What is Stelar evolution pteridophytes?
Stele is the central cylinder or core of vascular tissue in higher plants and Pteridophytes. It consists of xylem, phloem, pericycle and medullary rays and pith if present. The term stele has been derived from a Greek word meaning rod or column.
What is Stelar system and its types?
Definition of Stelar System: According to them, the fundamental parts of a shoot are the cortex and a central cylinder, is known as stele. Thus the stele is defined as a central vascular cylinder, with or without pith and delimited the cortex by endodermis.
What are the main points in Stelar theory?
the theory describing the structure of and the interrelationships between various types of steles in higher plants. The greater part of the stele is composed of vascular tissues—xylem (wood) and phloem (bast)—which are arranged differently in different types of steles.
Who proposed the Stelar theory?
The concept of the stele was developed in the late 19th century by French botanists P. E. L. van Tieghem and H. Doultion as a model for understanding the relationship between the shoot and root, and for discussing the evolution of vascular plant morphology.
What represents the Gametophytic generation in pteridophytes?
In ferns gemetophytic generation is represented by heart shaped prothallus….Question : The gametophytic generation in pteridophytes is commonly called.
| Question | The gametophytic generation in pteridophytes is commonly called |
|---|---|
| Class | 11th |
What is Actinostele in botany?
Definition of actinostele : a vascular core (as in most roots and some stems) having the xylem and phloem in alternating or radial groups within a pericycle — compare stele.
What is a Stelar system?
Definition of Stelar System: Thus the stele is defined as a central vascular cylinder, with or without pith and delimited the cortex by endodermis. The stele of the stem remains connected with that of leaf by a vascular connection known as the leaf supply.
What is Stelar?
STELAR: The Satellite Television Extension and Localism Act Reauthorization—allows satellite companies to deliver distant television stations into homes, instead of the local broadcast stations that provide critical news and weather updates. DISH delivers local broadcast stations in every community across the country.
What are the economic importance of pteridophytes?
Pteridophytes commonly known as Vascular Cryptogams, are the seedless vascular plants that evolved after bryophytes. Besides being a lower plant, pteridophytes are economically very important. Dry fronds of many ferns are used as a cattle feed. Pteridophytes are also used as a medicine.
Which is the first cell of gametophytic generation in pteridophytes?
Microspore
Microspore or pollen grain is the first cell of gametophytic generation.
What is the dominant generation in pteridophytes?
In pteridophytes, the gametophyte is dominant, while sporophyte is a dependent generation.
What is Actinostele and protostele?
Actinostele is a variation of the protostele in which the core is lobed or fluted. This stele is found in many species of club moss. Actinosteles are typically exarch and consist of several to many patches of protoxylem at the tips of the lobes of the metaxylem.
What are the different types of stele found in pteridophytes?
There are several types of stele found in pteridophytes which are: 1 Protostele 2 Siphonostele 3 Solenostele 4 Dictyostele 5 Polycyclic stele 6 Eustele 7 Polystele
What is Stelar organization in pteridophytes?
This type of stelar organization is the most complex one amongst all vascular cryptogams (pteridophytes). Such type of steles are always siphonostelic in structure. A typical polycyclic stele possesses two or more concentric rings of vascular tissue. This may be a solenostele or a dictyostele.
What are the protostelic conditions of pteridophytes?
Majority of the pteridophytes show protostelic conditions in their rhizome, stem or roots. This is the most primitive type of protostele. Here the central solid smooth core of xylem remains surrounded by uniform layers of phloem (e.g., in Selaginella spp., Gleichenia, Lycopodium).
What are the characteristics of protostelic stele?
In protostele, the vascular tissue is a solid mass and the central core of the xylem is completely surrounded by the strand of phloem. This is the most primitive and simplest type of stele. Pith is absent in protostele i.e. it is non-medullated. Majority of the pteridophytes show protostelic conditions in their rhizome, stem or roots.