Strobilus of Equisetum telmateia subsp. The small white protuberances are accumulated silicates on cells. Spores[ edit ] The spores are borne under sporangiophores in strobili , cone-like structures at the tips of some of the stems. In many species the cone-bearing shoots are unbranched, and in some e. In some other species e. Horsetails are mostly homosporous , though in the field horsetail, smaller spores give rise to male prothalli.
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The sporophytic plant body of Equisetum is differentiated into stem, roots and leaves Fig. In majority of the species, all the shoots are alike and chlorophyllous and some of them bear strobili at their apices e. Sometimes shoot shows dimorphism two types of shoots i. Some shoots are profusely branched, green chlorophyllous and purely vegetative. The others are fertile, unbranched, brownish in colour achlorophyllous and have terminal strobili.
The underground rhizome and the aerial axis appear to be articulated or jointed due to the presence of distinct nodes and internodes.
Externally, the internodes have longitudinal ridges and furrows and, internally, they are hollow, tube-like structures. The ridges of the successive internodes alternate with each other and the leaves are normally of the same number as the ridges on the stem. Internal Features of Stem: In T. The epidermal cell walls are thick, cuticularised and have a deposition of siliceous material.
Stomata are distributed only in the furrows between the ridges. A hypodermal sclerenchymatous zone is present below each ridge which may extend up to stele in E. The cortex is differentiated into outer and inner regions. There is a large air cavity in the inner cortex corresponding to each furrow and alternating with the ridges, known as vallecular canal.
These are schizolysigenous canals extending the entire length of internodes and form a distinct aerating system. New leaves and branches of Equisetum are produced by the apical meristem, however, most of the length of the stem are due to the activity of intercalary meristem located just above each node. The activity of intercalary meristem causes rapid elongation of the inter- nodal region.
The stele is ectophloic siphonestele which is surrounded by an outer endodermal layer. An inner endodermis is also present in some species of Equisetum e. Vascular bundles are conjoint, collateral and closed. In the mature vascular bundle, protoxylum is disorganised to form a carinal cavity which lies opposite to the ridges.
The metaxylem tracheids scalariform or reticulate are present on both sides of the phloem. In some species vessels with reticulate perforations are reported. The central part of the internode of aerial shoot is occupied by a large pith cavity which is formed due to rapid elongation of the internodal region.
The vascular bundles remain unbranched until they reach the level of node. At the nodal region, each vascular bandle trifurcates divided into three parts. The middle branch of the trifurcation enters the leaf. There are no vallecular or carinal canals at this level.
In addition, a plate of pith tissue occurs at the node which separates one internode from another. The internal structures of the shoot of Equisetum is peculiar because it shows xerophytic as well as hydrophytic features. The xerophytic features are: i Ridges and furrows in the stem, ii Deposition of silica in the epidermal cells, iii Sunken stomata, v Reduced and scaly leaves, and vi photosynthetic tissue in the stem.
The hydrophytic characteristics on the other hand are i we developed aerating system like carinal canal, vallecular canal and central pith cavity, and ii reduced vascular elements. Root: The primary root is ephemeral. The slender adventitious roots arise endogenously at the nodes of the stems.
The epidermis consists of elongated cells, with or without root hairs. The cortex is extensive; cells of the outer cortex often have thick walls sclerenchymatous and those of the inner cortex are thinner parenchymatous. The stele is protostelic where the xylem is triarch or tetrarch, or, in smaller roots, may be diarch. A large metaxylem element is present in the centre of the stele and the protoxylem strands lie around it.
There is no pith. Leaves: The leaves of Equisetum are small, simple, scale-like and isophyllous; they are attached at each node, united at least for a part of the length and thus form a sheath around the stem. The sheath has free and pointed teeth-like tips. The number of leaves per node varies according to the species. The species with narrow stems have few leaves e.
The number of leaves at a node corresponds to the number of ridges on the internode below. The leaves do not perform any photosynthetic function and their main function is to provide protection to young buds at the node. Reproduction in Equisetum: Equisetum reproduces vegetatively and by means of spores.
Vegetative Reproduction: The subterranean rhizomes of some species e. The tubers develop due to irregular growth of some buds at the nodes of the rhizomes. Reproduction by Spores: Spores are produced within the sporangia. The sporangia are borne on the sporangiophores which are aggregated into a compact structure termed strobilus or cone or sporangiferous spike.
