Explain briefly the following term with suitable example :-
(i) protonema
(ii) antheridium
(iii) archegonium
(iv) diplontic
(v) sporophyll
(vi) isogamy

Explanation

Protonema . It appears due to germination of spore in moss . It is the gametophytic stage which is creeping green branched and filamentous . Form this leafy stage of moss gametophyte appears . (ii) Antheridium . It is multicellular jacketed male sex organ . Each antheridium which is usually round or club shaped is surrounded by jacket protecting the mass of androcytes. Androcytes or sperm mother cells form number of sperms or male gametes .
(iii) Archegonium . Archegonium is female sex organ in bryophytes and pteridophytes and gymnosperms. It bears a tubular neck and swollen lower venter. Neck usually contains one or many neck canal cells . In venter egg (oosphere ) and venter canal cell are present e.g Marchantia , Funaria , Ferns , Pinus etc .
(vi) Diplontic life cycle. Refer chapter -3 plant life cycles and Alternation of generations page 36 - 37 .
(v ) SporophyII . Modified leaf bearing sporangia are called sporophylls . Thy may be of two types i..e . microsporophylls and meagasporophylls. Microsporophylls bear microsporangia and megasporophylls bear microsporangia and megasporophylls bear megasporangia . They may get clustered to form male cones and female cones respectively.
e.g sporophyll - Ferns
Microsporophylls and megasporophylls - Pinus .
(vi) Isogamy. It is the fusion of gametes where both the fusing gametes are morphologically and physiologically identical.