Gymnosperms (gymnos: naked, sperma: 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, medium sized and 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 tap root system. Roots can be in associated with fungus commonly known asmycorrhiza e.g. Pinus
or in some genera specialized roots called coralloid roots are associated with cyanobacteria for nitrogen fixation e.g.Cycas
Stems can be branched as in case of Pinus or unbranched as in case ofCycas
Leaves of gymnosperms can be simple or compound with well developed tolerance power for getting adapted to extreme conditions. Needle like leaves with thick cuticle and sunken stomata are seen in case of conifers which help in reducing surface area and water loss.
Gymnosperms produce haploid but different male and female spores. Male spores are known as microspores where as female spores are known as megaspores. 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 or male strobili are supported by modified leaves known as microsporophylls. Microsporophyll bearsmicrosporangium in which microspores are produced. Microspores divide inside the microsporangium to produce male gametophyte known as pollens which contains two sperm nuclei.
Female cone occupies the higher end of the tree. Female cone also known as female strobili is surrounded bymegasporophylls as modified leaves which bear megasporangium also known as nucellus. Megasporangium is covered by envelope and this structure is known as ovule. One of the cells of this megasporangium differentiates intomegaspore mother cell which divided meiotically producing four megaspores. Megaspores are produced inside this megasporangium. One of this megaspore develops into female gametophyte which develops inside megasporangium and bears two or more female sex organ or archegonia.
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. Fusion of female and male gametophyte results in zygote formation which further develops into embryo. Ovules are further developed into seeds.