Equisetum
Class Sphenopsida
Order Equisetales
Family Equisetaceae
Genus Equisetum
Distribution
Equisetum is the only living representative of the family Equisetaceae. It is commonly known as Horse tail (aerial shoot with closely arranged whorls of branches look like a tail of a horse) or scoring rushes (due to sand papery texture due to deposition of silica).
The genus is represented by 32 species, found all over the world except in Australia and New Zealand. Most species occur in the north Northern temperate zone but they are also known in Arctic, the southern and temperate and the tropics of both the hemispheres.
In India it is represented by about 7 species. E. arvense is a cosmopolitan species. E. debile grows along the banks of sandy or swampy soil and is found even in the Gangetic plains. Other Indian species are E. diffusum, E.ramossissimum, E. maximum, E. dubium.
Class Sphenopsida
Order Equisetales
Family Equisetaceae
Genus Equisetum
Distribution
Equisetum is the only living representative of the family Equisetaceae. It is commonly known as Horse tail (aerial shoot with closely arranged whorls of branches look like a tail of a horse) or scoring rushes (due to sand papery texture due to deposition of silica).
The genus is represented by 32 species, found all over the world except in Australia and New Zealand. Most species occur in the north Northern temperate zone but they are also known in Arctic, the southern and temperate and the tropics of both the hemispheres.
In India it is represented by about 7 species. E. arvense is a cosmopolitan species. E. debile grows along the banks of sandy or swampy soil and is found even in the Gangetic plains. Other Indian species are E. diffusum, E.ramossissimum, E. maximum, E. dubium.
Habitat
Equisetum grows under various habitats but thrives well under damp and amphibious conditions. Commonly they are found along the banks of rivers, streams ,( E. debile, E. protease) and swampy places (E.palustris). E. debile grows under hydrophytic as well as xerophytic conditions. E.avernse grows in open grasslands, railway embankments, exposed sandy and dry places. E. avernse is commonly called field horse tail.
According to Vogt, few Equisetum species are used as ecological indicators, specially to indicate the mineral content of the soil in which they grow. According to Benedict, certain Equisetum species accumulate minerals including gold and can therefore well be used to determine the presence of minerals in the soil.
Sporophyte
External morphology
The plant body of Equisetum represents the sporophyte generation. All species are well branched, perennial herbs, containing a horizontal underground rhizome from which arise many roots towards lower side and many erect aerial shoots towards upper side.
Rhizome
Main stem is an extensively branched, sympodial, dark brown, rhizome. The rhizome penetrates deep into the soil. The rhizome presents a jointed appearance due to presence of distinct nodes and internodes.
On its nodes are present many scaly leaves. The scaly leaves are small, slender and united laterally with each other to form a sheet on the node.
The rhizome gives off aerial as well as subterranean branches that alternate with the scale leaves. A branch primordia, alternating with each leaf, is present on the node.
Aerial stem
From the rhizome, the aerial shoots arise towards upper side. They are conspicuously jointed and are green, rough and stiff. They are abrasive due to deposits of silica.
The jointed appearance is due to the presence of distinct nodes and internodes.
The nodes bear whorled leaves that are laterally fused at the base. The internodes are long and hollow and are longitudinally rigid and grooved.
Each ridge corresponds to a leaf at the node above and the ridges in the successive internodes alternate with one another.
Another characteristic feature of the stem is the presence of an intercalary meristem that is present at the base of the internodes and just about the node. The meristematic region is protected by the leaf sheath. The activity of this meristem is responsible for the increase in length of the internode.
The aerial stem maybe branched or unbranched. In E. arvense the Ariel princess or profusely branched the branches arise in whorls at the node. They alternate with leaves.
In most spaces the aerial branches are distinguish as sterile and fertile branches.
Sterile branches are green with whorl of scaly leaves at each node. They are photosynthetic. At each node whorl of lateral branches arise, which are assimilatory in function. Each whorl bears an equal number of branches to that of leaves.
