question_answer 8)

Explain briefly the following terms with suitable examples, (i) Protonema (ii) Antheridium (iii) Archegonium (iv) Diplontic (v) Sporophyll (vi) Isogamy.  

Answer:

(i) Protonema It is the juvenile stage of a moss. It results from the germinating meiospore. When fully grown, it consists of a slender, green, branching system of filaments called the protonema. (ii) Antheridium The male sex organ of bryophyte and pteridophyte is known as antheridium. It has a single-layered sterile jacket enclosing a large number of androcytes. The androcytes metamorphose into flagellated motile antherozoids. (iii) Archegonium The female sex organ of bryophytes, which is multicellular and differentiated into neck and venter. The neck consists of neck canal cells and venter contains the venter canal cells and egg. (iv) Diplontic A kind of life cycle in which the sporophyte is the dominant, photosynthetic, independent phase of the plant and alternate with haploid gametophytic phase is known as diplontic life cycle. (v) Sporophyll The sporangium bearing structure in case of Selaginella is known as sporophyll. (vi) Isogamy It is the process of fusion between two similar gametes, i.e., Chlamydomonas.