Describe the important characterstics of gymnosperms.

Explanation

The important general characters of gymnosperms are as follows `:`
(i) The gymnosperms plant body is called sporophyte. It is differentiated into stem, leaves and roots.
(ii) The leaves are dimorphic or of two types. These are foliage and scale leaves.
(iii) Presence of scale leaves thick bark sunken stomata, tranfusion , tissue and thick hypodermis are some of the xerophytic adaptation in gymnospermic plants.
Plant possess vascular-tissues i.e., xylem and phloem. They are arranged in vascular bundles.
(v) Secondary growth occurs in all gymnosperms with manoxylic wood in cycads ( Cycas ) and pycnoxylic wood in conifers ( Pinus) .
(vii ) Gymnosperms are heterosporous i.e., they produce two different kinds of spores, the male microspores and the female megaspores. The spores are borne inside sporangia.
(viii) The two types of sporangia are borne on special leaf like structures, called sporophylls. The microsporangia are borne on microsporophylls and the megasporangia are borne on megasporophylls. The sporophylls are usually aggregated in the form of compact structure, called cone or strobili.
(ix) Pollination is anemophilous ( wind pollination ).
(x) Each ovule is surrounded by integuments. It encloses the nucellus and a female gametophyte formed from the haploid megaspore. The female gametophyte contains archegonia.
(xi ) Each pollen gram germinates further inside the ovule and gives out a pollen tube.
(xii) The pollen tube reaches upto the egg cell and releases the two male gametes. One of the male gamete fertilzes the egg, forming a diploid zygote.
(xiii) The diploid zygote develops into an embryo and ovule becomes a seed. The wall of ovule becomes the seed coat.
(xv) The seeds of gymnosperm do not occur inside the fruits. They are naked and remain attached to the megasporophyll. The rip and dry seeds are shed. Each seed contains a young sporophyte in the form of dormant or inactive state.