Spores, Sporangium and Sorus

Spores, Sporangium and Sorus Pteridophyta produce spores as a means of reproduction. Spores in this group of plants are generally located on the abaxial part of the leaves. Spores are produced by meiosis in a spore box (sporangium, plural: sporangia). A collection of sprorangia known as sorus is one of the characters to identify Pteridophyta plants. Sorus that number more than one are called sori. Leaves that have sori are called sporophyll leaves. Not all leaves in Pteridophyta have sori, sometimes there are certain leaves that do not have sori, which known as trophophyll leaves. This type of leaf has a function to carry out photosynthesis process. Sporangia that aggregate and form a sorus are protected by a structure called the indusium. Meanwhile sporangia covered by a structure called the annulus. This annulus will rupture and causes spores to come out. The sorus on the sporophyll leaves will change color according to the level of maturity of the spores contained in it. The spores still young is indicated by the sorus which is still green, increasingly The dark color of the sorus indicates that the spores inside are on their way to spore maturity Indusium is also an important identification character in pteridiophyta. Indusium that resembles a kidney form indusium reniform. Meanwhile, Indusiumorbicular is a circular shape of the indusium. Linear indusium has a narrow elongated indusium shape. Indusium attachment can in the form of peltatus (stalk in the middle) or lateral (attached to the side). When the sporangium matures and dries, the water contained in it in the annulus cells will evaporate so that the cell walls in the annulus have Capillarity forces caused by water molecules in cells react strongly each other and causes the annulus to bend at the outer surface. This event occurred in an area where no thickening occurred cell wall (stomium) so that structurally this part has weaker strength compared to the experiencing part thickening. This bending causes the stomium to be pulled and followed by the annulus. When the annulus cells are fully retracted, all the water evaporates inside the cell and causes the cell to experience capillarity and the annulus to collapse forward and release spores There are various types of spores in Pteridophyta plants characteristics. Observation of spores in pteridophytes must be viewed from this perspective shape, size, aperture type and external ornamentation type. Spore form The shape of the spores in ferns consists of a round shape (ovoid/ovatus), irregular (globose), elliptical, and triangular. The round shape (ovoid/ovatus) is found in the species Dryopteris concolor, while the elliptical shape is found in Asplenium nidus. Triangle shape found in Adiantum caudatum and the globose form found in species Trachypteris sp. which is often found on the Madagascar islands. Spore size The size of the spores in Pteridophyta plants varies greatly. this size grouped into six categories, namely very small spores, small, medium, big, very big and giant (gigantic). Aperture Type The sporangia that produce spores are initially attached to each other form tetrads. In some cases this tetrad shape is maintained, but usually this form will separate and leave scars or lines attachment. This scar is called an aperture. The aperture shape consists of: Trilete, monolete and alete shapes. Triplet scars can be seen from the scars which is Y-shaped in the tetrahedral tetrad. In this type of aperture, 3 are visible laesura branching. The spores produced in this type of aperture include: round or triangular shape. Monolet scars are the most common scars simple and almost invisible, minus (-) and resulting from tetragonal tetrad. In this type of aperture, the visible leusura is linear. The shape of the spores that come out of this type of aperture is elliptical. Ornamentation Type The type of ornamentation seen from the surface of the spore wall has a shape which differ among several types of pteridophyta. This type of ornamentation is between other types are psilate, perforate, foveolate, scabrate, gemmate, verrucate, echinate, and reticulate. Psilate is a type of surface that is smooth, flat and slippery. Perforate is a type of surface that has holes with a size of less than 1 µm, while the foveolate type has holes with sizes reaching 1 µm. Scabrate has an isodiametric shape with a size of 1 µm, gemmate type has a size of more than 1 µm, while the verrucate has an isometric one more than 1 µm high. The clavate type has a shape like a stalk with the base is narrower in height and wider in size. The echinate type is shaped like spines, while the reticulate has a shape such as nets or nets.