Reproductive Structures of Pteridophyte

The Pteridophyte sporophyte, besides being a prominent component of soil and vegetation, is an important ornamental plant in gardens and lawns. Indoors, its gracefulness and shape fit it ideally as a plant for pot culture in hallways and living rooms, especially during the months of November to March. Transportation of whole plants from one place to another without damage is attempted by packing them in sand, decomposed silt, ashes, or sawdust.

Despite their rich horticultural value, many Pteridophytes are vanishing from nature due to indiscriminate destruction of their natural habitats and capturing of species for ornamental purposes. The best means of conservation is an adequate botanical knowledge of these plants, together with their habitats. The approaches of the non-destructive collection of herbarium specimens are now being stressed. The collection is also supplemented with data regarding the locality and habitat, so as to make it depictive as well as meaningful. Such a collection, if possible to preserve along with a good mascot, would serve the purpose of education as well as bring nature into a classroom setting.

Pteridophytes, including ferns, horsetails, and lycophytes, form one of the largest groups in the plant kingdom, comprising some 14,000 species in about 300 genera. Pteridophytes differ from bryophytes in that they possess vascular tissues and produce true sporophytes; ferns are well developed sporophytes which are genotypically diploid and dominant and have more than one type of vegetative organ. It is believed that ferns might become extinct in future if the changes in climate which took place in the tertiary period would again occur on a world-wide scale. felt that the economic importance of ferns is more widely recognized than ever before. They were an important ornamental plant long before applicant status was granted. They were used as sentiments for decoding personality characteristics from the Victorian age through the 1940s.

Sporangia

Among different groups of pteridophytes, consideration of sporangial types helps to sort the ones of interest. Sporangia may vary in relation to their structure, arrangement of the sporophytes, or the method of production. In pteridophytes considered as spore plants, sporangia are the reproductive organs which produce spores. Given minute size of spores, they are of significance in physical examination. Analysis based on the differences in shape, size, ornamentations, and arrangement of the sporangia gives ample information besides the taxonomic value. In addition, sporangia fall under two natural divisions, namely eusporangiate and leptosporangiate. Eusporangiate sporangia are those which arise from one or more hypodermal cells. As the sporangia mature, longitudinal splitting occurs on the ventral surface and results in the liberation of numerous spores at one time.

The sporangium has attained various modifications to suit the environmental conditions in relation to different groups of the pteridophytes. Viewed from the surroundings of their spore mother cells and the dehiscence mechanism, these sporangia are classified into four major groups. Leptosporangia are sporangia which are characterised by the fact that they arise in a simple manner from a single epidermal cell, the sporangeous tissue consisting of a single layer of cells and which disrupt to the escape of spores. Then there are the eu sporangia which arise in a complex manner and are formed by the division of one or more epidermal cells and accompanying expansion, for example, the marattia type. These eu sporangia produce a large number of comparatively large spores in diameter. There are further a number of species which possess sporangia possessing characters which place them definitely between the two extremes, and these are all grouped together in the protospore type or those possessing pteroidiaceous niods.

Gametophyte Development

The prothallus is herbaceous, typically green, and has well-defined epidermis covered with 1–layered thin-walled hairs. In most cases, it starts a few days after spore germination. The first division of the germinating spore is symmetrical equatorial and yields two cells. The upper cell is obstructed and produces the dorsal and oldest part of the prothallus. The lower cell is larger, to which the collar is attached, later followed by the underdeveloped paper-thin lobes. The initial cell of the prothallus is oval or campanulate, with large vacuoles displaced towards the crushed basal portion. Growth occurs due to the repeated dichotomy or trichotomy of the initial cell segment, followed by the api1 bene branch growth type.

The prothallus continues to grow and get firmly attached to the substratum, undergoing a warped distortional metamorphosis until it looks like a drooping lamb’s tongue. The mid-prothallial cells are flat, whereas the ventral cells are more elongated and curve downwards, causing an oblique angle between the two dorsal longitudinal planes. Fronds are borne unexpectedly on three or more places, slightly curved and with shallowly lobed peltiform stalks embracing the lamina. Deeply fringed and lobed leaves are borne on older plants. The only anisotopes are produced in some young fronds in or near the axils of the flank leaves which are lifted up and slightly incurved, each accompanied by two smaller dorsal leaves. A balance is kept between the frond production rate and closure of the fork, erecting progressively longer, wider and more crowded fronds with narrower angles.

The prothallus begins to develop in one to two weeks after favorable conditions (water, warmth and light) are provided for intending germination. As seen in the transverse section, the recently germinated spore is closed and hemispherical in shape with a clear exterior and smooth surface, probably being more or less hydrated. With the commencement of growth, the exospore becomes irreversibly separated from the megasporangial tuff due to the loosening of attachments around or through a stout and short stalk. The dehiscence of the gall barnacle is followed by initial and division-elongation stages. The dehisced capsules are freely floating about in the water with a translucent vainglory-shaped outline.