Fertile branches are unbranched, non chlorophyllous and terminate into strobilus at the apex. In many species, the fertile branches die as soon as the spores are released. In other species the fertile branch is green and after the cone sheds the spores, it behaves like the sterile branch
Equisetum grows under various habitats but thrives well under damp and amphibious conditions. Commonly they are found along the banks of rivers, streams ,( E. debile, E. protease) and swampy places (E.palustris). E. debile grows under hydrophytic as well as xerophytic conditions. E.avernse grows in open grasslands, railway embankments, exposed sandy and dry places. E. avernse is commonly called field horse tail.
According to Vogt, few Equisetum species are used as ecological indicators, specially to indicate the mineral content of the soil in which they grow. According to Benedict, certain Equisetum species accumulate minerals including gold and can therefore well be used to determine the presence of minerals in the soil.
Sporophyte
External morphology
The plant body of Equisetum represents the sporophyte generation. All species are well branched, perennial herbs, containing a horizontal underground rhizome from which arise many roots towards lower side and many erect aerial shoots towards upper side.
Rhizome
Main stem is an extensively branched, sympodial, dark brown, rhizome. The rhizome penetrates deep into the soil. The rhizome presents a jointed appearance due to presence of distinct nodes and internodes.
On its nodes are present many scaly leaves. The scaly leaves are small, slender and united laterally with each other to form a sheet on the node.
The rhizome gives off aerial as well as subterranean branches that alternate with the scale leaves. A branch primordia, alternating with each leaf, is present on the node.
Aerial stem
From the rhizome, the aerial shoots arise towards upper side. They are conspicuously jointed and are green, rough and stiff. They are abrasive due to deposits of silica.
The jointed appearance is due to the presence of distinct nodes and internodes.
The nodes bear whorled leaves that are laterally fused at the base. The internodes are long and hollow and are longitudinally rigid and grooved.
Each ridge corresponds to a leaf at the node above and the ridges in the successive internodes alternate with one another.
Another characteristic feature of the stem is the presence of an intercalary meristem that is present at the base of the internodes and just about the node. The meristematic region is protected by the leaf sheath. The activity of this meristem is responsible for the increase in length of the internode.
The aerial stem maybe branched or unbranched. In E. arvense the Ariel princess or profusely branched the branches arise in whorls at the node. They alternate with leaves.
In most spaces the aerial branches are distinguish as sterile and fertile branches.
Sterile branches are green with whorl of scaly leaves at each node. They are photosynthetic. At each node whorl of lateral branches arise, which are assimilatory in function. Each whorl bears an equal number of branches to that of leaves.
Fertile branches are unbranched, non chlorophyllous and terminate into strobilus at the apex. In many species, the fertile branches die as soon as the spores are released. In other species the fertile branch is green and after the cone sheds the spores, it behaves like the sterile branch
Leaves
Equisetum is micro fillers the leaves are simple irregular surface and extremely reduced in size they arise in viral at each node and their number varies with species.all the leaves are late relief use a sheet around the base of the internals the sheet and pointed teeth like tips. the leaves are mainly protective in function and in some species the leaves become dead and scale like at maturity the leaves do not perform any photosynthetic function at each node alternating with the leave there is a branch primordium the leave as a single median when they are usually without chlorophyll
Roots
The roots develop from the nodes of rhizome or from the base of the stem. They are long, slender, well branched and adventitious.
The roots arise indigenously from the pericycle. The roots are extensively branch and have a root cap at their tips
Equisetum is micro fillers the leaves are simple irregular surface and extremely reduced in size they arise in viral at each node and their number varies with species.all the leaves are late relief use a sheet around the base of the internals the sheet and pointed teeth like tips. the leaves are mainly protective in function and in some species the leaves become dead and scale like at maturity the leaves do not perform any photosynthetic function at each node alternating with the leave there is a branch primordium the leave as a single median when they are usually without chlorophyll
Roots
The roots develop from the nodes of rhizome or from the base of the stem. They are long, slender, well branched and adventitious.
The roots arise indigenously from the pericycle. The roots are extensively branch and have a root cap at their tips
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