Gymnosperms - Structure, Classification & Reproduction

Most gymnosperms lack vessels, but Gnetum is a notable exception that possesses vessel elements in its xylem.

Sequoiadendron giganteum is the sole living species in the genus Sequoiadendron. Giant sequoia specimens are the most massive trees on Earth.The name "Wellingtonia" has persisted in England as a common name, also known as giant redwood, sierra redwood, sierran redwood, Wellingtonia  or simply big tree.

Roots in some genera of gymnosperms have fungal associations in form of mycorrhiza which is associated with N$ _2$ fixing cyanobacteria. For example, pinus.

• Conifers have non-motile sperm that needs to be moved along the pollen tube.
• Cycads have motile sperm with flagella (they have multiple flagella) that help them move to the egg along the pollen tube.

Gymnosperms are seed plants that lack flowers, relying primarily on wind for pollination. Wind pollination ensures efficient transfer of pollen from male to female cones over large distances. Animals and insects are typically involved in angiosperm pollination.

Progymnosperms are an extinct group of vascular plants that evolved from trimerophytes and served as precursors to seed plants and conifers. Fossil evidence indicates that they first appeared and diversified during the Devonian period. They are characterized by having fern-like foliage and secondary wood.

The wood of several Gymnosperms, particularly those of conifers is used in paper industry. Conifers wood is used as a structural timber and for making furniture.

Sequoia is the largest species on the planet. It belongs to the family Cupressaceae of Coniferales.

Conifers that belong to the largest and the economically most important component group of the gymnosperms and are known to consists of both living and fossil taxa. Represented by a number of species, the stems of conifers are composed of a woody axis containing primitive water- and mineral-conducting cells- tracheids. All living conifers are woody plants, and mostly evergreen trees, with a monopodial growth form.

Gymnosperm structural strength comes from tracheids (long tapered water-conducting cells) and wood fibers (thick-walled supportive cells). Vessels are mostly absent in gymnosperms (except Gnetum). Wood parenchyma stores nutrients but provides minimal structural support compared to fibers and tracheids.

Cycadofilicales, also known as Pteridosperms or seed ferns, are an entirely extinct order of gymnosperms.

Ephedra and Gnetum exhibit double fertilization, a process typically associated with angiosperms, making them exceptions among gymnosperms.

Ginkgo biloba is often called a living fossil because it has remained virtually unchanged for millions of years.

Deodar cedar is a conifer, evergreen, broadly pyramidal with gracefully pendulous branches, drooping central leader, spreading and flat-topped with age. Long branches bearing spur-like stems with whorled needles. Leaves are light blue or grayish green and softer. Deodar is not a dicot, fern or mosses. 

A sporophyll is a leaf that bears sporangia. Both microphylls and megaphylls can be sporophylls. In heterosporous plants, sporophylls (whether they are microphylls and megaphylls) bear either megasporangia and thus are called as megasporophylls, or microsporangia and are called as microsporophylls. The dicotyledons, also known as dicots, were one of the two groups into which all the flowering plants or angiosperms were formerly divided. Chlorophyll is the molecule that absorbs sunlight and uses its energy to synthesise carbohydrates from CO$ _2$ and water. Monocotyledons, more properly referred to as monocots, are flowering plants whose seeds typically contain only one embryonic leaf, or cotyledon. 

Conifers are most abundant in cool temperate and boreal regions, where they are important timber trees and ornamentals, but they are most diverse in warmer areas, including tropical mountains. They are the largest group of gymnosperms.
 The largest group of living gymnosperms are the conifers (pines, cypresses and relatives) and the smallest is ginkgo, a single living plant species found in China.
There are around 1000 species of gymnosperm. 

Cycas is dioecious in nature since it produces micro and megaspores in the micro and megasporangia. The micro and megasporangia are born on microsporophyll and megasporophyll respectively.

• The correct answer is 'false'

In conifers, the sporangia (microsporangia and megasporangia) are borne on specialized leaves called sporophylls, which are arranged in cones.

Ginkgo biloba is the classic example of a living fossil among gymnosperms.

Ginkgo is widely recognized as a living fossil that has shown little morphological change over geological time.

Ginkgo is considered an evolutionary link or intermediate form between cycads and conifers due to its unique combination of primitive and derived traits.

In pleurocarpous condition the sex organs are borne on short lateral branches.

Conifers are typically found in cool, temperate regions, and in India, they are characteristic of the Himalayan mountain range.

Taxus brevifolia is the scientific name for the Pacific Yew, a gymnosperm known for producing taxol.

Gnetum resembles angiosperms by having vessel elements in the xylem and lacking archegonia in the female gametophyte.

Cycadopsida is a class within the division Gymnospermae. The other options listed (Pteropsida, Sphenopsida, Lycopsida) are classes of Pteridophytes.

Ginkgo biloba is commonly known as the Maidenhair tree. It is a unique species of gymnosperm with no living relatives.

Gnetales are unique among gymnosperms because they possess vessels in their xylem, a trait typically associated with angiosperms.

Ephedra is a bushy trailing, climbing or creeping herbaceous gymnosperm. It is a genus of gymnosperm shrubs. It is used as medicine for treating asthma, hay fever and cold. 

• Gametophytes of liverworts, mosses, and ferns are independent and so are free-living.
• Gymnosperms and some ferns are heterosporous, meaning has two different types of spores.
• Sexual reproduction in Fucus, Volvox, and Albugo is monogamous meaning they have small flagellated male gamete and large non-flagellated female gamete.
• The sporophyte of moss is more elaborate than the liverworts.
• Pinus is monoecious while Marchantia is dioecious.

The Cordaitales and the Benneitales are the two extinct lines of Gymnosperms. The former existed during the paleozoic and early mesozoic era and have been regarded as an ancestral stock from which the modern conifers and Gnetales might have originated.

Ephedrine is a medicinal preparation obtained from the plant Ephedra, a genus of Gymnosperm and the only genus in its family, Ephedraceae, and order, Ephedrales. While there are various species of Ephedra, which are widespread, these are native to North America, south America, southern Europe, Africa central Asia and China. The plants of the genus Ephedra, especially E. sinica has been traditionally  used for a variety of medicinal purposes, including treatment of asthma, common cold and hay fever.

Sequoia trees are evergreen conifers. It is a member of Coniferale, family (also known as Pinnales). It is an evergreen, long-lived, monoecious tree living 1,200–1,800 years or more. It is a typically reddish brown tree with a brownish soft thick bark and are found on the western slopes of California.

The conifers are cone-bearing seed plants. Most are trees, some are shrubs. They are formally the division Pinophyta or Coniferophyta. 

Conifers are a magnificent group of gymnosperm plants that produce seeds without fruit or flowers. They include some incredible trees, such as the 'Giant Sequoias' of North America, that can grow over 110 m tall.

Conifers are all woody plants, mostly trees and a few shrubby species, they have either needle-like or scale-like leaves and most species are evergreen. They include the economically important pines and many other timber species that are exploited for use in construction and paper.

Gymnosperms have archegonia but no antheridia. The plants of this division are heterosporous. While the microspores or pollen grains produce the male gametophyte, the single megaspore within megasporangium (nucellus) develops into a female gametophyte, that bears two or more archegonia or female sex-organs. Also, there is no antheridium in which the sperm are produced.

Cycadofilicales, also known as Pteridosperms or seed ferns, are an extinct group of gymnosperms known only from the fossil record.

Gnetum is a genus of gymnosperms that lacks archegonia in its female gametophyte, which is a significant evolutionary departure from most other gymnosperms.