`star` Introduction
`star` Vegetative Structures
`star` Reproductive Structures
`star` Life Cycle


โ—The gymnosperms (๐˜จ๐˜บ๐˜ฎ๐˜ฏ๐˜ฐ : naked, ๐˜ด๐˜ฑ๐˜ฆ๐˜ณ๐˜ฎ๐˜ข : seeds) are plants in which the ovules are not enclosed by any ovary wall and remain exposed, both before and after fertilisation.

โ—The seeds that develop post-fertilisation, are not covered, i.e., are naked.

โ—Gymnosperms include medium-sized trees or tall trees and shrubs.

โ— One of the gymnosperms, the giant redwood tree ๐˜š๐˜ฆ๐˜ฒ๐˜ถ๐˜ฐ๐˜ช๐˜ข is one of the tallest tree species.


โ— The roots are generally tap roots.

โ— Roots in some genera have fungal association in the form of mycorrhiza (๐˜—๐˜ช๐˜ฏ๐˜ถ๐˜ด).

โ— In some others (๐˜Š๐˜บ๐˜ค๐˜ข๐˜ด) small specialized roots called coralloid roots are associated with N2- fixing cyanobacteria.

โ—The stems are unbranched (๐˜Š๐˜บ๐˜ค๐˜ข๐˜ด) or branched (๐˜—๐˜ช๐˜ฏ๐˜ถ๐˜ด), ๐˜Š๐˜ฆ๐˜ฅ๐˜ณ๐˜ถ๐˜ด).

โ—The leaves may be simple or compound.

โ—In ๐˜Š๐˜บ๐˜ค๐˜ข๐˜ด , the pinnate leaves persist for a few years.

โ—The leaves in gymnosperms are well-adapted to withstand extremes of temperature, humidity and wind.

โ—In conifers, the needle-like leaves reduce the surface area. Their thick cuticle and sunken stomata also
help to reduce water loss.



โ— The gymnosperms are heterosporous; they produce haploid microspores and megaspores.

โ—The two kinds of spores are produced within sporangia that are borne on sporophylls( microsporophyll and megasporophyll) which are arranged spirally along an axis to form lax or compact strobili or cones.

`color{Violet}"Male Structures"`:

โ— The strobili bearing microsporophylls and microsporangia are called microsporangiate or male strobili.

โ— The microspores develop into a male gametophytic generation which is highly reduced and is confined to only a limited number of cells.
โ— This reduced gametophyte is called a pollen grain.

โ—The development of pollen grains takes place within the microsporangia.

`color{Violet}"Female Structures"`:

โ— The cones bearing megasporophylls with ovules or megasporangia are called macrosporangiate or female strobili.

โ—The megaspore mother cell is differentiated from one of the cells of the nucellus.

โ—The nucellus is protected by envelopes and the composite structure is called an ovule.

โ— The ovules are borne on megasporophylls which may be clustered to form the female cones.

โ— The megaspore mother cell divides meiotically to form four megaspores.

โ—One of the megaspores enclosed within the megasporangium (nucellus) develops into a multicellular female

gametophyte that bears two or more archegonia or female sex organs.

โ—The multicellular female gametophyte is also retained within megasporangium.

โ—The male or female cones or strobili may be borne on the same tree (๐˜—๐˜ช๐˜ฏ๐˜ถ๐˜ด) or on different trees (๐˜Š๐˜บ๐˜ค๐˜ข๐˜ด).


โ— In gymnosperms the male and the female gametophytes do not have an independent free-living existence.

โ—They remain within the sporangia retained on the sporophytes.

โ— The pollen grain is released from the microsporangium. They are carried in air currents and come in contact with the opening of the ovules borne on megasporophylls.

โ—The pollen tube carrying the male gametes grows towards archegonia in the ovules and discharges their contents near the mouth of the archegonia.

โ— Following fertilization, zygote develops into an embryo and the ovules into seeds.
โ—These seeds are not covered.