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
Sl. No. Eusporangium Leptosporangium
1 Eusporangium is developed from a group of initial cells. Leptosporangium is developed from a single initial cell.
2 Sporangial initial undergo a periclinal division to form an outer layer and an inner layer of cells. Sporangial initial undergo a periclinal division to form an outer cell and inner cell.
3 The outer layer of cells produces the sporangial wall. The entire components of the sporangium such as stack, sporangial wall, and sporogenous tissue are produced only from the outer cell.
4 The inner layer of cells produces the spore mother cell, which latter undergo meiosis to produce haploid spores. Inner cell does not have any role in the further development of Leptosporangium.
5 Adjacent cells of the sporangial initial may also contribute to the formation of wall or stack of the sporangium. Adjacent cells do not have any role in Leptosporangium development.
6 The eusporangial wall is multilayered. The leptosporangial wall is single layered.
7 The Eusporangia is comparatively large. Leptosporangia is comparatively small.
8 Produce a large number of spores (100 to 1000). Spore number is very less, usually just 64.
9 The tapetum* is developed either from the inner layer of the wall or outer layers of archesporial** cells or from both. The tapetum is always developed from the peripheral cells of the archesporium.
10 The sporangial stalk is thick, short, and many layered. The sporangial stalk is narrow, long and usually 1 to 2 layers thick.
11 No specialized dehiscence mechanism for the sporangium. Dehiscence of sporangium is facilitated through the Annulus*** and Stomium****
12 Eusporangiate development is found in all vascular plants (Pteridophytes, Gymnosperms and Angiosperms) except Leptosporangiopsida. Leptosporangiate development is present only in some advanced Pteridophytes (members of Leptosporangiopsida called true ferns).
13 Eusporangia occurs either singly or on specialized sporophylls which aggregated to form a cone or strobilus. Leptosporangia occurs usually as clusters on the lower surface of vegetative leaves, often covered with a protective layer called inducium.
14 Euporangia is considered as a primitive type of sporangia. Leptosporangia is considered as advanced type.
15 Example: Psilotum, Selaginella, Cycas Example: Ferns such as Pteris, Nephrolepis, Adiantum
*Tapetum: The nutritive layer of a sporangium which nourishes the developing spores.
**Archesporial cells: The diploid spore mother cells inside the sporangial wall.
***Annulus: The thick walled portion of the sporangial wall of Leptosporangia
****Stomium: The thin walled portions of the sporangial wall of Leptosporangia. Annulus and stomium facilitate the rupture of sporangia and liberation of spores in the Leptosporangia.