However, they may be borne terminally on a strictly non- chlorophyllous axis e. On the under surface of the sporangiophore disc elongate, cylindrical hanging sporangia are borne near the periphery in a ring. The axis bears a ring-like outgrowth, the so-called annulus immediately below the whorls of sporangiophores which provide additional protection during early development.
Development of Sporangium: The mode of development of sporangium is eusporangiate, as it is not entirely formed from a single initial.
Sporangia are initiated in single superficial cell around the rim of the young sporangiophore. The periclvnal division of the sporangium initial forms an inner and an outer cell. The inner cell, by further divisions in various planes, gives rise to sporogenous tissue.
The innermost layer of the sporangial wall differentiates as the tapetum. The sporogenous cells separate from each other, round off and eventually transform into spore mother cell.
All but the two outermost wall layers disorganise to form periplasmodial fluid. Each spore mother cell undergoes meiotic division reductional division and produces spore tetrad. All spores in a sporangium are of same size and shape i. The inner layer is generally compressed and the cells of the outer layer have helical thickenings which are involved in sporangial dehiscence. Dehiscence of Sporangium: At maturity, the strobilar axis elongates, as a result the sporangiophores become separated and exposed.
Then the sporangium splits open by a longitudinal line due to the differential hygroscopic response of the wall cells. Spores: The spores are spherical and filled with densely packed chloroplasts. The spore wall is laminated and shows four concentrate layers. The innermost is the delicate intine, followed by thick exine, the middle cuticular layer and the outermost epispore or perispore.
The intine endospore and exine exospore are the true walls of the spore. The outer two layers i. At maturity, the epispore the outermost layer splits to produce four ribbon like bands or strips with flat spoon-like tips. These bands are free from the spore wall except for a common point of attachment and remain tightly coiled around the spore wall until the sporangium is fully matured.
These are called elaters Fig. The elaters are hygroscopic in nature. These uncoiled elaters become entangled with the elaters of other spores. The elaters of Equisetum are different from those of the bryophytes Table 7. Gametophyte Generation: Equisetum is a homosporous pteridophyte. The germination takes place immediately if the spores land on a suitable substratum. The spores swell up by absorbing water and shed their exine Fig. The first division of the spore results in two unequal cells: a small and a large cell Fig.
The smaller cell elongates and forms the first rhizoid. The larger cell divides irregularly to produce the prothallus. If a large number of spores are developed together within a limited space, then the prothalli formed are of thin filamentous type.
But a relatively thick and cushion-shaped prothalli are formed from sparsely germinating spores. They are dorsiventral and consist of a basal non-chlorophyllous cushion-like portion from which a number of erect chlorophyllous muticellular lobes develop upwards. Unicellular rhizoids are formed from the basal cells of cushion Fig.
Sexuality in Equisetum: The gametophytic plant body bears sex organs i. The gametophyte are basically bisexual homothallic i. Although, some unisexual dioecious members are also reported Fig. Some are initially unisexual and then become bisexual. This early sex determination appears to be related to the environmental conditions viz. Ducket , in order to explore the sexuality in Equisetum, observed that some of the fragments of male gametophyte remained male throughout the successive subcultures under laboratory conditions.
Some other fragments produced archegonia, which subsequently bore antheridia in increasing numbers. However, Hanke observed that gametophyte of Equisetum bogotense were unisexual bearing antheridia and never change to bisexual type. However, the initial male gametophyte of E. A study of sexuality based on enzymatic analysis revealed the intragametophytic self- fertilisation in E. Equisetum is homosporous and, therefore, definite sex-determining mechanism is absent.
But, the sexuality demonstrated by some of the members appears to be related to environmental factors. Therefore, it is termed as environmental sex determination.
EQUISETUM BOGOTENSE PDF
Viewed bootense TEM, the exospore is a thick layer of fine granular material, while perispore is a thinner layer of dense, separate orbicules. It can be downloaded from the Internet. Equisetum bogotense Images The plant is often gathered from the wild for local medicinal use and is sold in local markets. Now containing plants. The gogotense has a history as a traditional equiestum remedy, and a study of its diuretic effects on humans showed significant increases in urinary sodiumpotassiumand chloride. Human and animal trials of indicate that E. The tapetum disintegrates towards the end of the sporogenesis, leaving spores free within the sporangial cavity.
Equisetum: Habitat, Structure and Reproduction