Prof. Sabale R. R. (M. Sc.)
Prof. Sabale R. R. (M. Sc.)
Dept. Of Botany
LBS College Of Arts Commerce and Science,Satara.
DEVSION – CALAMOPHYTA
CLASS – EQUISETANAE
ORDER - EQUISETALES
FAMILY – EQUISETACEAE
GENUS – EQUISETUM.
Habit : -
The sporophyte of Equisetum has perennial , branched and creeping underground rhizome , which gives annual erect aerial two typed branched. The aerial branches are herbaceous and usually grow to a height of 10 – 60 cm and few millimeters to 10 cm in diameters. There are some species like E. gigantium grows up to 13 meters long.
Plant body differentiated into root , rhizome, aerial branches and leaves. Tuber develops on rhizome at nodal. Roots are produces on lower side of node on rhizome. The main stem is underground creeping and perennial rhizome. Leaves are simple, small, scaly whorled, Fused and non-chlorophyllous. Stem is differentiated into nodes and internodes.
There are two types of branches that are branches of unlimited growth and branches of limited growth. Internodes are with ridges and furrows. Branches of unlimited growth are sterile & give rise lateral branches .Branches of limited growth are fertile
T. S. of Stem :-
T. S. of aerial stem passing through internodes is wavy. It is differentiated into epidermis, cortex & stele.
Epidermis: - It is cuticularized with silicified cells . Stomata is present in the grooves
Cortex: - It is differentiated into outer & inner cortex. Outer cortex below the ridges is clerenchymatous. Beneath the ridges elongated chlorenchymatous cell present.The inner portion of cortex is large & thin walled parenchy- matous. Large vallecular canal present below the grooves. Endodermis surrounds ring of V. B.
Stele:- It is siphonostele. Pericycle is present below the endodermis. V. B. are collatral & endarch & lies below each ridges. Large pith cavity present at centre. Rest of tissue of vascular strands is parenchymatous.
T. S. Of Root :-
T. S. of root shows epidemis, cortex & stele.
Epidermis :- It is single outermost protective layer . Some cell of epidermis elongates to form root hairs.
Cortex :- It lies below epidermis . It is differentiated into an outer sclerenchymatous cortex & inner parenchymatous cortex. Endodermis is two layered.
Stele : Pericycle is absent. A large metaxylem is present in the center of the stele & protoxylem strand surround it . Phloem is present between protoxylem strand .Stele is protostele.
Equisetum reproduces by vegetative and sexual method
The underground rhizomes of some species form tuber, which help in vegetative prorogation.
These tubers develop due to irregulae growth of some branches buds at node of rhizome. After detachment from the parent plant and on return of favorable condition they grow into new plants.
Reproduction by Spores :-
Equisetum is homosporous pterdophyte The spores develop within sporangia borne on sporangiophores. The sporangiophores are aggregated into a compact cone or strobilus Strobilus are borne terminally on vegetative shoot or fertile shoot.Strobilus has a central massive axis & a large number of sporangiophores .Each sporangiophores is a stalked structured with hexagonal peltate disc at distal end. On the underside of sporangiophores disc 5 to 10 sac like sporangium is develops from a group of initials ( eusporangiate).The mature sporangia are sac-like structure attached to the underside of the peltate disc of the sporangiophore
The spores are spherical, uninucliated & green . The spore is 4 layers i. e. perispore middle layer, exine & endospore. The perispore splits into 4 strips or band which separate and arise from a common point on the spore. These are called elaters.
The elaters are hygroscopic. They also act as parachute &help spores to float in air.
The spore germinates shortly after shedding. The spore germinates on a suitable substratum. They swell by absorption of water. It divides unequally and produces a small rhizoidal cell & large cell. The former develops into first rhizoid where as latter give rise to prothallus. The prothalli are basically monoecious and heterothallism develops only under adverse environmental condition. The male sex organ antheridia & female sex organ archegonia develops on protallus
FERTILIZATION AND DEVELOPMENT:-
The antheridia give rise male gamete anthropoids and archegonia give rise female gamete egg. Before fertilization, the neck canal cell and Venter canal cell disintegrate and forms a path for entry of antherozoides.The anthropoids move towards archegonia and only one of them fuses with egg to from zygote. The diploid zygote develops into embryo which forms a new sporophyte .