Question

Compare and contrast bipolar vs unipolar and heterotrichous germination in sea algae.

in spore germination **

Answer 1

Bipolar vs Unipolar and heterotrichous germination

Unipolar spore germination

(1) Spores formed by the repeated division of a mother cell of the macroscopic thallus into 16 or fewer division products. Before germination spores are enlarged under photoperiods (less than 12 h light /24 h) and give rise to the Conchocelis-phase.

(2) Spores are formed within a specialised structure called monosporangium. Monosporangia formed under photoperiods on the Conchocelis-phase (greater than 12 h light /24 h).  Spores reproduce the Conchocelis-phase.

Bipolar spore germination

(1) Cell division prior to spore formation is not different from vegetative cell division. The vegetative cells of the macroscopic thallus functioning as monospores to reproduce that phase. It is commonly functional at photoperiods of less than 12 h light /24 h.

(2) Cell division prior to spore formation distinct from vegetative cell division. Before germination the cell enlargement of the division products occurs, resulting spores formed under photoperiods of less than 12 h light /24 h. Two events occurs: First, spores formed by the repeated division of a mother cell of the macroscopic thallus into 16 or fewer division products and spores reproduce the macroscopic phase. Second, spores formed by the division of a plantlet cell of the Conchocelisphase into 2 to 4 division products. From this a plantlet cell may function as a monosporangium producing a specially formed monospore. All the cells from the fertile cell rows giving rise to the macroscopic phase.

Heterotrichous germination

Many algae are heterotrichous having the thallus differentiated into a prostrate portion and an upright or projecting system. Some cells in the filaments divide several times in different planes resulting in two parts; branched filaments and aggregates of parenchymatous tissue.