous.

Microspores or megaspores are haploid. They are produced in sporangia borne on sporophylls.

The sporophylls are arranged spirally along an axis forming lax or compact strobili or cones.

Male and female reproductive organs are present on separate cones.

Strobili bearing microsporophylls and microsporangia are called microsporangiate or male strobili.

Cones bearing macrosporophylls and macrosporangia are called macrosporangiate or female strobili.

The male and female cones or strobili may be borne on the same tree (Pinus) or on different trees. (Cycas)

Ovules are borne on megasporophylls which are clustered to form a female cone.

Megaspore mother cell divides meiotically to form haploid megaspores.

One of the megaspores develops into a multi-cellular female gametophyte or female sex organs

The male and female gametophytes in gymnosperms do not have an independent existence, unlike bryophytes and pteridophytes.

The pollens are released from the microsporangium and are carried with air currents to the ovules.

After fertilization zygote develops into an embryo, and the ovules into seeds. The seeds are naked.

Revision

Gymnosperms are formed from the words Gymnos meaning naked and sperm meaning seed. It means Naked seed.

The main plant of a gymnosperm is sporophyte and heterosporous.

Reproduction: The haploid is of two types: microspores and megaspores.

The pollens are released from the microsporangium and are carried with air currents to the ovules.

After fertilization zygote develops into an embryo, and the ovules into seeds. The seeds are naked.

The End.