Question

Stellate chloroplast is found in
A. Zygnema
B. Spirogyra
C. Coleochaete
D. Oedogonium

Answer 1

Hint: One of the filamentous freshwater algae of division Chlorophyta, genus as Zygnema features two stellate chloroplasts per cell which are often found alongside with Spirogyra. Chloroplasts are that part of plants which enables them to carry out the process of photosynthesis – converting light energy into chemical energy through cellular respiration.

Complete answer:
Zygnema, which is a genus of freshwater filamentous alga, has almost about \[100\] species. These algae grow as mass of filaments which are free floating. The young plants are found to be anchored to streambeds with the help of holdfast. Filaments of Zygnema forms yellow-green to bright green colored tangled mats, which are composed of elongate barrel-shaped cells. Each of these has two star-shaped stellate chloroplasts which are arrayed alongside the axis of the cell.

Hence the correct answer is option A. Zygnema.

Additional Information:
Chloroplasts are stellate in Zygnema whereas ribbonlike in Spirogyra and are wound around the inside of the cell like a spiral, which gives the genus its name. Spirogyra and Zygnema are the best-known members of Zygnematales, and because of its beauty under a microscope, these organisms are commonly used in biology classes as examples of the “green algae”. However, in general, the Zygnematales are not representative of the green algae, and have many unusual features which suggest that they are closely related to plants than to other green algae. The filaments of mature Zygnema tales grow when cells in the chain divide, which further develop into two new full-sized cells. Some of these species produce rhizoids on one end of the filament to help them anchor in water objects.

Note:
Zygnema species, because of their sexual reproductive means by conjugation, are classified as conjugate algae of phylum Gamophyta. Zygnema species can reproduce asexually, sexually, or vegetatively depending upon the external conditions. The filaments are coated with a thin mucilage layer, resulting in the soapy nature of strands of Zygnema.