Spore Morphology

A: SPORE MORPHOLOGY OF ALGAE, FUNGI AND BRYOPHYTES

Algae produce different types of spores known as akinetes, endospores, exospores, zoospores, aplanospores, oxospores, zygospores, oospores and cysts. Most of these spores are produced asexually, where as few of them are produced during sexual reproduction.

The morphology of some of these spores is helpful in algal taxonomy. However, as the algal spores do not find any applications, the algal spore morphology has been the most neglected.

In the family Zygnemaceae, the genera can be identified on the basis of the colour of zygospores. For example, Sirogonium produces black zygospores where as the zygospores with various shades of blue are produced by the species of Zygnema, Zygnemospsis and Zygonium. In addition to colour, the wall of the zygospores is known to be variously sculptured. Some of these sculptured patterns include granulate, verrucose, wrinkled, reticulate, foveolate, denticulate, punctate, scrobiculate, grooved and ridged.

The spore wall in Bulbochate elatior is scrobiculate whereas in B. intermedia, it is longitudinally ribbed. The spores of Oedogonium echinospernum have a typically echinate spore wall.

Charophytes produce oospores, which have been worked out in detail on account of their occurrence in the fossil sediments also. The oospores, which are either colourless or pale yellow to black in colour are characterized by a wall-possessing curved ridges. The number of these ridges is an important character in the classification of the living and fossil Charophytes. The oospores are further characterized by a spore wall which may be finely granulated, reticulated or tuberculated.

The fossil charophyte fruits are represented by a calcarious hollow body showing clearly the spiral arrangement of the envelope. Such fossil charophyte oogonia have been described as Gyrogonites from the late tertiary limestones in the vicinity of Gokak falls in Karnataka, India.

Akinetes, which are known to be thick-walled resting spores among the blue green algae, are very characteristic. These akinetes are either smooth, sculptured or papillate or without papillae. The akinetes vary considerably in their shape such as spherical, cylindrial or ellipsoidal.

Thus, it can be concluded that algal spore morphology is useful only in the interpretation of phylogeny and taxonomy of algae.

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