Botany lecture notes

Difference between Microspores and Megaspores: Comparison Table

microspores vs megaspores

Microspores vs Megaspores
(Similarities and Differences between Microspores and Megaspores)

Microspores and megaspores are sexual spores produced by vascular plants (some Pteridophytes and all Gymnosperms and Angiosperms) for sexual reproduction. Both microspores and megaspores on germination produce the respective gametophytic generations. The gametophytes on maturation produce sex organs and gametes to establish the fertilization and thus to complete the life cycle. The production of different types of spores with different functions and sexuality is called Heterospory. The heterosporous condition was first evolved in Pteridophytes and it is considered as the prerequisite for seed habitat.

Learn more: Heterospory and Seed Habitat

The present post discusses the similarities and differences between microspores and megaspores with a comparison table.

Similarities between Microspores and Megaspores

Ø  Both microspores and megaspores are sexual spores.

Ø  Both are produced by the diploid sporophytic plants.

Ø  Both are haploid spores produced after reduction division of spore mother cells.

Ø  Both spores are produced in specialized structures called sporangium.

Continue reading

Botany lecture notes

Heterospory and Seed Habitat in Pteridophytes (Short Notes)

Significance of Heterospory

Heterospory and Seed Habitat
(Origin of Seeds and Seed Habitat in Vascular Plants from Heterospory)

Heterospory is the production of two or more types of spores

Heterospory is a condition of the production of more than one type (usually two) of spores in a single plant. These two types of spore differ in their formation, structure and most importantly its functions and sexuality. In Pteridophytes, these two spores are called as Microspores and Megaspores.

(1). Microspores:

Microspores are small sized spores produced in large numbers inside the microsporangium. They are male spores which on germination produce male gametophyte.

(2). Megaspores:

Megaspores are comparatively large spores produced in limited numbers (1 to 4) inside the megasporangium. They are female spores which on germination produce the female gametophyte.

Learn more: Difference between Microspores and Megaspores

The production of two types of spores with different sexuality was first evolved in Pteridophytes. Even though, the condition of heterospory is now represented only by eight living species of Pteridophytes, they are Selaginella, Isoetus, Marsilea, Salvinia, Azolla, Pilularia, Regnellidium and Platyzoma.

Continue reading

Botany lecture notes

Difference between Leptosporangium and Eusporangium (Comparison Table)

Leptosporangium vs eusporangium Development

Eusporangia vs Leptosporangia
(Similarities and Differences between Leptosporangia and Eusporangia of Pteridophytes)

Sporangia are the specialized spore producing structures found in plants. In Pteridophytes, two types of sporangia are present. The two types of sporangia are (1) Eusporangium and (2) Leptosporangium. This classification is proposed by Goebel in 1881 based on the developmental pattern of sporangia. The spores produced in the Eusporangium are called eusporangiospores and those produced in the Leptosporangium are called leptosporangiospores.

Eusporangium: The sporangium develops from a GROUP of INITIAL cells and such a development is called development.

Leptosporangium: The sporangium develops from a SINGLE INITIAL cell and such a development is called Leptosporangiate development.

The present post describes the Similarities and Differences between a Eusporangium and Leptosporangium.

Similarities between Eusporangium and Leptosporangium

Ø  Both Eusporangia and Leptosporangia are the spore producing structures in vascular plants.

Ø  Both are formed on the sporophyll (a specialized leaf) of the diploid sporophytic plant.

Ø  Both produce haploid spores after meiosis.

Ø  The first division of the initials of both sporangia is periclinal (transverse division).

Difference between Eusporangium and Leptosporangium

Continue reading

Botany lecture notes

Pteridophytes: General Characters (with Power Point Presentation – PPT)

General Characters of Pteridophytes

Pteridophytes General Characteristics
(General Characters of Pteridophytes – The Vascular Cryptogams)

Pteridophytes are plants with Feather like Leaves

Pteridophytes are a group of primitive land plants belongs to the Cryptogams. They are the first evolved plant group with vascular tissue system for the conduction of water and food materials. Due to the presence of vascular tissue, they are called as Vascular Cryptogams. The term Pteridophyte is derived from two words ‘Pteron’ meaning feather and ‘phyton’ meaning plant. Thus, Pteridophytes are the plants with Feather-like leaves. Pteridophytes occupy the intermediate position between Bryophytes and Phanerogams (seed plants). The important characteristics of Pteridophytes are summarized below:

Pteridophyta General CharactersØ  The division Pteridophyta includes primitive living and fossil vascular plants.

Ø  They were originated in the Silurian period and flourished in the Devonian period.

Ø  They are known as ‘Vascular Cryptogams’ – cryptogams with vascular system.

Ø  They show heteromorphic alternation of generation with prominent Sporophytic and Gametophytic phases.

Ø  The main plant body of Pteridophyte is the sporophytic plant (diploid).

Ø  The gametophytic and sporophytic generations are two independent plants (not physically connected).

Habit and Habitat of Pteridophytes

Ø  Pteridophytes show much variation in form, size, and habitat.

Continue reading

Botany lecture notes

Types of Stelar Systems and its Evolution in Pteridophytes and Higher Plants with PPT

types of steles in pteridophytes

Stelar Evolution in Vascular Plants
(Origin and Evolution of Stele in Pteridophytes and Higher Plants)

What is stele? What are the components of stele?

Ø  Stele is the central cylinder or core of vascular tissue in higher plants.

Ø  The stele consists of xylem, phloem, pericycle and medullary rays and pith if present.

Ø  The term ‘stele’ was for the first time used by Van Tieghem and Douliot in 1886 in their ‘Stelar Theory’.

What is ‘stellar theory’?

Ø  Proposed by Van Tieghem and Douliot in 1886.

Ø  Major highlights in stellar theory are:

$.  The stele is a real entity and present universally in all axis of higher plants.

$.  The primary components of stele are xylem and phloem.

$.  Tissues like pericycle, medullary rays and pith are also the components of stele.

$.  ‘Stelar theory’ also says that the cortex and the stele are the two fundamental parts of a shoot system.

$.  Both these components (stele and cortex) are separated by the endodermis.

$.  In higher vascular plants (Pteridophytes, Gymnosperms and Angiosperms), the leaf traces are large, and it appears that they play an important role in the vascular system of the axis.

$.  The whole set-up of leaf traces appears as a composite structure in these plants.

$.  Such composite structures do not remain within the limits of stellar theory of Van Tieghem and Douliot.

What are the different types of steles in plants (Pteridophytes and higher plants)?

Ø  On the basis of ontogeny and phylogeney, there are THREE broad categories of steles in vascular plants.

Ø  They are:

(1).  Protostele

(2).  Siphonostele

(3).  Solenostele

Continue reading