What are Gymnosperms?
Gymnosperms ( Gymnos: naked, sperm: seeds) were the first seed plants that bear naked seeds and ovules.
In this group of plants, ovary walls are not present to cover ovules. Gymnosperms mainly include shrubs and medium-sized tall trees. Gymnosperms along with angiosperms constitute the spermatophytes or seed-bearing plants. Are you in search of Gymnosperms Homework Help contact us with all your instructions and notes for assistance?
Gymnosperms mainly possess a taproot system. Roots can be associated with a fungus commonly known as mycorrhiza e.g. Pinus
or in some genera, specialized roots called coralloid roots are associated with cyanobacteria for nitrogen fixation e.g. Cycas
Stems
Stems can be branched as in the case of Pinus or unbranched as in the case of Cycas
Leaves
Leaves of gymnosperms can be simple or compound with well-developed tolerance power for getting adapted to extreme conditions. Needle-like leaves with thick cuticles and sunken stomata are seen in the case of conifers which help in reducing surface area and water loss.
Fertilization
Gymnosperms produce haploid but different male and female spores. Male spores are known as microspores whereas female spores are known as megaspores. The sporophyte is the dominating phase in this group of plants. Sporophyte bears reproductive structure known as cones which are surrounded by modified leaves known as sporophylls. Sporophyll bears sporangium in which spores are produced.
Male cones
Male cones or male strobili are supported by modified leaves known as microsporophylls. Microsporophyll bears microsporangium in which microspores are produced. Microspores divide inside the microsporangium to produce male gametophytes known as pollens which contain two sperm nuclei.
Female cones
The female cone occupies the higher end of the tree. The female cone also known as female strobili is surrounded by megasporophylls as modified leaves that bear megasporangium also known as nucellus. Megasporangium is covered by the envelope and this structure is known as an ovule.
One of the cells of this megasporangium differentiates into megaspore mother cell which divided meiotically producing four megaspores. Megaspores are produced inside this megasporangium. One of these megaspores develops into a female gametophyte which develops inside the megasporangium and bears two or more female sex organs or archegonia.
Pollination
From the microsporangium, pollen grains are released. These pollens are carried by wind to the opening of ovules. Pollens develop towards archegonia and discharge sperm nuclei near it. The fusion of female and male gametophytes results in zygote formation which further develops into an embryo. Ovules are further developed into seeds.